No spark after repairing wire connector

Tiny
CWKERR007
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
Son in law brought it to repair so it has multiple wiring issues from past repairs! I put a new fuel pump, filter, distributor, ignition module, coil, wires, plugs, and it did fine for a day then it ceg crank sensor, and cam sensor, and you could turn it off and crank it back up and it would have the code and run bad. So, they had spliced the lines to the crank senso so I put a new pigtail on and new crank sensor now it won't start, you can hear the pump run but no spark, all fuses are hot and good. There is power to coil and cont mod and power to the crank sensor, and no security light. So why won't it fire?
Monday, December 27th, 2021 AT 6:27 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

If you have a live data scan tool, check to see if there is an RPM signal when the engine is cranking.

Also, is the new harness you used specifically for this vehicle?

I attached a pic below showing the three wires at the sensor. The pink wire, ignition feed, receives power from the ECM 1 fuse in the under-hood fuse box. Confirm there is power to the fuse and the fuse is good.

Next, the yellow wire should be the low voltage from the VCM and the purple wire is the sensor signal to the VCM. Check those as well.

Let me know about the RPM signal, the fuse, and if you have questions about the wiring.

Take care,

Joe

See pic below.
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Monday, December 27th, 2021 AT 7:00 PM
Tiny
CWKERR007
  • MEMBER
  • 4 POSTS
Yes, the pigtail I put on it is the proper one and yes I checked the voltage to the CKP the +had 11.9 and the ground-shows the same but the signal wire with the CKP plugged in shows 1.5 volts and does not pulse when I turn motor by hand. Also, the old CKP showed 7.5 volts so I replaced it with new and new showed 1.5. So, I returned it for a better brand and it shows 1.5 plugged in and it does not change voltage as the motor turns by hand.
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Monday, December 27th, 2021 AT 8:42 PM
Tiny
CWKERR007
  • MEMBER
  • 4 POSTS
And let me say now thanks for the response; you guys are great for having this for help! Let me give you some more info on this problem; I checked the pink wires on the other connectors that were ass with the ignition, and they all have full voltage and grounds, it is the signal that is missing in all of them. One more thing, when the old CKP was in I could turn over by hand and the fuel pump would kick in a little as I went but with the new CKP it turns on with key on but that is all turning the motor does not affect it.
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Monday, December 27th, 2021 AT 8:54 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

The only question I have is if turning the engine by hand is able to create a strong enough signal. Also, have you confirmed the target ring is in good condition?

Joe
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Monday, December 27th, 2021 AT 9:04 PM
Tiny
CWKERR007
  • MEMBER
  • 4 POSTS
The truck as running before I replaced the CKP and that is how they said to test on this site. Yes, you can see the ring where to I get a pin con number diagram to check the signal up top by the ECM?
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Wednesday, December 29th, 2021 AT 9:36 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
There are 4 connectors at the VCM. If you look at the attached pics, I included all of them. In pic 1, I highlighted the pin numbers related to the crankshaft position sensor. It will be the blue connector on the module.

Let me know if this helps.

Joe
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Wednesday, December 29th, 2021 AT 4:06 PM

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