** 1981 eldorado 6.0 fuel problems! Any information will help!

[Jonathan Johnson]

Oh BTW  he said he bought the car with the extra ecu's in it. He assumed they were there to get the 8 6 4 working correctly 

[TJ Hopland]

Its supposed to be pink but at this age it could easily look orange.  Yes its by itself.   The triple one should lead into the bottom of the distributor.   The 4 pin is the control one that goes to the ECU.  I think without that connected the distributor will go to a stand alone limp mode and work but with EFI that doesn't really help because the distributor and that connection is where the computer gets its RPM signal from to know the engine is turning and it should inject fuel.   I would not think a problem with that circuit would be preventing the fuel pump from running so I'm not too worried about that yet.

The reason I'm interested in the orange wire is that appears to be the same circuit/wire that tells the ecu to turn on.  Its not its power feed, its just apparently a signal wire.  If that wire is staying on that would explain why the ECU seems to be staying on not to mention many other things that would also be on if that circuit is on or being back fed for some reason.

One of the things I'm trying to help you discover is if someone has done some odd mods trying to solve a problem.  Its tricky since we don't even know for sure what problem they were trying to solve.   

[Jonathan Johnson]

Ok I'm checking it now

[TJ Hopland]

Interesting that apparently the 8-6-4 wasn't working for the last owner.  That's one area people sometimes make a mess of things with these cars. I have seen some pretty crazy mods related to that system that really can screw things up.  All it takes is disconnecting 1 wire to disable or enable it and that won't effect any other aspects of the car.  Most of the bad mods just make em run poorly so I'm not worried about that yet since we have the more basic issue of finding out why the fuel pump isn't running. 

[Jonathan Johnson]

Hey tj is there anyway I can send you pics now that I'm looking over this with a bright light I'm seeing some odd things

[Jonathan Johnson]

Hey tj I just realized something, when I get into the car without putting the key in the ignition,  the security system light flashes, also when I out the key into the ignition without moving it to any position the security light continues to flash, but when I turn the car to the on position it does go away. Could my security system be disabling my fuel?

[81 BENY Biarritz]

Hi Jonathan, the security light sounds like it is operating normally.  If you have the owners manual it will tell you how it works.  It does not interupt the fuel pump but does have a relay that will interupt the starter circuit if the alarm is tripped.  You will know if it is tripped as the lights and horn flash at the same time, so that is not your issue.
The fuel pump only runs for 2 or 3 seconds after the key is turned to the RUN position and the engine is not cranking.  When the engine is cranking the ECM should get a signal from the distributor that tells it that it is OK to continue to run the fuel pump so if your are cranking the engine you should get fuel pressure at the Shraeder valve (although this may not be the safest way of testing). 
Please check your original posting on the "fried ECM" thread as I posted the correct Part #s for the ECM depending on your VIN #.  Hopefully you still have the original paper sticker attached to one or more of them.  Also if you do decide to purchase a replacement please note that there are two EPROM chips inside that need to be the correct ones and need to be transferred into the replacement.
I will send some drawings tonight of the electrical circuits and where the fuel pump relay is located.  Dave

[Jonathan Johnson]

Great thanks Dave for all the info, I really appreciate it!

[Jonathan Johnson]

Hey Dave also,  I'll send you what numbers are on the ecms I have, do you need my Vin as well? So just to be clear you feel as if the ecm may have a issue or maybe the person attempting to replace them didn't realize they need to have correct Eprom when swapping? Oh also , your correct i have checked that fuel vslve right by the tbi and its bone dry. Thanks again

[Jonathan Johnson]

One other quick thing,  how can I verify what ecm and what eprong are supposed to go into my car?

[TJ Hopland]

Dave, is 81 same as 80 where the fuel pump relay powers up 3 fuses, injectors and fuel pump?   I suppose the location and pinout of the fuel pump relay would be useful too.   He could pull the relay and probe the socket to see if the +12 source is there then check the coil side while cycling the key.  Maybe it is getting the signal from the computer to turn on but its ground is missing or something simple like that. 

[Jonathan Johnson]

Just want to update you guys on the ecm situation

#1 in the trunk looks pretty beat up sounds likestuff is rattling in it with no stickers, pretty sure this one is totally junk.


#2 in the trunk has junk yard markings on it..like yellow pen markings and this one does have stickers on it. Service number is 1225120
Then is says kc 865426
Reference code is 161tbI2


#3 The ecm in the car that is currently plugged in has the same marks on it as #2
1225120
161tbi2

Hope this isn't confusing, thanks again

[79 Eldorado]

#1 in the trunk looks pretty beat up sounds likestuff is rattling in it with no stickers, pretty sure this one is totally junk.

When cars are this old NEVER assume anything is "totally junk". Never throw away a part which you think you can simply buy an aftermarket replacement for. We can find ourselves in the realm of needing to swap parts from the parts (assemblies). If the smallest thing in the "totally junk" part is good you may never know when you will need it until you do. Who knows it might be the source of the EPROM you need.

I won't bore you with specific examples but I've encountered things like that before.

Scott

[81 BENY Biarritz]

Hi Jonathan, your ECM's with Part #1225120 are the later version which were used after VIN # ending in 617927.  As for the EPROMs, if you slide open the little metal sliding door you will see both of them underneath.  The correct ones for an Eldorado (or Seville) with that ECM part # will end in KJ typically.  If it ends in LY or AAF then the chips are actually for a limousine or if it is KK then they are for a Fleetwood or de Ville.  The engine will probably run with either but there will be some differences for driveability/emissions.  I will scan the electrical drawing that you need shortly.   Dave   

[81 BENY Biarritz]

Hi Jonathan,  here is the scan.  There are three pages and the text should help with understanding how it works.
This is from the "Cadillac 1981 Electrical Troubleshooting Manual" which is silver coloured like the Service Information manual that you already ordered, only much thinner.  If you intend to keep the car it will be worth purchasing. Just watch out to get the one for the Eldo/Seville models as there is a separate manual that looks exactly the same for the Fleetwood/DeVille models, or you can buy the one that has both.  Good luck with it.  Davescan0057.pdf

[81 BENY Biarritz]

A couple of pictures of the wiring at the distributor also, since you said yours looks tampered with.  Dave

[81 BENY Biarritz]

This is a scan of the input signal from the distributor that is required for the ECM to send the signal to the fuel pump relay to keep running when the crank signal is sent.   Dave

scan0058.pdf

[TJ Hopland]

Interesting, more changes than I would have expected between 80 and 81.  80 its a little easier to guess what may be going on inside the ECU. It would be really interesting to see all the engineering notes that lead to these changes. 

Dave, what feeds the 'relay convinence center' fuses for the fuel pump and ECS fuse?  Is that still the same path as the pink wire that ends up at the distributor?  If so my test with the test light between the pink wire and ground would still be worth doing to see if that circuit is turning on and off with the key.

Next I would be looking at the ECS and fuel pump fuses to see if they are live with the key on. Test light between ground and both sides of both fuses.

Next would be remove the fuel pump relay and stick the test light in 2 and 5?  Cycle the key off then on and see if the light lights for a second or two. 

I see some other good places to test but but will wait till we hear the results of these first ones.

And another Dave question, looking at the entire ECU diagram do you see any ins or outs that may indicate something inside that would make the noise he is hearing?  Or is it like the 80 where all the noisy stuff looks to be external?

 

[Jonathan Johnson]

Hey I wanna post some pictures but I'm not sure how to I don't see any things I can push to add pics, could you guys help me? Thanks

[Jonathan Johnson]

Hey Tj and Dave thanks a ton for all the info, I'm going to contact you all tomorrow with the results from both of your comments, this is giving me hope that I'm getting closer to diagnosing this little gremlin,