Crank No Start

[Schimpfy]

Thanks for the suggestions, guys. I finally had a bit more time to dig into this...if 30 minutes counts.

After further troubleshooting I've determined that there is no signal to the ICM or the coil while the engine is cranking. The next step was to check the crank sensor as mentioned earlier. My signal is showing constant ~10.5VDC. It doesn't fluctuate when the key is in the on position and while rotating the motor manually. I had to quit for the evening before I could check to if the 12VDC power was there so that'll probably be next. Further ideas most welcome.

 

[Schimpfy]

1st time responder. I have similar conditions with my '00 Yukon Denali. In my case, the Theft Deterrent system is the culprit. And I blame FRED.

Friggen
Ridiculous
Electronical
Device

Does your "Security" light begin flashing when you turn on the key? If so, you have been spinning you wheels loading up your parts cannon

Do a key relearn. Ignition key on for 10 min, off for 30 seconds. Key back on and if the "Security" light goes off, she'll likely start

I missed this when I was reading through earlier. Honestly, I haven't even looked at that. I'll check that out too.

 

[someotherguy]

Negative.. Passlock behavior = allow engine to crank, allow engine to start, if correct resistor value is not read from tumbler (whether due to actual theft attempt, or problem anywhere in the Passlock circuit) then shut down immediately. Key thing here is the engine WILL start, if only for just a very brief moment. It will start.

It's not a bad thought, so don't take my comment wrong. Just an FYI though so you don't waste time down that path as Passlock problems can drive you mad. Chasing Passlock when it's NOT the problem can driver you madder...

Richard

 

[stutaeng]

I think you are in the right path checking crank position sensor. If the crank sensor is not producing signal, then the ECM can't possibly be commanding for spark. Unfortunately, that sensor is kinda hard to get to, and usually in a greasy location!

I'm not sure how the Passlock system works, but always read the "SECURITY" light would illuminate if that's the problem. Of course, assuming the lightbulb on the dash even works!

 

[Schimpfy]

I've already changed the crank sensor out previously...very greasy/oily. My issue that I'm stuck on now is the constant 10V that I'm getting on the signal wire when it should be the on/off ~5V as the engine is rotated.

 

[Schurkey]

What happens if you flip your meter to AC?

 

[stutaeng]

I'm assuming you are using this article:
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-2

It does say the signal should be "on-off" 5 V DC. Not sure why you would be getting constant 10VDC...Other than sensor is faulty. Are you checking this with connector plugged in, right? Like backprobbing the wire connectors? Have you also checked the 12VDC+ and the ground?

 

[1998crewcab]

Check your distributor pickup coil for Hall effect in Ac mode with multimeter for proper voltage while cranking
You get fuel pressure for a short time (normal) them no pressure cause computer does not see pulses from distributor
Hence no spark
Easy to check before throwing parts at it.
Check plugs for fouling also because of the cranking with no start.

 

[1998crewcab]

And while cap is off you can watch rotor turn while cranking
With key off you can turn rotor maybe 1/4 inch
Someone correct me if I am wrong
It should look like it’s riding up the gear a bit
Hard to explain but you have to do a couple of good ones to feel a bad one with worn gear.

 

[Schurkey]

Check your distributor pickup coil for Hall effect in Ac mode with multimeter for proper voltage while cranking

96-newer Vortec has no pickup coil.

A pickup coil does not produce a "Hall effect".

You get fuel pressure for a short time (normal) them no pressure cause computer does not see pulses from distributor
Hence no spark

The computer is looking for pulses from the crank sensor, not the pickup coil--since there is no pickup coil.

There is a cam sensor, which should be aligned to the crank sensor plus or minus 2 degrees. The computer does not use that sensor for spark timing.

Check plugs for fouling also because of the cranking with no start.

Not a bad idea.