Crank, No Start
Thread Starter
Teching In
Joined: Dec 2024
Posts: 5
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From: West Central MO
Crank, No Start I have a 1988 S15 that I installed a 2003 5.3 in about 6 months ago. It has been my daily until what I thought was the crank sensor going bad. It would sputter and some times stall under light acceleration for a day or so and then one time right after I started it up it died and wouldn't restart.
The next day I just decided to try starting it before work and it fired right up and then proceeded to die and not restart. I did some research and thought that a crank sensor seemed a likely fix. So I got a crank sensor and installed, had a bit of a time as its pretty tight down there, and it has never fired since.
According to my scanner it doesn't read any signal from the Maf, cam, or crank sensor but the Map and Iat sensors read correct values. I've checked all the grounds, both with visual inspection and a voltameter, and I haven't found anything wrong to date. I've also replaced the PCM for another one, no change. I've checked pcm grounds and power, the fuel pump runs and has pressure to the rail although it isn't getting spark so that doesn't matter much. All sensors have ground and power and verified continuity to the pcm. The Crank sensor does read some AC voltage at the PCM via the signal wire.
I've tested more things that I can't remember just right now, but I sure love more ideas on what might be the problem or things to check. I would upload a .hpl file but the site won't let me. I think my problem is somewhat clear.
The next day I just decided to try starting it before work and it fired right up and then proceeded to die and not restart. I did some research and thought that a crank sensor seemed a likely fix. So I got a crank sensor and installed, had a bit of a time as its pretty tight down there, and it has never fired since.
According to my scanner it doesn't read any signal from the Maf, cam, or crank sensor but the Map and Iat sensors read correct values. I've checked all the grounds, both with visual inspection and a voltameter, and I haven't found anything wrong to date. I've also replaced the PCM for another one, no change. I've checked pcm grounds and power, the fuel pump runs and has pressure to the rail although it isn't getting spark so that doesn't matter much. All sensors have ground and power and verified continuity to the pcm. The Crank sensor does read some AC voltage at the PCM via the signal wire.
I've tested more things that I can't remember just right now, but I sure love more ideas on what might be the problem or things to check. I would upload a .hpl file but the site won't let me. I think my problem is somewhat clear.
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
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From: Dade City, Fl.
I concur with the_merv. Did you use and modify a factory harness? Double and triple check the power and grounds to the circuits you say are not reporting on your scanner. as you stated, it will not fire up if there is not a signal to the pcm to "tell" it when to spark.
Thread Starter
Teching In
Joined: Dec 2024
Posts: 5
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From: West Central MO
Well I guess I agreed with you guys enough that after messing around with a multimeter some more I broke down and ordered a whole new harness. Originally I did just modify the stock harness witch i thought might be the problem. I also kind of wanted to rewire the engine bay anyways so i seemed like a good time.
I got the harness from Nathan Wei it arrived and I installed it and guess what, zero difference. So back to square one only now i can hardly blame wiring. I got a new crank sensor I'm going to install tonight so we'll see I guess. Might have to swap a 350 or something into this heap. A ford friend said I needed a 302
I got the harness from Nathan Wei it arrived and I installed it and guess what, zero difference. So back to square one only now i can hardly blame wiring. I got a new crank sensor I'm going to install tonight so we'll see I guess. Might have to swap a 350 or something into this heap. A ford friend said I needed a 302
Thread Starter
Teching In
Joined: Dec 2024
Posts: 5
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From: West Central MO
I installed the new Crank Sensor to no avail.
All the fuses on both the truck fuse box, the old harness fuse box, and the new harness fuse box are good. Also good 11.5 volts to the CKP and maf. 0 ohm ground to cylinder head from both sensors. .5 volts AC on the CKP signal wire at the pcm connecter. The O2 sensors and map read correct values on the scanner. Coils and pcm have power while cranking fuel pump also runs while cranking. Pcm has all good power and grounds. I've tried several different tune files including a couple that i have ran it on.
My best guess right now is that my old harness was doing something that was damaging the pcm when I plugged it in or something. I have tried two of them but on the old harness too.
It is probably something simple I'm missing cause that's usually how it goes.
All the fuses on both the truck fuse box, the old harness fuse box, and the new harness fuse box are good. Also good 11.5 volts to the CKP and maf. 0 ohm ground to cylinder head from both sensors. .5 volts AC on the CKP signal wire at the pcm connecter. The O2 sensors and map read correct values on the scanner. Coils and pcm have power while cranking fuel pump also runs while cranking. Pcm has all good power and grounds. I've tried several different tune files including a couple that i have ran it on.
My best guess right now is that my old harness was doing something that was damaging the pcm when I plugged it in or something. I have tried two of them but on the old harness too.
It is probably something simple I'm missing cause that's usually how it goes.
