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Crank No Start

Michael Schimpf
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Michael Schimpf New Member

Michael Schimpf

Posted
Posted

Hey, all.

 

First post...here goes.

 

Need some help troubleshooting a crank no start issue. I tried a search, but didn't find what I was looking for so if this has been asked before please let me know.

Anyway...

99 K1500 5.7 is cranking, but not starting. The steps I've taken so far are:
1) Tested fuel pressure - 55psi.
2) Tested for spark at all the cylinders - nothing.
3) Tested for spark from the coil to the cap - nothing.
4) Tested voltage to coil and ICM - good at 12V.
5) Checked signal from ICM to coil - good continuity.
6) Swapped coils with known good one, twice - nothing.
7) Swapped ICM with known good one - nothing.
? Checked switching signal from PCM to ICM - on with key in off position.

So, I stopped there because based on what I understand the switching signal is only suppose to be on when the engine is rotating. Why would it be on if the key is off?

API_ERIC New Member

API_ERIC

Posted
Posted (edited)

Check the wires near, and I mean right behind the plugs for the ICM and other related plugs.   Broken wires are not always obvious.   Follow the electricity. 

 I once was graced with an intermittent die while running and/or no start.  Turned out to a broken wire that was still connected by sheath and as it would make intermittent contact.   Hit a bump, or wiring get hot, and no run or no start. 

Edited by API_ERIC
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James Howell Enthusiast

James Howell

Posted
Posted

Check crank position sensor or wires to it.

 

I believe the CPS reads the position of the crank and sends a signal to the pcm which in turn sends a signal to the ICM to tell the coil to fire. The camshaft position sensor can do the same thing I think but usually it will still fire. The CPS is a hall type sensor and when it fails you get a no start condition as with the ICM as well. 

 

Look up the diagram for the ICM and see which one is the signal wire (12v) from the pcm and have your girlfriend or a buddy turn it over while you probe that wire with a multi meter.  Every time the cps tells the pcm to send the signal to the ICM to fire the coil, you should see something on the multimeter. If you don't see anything then try changing the CPS. Another way is if you have a scan tool that reads cranking rpms, it should read zero if the cps has failed. 

 

One other thing I would suggest it to read the codes somehow and post them. The crankshaft position sensor can have an effect on starting if it has completely failed as well. Best read them codes or else start dumping money on parts

 

KINGENGINEMAINTENANCE Enthusiast

KINGENGINEMAINTENANCE

Posted
Posted

Agree on crank sensor/cam sensor. Also you can test it with a voltmeter but the engine has to be cranking when you test it (hall effect). Have a buddy crank it while you test the crank sensor for voltage. Or just swap it out and know you have a new crank sensor either way. I believe it should read 5 volts! Peace and good luck!

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