Hey All
I am new to the forum , looking for some insight in a problem I have with a
97 c3500 5.7l gas ,Manuel trans, chyenne dump dally , motor has been rebuilt , 3 years ago , I use the truck litely (its a spare truck just use fr the property maitance).
I has a problem for no rhyme or reason when I use for bit 10 minutes to an hour , if I shut it off it does want to restart, it stumbles , on a couple of cylinders, revs . if I step on throttle it will race up stumble then die, it does not want to run , I let it sit for hours or next day and it will start up and run, it is horrible, last year got stuck had it towed to shop ,they check it the next day started it right up and said they found nothing, it's a problem I have been trying to correct since then and is driving me crazy, (Also trying to not spend crazy ,unlimited amounts of $$ to fix it, So I have check the fuel supply system ,ie; the fuel sending unit the fuel screen on it ,the fuel tank, the in line fuel filter, replace them, and it doesn't correct the problem It is staring to happen more often , it seems like after it runs for bit , but there is no pattern, 10 minuets or more , So I'm now thinking it might be the ECU, which I'm okay with changing but I'm trying to get some advice on hearing if that could be an issue, I don't know how to check it to find out if it is the ECU,
ALL Thoughts and Ideas would be Greatly appreciated, Thanks in advance,
Thanks,
v. Mike M.

 

Let’s start with the basics of testing. The tricky part is you’ll need to catch it when it’s hot and acting up. When it does, check for spark. Even though you said it starts and dies, a weak spark can still cause that behavior. It could also be a heat-related ground issue that messes with a sensor signal.

You mentioned checking the fuel system, but did you check fuel pressure? Watch to see if it drops after shutting it off, if it does, that could point to a leaking injector or a failing fuel pressure regulator.

If you have access to a scan tool, look at the live data and see if it’s registering RPM while cranking.

One common culprit in these trucks is the ignition control module (ICM). They’re known to act up when hot as they start to fail.

 

Thanks IA
for responding, I just ordered a ICM ,no scan tool, I'm older and the Computer stuff is not my strong suit, as for catching it when it happens that is tough, it is very random, although it does see to be happening more often, as for the leaking fuel injector, they were replaced when the motor was rebuilt 4 or 5years ago about 6 or 7 thousand miles ago,
Any insight into checking the ground issues that you mentioned,
I appreciate you taking the time to try to help me out,
Thanks,
Mike M.

 

There are a few important ground connections on these trucks. I’d start by checking the main ground from the battery to the engine block (or possibly to the frame), as well as the smaller ground to the radiator support. Don’t forget the braided ground strap from the firewall to the back of the passenger-side cylinder head. Make sure to inspect all of them for corrosion or heavy rust.

When I worked at AutoZone about 20 years ago, we had a tester specifically for ICMs. I would test them multiple times to heat them up as much as possible to see if they would fail. This is another option—you can have the ICM tested at some parts stores.

 

Thanks
I will check and clean up the grounds , the truck is a little crusty in some spots . so cleaning them up probably needs to be done, I'm just going to replace the icm and see if I get the old one tested just for SH$TS and Giggles ,
I post the results early next week when I get this stuff done,
Thanks,
Mike M.