Hello again gentlemen. Today I am working on a customer's 89 k2500. To spare no detail, it's a Cheyenne equipped with a 350 and a th400. Anyhow, he brought it to me last week with a crank no start problem. It had been sitting a while so the battery was dead and wouldn't hold a charge so I replaced it. It fired right up on the first try, I drove it, ran well. Parked it in the shop to work on the other things that needed done (tuneup, fuel and air filters, tank replacement). Didn't get to it until today. So I go to start it and it fires up, moved it etc. Shut it off and left it sit a couple hours. Then it wouldn't start. Injectors aren't spraying, no spark. Parts I've tested or replaced include: new distributor asy(figured the problem was either the pickup or icm), 3 different icms (even tried the one from my personal truck), new coil, coil wire, ecm (again, from my truck). I have 12.14 volts with key on at the pink coil wire. Triple checked my distributor and coil connections. I have 11 psi fuel pressure, and replaced fuel filter. I've got a 12.14 constant voltage with key on to the injectors, but obviously no ground to the noid light when cranking. 12.14 does seem low at the coil, as the battery shows 12.36, not sure why it's that low. Could that be the problem? I can't think of anything else to check besides connections. Please let me know what you guys think, and if im missing anything. I'd really like to get this customers truck back on the road. Thanks!!
89 2500 crank no start.
- Thread starter Jebadiah
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Often, that's a distributor issue--pickup coil including magnet, maybe ignition module. Potentially, broken wires connecting distributor to ECM.
That kinda rules-out the distributor and internal parts. Could still be wire harness.
Seems low, but not entirely unreasonable.
Again, lower than optimal, but not unreasonable.
That IS unreasonable. Charge the battery. Typical open-circuit voltage should be 12.6--12.8, depending on battery construction.
It's "a" problem, it's not "the" problem. That truck should start and run with the battery having lower voltage than that.
Connections, broken wire(s).
Find out if the ECM has an RPM signal when cranking. Kinda thinking that when it does, it starts. When it doesn't, it won't.
It didn't start before so that's why I changed them. Would be the reason my post said it came for crank no start issue. It's just intermittent apparently
evilunclegrimace
Does not always play well with others
Time for a tap test. Pull the glove box to access the ECM, pop it loose from its mounting point and give it a rap with your knuckles while someone tries to start the truck.
I tried using the known goof ecm from my truck. Same year 350.
I ran down the troubleshoot chart in my gm service service manual. Icm, coil, and wiring. All signals test good as per gm's spec. The only thing that is out of spec is the pickup coil at 500 ohms when gm is calling for 700-1500. Both the original and new distributors pickup coils are reading 500 ohms so I'm guessing that must be the problem if all other tests prove ok. My service manual also says if there is no spark then the injectors will not drive so I guess there is that too. I've also tried running a jumper wire from the battery ground to the distributor housing and coil bracket in case they were seeing improper ground. As far as I can tell, the ecm needs to see an rpm input to complete the ground circuit for the injectors, but testing rpm signal as per the manual, the ecm is getting that signal. Am I correct in saying this or am I misinterpreting the manual?
If the ECM is getting an RPM signal, I'm not so concerned about the pickup coil resistance. The pickup coil output is sufficient to trigger the ICM, which sends it's signal to the ECM--thus the RPM signal. And we know this is working because there is an RPM signal.
Still up for grabs, is that the ECM would process the signal, modifying the timing to adjust the spark advance, and then sending the signal back to the ICM that triggers the ignition coil.
Considering that you might have an ECM problem, or a failing wire harness, though. An intermittent wire connection between any of those parts could cause the no-spark, no-injection issue.
Still up for grabs, is that the ECM would process the signal, modifying the timing to adjust the spark advance, and then sending the signal back to the ICM that triggers the ignition coil.
Considering that you might have an ECM problem, or a failing wire harness, though. An intermittent wire connection between any of those parts could cause the no-spark, no-injection issue.
