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1994 Oldsmobile 88 Olds 88 won't start

Tiny
COPENHAGEN80355
  • MEMBER
  • 1994 OLDSMOBILE 88
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 175,000 MILES
A buddy of mine has a 1994 Olds 88 with a 3.8 V6. When he bought the car 2 years ago it needed a new ECM which he replaced. Until recently the car was working fine. A few months ago the check engine light started coming on. When it was on the car would idle and run rough and the transmission would slip and there was just an overall loss of mid-range power. After awhile the check engine light stayed on all the time. Then about a couple weeks ago the car would just randomly not start. You would know when it wasnt going to start because if when you opened the door and the dome light didnt come on it wouldnt start, which I found very odd. If you opened the door and the dome light came on it would start fine although still run poorly. When it wouldnt start it would crank but no fire. He said the ECM went bad again because that was the same exact thing it did when he got the car, and a new ECM cured it. If you let it sit for awhile and cycled the ignition a couple times it would start. Sometimes it would only need to sit for a few minutes, other times a day or more. About a week ago it left him sit and we could not get it started so we decided to replace the ECM, and the car ran fine. No rough idling, no slipping trans, and great power. It ran like new again. For about 3 days it ran fine, then all at once the check engine light came on again and it died once more. After doing some research I thought maybe the PROM went bad and wasnt delivering fuel. He had a spare PROM that he swears is good which we put in and nothing. So thinking it was a faulty ECM, we once again replaced that and still nothing. No dome light and it will just crank and crank. Ive been working on vehicles since I was old enough to hold a wrench and this one has me perplexed. The oddest part about it to me is the whole dome light thing. I had similar problems on a 1976 Chevy pickup but that is a completely different beast. That turned out to be a bad fusible link. Any help would be greatly appreciated, he relies on this car to get to work and presently he is borrowing my old chevy truck to get to work and back and im at my wits end with this car. Thank you so very much.
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Monday, January 26th, 2009 AT 3:00 PM

18 Replies

Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Ok first off has a scan been done to see why the engine light is on? Do you have a digital multi meter to do other tests if needed? Do you know how to do the paper clip trick to get the engine light to flash? If not then here is what you do you get a paper clip and bend it so the ends will be the same length and then you jump it accross term B and A then turn the key on and you should see the engine light blink. Now it will blink a 12 at first which it one flash a short pause and 2 blinks and a longer pause and then the next code. It may pause as long as 30 seconds between codes. Write down the codes and get them to me and I will look them up and see what the car is telling us. Here is a pic and at the bottom of it is the diagnostic port that you will using the paper clip on ok. See where is say's diagnostic test with the arrow pointed to it.


https://www.2carpros.com/forum/automotive_pictures/249564_Graphic_31.jpg

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Monday, January 26th, 2009 AT 3:56 PM
Tiny
COPENHAGEN80355
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I tried the paper clip trick and it didnt work. I bent and cut a paper clip and put it in ports A and B like you said and turned the key on and the check engine light stayed on solid the whole time. I also check for fuel and spark and it is getting both.
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Tuesday, January 27th, 2009 AT 11:36 AM
Tiny
COPENHAGEN80355
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  • 12 POSTS
Actually we just checked it again and it was just fuel laying in the lines. The pump isnt pushing any fuel. Im going to guess its not the pump itself but possibly a relay somewhere, or maybe both of his PROMs are bad. The reason I dont think it is the pump itself is because the times we actually have got it running, it runs and idles like crap and the tranny slips.
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Tuesday, January 27th, 2009 AT 11:50 AM
Tiny
COPENHAGEN80355
  • MEMBER
  • 12 POSTS
Sorry to keep making so many posts but im trying to keep you filled in as I go along. I just checked the fuse for the fuel pump and it is ok, and the fuse box is getting juice when the key is turned on. Would the relay for the pump be before the fuse box or in between the fuse box and pump? I looked in the trunk for a fuel pump switch and found nothing, and the haynes manual doesnt really give you a location on the fuel pump relay and if it has a switch in the trunk or not. I have a few errands to do, after bit im going to jack the car up and check voltage at the pump.
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Tuesday, January 27th, 2009 AT 12:40 PM
Tiny
COPENHAGEN80355
  • MEMBER
  • 12 POSTS
I checked the wires at the pump with a test light, and I dont think im hallucinating but it looked to me like the pump is getting juice wether the key is on or off. I checked them at the plug where the pump plugs into the harness underneath the car by the tank and there are four wires (2 hot 2 ground im guessing) and the 2 hot wires were hot wether the switch was on or off. Im not sure which side of the plug I was on not that it matters I dont think. But in the fusebox the fuse was only hot when the key was on. Is there anything else in between the fusebox and fuel pump? Im at a complete loss here and am about ready to pull my hair out.
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Tuesday, January 27th, 2009 AT 3:35 PM
Tiny
RACEFAN966
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Ok with the light staying on your computer is not comunicating so it is probably a bad prom. I will look further into that.
The fuel pump relay is inside the car on the passanger side behind the dash.
With all that you have said you have been finding it sounds like the computer is doing what it wants when it wants. I would first check grounds to the computer make sure none are shorted.
Here is what you need to do now to test the PCM ok. Jump Term A and B again turn key on and see if anything has changed If light still stay's on then turn key of leaving jumper in place and disconnect the PCM and then turn key back on and see if the light came on if it did then you need to repair the short in the brown and white wire.
If the light stayed off then check to make sure the PROM is poperly installed if it is then disconnect the battery to clear codes and then reconnect and check the light again if there are no changes then the PROM is bad. Now what needs to be figured out is why is this car killing computers by checking ground to the computer. Let me know what you find.
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Wednesday, January 28th, 2009 AT 10:15 AM
Tiny
COPENHAGEN80355
  • MEMBER
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I did the procedure to check the PROM but it doesnt check out. I tried this with both PROM's he has for the car and neither of them checked out. But, could a bad ground for the computer also cause this? I honestly dont believe its the PROM, but I will keep it in mind as a last resort. Now that ive sat down and thought about it, to me all signs seem to point to a bad ground somewhere. Which wires does the computer use to ground itself or doesnt it use any of the wires? Im pretty much at a loss figuring out where the computer grounds, the Haynes manual has absolutely no information on that. Also, where does the fuel pump ground at? Maybe that could be the culprit too, and I'd be willing to bet that is why the dome light doesnt come on when the car wont start. Due to a bad ground somewhere. For the time being, I found and pulled out the fuel pump relay, im going to test that using the procedure in the Haynes manual.
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Thursday, January 29th, 2009 AT 1:54 PM
Tiny
COPENHAGEN80355
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Relay checks out. So we have it pretty much narrowed down to Bad computer ground, bad fuel pump ground, or bad PROM. Get back to me with info on where the computer grounds ASAP as I believe this is our culprit. If I find anythng else I will let you know. Thanks so much.
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Thursday, January 29th, 2009 AT 3:23 PM
Tiny
COPENHAGEN80355
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I got to looking at the ALDL yesterday and realized something. Ports A and B have no wires in them! There are actually only maybe 5 or 6 wires in the ALDL and if the diagnostic wires are there, they arent where theyre supposed to be. So that pretty much rules the PROM out, its not the PROM's fault we cant communicate with the ECM. Im putting it in a garage today and im gonna jack it up and try to trace the wiring for the fuel pump to see if I can find where it grounds at and check it, then I have to figure out where the computer grounds at if the pump wiring is good.
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Friday, January 30th, 2009 AT 9:42 AM
Tiny
RACEFAN966
  • MECHANIC
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Ok do the prom's have the same number on them? Now unplug the ECM and set you multi meter to read at least 50 thousand ohms and put the neg of mutli meter to case of computer and then use the possitive to probe each connector on the ecm harness do they all have at least 50k ohms? If this checks out then the ECM is no good. Let me know what you find.
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Friday, January 30th, 2009 AT 11:08 AM
Tiny
COPENHAGEN80355
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Ok did what you said and not all wires had resistance, but the ones that did all had over 50K ohms. I would say a good half of them had resistance.
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Friday, January 30th, 2009 AT 11:51 AM
Tiny
COPENHAGEN80355
  • MEMBER
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Ive been tracing wiring all afternoon looking for a short or bad ground. I had just climbed out of the trunk and was looking at the wiring diagram in the manual, and said "I wish this (expletive) thing would start!". At that moment, the dome light came on. I hit the key and it fired right up. Check engine light is on and it coughs and sputters when you give it fuel but it started. How long this will last I dont know. Magical forces at work. You decide.
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Friday, January 30th, 2009 AT 2:48 PM
Tiny
RACEFAN966
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Good now it runs somewhat. Now can you try to see if the engine light will give you any codes so we can see why the light is on. Let me know how it goes.
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Friday, January 30th, 2009 AT 10:58 PM
Tiny
COPENHAGEN80355
  • MEMBER
  • 12 POSTS
Well like I said I thought the same thing but there are no diagnostic wires in the ALDL plug so I cant jump the wires with a paper clip. They arent there. If they are there, their not in the right position in the plug. Just in case, do you know what colors the wires are? If I can find them I will do the paper clip thing and if I get any trouble codes I will let you know.
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Sunday, February 1st, 2009 AT 10:28 AM
Tiny
RACEFAN966
  • MECHANIC
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If you refer to the previous pic it has the wire colors there I think it is black and white and all you need to do is ground it and that will make the MIL light do its talking ok. Let me know what you find.
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Monday, February 2nd, 2009 AT 12:45 PM
Tiny
PENSACOLADAD
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I too have the same trouble. Have you found any answers?
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Sunday, June 28th, 2009 AT 8:25 PM
Tiny
KEVIN1575
  • MEMBER
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I HAVE THE SAME PROBLEM WITH A VEHICLE IN MY SHOP.
YOU HAVE A SHORT. AS I HAVE FOUND AFTER LOOKING FOR SOME TIME TODAY, I FOUND THAT THE DIMMER SWITCH SHOULD BE TURNED AS IF YOU WERE TURNING ON THE DOME LIGHT, BY DOING SO THE VEHICLE WILL RUN.
ALSO THE WINDOWS SEEM TO RUN ON THE SAME CIRCUIT. DOME LIGHT OFF AND DRIVER DOOR OPEN NO RUN AND NO WINDOWS, DOOR OPEN DOME LIGHT ON WINDOWS WORK AND CAR RUNS.
I WILL GIVE A VERDICT ON THIS CAR TOMMORROW AS I WILL FIGURE IT OUT!
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Saturday, September 10th, 2011 AT 6:52 AM
Tiny
RACEFAN966
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Sounds like the BCM Body Control Module. Do you have the means to do some testing on it?
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Tuesday, September 27th, 2011 AT 4:18 AM

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