Intermittent Crank no Start
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Just to be clear, I was more referring to wiggling the wiring harness from the ICM and CKP as they head back towards the ECM...not so much wiggling at the ECM to get it to stall. Maybe should have been more clear on that
Currently I am leaning towards the ignition switch/circuit or the CKP sensor/circuit. It's kind of good thing (for diagnostic purposes) that you are getting crank no start. Next time it has crank no start, watch your tach, the needle should flutter a tiny bit while cranking. This would indicate that there is a crank signal which should rule out a CKP/circuit problem.
There is a good video I'll find that can help diagnose if there is an ignition switch problem. Of course you're dealing with an issue that while your in the midst of testing, the truck may be ready to start and not be in the no crank situation so the test won't be helpful at that specific moment. I'll find that video and will post. It's faster and more visual than me typing it out.
Currently I am leaning towards the ignition switch/circuit or the CKP sensor/circuit. It's kind of good thing (for diagnostic purposes) that you are getting crank no start. Next time it has crank no start, watch your tach, the needle should flutter a tiny bit while cranking. This would indicate that there is a crank signal which should rule out a CKP/circuit problem.
There is a good video I'll find that can help diagnose if there is an ignition switch problem. Of course you're dealing with an issue that while your in the midst of testing, the truck may be ready to start and not be in the no crank situation so the test won't be helpful at that specific moment. I'll find that video and will post. It's faster and more visual than me typing it out.
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Joined: Nov 2011
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From: Pennsylvania
So the truck is not running now? As far as tach goes, seeing a bump/flutter on the needle while cranking tends to confirm a CKP signal, it's more of a field test for when you don't have someone to crank the engine while you are under the hood.
Did you check with your test light, as shown in the video, that the light lit with the key on at the coil connector?
If you didn't, and the truck is not currently running (or next time it cranks/no starts on you), disconnect connector at the ignition coil, test light connected to B(-), with key in the run position (KOEO), touch (don't shove) the test light to the pink wire terminal on the harness side connector to see if it lights. If it does light, while you are still holding the test light at the pink light connector, have someone crank the engine to see if it stays lit then also.
Let us know the results from that.
It is pretty unlikely, though of course not completely impossible, that your ECM needs to be replaced. Let's try diagnosing so you don't waste money on an ECM you end up not needing.
EDIT:
The idea behind wiggle testing is to try to get it to stall when it's running, just like you did when you found the bad connector. This way your in your driveway/garage with time to work and tools handy on it if you do get it to stall.
Did you check with your test light, as shown in the video, that the light lit with the key on at the coil connector?
If you didn't, and the truck is not currently running (or next time it cranks/no starts on you), disconnect connector at the ignition coil, test light connected to B(-), with key in the run position (KOEO), touch (don't shove) the test light to the pink wire terminal on the harness side connector to see if it lights. If it does light, while you are still holding the test light at the pink light connector, have someone crank the engine to see if it stays lit then also.
Let us know the results from that.
It is pretty unlikely, though of course not completely impossible, that your ECM needs to be replaced. Let's try diagnosing so you don't waste money on an ECM you end up not needing.
EDIT:
Last edited by rockp2; Apr 22, 2024 at 06:21 PM.
Thread Starter
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Beginning Member
Joined: Apr 2024
Posts: 12
So the truck is not running now? As far as tach goes, seeing a bump/flutter on the needle while cranking tends to confirm a CKP signal, it's more of a field test for when you don't have someone to crank the engine while you are under the hood.
Did you check with your test light, as shown in the video, that the light lit with the key on at the coil connector?
If you didn't, and the truck is not currently running (or next time it cranks/no starts on you), disconnect connector at the ignition coil, test light connected to B(-), with key in the run position (KOEO), touch (don't shove) the test light to the pink wire terminal on the harness side connector to see if it lights. If it does light, while you are still holding the test light at the pink light connector, have someone crank the engine to see if it stays lit then also.
Let us know the results from that.
It is pretty unlikely, though of course not completely impossible, that your ECM needs to be replaced. Let's try diagnosing so you don't waste money on an ECM you end up not needing.
EDIT:
The idea behind wiggle testing is to try to get it to stall when it's running, just like you did when you found the bad connector. This way your in your driveway/garage with time to work and tools handy on it if you do get it to stall.
Did you check with your test light, as shown in the video, that the light lit with the key on at the coil connector?
If you didn't, and the truck is not currently running (or next time it cranks/no starts on you), disconnect connector at the ignition coil, test light connected to B(-), with key in the run position (KOEO), touch (don't shove) the test light to the pink wire terminal on the harness side connector to see if it lights. If it does light, while you are still holding the test light at the pink light connector, have someone crank the engine to see if it stays lit then also.
Let us know the results from that.
It is pretty unlikely, though of course not completely impossible, that your ECM needs to be replaced. Let's try diagnosing so you don't waste money on an ECM you end up not needing.
EDIT:
The idea behind wiggle testing is to try to get it to stall when it's running, just like you did when you found the bad connector. This way your in your driveway/garage with time to work and tools handy on it if you do get it to stall.
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Update: now about 90% sure the main problem is the ECM. Found out that if we unplug and plug back in the battery while it's dead it starts. which suggests that letting the computer reset itself allows it to start. also when checking live data on the car the numbers coming from the MAF sensor were really off so we unplugged the MAF and the computer still gave a reading from it. If completely replacing the ECM fixes things will update again
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the guy we bought it on said they had welded on a straight pipe because the catalytic got stolen so were thinking they might have accidently fried the ecm.
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