Engine will not start after upgrades**help**

[east302]

Sounds like a definite voltage short and then some issue in the ground side...a problem with the ground wire to the VCM, a bad connection at the VCM or a bad VCM.



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[eyesi]

http://www.gmt400.com/threads/96-tahoe-dies-while-driving-and-wont-start.39188/

check the vcm grounds first, or be like Nightflyer, he was told wath to do at beginning of post, (to check grounds) and days later he "found" the response in another forum, it was vcm grounds, he told
Read the entire post, you will found how to doit there

 

[Denali_high]

I gave up guy's..none of this worked...trucks just gonna sit till i do a motor swap

Ive put well over $1500 in this motor... I have to call it quits sometime.. It will get all the computer bs ripped off of it and carbed for another project.

Was so excited to get this truck..now its just depressing me

 

[east302]

Yeah, sometimes we all need a break before we throw something through the windshield.

So, in the end, you had no voltage from fuse to CKP sensor and no ground from the VCM to the sensor?


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[Denali_high]

Yeah, sometimes we all need a break before we throw something through the windshield.

So, in the end, you had no voltage from fuse to CKP sensor and no ground from the VCM to the sensor?


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I have power to the ckp sensor and ground to the vcm.

Im gonna pull the timing cover soon and investigate why the code keeps popping up even though its new

 

[east302]

Is the CKP sensor sending a signal to the VCM? See page 2 of link below...

http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-2

The code comes up because the VCM isn't seeing the sensor's signal. Without the signal, the VCM will not know when to signal the coil so you won't have spark...or fuel, either. I don't think the VCM would know when to ground the injectors.

If you have voltage and ground at the CKP sensor, then it must be missing the signal due to a bad sensor, a short in the signal wire or bad connection(s) at the sensor or VCM. Last possibility would be a bad VCM.

I'd check for a signal from the sensor using that link and see if it's a bad part. If that shows that it is sending a signal (but it's just not making it to the VCM), then check the condition of the signal wire to the VCM (yellow, circuit 573) and the VCM connectors, particularly the blue C1 (CKP pins #28 & 31) and the grounds (pins 17 & 18) on white C3.

See post above from eyesi--he linked another thread where someone had an issue with VCM grounds causing a crank but no-start.

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Also, make sure the sensor mounting surface is clean.

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