Hi all.. new to the forum, but far from new to the Cadillac world. I type a lot, so bear with me. I've had a few Cadillacs come and go over the years, including '61 and '70 convertibles as well as a '75 Fleetwood limo, and currently have a '72 Sedan deVille, and this '76 Coupe deVille I just picked up.
I am new to the world of Cadillac fuel injection, however. This EFI 500 is new to me, and this is a car that sat for a number of years and needs a bit of help to get it going. My first step is researching this system to fully understand it and all of its key parts before I dig into it. I'm very familiar with modern computer controlled EFI systems, but this is a little different. First question: Will the factory shop manual have in depth technical info on the system, or is there a better source out there?
Next question.. in the real world we live in today where things often go quite differently than the engineers intended, is this EFI system going to be a constant pain to keep it running right? Will it be reliable? I plan to use this car for long road trips, and the very last thing I want is to have regular breakdowns that are essentially unfixable on the side of the road due to zero parts availability. My inclination is to install a correct intake/carb/distributor/mechanical fuel pump on it and know that it will be reliable, consistent and run very well. I know there is an enthusiast base for these EFI systems, but it will quickly lose its charm to me if I have to spend a lot to get it sorted out and routinely have to fix it or have issues. It's not the fact that it is EFI that scares me, it's the fact that it is old, early EFI made before the OEMs really sorted EFI out well, combined with limited parts availability. Many early innovations started off as fine ideas, but took years or decades to really sort out well. I'd like to find out the real truth behind these systems and running one today.
I appreciate any input you all have, especially real world experiences of owning one of these and driving it regularly. I plan to put some real miles on this car, as I use my all my cars as they were intended, they don't just sit around the garage looking pretty. This is an 82k mile car that is a little rough around the edges, but is well worth saving, and I intend on making sure it stays on the road for many, many more years to come!
You have come to the right place. We have one member that knows these inside out and test and repairs the ecus. We also have a couple other members that are making some of the no longer available parts for them. I'm sure they will be along soon to offer help and advise.
As to how big of a pain it is I can't answer that, I have been around them but never really lived with one long term. Its a very rare these days system for the 500 but the same system was standard equipment on the 76-79 Seville so there were a bunch of them on the roads at one time. The only other engine you could get on those Sevilles was the diesel in 78-79. 79 Eldos and CA 80 Eldo and Seville could have had em too so they were not as rare as one may think. Today? I'm not real sure, obviously a majority of those cars no longer exist.
One question you have to ask when considering a carb and related systems is how many people are really good at working on those and what quality parts are available for those? Not many people can or want to work on an old car anymore and the parts we can get today are often garbage.
For maintaining 70s Cad EFI cars I highly recommend having the blue &
white book: CADILLAC ELECTRONIC FUEL INJECTION DIAGNOSIS
Manual 1099984 / S-1453. Its usually available on EBay, currently eBay
item number: 165136935730 and others. Get a paper book, not a CD.
In order to properly service that car, you should have at least the 1976
CADILLAC SHOP MANUAL, Cat No. S-1152.
I have driven one of those systems for a quarter century.
For more info, or getting an ECU repaired, email me at
bcroe@juno.com
That EFI was state-of-the-art when designed, one of the
first using Integrated Circuits in an analog processor.
But the single IC 8 bit microprocessor was invented in
1972, so analog was completely obsolete when 80 models
came out with digital EFI. Bruce Roe CLC #14630
Quote from: TJ Hopland on October 02, 2023, 08:45:30 PMYou have come to the right place. We have one member that knows these inside out and test and repairs the ecus. We also have a couple other members that are making some of the no longer available parts for them. I'm sure they will be along soon to offer help and advise.
As to how big of a pain it is I can't answer that, I have been around them but never really lived with one long term. Its a very rare these days system for the 500 but the same system was standard equipment on the 76-79 Seville so there were a bunch of them on the roads at one time. The only other engine you could get on those Sevilles was the diesel in 78-79. 79 Eldos and CA 80 Eldo and Seville could have had em too so they were not as rare as one may think. Today? I'm not real sure, obviously a majority of those cars no longer exist.
One question you have to ask when considering a carb and related systems is how many people are really good at working on those and what quality parts are available for those? Not many people can or want to work on an old car anymore and the parts we can get today are often garbage.
Thanks.. I restore classic American cars for a living and for my enjoyment, and have a particularly keen understanding of carburetors, distributors and tuning them properly. I've built many carburetors, including more than a few Quadrajets, so getting a carb/distributor setup on this engine right will be no challenge whatsoever. It will run great and be rock solid reliable, hence my inclination to go that direction. There are enough parts available for Quadrajets where that is no concern whatsoever, especially metering rods, jets and springs, so tuning is no issue, and if I go carb I would ditch the HEI distributor and run a Pertronix billet distributor. Very easy to perfect the advance curve, adjustable vacuum advance, rock solid reliable, readily available. Have installed many dozens of them in customer's cars as well as my own, and have yet to see one have any kind of failure. I have seen many HEI ignition module failures over the years, and shy away from them if at all possible. Not to mention, finding the advance weights and springs to dial them in is no easy task any more.
Quote from: bcroe on October 02, 2023, 11:33:10 PMFor maintaining 70s Cad EFI cars I highly recommend having the blue &
white book: CADILLAC ELECTRONIC FUEL INJECTION DIAGNOSIS
Manual 1099984 / S-1453. Its usually available on EBay, currently eBay
item number: 165136935730 and others. Get a paper book, not a CD.
In order to properly service that car, you should have at least the 1976
CADILLAC SHOP MANUAL, Cat No. S-1152.
I have driven one of those systems for a quarter century.
For more info, or getting an ECU repaired, email me at
bcroe@juno.com
That EFI was state-of-the-art when designed, one of the
first using Integrated Circuits in an analog processor.
But the single IC 8 bit microprocessor was invented in
1972, so analog was completely obsolete when 80 models
came out with digital EFI. Bruce Roe CLC #14630
Thanks, I'll look into getting both. I too prefer actual manuals, not CDs or online manuals.
If I'm going to keep this car running on the factory fuel injection, I'm going to not only want to freshen up all the key parts that I have now, but will need spares as well. Do you have any spare ECUs for sale? What about sourcing the fuel pumps? I believe I found a source for the in-tank pump, but not the high pressure inline pump. Any ideas?
I have had several of these systems over the years, with Mercedes and Cadillacs. I do appreciate them, fully restored and maintained them.
That said, your system sounds significantly neglected. I am in a similar situation with 2 VINTAGE Bosch EFI and knowing what I know now...
I believe I will 'start over' with a modern EFI and save myself. I have converted a 500 (carbureted version).
Quote from: V63 on October 03, 2023, 01:08:11 AMI have had several of these systems over the years, with Mercedes and Cadillacs. I do appreciate them, fully restored and maintained them.
That said, your system sounds significantly neglected. I am in a similar situation with 2 VINTAGE Bosch EFI and knowing what I know now...
I believe I will 'start over' with a modern EFI and save myself. I have converted a 500 (carbureted version).
I thought about adapting a modern ECU, TPS, O2sensor, etc. to this system, retaining mainly the intake, injectors and fuel rails.. but for what benefit? Modern EFI does offer some benefits over carb, but when comparing to a well-sorted carb setup the difference is not monumental. This won't be an all-weather car for me - it won't see deep freeze or 100+ degree weather, so the benefits of EFI over carb become less pronounced.
A modern sequential EFI system may offer a slight fuel economy benefit over batch fire injection.. but I can't see it being much.
I know it sounds like I've made my decision to just go carb.. I haven't. I'm open to the idea of retaining the factory EFI, if the reasons are compelling to do so.
In general, I'm kinda 'done' with carbs unless it's a 6 volt car.
The early Bosch EFI system has tried many a car guys patience and that was when you could find the parts readily. It is best to consider it most challenging at this point in time, especially with blended fuels.
It would take someone with most determination to find satisfaction above the frustrations.
I have a 79 El Dorado EFI that has 215k miles on it. The only EFI parts I have replace are the fast idle valve, injector o-rings, and the in-tank low pressure fuel pump. The o-ring seals started to leak fuel and were hard as rocks. The in-tank fuel pump did not fail, car quit running and had no fuel pressure. When I removed the fuel tank and fuel sender, I found the hose between the pump and sender line had split. It runs great, passed its last emission test in AZ (have since moved). and gets great mileage for a 70's car.
I would say don't give up yet. Play with the system a bit so you understand it then decide if you want to keep it. If you decide not to I would guess you could sell it for parts to someone that is trying to keep one going. The Seville's used an Olds engine so the Cad engine specific parts are much less common and often times people 'getting rid' of the systems damaged things removing them so they were not even able to keep other systems alive.
I have run and am still running an aftermarket EFI and I would say given your experience with carbs and not intending to run in any extreme conditions I would agree its probably not worth the trouble. Most people don't have the experience or access to people that can work on carbs anymore so it doesn't matter which direction they go its going to be a hard road either way.
Oh and being a RWD car you should have the option to go with something like the Edelbrock intake if you wanted to. In the FWD Eldo's the engine sits up much higher so you can run into hood clearance issues.
Thanks guys.. I actually have a spare factory intake and Quadrajet sitting around, so it's an easy swap.
I should have provided some more background.. this is a car that I believe was parked in the late '90s and sat for more than two decades. The seller says his mobile mechanic tried to get it fired up a year or so ago, but did nothing more than put a battery in it and crank it over with nasty old oil. He said it would only run when he dribbled fuel into the intake. Needless to say, this guy does not sound confidence inspiring. But he *says* the fuel pumps did not come on, so who knows.
The fuel tank is absolutely full of NASTY smelling varnish, so I'm obviously going to drain it out and clean it, but I'm concerned about the rest of the system as well, particularly the injectors. If they're badly varnished as well, they would need serious cleaning or replacement.
Here's another question: Does this EFI system add any appreciable value to these cars? If I remove it I would not simply throw any of it away. I would either save it all and put it on a shelf, or sell it if someone wants it. What are these parts worth to sell if I were to go that route? I have everything, including the gold lid air cleaner.
It sounds a major overhaul of the system and you would lucky if you can save the fuel tank. The fuel pumps are probably toast. Possibly computer related fuel pump service circuit that can be done by specialist Bruice on this forum. The 8 injectors would need to be each (at a minimum) need to be cleaned and test sprayed . There used to be serviced that did that but they seem to have vanished.
The systems are rare but more rare are those that are determined enough to tackle them (at this time). So it's supply and demand as to value. I have a few used systems myself. And at least one more coming up.
I am only trying to be 'realistic' in my advice, but if you elect to restore the original EFI that's admirable and appreciated as well!
Quote from: MultipleCaddiesIf I'm going to keep this car running on the factory fuel injection, I'm going to not only want to freshen up all the key parts that I have now, but will need spares as well. Do you have any spare ECUs for sale? What about sourcing the fuel pumps? I believe I found a source for the in-tank pump, but not the high pressure inline pump. Any ideas?
Getting an old car roadworthy again is a big project, here it includes
tires, timing chain set, and total rebuild of the brake system. All pipes
running front to back need attention, here in the rust belt that means
replacement of exhaust, fuel, and brake lines. That 76 has the additional
electronics of the EFI system. The ignition is not tied into the EFI.
Learning another system is another challenge, at least there are books
fully explaining the 70s Cad EFI. Judging from a couple hundred ECUs
repaired here this century, close to half went on 75/76 500 engines, about
as many on the Olds small block cars, and a few on 77/79 425 engines.
Apart from mechanical engine requirements, these are all nearly identical
externally, with internal ECU variations for the ap. Drawings for the ECU
wiring, and some sub systems, are available.
Over the years, some EFI failures dominated, esp with the fuel pump
control. Simple fixes have been worked out and are easily retro fitted
when the ECU is checked out. Some part problems have been solved
with new (and IMPROVED) replacements. Old electronics can fail,
even on the shelf. It is good to carry a spare ECU if you can find one,
the demand has driven the 500 ECU market price up to 4 figures. I have
a couple 500 ECUs with some updates for about half that price.
Fortunately original ECUs are not costly to repair. Note most 70s ECU
sources do not have means or parts to actually test or repair them.
To restore the EFI you will need to go thru the entire fuel system,
from the injectors all the way back to the pump inside the tank.
The hoses and injector seal will see up to 40psi, any not replaced by
this time are a fire hazard, if not already leaking. If you decide to use a
carb, you will still need to go thru that system, changing out the intake
manifold, fuel lines including a mechanical pump, and the tank unit.
The original HEI will work fine, its extra SPEED SENSOR outouts can
be ignored. I like HEI because anyone can service them, they do not
get wetted down and missing like smaller caps, parts are cheap if you
did not find enough in the junk yard, and the whole system is just one
component. Modules can fail, I carry a spare that is easily replaced on
the road, no re timing required.
It is possible to use the original 76 port injection system to convert to
sequential injection. But that requires a new ECM to be dialed in,
new temp sensors, a new throttle position sensor, and a new wiring
harness to convert from high side bank drive to low side individual
injector drive, and another pump control. I actually did this on my 79,
using an original speed sensor as the cam sensor. But the ECM chosen
was not capable of properly driving the original peak and hold injectors.
Before I solved this problem, I relocated and that system is still in a box.
If you do change out the HEI and EFI, there are other owners who
could use the spare parts. You would be removing the intake with its
injectors, throttle body, and temp sensors, and fuel rail, HEI, fuel filter
mounted where the mechanical pump goes, wiring harness to the ECU,
the ECU, frame fuel pump, and tank unit. good luck, Bruce Roe
Yikes! All this is adding up to mean I'm very likely just going to go carbureted. I just don't see enough benefit in spending significantly more to get the EFI sorted out, and still be a somewhat unreliable system. Also, being batch fire injection with a simple TPS that appears more to be a switch than a variable resistor, along with no ignition timing control, I don't see this system having the refinement or fuel economy advantage like modern systems do. I have a hard time believing it would run much, if any better than a well sorted carburetor.
Getting all of the other bits on this car sorted out is easy stuff.. I have resurrected many a classic car that was parked for decades, and am well familiar with everything else it will need. I already made a big parts order to cover most of the other long-neglected maintenance items it will need at a minimum. Once I really dig in I know I will find even more. This is one part of the process I really enjoy, in fact. And frankly it's pretty easy stuff. Seals, gaskets, hoses, belts, fluids, brake hydraulics, etc. are all easy stuff on these cars. No sweat. It would be quite different if I had to trust some knucklehead inexperienced shop to do it all, and pay dearly for the privilege.. but that's no concern for me. Plus, this is a totally unmolested original car that hasn't been hacked up by idiots, so I only need to fix what time and usage has worn out, not the mistakes of others.
More than likely, once I verify that the engine and trans are good they will come out for a full reseal of both. I'll swap the intake and everything else, freshen up the engine bay, make whatever changes I need to the fuel tank, pickup and lines, and be back on my way.
Up here in the dry desert environment of northern Nevada we don't have the midwest and east coast rust issues some of you guys suffer with. This car has very obviously not seen much if any snow season driving, it is very solid underneath. The hard fuel and brake lines are in excellent shape, and the fuel tank will probably be fine as well, based on my experience here. And if not, time for another one. That's not something I'm particularly concerned about, they're not difficult to find.
So the next question is.. would anyone here be interested in buying all of the EFI parts off of this car if I decide to take it all off and sell it? I would not want to sell the system in pieces, but as a complete system, including fuel lines, pumps and everything.
The other option - that I am NOT leaning towards - is converting to a modern EFI system using only the intake, injectors and fuel rails from the original system. Something like a Holley HP with an appropriate MSD distributor for proper timing control as well, and a modern TPS and O2 sensor, among other things. Then I'm sure I could realize the refinement benefit of real modern EFI, with real tune-ability. But now we're talking $3,000+ just for parts, plus a LOT of time getting it sorted out. Again, I just don't see the benefit.
I think the cheapest route is fix what you have, next is convert to a
carb, most expensive and setup time consuming is adapt some other
EFI system. That 76 HEI ignition is exactly the same for a carb or EFI.
Yes 76 EFI uses a clever switch for throttle position changes, probably
the most reliable part of the system and more reliable than that cheap
pot later used.
I see the 70s system as an attempt to meet current and future emissions
requirements, mine was certainly much better than my same engine cars
with a carb. Ignition timing is very important, needs a digital system to
build a 3 dimensional timing map and add other inputs (like temp), instead
a pair of 2 dimensional curves from the rpm and vacuum.
The trans must come completely apart to change out hardening seals on
the clutch pistons. The chain cover is best glued back on to avoid leaks.
good luck, Bruce Roe
Can someone explain to me why the carbed cars were rated at 190 horsepower and 360 lb ft torque while the EFI ones were rated at 215 and 400 respectively? It seems like a huge jump in power just for a change in fuel delivery
simple answer : better Fuel management!
Quote from: V63 on October 03, 2023, 06:36:41 PMsimple answer : better Fuel management!
That seems unlikely, since many different Quadrajet-equipped engines made close to 400hp, and the '70 500 in particular was rated at 400hp. Many of these engines made close to or above 500 foot pounds of torque as well. The Quadrajet is an excellent carburetor and was well refined by the '70s.
This brings up another question: Were there any differences in engine internals between the carb and EFI cars in '76? GM was very fond of using different heads and camshafts on 2bbl vs. 4bbl engines, so it would not surprise me at all if there were similar differences between carb and EFI on these Cadillac 500s. Not to mention differences in timing curves.
There were no internal
engine differences that I am aware of.
The distributor was specific however.
The fuel tank was special.
One advantage to the port fuel injection that was unique to the Cadillac big block was the elimination of the overall poor performance of the upside down intake runners with a wet intake. Fuel injected big blocks (when working right, at this point few of them are unless they've been sorted) do idle smoother, tip in better and pull harder without the atomization bottleneck the intake design encouraged.
Ironically they stepped backwards in this regard with the DFI system in 1980 which necessitated a wet intake again.
The same basic system when used on the Olds seems to have less butt dyno power than the 4bbl version.
I found the fuel injection to actually be more thirsty than the carburetor.
The Cadillac big blocks were incredibly smooth and nice throttle response. Agreed on the fuel economy...very heavy beasts. The 75-79 Seville always seemed under powered... adequate but lacking.
One thing interesting about the Bosch system from 1975-80 (1980 California), was that when Mercedes had it before Cadillac, it fired in
4 phases (2 injectors each) but Cadillac only had 2 phases (4 injectors), that has to be less efficient and I always wonder why that was changed.
My opinion, the Seville needed the small block
403 engine, which is a direct bolt in for the
350. Just retune the EFI a bit (like my car),
but unfortunately the EFI started for 76 and
403 was not available till 77. The other thing
it needed was better gearing. Unfortunately no
4 speed auto was available for 76, and the switch
pitch TH400 was long gone. Again a bolt in, the
latter took a whole second off my 0-60.
I know little of the Bosch, but have not seen it
as having a lot in common with the Cad EFI.
Firing a high side driven peak/and/hold injector
bank requires a medium power circuit with heat sink,
so using 2 instead of 4 definitely has cost and
space savings. Bruce Roe
IF you were to go with a modern aftermarket EFI system I think there would be many downsides to using the original EFI intake. There was nothing even remotely standard about how anything fit that intake. The TB flange was unique. I think the injector diameters and heights were also unique so you would end up having to modify a lot of thing to still end up with some oddball stuff that may be hard to source parts for.
I believe the Edelbrock intake has flat areas ready to be drilled for injectors and then you also have a standard TB flange and non of the linkage clearance issues you get with the Cad intake. Just about anything that isn't a Q jet will have clearance issues with what ever hangs down below the throttle shaft on a stock intake.
The stock intakes are 'upside down' because of the Eldorado being FWD. The Eldo engine sits up high to leave clearance for the drive shaft to go below the crank and they apparently decided to use the same intake on all the cars rather than have the Eldo have its own.
The way things are all adding up, I'm going to go carbureted. I just don't see the benefit of putting the time, money and effort into this EFI system when I know a carb setup will be rock solid reliable. Plus, I already have a spare intake and a fresh Quadrajet ready to go, so there is little for me to have to search for.
I'm also quite confident that with appropriate carb and distributor advance curve tuning, I'll be able to make up for the difference in power output and maybe a little extra. Emissions era tuning was NOT geared towards best performance, but I have no such concerns with that now. I'll be using an earlier non-EGR setup on it, eliminate the smog pump, and tune it for best performance. Wouldn't surprise me if I find a couple-few dozen long lost horses in this thing.
I've been heavily into my entire system. When I bought the car I was afraid of the unknown. I'm having one problem currently but I will work through it. The system is complicated but at the same time not really. I really like the EFI system and there's no way I would get rid of it after getting deeper into it.
If the prior owner was correct, pumps were not coming on, then you need to determine why. The fuel pump relay is inside the ECU and Bruce, who has replied here, has mentioned that high percentage of ECUs have damaged/burned pins powering the pumps. He has a preventative measure fix which is an external FP relay. I installed it on my 79 and documented it for others to follow here:
https://forums.cadillaclasalleclub.org/index.php?topic=153100.msg414525#msg414525
The white and blue book was posted by a member and is also commonly available on eBay. See post nr 6 of this thread: https://forums.cadillaclasalleclub.org/index.php?topic=167249.msg511579#msg511579
Replacement injectors are available. I sealed mine with flourosilicone o-rings instead of the ones commonly in the kits because flourosilicone should be better if you plan to run alcohol containing fuel and alcohol free.
Temperature sensors are incredibly easy to check, speed sensor incredibly easy to check. Fuel pressure port is in an easy place to attach a gauge on my car.
My tank was very clean, from Texas, I even found a build sheet on top of the tank. Mine could have convinced most people it was NOS new after I used a dry toothbrush to remove the Texas dust. I changed the in-tank pump but the OE worked. The soft line looked a bit like a marshmallow but it wasn't hard and it didn't appear to be leaking.
I do plan to now replace the in-tank once again but with a high pressure pump to go to a single pump system. The problem I'm having seems to be fuel volume related. My high pressure pump works but under load it doesn't seem that it's up to task anymore. There are external replacements but none seemed to be perfect drop-ins.
Because it's a maintenance item which you would likely change be careful with the fuel filter gasket. Mine started leaking not long after acquiring the car and once recently. I did find that the AC Delco GF157 filter comes with a seal which is taller than the one I removed. It was just over 4mm instead of 3mm and that filter gasket blew-out on me. I questioned it when I installed it but it was AC Delco so they should know what they're doing. I would avoid repeating that like the plague. I don't like FRAM filters but the FRAM replacement, which could be sourced same day while 70 miles from home, had the roughly 3mm thick gasket. The AC Delco gasket had lipped out of the filter housing lip.
You can do what you want but the OE EFI system is pretty nice. It has no feedback so it only knows what the inputs tell it. Two temp sensors, TPS, speed sensor, and MAP sensor inside the ECU. As a safety item, if the speed sensors stop, then the pump power is killed.
I guess your problem could be the ECU main fuse blew or the ECU pins are burned, or possibly something happened where it isn't getting the signal from the speed sensors. You can see if the pumps come on by powering a wire which unplugs just behind the tank. At least that's where it is on my car. It's in a separate, single wire, connector which looks a lot like an early Delphi weatherpack.
Too cool to dump the EFI and either way you need to go through the system. The in-op will likely be something simple if you take the time to diagnose it.
Scott
I'm less concerned about diagnosing whatever the issue is now and much more concerned about real world reliability in the long run. I'm contemplating a trip to Florida in this car in a few months, and the last thing I want is an unreliable car for a 6,000+ mile roadtrip. The lack of easy parts availability is a big concern out there on the road, especially parts that I can't easily fix myself on the side of the road.
I'm going carb. I'm going to post this whole system for sale I think. I know once I remove it, it will never go back on the car, and this car isn't in any kind of collector quality condition where it will fetch any real money if I ever sell it, so I'm not concerned about retaining it. If anyone is interested, let me know. I'll be getting to it in the next couple weeks here.
79 Eldorado,
You can check the pump volume by connecting you fuel pressure gauge to the port on the rail and removing the hose from the gauge. You should get a pt of fuel in just a few seconds. Check the specs. If it's low, pull the high pressure pump inlet line and see the low pressure pump passes a volume test. If not, I would suspect that the "marshmallow" coupling from the low pressure pump to the fuel line on the sender is leaking causing the low volume issue. Also, have you checked the dead head pressure of the high pressure pump? If you pinch off the return line from the fuel rail, the original Bosch pump would develop over 100 psi new. If your pump developes 80+ psi it work OK. Max regulated pressure is only around 60 psi.
Larry,
It acted basically the same after I changed the in-tank pump which included submersible Gates hose and clamps. I did also pinch-off the return line and I got about 65psig. I thought that was a number you mentioned in another post and because it seemed like a good check I did it. That check was before I changed the in-tank low pressure pump. I only changed the low pressure pump at the time because I had an exhaust appointment, 140 mile round trip, which I may not have been able to reschedule until next year. It wasn't running perfectly but I made it. Had I had more time I would have gone directly to a single high pressure pump but I would have needed to have one in-hand and I did not.
Exhaust is done and I added an AFR gauge. Today I replaced the in-tank with a high pressure pump; Walbro GSS342. This car just seems to want more work done to it and it always seems to know when it's within 500 feet of the garage. There's more to it, even more than I listed below, but I don't want to continue to go off-topic.
MultipleCaddies mentioned a long trip. Most of the work I've had to do has nothing to do with the EFI system. The timing chain on my car had the nylon coating and the factory aluminum intake started to weep. I went through everything sitting on the intake when I changed it. I also realized the front cover was leaking at the balancer area, balancer was worn, so now it's new. I put a re-manufactured starter on it because the starter solenoids are now more than half the cost of replacing the starter. That starter worked perfectly for 2 weeks until the solenoid would kick the Bendix but the starter wouldn't turn. The new starter came and it had a short solenoid. My car has a battery cable with a molded plastic guide on it to keep it in exactly one position as it passes by the right side output shaft. That meant the shorter solenoid caused the positive cable to be short by 3/4". AutoZone went out of their way to get the proper solenoid on the starter and all was fine but out of curiosity we ordered another starter and it came with the correct solenoid... once again all was fine, this time for 10 days, and then the rear of my oil pan developed a leak. I had to pull the final drive out to do that job and of course the starter again. I could now do a starter on the car wearing a blindfold.
It's very possible that the 1976 is easier to find parts for but my point is these are old cars and, at least in my case, you cannot always get the parts in the same day even for a carburetor version like my 1979 Toronado. When I was doing the intake I did rebuild the distributor as a non-ESS version. That was because that is essentially the "only" part which "we" (the 70's EFI owning community) has not come up with a solution for and like MultipleCaddies I didn't want a failure which I didn't have a solution for.
MultipleCaddies, remember that the fuel supply is on the driver side, not the passenger side like most GM carburetor cars of that time, so include some planned re-route to what you need for conversion. Or possibly you could use an in-tank pump and simply find a regulator for the lower pressure required by the carb. I think that's the way I would probably do it. So you could retain the aft part of the EFI. You could also still signal the pump(s) with the ECU controlled relay and you could keep the speed sensor set-up for the safety of shutting off the pump. If you did that then you would at least have the benefit of not having to pump the crap out of the carb system after storage when the fuel evaporates from the fuel bowls or leaks as was common with the original QJet bowls.
One other point about the age of these cars. When I rebuilt my distributor I realized that my pick-up coil wire was about to break. Even though it was a pick-up coil which supports a 5 pin module the problem was not specific to EFI. That could be a time bomb in any 40+ year old car.
Scott
All of the typical old car foibles are old hat to me. I've resurrected many a neglected vehicle, I know not to try to chase foreseeable issues one at a time as they come up, but simply address them all ahead of time. I restore classic American muscle cars professionally, and part of that comes with the knowledge that 50 year old cars are absolutely full of worn out parts. Doubly so when old cars sit for half their life. Trying to limp them along fixing one thing at a time as they break just results in endless frustration and builds resentment with the car. Totally counterproductive. If you're going to own and drive a classic car today and want to actually put some miles on and enjoy it, you have to be proactive and address all of the common, predictable issues before you try to drive it. Hence why I'm so hesitant to run an old EFI system where most of the parts just aren't available any more, and even at it's best is still more complicated and potentially unreliable than a simple carb setup.
What I've actually decided to do in the meantime is prep a known good running 79k mile 472/TH400 combo that I have sitting here and swap it into the car for now instead. All gaskets and seals on both engine and trans will be replaced, new fuel pump, new oil pump, new water pump, it already has a freshened up Quadrajet with ethanol-resistant needle and accelerator pump, a new Pertronix distributor, new plugs and wires, new timing chain and sprockets, and most importantly it's a proven good runner that I've put some miles on. I'll set the original 500/TH400 aside for later freshening up.
I'll investigate this fuel tank, and if need be I'll swap it out with a standard carbureted tank (since people say they're different). I will absolutely NOT run a needlessly unreliable electric pump setup with a 50 year old computer that can leave me stranded for no reason. Making a fresh new hard fuel line from tank to engine is easy, I've made many such lines. Nicopp and a two post lift make it a nice easy job, along with fresh ethanol-resistant stainless braided hose at both ends. A fresh new mechanical pump is extraordinarily unlikely to fail any time soon with regular use. And once this car is an established good runner, it will get regular use. My drivers do not sit for extended periods, they get used. Plus, ethanol-free fuel is readily available where I live, so apart from long road trips, it will always get ethanol-free fuel anyway.
Among other things this car will get before any long trips are all the brake hydraulics replaced or freshened up, all the axle seals and gear oil changed, front bearings repacked or replaced as needed, u-joints likewise, power steering hoses changed and fresh fluid, all coolant hoses and either a new or recored radiator, etc.. I won't leave anything mechanical to chance to before a long road trip. None of this is new to me. I've watched and learned from the many mistakes and tribulations of others, as well as my own experiences, to know better than to leave things to chance when driving old cars. They need a lot of attention, and I want to ensure that I get to decide when and where said attention is given, not wait for the car to tell me somewhere between Flagstaff and Gallup, or somewhere equally desolate where no parts or services are to be had. When you do the work yourself and know that it's done right, and you cover all your bases ahead of time, it really makes it so much easier to really enjoy a classic car. I have to make my customer's cars absolutely reliable for them, and I put the same effort if not more into my own.
I'll still carry a spare carb kit with me, probably a spare fuel pump, an old distributor and wires, and of course fluids. And thanks to some good wholesale closeout deals at Rockauto, a whole bunch of extra belts! Just in case. But with everything fresh I don't expect to need any of it.
MultipleCaddies,
One thing Cadillacs of this era seemed to be lacking was even a basic gauge set. In 1979 The Toronado came standard with a coolant temp gauge but you couldn't even get the Eldorado with an optional gauge pack. My point is , regardless of carb or EFI, it probably wouldn't be a bad idea to at least have a temperature gauge. Using a gauge you can often see something is happening before it becomes a real problem. I don't know your particular model well so not certain what they came with.
Scott
To justify the expense of EFI, Cadillac probably fudged the numbers so customers would feel better. Only an engine Dyno or rolling road would tell the answer. Who can honestly feel a modest jump in power on a Sherman tank-torquey 500?
I worked with Mercury outboard engineers in the late 1980s. When they put EFI on their new motors the BHP didnt change much at all, maybe 5-7 bhp. But they advertised it as a 20 bhp plus advantage.
One issue with small motors in the past, has been
lack of good spark advance control. My 2000 tractor
(20hp) had fixed timing, so it only was optimized
for one load and rpm point. Most EFIs these days
fix that with a programable multi dimension spark
table. I adapted one of the spark advance controls
to the tractor (the carb stayed) and it made a huge
improvment to overall performance, and approximately
15% better fuel mileage. I can imagine a similar
improvement on the outboard.
However, only with the 80s digital EFI did the Cad spark
advance get upgraded. The 70s stayed with a pair of
2 dimensional systems, independant vacuum and rpm
advances only. Bruce Roe