Just recently my 1976 8.2 liter fuel injected Fleetwood began running very poorly out of no where. It has been in the shop since September. The shop says the engine is running rich. They have replaced the injectors, checked the electrical, and had the ECM (electronic control module) rebuilt, to no particular success. They are out of ideas except to convert to a carburetor. I would like to keep the injection system. Any thoughts or references would be greatly appreciated. Thank you.
Who rebuilt the ECU? No mention of temp sensors? From the little info give here it sounds like they don't understand these systems.
Was it in the shop for this issue or this happened while it was there for a non engine related issue?
Thank you for your reply TJ. All I know is they sent it out to another shop for the rebuild. They have not mentioned temperature sensors. The car was not in the shop when the issue began, although a new battery was put in a couple of weeks before the problem began. Never had a previous issue. I agree with your assessment about their understanding of the system, which is why I am reaching out to this forum for some insight here. I will mention temperature sensors to them. Any additional insights greatly appreciated.
I don't know that much about the system either, most of what I know comes from reading here. There is an active member here that knows and repairs these systems that I'm sure will be along soon with more information and help.
I do know that these don't have any sort of memory or learning like newer stuff has so changing the battery should not have effected it at all. They also don't have any sort of built in diagnostics so troubleshooting isn't like even the slightly newer systems and not like carbs either so a unique process.
There is a coolant and air temp sensor that often seem to fail and I believe one of the failure modes is for it to tell the system that the engine is cold so it will run rich all the time.
Can't say thank you enough TJ. Looking forward to additional input.
Quote from: krbulman
Just recently my 1976 8.2 liter fuel injected Fleetwood began running very poorly out of no where. It has been in the shop since September. The shop says the engine is running rich. They have replaced the injectors, checked the electrical, and had the ECM (electronic control module) rebuilt, to no particular success. They are out of ideas except to convert to a carburetor. I would like to keep the injection system. Any thoughts or references would be greatly appreciated. Thank you.
Yes the problem is with the ECU, and the fix + test will probably cost
less than the postage. It certainly will cost less than changing it to a
carb. I do not know of any shop capable of the repair, of this analog
(before digital) ECU. But I can take care of it if you send the ECU.
Send me an email at bcroe@juno.com
Have had that EFI system on my 79 Eldo for 25 years, have reverse
engineered it. Bruce Roe CLC # 14630
If your're going to keep the car, invest in the blue and white Cadillac manual recommended by Bruce Roe (I see he is saying it's the ECU as I was typing) titled Electronic Fuel Injection Diagnosis. It's much better than the supplemented factory service manual for troubleshooting.
FYI: The troubleshooting table lists the following possible causes of 'rich operation' in order of probability:
Electrical connections (pretty helpful, eh?)
MAP hose leak or obstruction. A common failure mode from reading the forum. My hose was leaking
High Fuel Pressure
Vacuum leaks at throttle body
Dirty or sticking injectors: assume your problem is all of them running rich
ECU:
For what it's worth, Dean
Interesting he went right for ecu, I was expecting some more troubleshooting info. He is the man when it comes to these systems so if it says its an easy fix then it will likely be an easy fix. It will likely come back to you better than when it was new because he won't just fix the one thing that is broke now, he will hit all the common areas. He also has some updates that improve weak areas.
You guys are tremendous! I don't know what to say, TJ, Dean, and Bruce. Thanks for the input. Bruce, I will be in touch. As an aside, the reason I am so interested in preserving this car is was my dad was in the business back then and I had never seen a FI Brougham. When I got it, I contacted Tim Pawl and Paul Ayres about production numbers for a FI Brougham. Response was less ~than 100. BTW, 20k original miles. Much appreciated!
Quote from: TJ Hopland
Interesting he went right for ecu
The symptoms were normal to suddenly very rich, which I have
seen (dozens of times) caused by a failed integrated circuit in
the enrichment circuits. It could be caused by a leak in the MAP
hose or a shorted temp sensor, not much else does that. Best
to check it all, sometimes these ECUs have other faults not yet
realized. Bruce Roe
And that is why Bruce is the man.... Doesn't just blame the computer with no explanation.
You guys are incredible! LOL. Thanks.
Just to close the conversation, sent Bruce the ECU, got it back in 2 days, the car is back in our garage. Thanks guys.
So Bruce's ecu repair has fixed the car?
Awesome diagnosis and repair Bruce!
Just curious but other than going after most likely known problems is there any way to read data from one of these? (were obd1 ports a thing in 76? :o )
Quote from: INTMD8. So Bruce's ecu repair has fixed the car?
Awesome diagnosis and repair Bruce!
Just curious but other than going after most likely known problems is there
any way to read data from one of these? (were obd1 ports a thing in 76? :o )
This early 70s design did not use digital processing, as the microprocessor
was just about to be invented. So no obd1, worked with analog computing.
Probably that is why the usual support houses do not reach back before 1980.
Another one got fixed since that one. Bruce Roe
Quote from: bcroe on December 30, 2019, 09:06:37 PM
The symptoms were normal to suddenly very rich, which I have
seen (dozens of times) caused by a failed integrated circuit in
the enrichment circuits. It could be caused by a leak in the MAP
hose or a shorted temp sensor, not much else does that. Best
to check it all, sometimes these ECUs have other faults not yet
realized. Bruce Roe
The MAP hose is the one that plugs into the back of the ECU, right, Bruce? I ask, because, if there was any activity inside the passenger compartment, even as mundane as vacuuming the carpet, one could easily knock that hose loose. I had that happen to our Seville. I could hear the vacuum leak, but some may not, depending on circumstances.
Just a point to note, because that's an easy fix.
Quote from: Gene Beaird
The MAP hose is the one that plugs into the back of the ECU, right, Bruce? I ask, because, if there was any activity inside the passenger compartment, even as mundane as vacuuming the carpet, one could easily knock that hose loose. I had that happen to our Seville. I could hear the vacuum leak, but some may not, depending on circumstances.
Right, it plugs in on the heat sink fin side. There is a hose inside which also
can fail. Best to pull a vacuum at the throttle body end, to detect any leak.
Lately the GATES 27043 hose I have been using internally, is made of a
rubber that CONDUCTS ELECTRICITY. So I have been putting heat shrink
insulation over them to assure no shorts, tape would work.
good luck, Bruce Roe