Bad ECM?
Thread Starter
4th Gear
Joined: Nov 2007
Posts: 4
Likes: 0
From: California
Bad ECM?
Hello everyone! Newbie here!! I have a 86 automatic coupe. On the way to the store the engine just died. Tried to start a few times and the starter just cranked, could'nt get it to fire. Popped the hood and looked around for anything obvious, nothing. Got back in the car tried again and it fired right up and ran fine back to the house(approx 10 mi). Next morning tried to take it to work but got around the corner and it died. Same thing tried a few times nothing, waited a while and it fired up. Drove car home, shut it down and tried to restart it, nothing. Now it wont start even after letting it set for a while. No check engine light through all of this. Even so, I jumped the computer for any possible stored trouble codes, I didnt get any diagnostic code reaction, not even the first series of 12-12-12(system operating correctly code). I checked the jumper to make sure I had a good connection and I did. I have jumped codes in the past and every time I got the 12-12-12 (system operating correctly code) followed by the stored codes. I will have to wait until tomorrow to do more extensive troubleshooting, spark, fuel delivery and so on. However if the ecm is bad there is no sense in troubleshooting any further. Any suggestions??
Thanks.
Thanks.
Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
Bad injectors can cause intermittent problems. With the ignition off, pull each injector plug and measure the resistance across the two injector prongs. They should all be near 17 ohms or so without any being very different. Try this cold and then hot to make sure that nothing changes with heat.
But first, try the basics like you said. Put a fuel pressure guage on the shrader valve and monitor for proper readings at around 39 psi or so. Put a timing light lead on a plug wire to check for spark when it won't start.
But first, try the basics like you said. Put a fuel pressure guage on the shrader valve and monitor for proper readings at around 39 psi or so. Put a timing light lead on a plug wire to check for spark when it won't start.
Thread Starter
4th Gear
Joined: Nov 2007
Posts: 4
Likes: 0
From: California
Hello all
I am still having problemsgetting the 86 coupe started. Just a quick question for all the ecm gods!!
If the "service engine soon" light is non-responsive in any key position, whether in the "on" or "run" position and also non-responsive in the diagnostic mode (with jumper wire in place). Does this mean the ecm is bad??? Checked for a burned out bulb or a bad bulb connection and everything is good.
I am still having problemsgetting the 86 coupe started. Just a quick question for all the ecm gods!!
If the "service engine soon" light is non-responsive in any key position, whether in the "on" or "run" position and also non-responsive in the diagnostic mode (with jumper wire in place). Does this mean the ecm is bad??? Checked for a burned out bulb or a bad bulb connection and everything is good.
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Being new a good thing to learn is to use the Search function, main menu bar, Advanced, Include Archive posts and search the C4 forums... Theres tons of info and good material, another place is the C4 Tech Tips, Read and learn... Also since it hasn't been said already, get the FSM (Helms) manual, you'll need it.
Team Owner
Joined: Jan 2003
Posts: 20,320
Likes: 248
From: Summerland B.C. Canada
If the "service engine soon" light is non-responsive in any key position, whether in the "on" or "run" position and also non-responsive in the diagnostic mode (with jumper wire in place). Does this mean the ecm is bad??? Checked for a burned out bulb or a bad bulb connection and everything is good.
Thread Starter
4th Gear
Joined: Nov 2007
Posts: 4
Likes: 0
From: California
Thanks for the quick response and the troubleshooting schematic!!!
Going back out to do more troubleshooting!
What manual did that schematic come out of? Where can I get my hands on one of those??
Going back out to do more troubleshooting!
What manual did that schematic come out of? Where can I get my hands on one of those??
Team Owner
Joined: Jan 2003
Posts: 20,320
Likes: 248
From: Summerland B.C. Canada
Factory service manual, available used in the for sale section here and Ebay. New ones here... http://www.helminc.com/
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Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
86
I had the exact same thing on my 86. change your starter.
The plastic starter brush holders shrink when cold, and expand when hot pulling the starter brushes off the commutator, and won't let the starter turn. I start it up, drive 1.5 miles to the store, shut it off, buy milk, get back to the car, and nothing.
Lights switch over to the start mode, everything is fine.
an hour and a half, 2 hours later..........vroooom, starts right up.
I went through the vats thing, the neutral start switch, the fuel pump, the distributor, etc. finally pulled the starter after checking it for volts when I turned the key.
change your starter, or rebuild it. my 86 thanks me for it every day.
The plastic starter brush holders shrink when cold, and expand when hot pulling the starter brushes off the commutator, and won't let the starter turn. I start it up, drive 1.5 miles to the store, shut it off, buy milk, get back to the car, and nothing.
Lights switch over to the start mode, everything is fine.
an hour and a half, 2 hours later..........vroooom, starts right up.
I went through the vats thing, the neutral start switch, the fuel pump, the distributor, etc. finally pulled the starter after checking it for volts when I turned the key.
change your starter, or rebuild it. my 86 thanks me for it every day.
Thread Starter
4th Gear
Joined: Nov 2007
Posts: 4
Likes: 0
From: California
Its fixed!!!!!!
Thanks to everybody for all the help!!!! Went out and checked the cluster of fusible links and found one that was bad, all full of corrosion. It was the battery feed to the C16 pin on the ECM. Replaced it with a new fusable link and all troubles went away!!