Burned/melted ecm

[youcancallmedusty]

On thanksgiving I was warming up my 1987 gmc v2500, after idling for a couple minutes I noticed it was stumbling and acting like it was running out of gas to the point of talking but then would come back to a normal fast idle while warming up, I was quite certain the tapping from the injectors got louder then normal when stalling and when it came back it would sound normal. It did it twice and I turned it off. After turning it off I noticed that magic circuit board smoke smell that lingers for days in the cab, I was on my way to a dinner party for thanksgiving so I decided to risk it and drive the 3 miles to it. Truck ran fine for the 6 mile round trip anlthough the idle stayed higher then normal (anorund 1k rpm, compared to the usual 650-750rpm) and I made it back home. The day after I started inspecting it and found this burned chip on the ecm, after researching it seems like where the chip connects to the 32 pin connector is for the injectors, I believe it’s d15,d16. After inspecting the wiring in the truck and engine bay and not finding any melted wires anywhere, I started probing the ecm to see if there was a short somewhere within the board which I could not find if there was. At this point I am past my experience level since I am not an electrical engineer and have a basic understanding of how pcbs work. I ohmed out the injectors and both where at 1.2 ohms and they do not short to ground, the truck will still run with the burned ecm. I bought a new one but I am hesitant to install it until I find the cause of the melted wires. The ecm is a 1227747, i believe the injectors are original, the ignition system is all about 5 months old and is a Davis unified ignition distributor and screamin demon coil. I inspected all grounds in the engine bay and none where loose and added two new ones, one near the coolant temp sensor where the ecm grounds and another on the firewall. What else should I test and inspect before plugging in a new ecm and injectors? I had to buy the ecm at oriellys so it costed twice as much as it should’ve so I am would be abit frustrated about burning up the new one. This is my work truck and daily driver so I have been driving it constantly all day long for 2.5 years doing mobile Rv technician work. I am proficient in using a multimeter and have a professional one, so wherever else I need to test I can, I am just not sure where else to look and what to test. Below are pictures of the ecm with the melted chip. Any suggestions would be appreciated

 

[youcancallmedusty]

The four center pins on the integrated circuit have continuity with each other and to ground, I am not sure if they are supposed since I have limited knowledge on how that part works but it seems if it melted and then they are most likely shorted together. Researching online it seems these circuits sometimes can just fail over time but I am still worried that there was something in the engine bay causing the problem. Circled in red are all the points that have continuity with ground

 

[Snoots]

I can't make out the numbers on the chip but I would expect it to be a regulator. Be careful probing the board with a DMM because the EPROM is very sensitive to backfeed from the meter.
If you can make out the number on the chip MOUSER may carry it.
Are you good a soldering?

 

[Radiohead]

Sounds like the driver chip checked out of the chat, which is weird since it still runs. Unless you find some wiring deficiency out in the loom or beyond, replacing the ecm makes sense, but I feel your reluctance.

 

[youcancallmedusty]

I can't make out the numbers on the chip but I would expect it to be a regulator. Be careful probing the board with a DMM because the EPROM is very sensitive to backfeed from the meter.
If you can make out the number on the chip MOUSER may carry it.
Are you good a soldering?

It’s a 24824b integrated circuit. It would be cool to replace it myself and have a back up if anything else goes wrong. I have a soldering iron but haven’t used it that much, just simple little connections, like if I break a spade connector on a board at work I can get that back in there and not have to replace the board, Next time I need to ask before poking around with my tester but thankfully it seems as if the prom chip is still fine. I bit the bullet after thinking about it and testing miscellaneous wires and things for 2 days and installed the new ecm from oriellys and it started, idled/warmed up and drove fine on my short test drive

Sounds like the driver chip checked out of the chat, which is weird since it still runs. Unless you find some wiring deficiency out in the loom or beyond, replacing the ecm makes sense, but I feel your reluctance.

With your advice you gave me motivation to be willing to chance the new ecm, I installed it, let the engine warm up and went on a test drive and everything is as it was, it seems like the original one just got old and tired. On a side note ever since I got the truck it had a mild surging issue during cold starts, it usually would go away once warm, after the new ecm was installed, I started it and it was pretty cold out (near freezing or below) and it sat for 2 days, it did not surge at all which was surprising. All of my friends thought it was a vacuum leak but I could never find one so if it stays that way it’s either the ecm or new grounds I installed

 

[Snoots]

DELCO - 24824

Buy 24824 DELCO , View the manufacturer, and stock, and datasheet pdf for the 24824 at Jotrin Electronics.

www.jotrin.com

Back to the ta ta's...

 

[squaredeal91]

Bad ground/s??
Is there a way to check ground resistance before cleaning?

 

[Radiohead]

Ask these fellers, they seem to know a fair bit about the subject

You must be registered for see images attach

 

[Snoots]

Bad ground/s??
Is there a way to check ground resistance before cleaning?

You can but it's not practical. Just clean it, use a dab of bulb grease or copper anti-seize and you're good to go.