Intermittent no start

Tiny
SUSANDOUG
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
I have a 5.3 ls engine that will sometimes not start does crank, after stop cranking the engine will start when tried again. Have changed components coil, plugs, wires also checked fuel pressure was okay, still no change. I have also put a GM crank sensor in but engine does not start at all it tries but will not start I cannot relearn this sensor unless the engine runs, I have tried two different sensors same thing. Put the old sensor back in and engine runs the same. As far as I know the sensor has never been changed. The engine also misfires at times but runs very good must of the time. Suggestion on why the new crank sensor won't start the engine and the correction, any help? Thanks
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Wednesday, June 24th, 2020 AT 7:27 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm not sure why the new sensor wouldn't allow the engine to start. I have, in the past, gotten bad ones, so that is possible.

As far as a relearn, there is just a variation relearn. It will not prevent the vehicle from starting.

Have you checked for diagnostic trouble codes? By chance, do you have a live data scanner? Last, when you try starting it, does it even seem like it's trying or does it just act like it's not getting fuel or spark?

Let me know if you have a live data scan tool. If you do, check for a few things for me. First, confirm there is an RPM signal when cranking. Also, check the engine coolant temp sensor reading to confirm that isn't way out of line. If you could record it cranking so I could hear it, that may be helpful as well.

Here is a link you may find helpful:

https://www.2carpros.com/articles/car-cranks-but-wont-start

Let me know what you find and if you have confirmed spark to the plugs, you said fuel pressure is within spec, and also if there is an injector pulse to the injectors.

I will watch for your reply.

Joe

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Wednesday, June 24th, 2020 AT 8:21 PM
Tiny
SUSANDOUG
  • MEMBER
Hi Joe, thanks for getting back to me so fast. I do have a scanner it does do live data so I can check those components you mentioned no codes have shown up yet. Like I mentioned it starts up most of the time and when it does not start engine could be hot cold or sit for two days. I can say when it does not start it seems that is trying to start, however when I install new sensor the engine seems to kick back. I will have to plug in the scan tool every time I start the engine so when it doesn't start I can check those parameters. It may take a little time to get back to you. Thanks, Doug
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Thursday, June 25th, 2020 AT 8:40 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Doug,

Let me know when you get the chance. I do have one question. You said when this happens, it seems to kick back. Does it seem like it's firing at the wrong time?

As far as the coolant temperature sensor, you would be surprised how many times they cause a no start simply by causing an extreme rich or lean fuel mixture. That's why I suggested checking it.

When you get the chance, let me know what is found. Also, if it happens and you do have an RPM signal and the ECT is correct, see if it starts using starting fluid. If it does, then we know it's a fuel related issue.

Take care,

Joe
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Thursday, June 25th, 2020 AT 9:15 PM

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