Need help with a 97 5.7 liter not getting spark

Marioman7989

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Hello everyone, I have a buddy with the same truck as me a 97 K2500. His engine cut out while driving and wouldn't start. I figured out he wasn't getting spark. So I tested all the main components. Even took the ICM and coil off mine and still wouldn't start. I then took my crankshaft position sensor off mine and through it one his. I still got nothing. But when I put my crankshaft position sensor back on my truck my truck won't fire now. Where it ran perfectly fine before I took my CKP off my truck. Any advice or suggestions would be great, thanks
 

1998_K1500_Sub

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Where it ran perfectly fine before I took my CKP off my truck. Any advice or suggestions would be great, thanks

IIRC, if the gap between the CKP and the tonewheel on the crankshaft is incorrect (by just a little), the engine won't start. You may wish to re-seat your CKP with this in mind.

Maybe someone here will comment. I swear there was someone else on GMT400 who had a similar problem, posted in a thread earlier this year.

Meanwhile, as for your buddy's engine:

- any codes? (check even if the SES light is off)
- fuel pressure?
- spark? (you seem to suspect yet never gave a reason why)

There's a longer checklist but this is a starting point.
 
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Marioman7989

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On my buddies rig I have checked fuel pressure and it was good. I pulled a spark plug wire off and a spark plug and didn't get any spark checked a few times. On his rig he had a P0305 and a P1351 code.
 

Marioman7989

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I did add a shim to my Crankshaft sensor and my truck fired up. Thanks for the input. Just gotta figure out my buddies rig. On my buddies rig I have checked fuel pressure and it was good. I pulled a spark plug wire off and a spark plug and didn't get any spark checked a few times. On his rig he had a P0305 and a P1351 code.
 

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Fuses good?

Coil and module getting power?

Distributor turns when you crank the engine? Vortec distributor gears are a high-failure item. Is there spark at the coil wire leading to the distributor?

How old are the cap 'n' rotor? Plug wires?

Connect a scan tool, look for RPM signal when the engine cranks. No RPM is probably crank sensor or crank sensor wire harness, or perhaps a failed ECM.
 

Marioman7989

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I have checked
-Fuses
-Coil
-Module
- Distributor does turn and rotate
-Crankshaft Sensor
All checks out. I'm double checking everything tonight though seeing if I missed something. I did figure out that the camshaft sensor on the distributor is giving me a wacky signal. According to the manual I should be getting 5.0 volts AC while cranking. I'm getting a high signal of about 16volt and then drops to nothing then back up high well past 5.0 volts. I've even tried switching my multimeter to DC volts and still got a sporadic reading. And I have tested my backprobe making sure I had a good connection. Also double checked where my ground is for my multimeter.
 

1998_K1500_Sub

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I'm getting a high signal of about 16volt and then drops to nothing then back up high well past 5.0 volts. I've even tried switching my multimeter to DC volts and still got a sporadic reading. And I have tested my backprobe making sure I had a good connection. Also double checked where my ground is for my multimeter.

Use an oscilloscope if you have access to one. If a DVM is only what you have, then Godspeed.
 

Marioman7989

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Definitely don't have one of those. Just a digital multimeter and a OBDII Bluetooth reader with the Torque app. I do have an old school Simpson multimeter with a needle though, which I'm sure isn't any better. However all the previous tests I've done with my digital multimeter have been pretty spot on. The test with the camshaft sensor though is totally wack and won't give me a solid or steady reading. I have even changed and checked my ground a few times and still am not getting a solid reading
 

1998_K1500_Sub

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I did figure out that the camshaft sensor on the distributor is giving me a wacky signal.

IIRC someone earlier this year stated that the camshaft sensor wasn’t mandatory on the 1996+ Vortecs; the engine would run quite well w/o it except the injectors would batch fire instead of sequentially fire.

Maybe someone can confirm. If I was at my computer I would pull up the service manual and check.
 
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