Will crank but does not start?

Tiny
TOWER85
  • MEMBER
  • 1997 GMC JIMMY
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 205,035 MILES
I have replaced the fuel pump, fuel filter, plugs and wires, cap/rotor, ignition coil, ignition switch in column and still not firing.
Saturday, June 24th, 2023 AT 8:38 PM

21 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

You've done a lot already. In most cases, a crank with no start is caused by either a fuel-related issue or an ignition spark. I realize you've replaced the fuel pump and several ignition components; however, we need to confirm we have what is needed.

Here is what I want you to try. See if the engine starts if you use starting fluid. If it does and then stalls, we know it's a fuel-related issue. If there is no change, then we need to check for an ignition spark at the plugs.

Here is a link that explains how this is done:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Let me know what you find.

take care,

Joe

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Saturday, June 24th, 2023 AT 11:06 PM
Tiny
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No spark at all with tester, what may be the issue? I've replaced the cap and rotor, maybe the distributor itself?
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Sunday, June 25th, 2023 AT 12:16 PM
Tiny
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Also, the ignition coil has been replaced.
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Sunday, June 25th, 2023 AT 12:17 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Have you replaced the crankshaft position sensor or the ignition control module? Do me a favor. Check to see if the tachometer moves at all when cranking. Or, if you have a live data scan tool, see if there is an RPM signal when cranking.

Take a look at this link and let me know your thoughts:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

I have a feeling that is the problem, but to confirm, I need to know if there is a signal.

Let me know.

Take care,

Joe

See pics below of ICM and CKP locations.
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Sunday, June 25th, 2023 AT 9:20 PM
Tiny
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I replaced the ICM with a lightly used one and had to rewire the connector for the crankshaft position sensor (once rewired it cleared the code in computer, so I hope I got it right) but I'll get new for both just in case.
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Monday, June 26th, 2023 AT 3:22 AM
Tiny
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Also the tachometer does move a little while cranking.
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Monday, June 26th, 2023 AT 2:38 PM
Tiny
JACOBANDNICKOLAS
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Hi,

If the tachometer is moving, the crankshaft position sensor should be okay. That leaves the ICM. Are you sure it was good, and did it come from the same year, make, and model vehicle?

One other thing (and don't laugh), remove the distributor cap and have a helper crank it to confirm the rotor is turning. Also, with the key off, disconnect the connector at the coil. Gently touch pin A (see pic 1) with a test light or voltmeter and have a helper turn the key to the run position. Does the test light turn on?

When you check the power supply to the coil, be careful not to damage the small pin in the connector. If it spreads or becomes deformed, it can cause an intermittent issue.

Let me know.

Joe
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Monday, June 26th, 2023 AT 10:03 PM
Tiny
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Put in a new camshaft position sensor and now the tachometer isn't moving. Rotor turns when I manually turned it to replace the CPS. Maybe I need a brand-new crankshaft sensor now, idk. I have a pocket scanner and no codes show up, can't afford to buy a good scanner nor do they rent them. I had to rewire the crankshaft sensor, maybe that's an issue.
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Tuesday, June 27th, 2023 AT 3:23 PM
Tiny
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Hi,

The crank sensor may or may not set a code. If the tachometer isn't moving, that is usually an indication of the sensor. Where did you get the sensor presently on the vehicle? Did it come from online? I ask because I have seen so many problems with low-cost online parts.

Also, were you able to confirm power to the coil?

Also, I attached a pic below from the powertrain wiring schematic. At the crankshaft position sensor, there should be a pink wire with battery voltage with the key on. Check that and see if you have power as well. Note that the pink wire also is spliced into the fuel injector's power supply as well as the ignition coil. We could have a faulty splice not allowing power to the CKP.

Let me know.

Joe
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Tuesday, June 27th, 2023 AT 6:54 PM
Tiny
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I have power to the coil, just hooked up a multimeter to the plug on the crank and I wired it wrong. Going to re-fix my fix and give it another try. The crank sensor is the one that came in the truck when I bought the vehicle. May have to buy another one just as a precaution.
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Wednesday, June 28th, 2023 AT 6:25 PM
Tiny
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Also the wires going to my crank sensor from the harness are orange pink and yellow.
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Wednesday, June 28th, 2023 AT 6:34 PM
Tiny
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Hi,

I just went to the powertrain wiring schematic, and it says the wires are orange, pink, and purple. See pic below.

Could we have a rogue wire? Is it possible the orange wire is just faded and appears yellow?

The wiring schematic below is from the factory, so I'm not sure what to tell you.

Let me know.

Joe

See pic below.
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Wednesday, June 28th, 2023 AT 9:19 PM
Tiny
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Dug further into the wire harness and the colors are pink, yellow and orange. Found the power one that gets power from the ignition but having trouble with the other 2.
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Saturday, July 1st, 2023 AT 6:10 PM
Tiny
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Hi,

Thinking it was a late or early production vehicle, I went from 1996 to 1998 and they are all the same. So, since we have two of the three colors correct, I have to assume the purple that I see and the orange you see must be for the same use.

So, the purple (your orange) is a signal ground from the PCM. Check for continuity to ground via that wire with the key in the run position. The yellow wire is the signal wire from the sensor.

It was the pink wire that powered from the ignition, correct?

Let me know.

Joe
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Saturday, July 1st, 2023 AT 7:59 PM
Tiny
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When key was in the run position the orange had the only power running to it.
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Saturday, July 1st, 2023 AT 8:31 PM
Tiny
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This is a better picture.
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Saturday, July 1st, 2023 AT 8:34 PM
Tiny
JACOBANDNICKOLAS
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Hi,

It looks like the wires spliced to the connector are the correct ones before the splices.

I attached a copy of your pic below. Tell me if the wire colors I indicated are correct. Also, it appears the pink wire was spliced to a black wire. Where does that go to? Where is the yellow wire not connected coming from?

Let me know.

Joe
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Saturday, July 1st, 2023 AT 10:31 PM
Tiny
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The black wire is going to the new and correctly wired plug. The other 2 I need to cut from what I thought was wired right replacement plug. The 2 wires going to the old plug are the one I need assistance with.
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Sunday, July 2nd, 2023 AT 9:35 AM
Tiny
JACOBANDNICKOLAS
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Hi,

I'm confused. LOL Not being there makes this difficult. The two wires going to the old connector (I believe it's the old connector) appear to be tied to a purple and yellow wire. Is that correct? If they are, what do you have going to the new connector?

If I was there, this would be much easier. LOL

Sorry for the confusion.

Joe
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Sunday, July 2nd, 2023 AT 1:48 PM
Tiny
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Figured out the order of wires relative to the new plug. Orange goes to ignition; pink goes to tachometer and purple goes to ignition coil output. I'm attaching a picture for future reference in correlation to the new crankshaft position sensor plug.
Your information was very helpful, and I hope this helps you to assist others.
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Thursday, July 6th, 2023 AT 8:14 PM

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