75 - 79, 80 Fast Idle Control Valve "FIV" Working on a replacement

[79 Eldorado]

Hi Bruce,
All of the things you mentioned were part of the two years worth of testing. So I do have some excuse for taking so long

While I was testing I tested 2 heating units which were around 13 Ohm and one which was around 16 Ohm. What we need depends a lot on the mass and how well the heat is transferred to the assembly. As you suspected the pin length also complicated things.

There were a couple of major break through instances which helped. The first was when I decided to CAD model the entire section of the TB and the second was realizing that these wax actuators are only consistent equalized at a pretty decent load and after sitting under load for around 30 minutes. In fact months were spent because I was concentrating too much on the "cold" load as the spec point and made worse because I didn't realize how critical the load was as the design point. What was worse was I had been communicating to the a partial load just based on the spring constant and not really in the assembled/ compressed cold position. To get within their actuator design range it was even better to use the load at full compression. By that I mean the spring compression once the pin is fully extended and the plunger compresses the spring as much as it can.

The 3D model and resulting workbook I developed allowed me to perfectly spec the pin length I needed. The wax actuators follow a curve so once you know a single point the curve gives you the rest.

I then did a lot of testing at ambient, in the car and on the bench, and with part which had been in my freezer over night on the bench test. Using the time versus temperature, known resistance, and known voltage I was able to create another workbook to estimate time at other conditions and using different resistance values. The resistance heaters have a standard tolerance of +/-10% so I used the workbook to develop an acceptable range. As I mentioned the supplier also agreed to reduce the standard tolerance to +/-6%.

In the chart I posted the "gap" measurement my workbook calculates that from information entered regarding plunger distance from the bottom of the TB. The actual gap is impossible to see but since I modeled all of the parts I can simply use math to "see" the value.

So the draw during heat-up for the first sample was around 0.92 Amps. The range should always be between 0.86Amps and 0.97 Amps. Once under control the electronics simply sample and prevent anything significant from passing through to the heating element.

None of the major components was off-the-shelf so it worked out that I was able to find supplier who were willing to create custom parts just for this application. I'm really pretty happy with the way they came out. I picked-up more brass heat sinks this morning so I will soon assemble 6 more parts (limited by the number of housings I have until the end of the 1st of January).

Scott

[79 Eldorado]

I'm posting the instructions I originally wrote when I sent Joel one of my prototypes (see attached pdf). I've updated it and added some pictures... It's a lengthy read but I wanted to be thorough. I was thinking about even adding a second page of pictures. Anyway if anyone is interested please take a look and suggestions are welcome...

Scott

[79 Eldorado]

Now listed on our forum here:
http://forums.cadillaclasalleclub.org/index.php?topic=162989.0

Scott

[bcroe]

Now listed on our forum here:    Scott.

OK, why does the replacement part care about power polarity?  The connector
is not really set up to control it.  Bruce Roe

[79 Eldorado]

OK, why does the replacement part care about power polarity?  The connector
is not really set up to control it.  Bruce Roe

The internal controller wires, for the controller I used, were +/- specific. I think it's because the controller needs a very small amount of power to monitor even when it cuts the power to the heating element (around 1/100th of an Amp). I verified which was the supply on the original vehicle wiring if the connector was assembled in the normal position and I assembled the wires accordingly.

The original connector appearance is different from top to bottom but yes if someone twisted the wires inside the TB, pretty easy to do, they could flip the electrical connector upside-down and the terminals themselves would not error proof against it. I suspect if the wires are swapped there would be no damage but instead current would never pass because the controller has no signal to allow power to pass. The prototype controllers were very expensive and I only had 3 so I didn't want to push my luck reversing the polarity when it was clearly indicated.

Maybe I should add a photo which shows which direction the connector should be assembled but probably the best way to ensure the proper orientation is to check the wiring harness for ground with the car off. I didn't try that but I suspect ground will always be grounded.

Scott

[bcroe]

The internal controller wires, for the controller I used, were +/- specific. I think it's because the controller needs a very small amount of power to monitor even when it cuts the power to the heating element (around 1/100th of an Amp). I verified which was the supply on the original vehicle wiring if the connector was assembled in the normal position and I assembled the wires accordingly.

The original connector appearance is different from top to bottom but yes if someone twisted the wires inside the TB, pretty easy to do, they could flip the electrical connector upside-down and the terminals themselves would not error proof against it. I suspect if the wires are swapped there would be no damage but instead current would never pass because the controller has no signal to allow power to pass. The prototype controllers were very expensive and I only had 3 so I didn't want to push my luck reversing the polarity when it was clearly indicated.  Scott

So that brings the question of, what is this controller?  Proprietary?  Bruce

[79 Eldorado]

So that brings the question of, what is this controller?  Proprietary?  Bruce

Yes, as I recall they made it a point to say that. I bought it based on specification and I asked a lot of durability and logic questions prior to making the decision. It uses a temperature probe to provide controller feedback. If the probe breaks it's error proofed to not pass power. It's programmable in their production to a set temp to cut power and a second temp to reset. Customizing the range you can basically set-up the device to avoid constant cycling. Since my heat sink has decent mass it also helps keep things stable. I verified with the supplier that it would be capable of many millions of cycles. I would need to dig for my assumptions but I basically determined the cycles with an extreme user. It was something like assuming a person would drive an average of 5 hours a day and 240 days out of the year for 15 years (again I would need to verify what I used exactly). I have it in a workbook someplace. The number of cycles was high but they were not concerned at all by the number.

Scott

[79 Eldorado]

Bruce,
I did just verify in the Electrical Trouble Shooting Manual the ground is always grounded. At least on our 1979's the supply wire should be dark blue and the ground is black but of course after 40 years both wires pretty much look the same color so probing for ground with the car off seems to be the best a good solution to make 100% certain the electrical connector hasn't been flipped.

Thanks for the comment. I will suggest how to check it in the installation instructions.

Scott

[bcroe]

Bruce,
I did just verify in the Electrical Trouble Shooting Manual the ground is always grounded. At least on our 1979's the supply wire should be dark blue and the ground is black but of course after 40 years both wires pretty much look the same color so probing for ground with the car off seems to be the best a good solution to make 100% certain the electrical connector hasn't been flipped.  Scott.

How about, check for 12V at the connector pins while the engine is
running?  It will not stay on if you just turn on the ignition.  There
is continuity to ground through the fuel pumps all the time, not many
ohms different from a short to ground.  Bruce

[79 Eldorado]

How about, check for 12V at the connector pins while the engine is running?  It will not stay on if you just turn on the ignition.  There
is continuity to ground through the fuel pumps all the time, not many ohms different from a short to ground.  Bruce

As Bruce suggested that's the best way to be certain. It's actually what I did to check it when I did it myself. I liked the idea of testing for ground with the car off but I wasn't aware of what Bruce wrote about a path to ground through the fuel pumps. I need to see if anything needs to be rewritten in the instructions.

Thanks Bruce,
Scott

[79 Eldorado]

A lot discussed but I realized the symptoms of a failing FIV were never really covered...

I mentioned I didn't initially realize my original Bendix/OE part was going bad. I knew it seemed to take a little longer for the RPM to drop than it seemed it should but I couldn't quantify it before all of the testing. When I actually measured it what should have been around 2 to 2.5minutes was 11.5 minutes. I determined that I was only getting partial heating from my OE/Bendix part.

Here are the signs:
-1 Reduces RPM but takes a lot more time than seems reasonable... if you don't wait you end-up shifting into gear at an elevated RPM. That was the problem my car had prior to installing the replacement.
-2 RPM never drops to a reasonable level... Elevated RPM all of the time because the valve no longer closes.. you may notice the car wants to accelerate by itself requiring the driver to tap the brakes. That was the issue Joel Howard experienced.
-3 No high idle RPM... If you have this issue you should check to see if your FIV is "latched" which means the clip has traveled far enough to lock the position of the plunger in the closed position. I recommend removing the clip because the wire is hardened and can be brittle. It seems to only serve the purpose of reducing the "loose" part assembly height to make the FIV easier to install. Cadillac may have done that to help protect the switch arm on the OE part. The replacement eliminated the arm.

My struggling OE/Bendix part wasn't as bad as one which had completely failed but it was still an incredible improvement once I installed the replacement. Because it's not always obvious I was trying to think of a way, probably limited to forum members, to try it before you buy it.

Scott

[79 Eldorado]

I'm adding a summary graphic showing a section view of some of the parts relative to each other as well as a graph showing proper operation versus a part I tested where the heating circuit was starting to fail. In this case the FIV was obviously taking too long to close the valve and thus very slow going from "Fast Idle" to stabilized / normal idle.

Scott

[bcroe]

That valve should be a great help to owners looking for solutions.  I have favored
solutions that replace or plug directly into original equipment, because any custom
work means now only that tech will understand or be able to maintain the system in
the future. 

I remember my 79 E running away from me, shortly after I got it.  There were plenty
of other issues too.  After shimming the valve, I just kept my foot on the gas as
needed cold, and worked on figuring out why the ECU gave the wrong fuel mixture. 
Starting cold idle was less a problem for me, I was usually only a couple stop signs
away from the expressway.  Never went to the trouble of measuring time. 

I have wondered, just how many of those 70s EFI cars are still out there running
fine, and how many got shoved into storage (or worse) because no mechanic knew
how to deal with EFI failures?  Any how many repairable 70s ECUs are lost on a
back shelf?  It would be good to get them all rounded up, and repaired when practical. 

I am hearing about broken 70s EFIs as much as ever, like another car every week. 
Previous century as I was starting to get a handle on my 79 details, another Cad
owner pointed out an Evil Bay auction of a lot of some 30 defective 70s Cad ECUs. 
I got them at an affordable price, after pointing out that they were just boat anchors
that nobody (at that time) could fix.  In time those and some other donations helped
me get on top of the 5 somewhat different years.  More recently the Cosworth Vega
entered the picture as a very close EFI relative.  Bruce Roe

[79 Eldorado]

That valve should be a great help to owners looking for solutions.  I have favored solutions that replace or plug directly into original equipment, because any custom work means now only that tech will understand or be able to maintain the system in the future. 

Thanks Bruce.

I have wondered, just how many of those 70s EFI cars are still out there running fine, and how many got shoved into storage (or worse) because no mechanic knew how to deal with EFI failures?  Any how many repairable 70s ECUs are lost on a back shelf?  It would be good to get them all rounded up, and repaired when practical. 

Between your ECU repairs and my sensors, it seems over some time, we might be able to estimate how many are out there. I've been pretty surprised at the numbers.

I am hearing about broken 70s EFIs as much as ever, like another car every week. Previous century as I was starting to get a handle on my 79 details, another Cad owner pointed out an Evil Bay auction of a lot of some 30 defective 70s Cad ECUs. I got them at an affordable price, after pointing out that they were just boat anchors that nobody (at that time) could fix.  In time those and some other donations helped me get on top of the 5 somewhat different years. 

I'm glad those 30 ECUs made it to your hands. My belief is the interest in owning an older vehicle, casual user or collector, has a lot to do with whether or not the particular car can be repaired. If there are no repair parts and no after market support cars tend to die off. Had I lost confidence in that part of it I certainly wouldn't have spent as much time as I did. The knowledge on this forum and the repair work you've done will give people confidence in keeping this era of cars viable farther into the future than would have been possible.

When I was looking for a replacement spindle I saw too many 79-85 Eldorados in junkyards which didn't look like they were that bad when they went it but I don't think I saw any 1979's and I suspect 80-85 are there due, in part, the HT4100 and maybe the newer system being even more of a "black box".

More recently the Cosworth Vega entered the picture as a very close EFI relative. 
Bruce Roe

I know I've mentioned this before but I assumed the sensor technology might be similar. I read a pretty good thread on a Cosworth forum and they explained a different operation but knowing the Cadillac sensor I suspected they may have misunderstood how the sensor(s) function because some of the things they mentioned made me think they were similar. I think you told me once they are not similar.

The special Cadillac diagnostic ECU, Kent-Moore J25400 is also the same part for the Datsun/Nissan "Z" EFI car (capture added in attachment from the Datsun Z forum). The only difference is a different overlay and I think some functions are dedicated to only Cadillac or only the Z. The wiring harness adapters are also different. I have some captures showing the Datsun/Nissan Z overlay and I captured the diagnotic tool manual posted for the Z because at the time I couldn't find the Cadillac instructions.

I'm adding the latest version of my removal/install instructions. I added a page dedicated to verifying polarity.

Scott

[bcroe]

From the design I can see, the Cosworth EFI design was first, with the 70s Cad
EFI being a very much improved development of that starting point.  Being an
analog computer, they both needed linear temp sensors which could be directly
translated to linear fuel changes.  The Cosworth did it using the common temp
curve of a silicon transistor, that sensor had mechanical problems.  The Cad
developed a very fine resistance wire sensor, linear enough.  But the Cad sensor
also tended to fail open circuit over time.   I think Scotts version will prove much
longer lived, years will tell for sure. 


Reasons they were not interchangeable, \included opposite sloped curve, different
amount of slope, and mechanically different.  Someone asking me about the temp
sensors is how I became aware of the Cosworth design, and I did some support
work including drawings, a temp sensor tester, and a bench ECU tester. 

I have pieces of several J25400 sets around here, intended for use on a car.  My
testing is on the bench, over a much wider situations than possible on a car, so I
never tried to get a J25400 operational.  The Cosworth owners wondered if it could
work for them, because the connectors and many other things are similar to the
Cad.  But the connectors are wired completely differently, and things like the temp
sensors make them incompatible. 

And I know zippo about the Datsun EFI, wonder how it fits into the above? How do
I get on the Datsun Z forum? Bruce Roe

[79 Eldorado]

...How do I get on the Datsun Z forum?
Bruce Roe

Bruce,
I found it by searching for the J25400 manual. In Google images I saw a lot of scanned pages and they all linked to that site. Because the Datsun Z uses that same J25400 those two systems seem like they must be the closest but that's just a guess. I found it again. Here you go:
http://datsunforum.com/efi-troubleshooting-kent-moore-j25400-analyzer/

If you made a curve for the Cosworth sensor and you know what the sensor should look like, mechanical interface details,  I'm pretty sure with enough time I could duplicate it.

It would be really interesting to know how close the Cadillac and Z car systems were. I was shocked when I learned that they used the same tester with just a different overlay and wiring harness adapter. I tried to ask a technical question on Bring-A-Trailer once because there are a lot of Z experts there but they really didn't appreciate a technical question which wasn't specific to the car which was for sale.

Scott

[bcroe]

Thanks Scott, I looked over some of the drawings at that site.  Despite both using a
J25400 test set, it appears the EFI systems are very different.  I would rather have
the Cad EFI than the Datsun.  Bruce

[79 Eldorado]

Once I realized it was a Z specific manual I never really looked at it closely; just assumed it would be better than nothing if I ever needed it.

After I read your reply I took a look at the temp sensor curve and it's reversed compared to our Cadillacs (Highest resistance at coldest temps for the Z). I guess the J25400 simply read the resistance and it was up to the user to see if the value was correct on the readout for the given temp.  So it was easy to combine that test.

Scott

[bcroe]

Yea about everything connected to the Datsun ECU is different from the Cad. 
Most notable is the mechanical air flap to measure air intake, a crude device
from an earlier generation.  Cad used a MAP, partly mechanical, but later made
completely solid state. 

I guess the pumps and injectors were the same.  Bruce Roe