Intermittently cranks once but will not start

Tiny
KURTBOEKER
  • MEMBER
  • 2006 HUMMER H2
  • 6.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Hello,

We've replaced the fuel pump, the starter, and switched all the relays around. The first time you turn the key it cranks like it is going to turn over. But after about 5 seconds it still doesn't start, so I stop trying. Then if you try a second time, a few seconds later, it won't crank. All the lights come on but the starter just won't move. When it won't start, the fuel gauge is always on empty. I say intermittently because some days it starts right up. Although I have heard some grinding noises. And many times when it does start, it seems to buck. Like it hesitates to start, then kicks back on the brake pedal and really fires up the engine for a 1/4 second. I hope that's enough information.
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Wednesday, December 4th, 2019 AT 5:39 AM

7 Replies

Tiny
AL514
  • EXPERT
Can you explain this kickback on the brake pedal? And has the check engine light been on at any point during this problem? Even though it does stay on consistently, there maybe a diagnostic code in the ECM. And is this problem associated with colder temperatures?
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Wednesday, December 4th, 2019 AT 6:05 AM
Tiny
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  • MEMBER
Thanks for the response! When it will not start, the check engine light is on. Otherwise, when it starts the check engine light is not on. I've taken it to 2 mechanics, both of whom are friends and I trust. One reported no codes, and the other reported a Service 4wd related code, but that is also intermittent, and does not correlate to when the truck will/won't start. I'm in Maine and it's really cold now, 20 degrees. But the truck had the same issue in the Fall, in 60 degree weather. The kick back on the brake pedal is like you're pushing on it to start the truck. It doesn't start immediately and it is hard to push. And then when it turns over, it pushes back on your foot a bit, and all the pressure goes out of the pedal. But it's like a hesitation, then an explosion.
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Wednesday, December 4th, 2019 AT 6:20 AM
Tiny
AL514
  • EXPERT
Okay, first check is turn the key on, not running, does the check engine light go out after a few seconds? It shouldn't stay on longer than a few seconds. Considering the amount of issues you're having let's start with the basics. The brake issue with having to push the pedal to start the truck is a strange problem. The ECM should be scan with a scan tool that can read all the modules in the system. The basic code readers can't check all the modules that need to be looked.
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Wednesday, December 4th, 2019 AT 7:29 AM
Tiny
KURTBOEKER
  • MEMBER
The check engine light stays on. One of my mechanics has a very good scan tool and there are no codes. Also, the gas gauge reads empty.
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Wednesday, December 4th, 2019 AT 8:53 AM
Tiny
AL514
  • EXPERT
I would start with fuel pressure, especially when it's not starting. And this is just related to the no start not any of the other issues. You may have a failing fuel pump. Pump issues can come and go. Just so we can rule out the pump. You may have more than one problem such as a faulty vacuum brake assist where the brake booster has an internal leak.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Wednesday, December 4th, 2019 AT 10:04 AM
Tiny
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  • MEMBER
Thank you. The fuel pump was replaced. Also the starter was replaced. I think it may be a ground wire. Will test tomorrow.
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Wednesday, December 4th, 2019 AT 4:46 PM
Tiny
AL514
  • EXPERT
Check every ground wire to the block and chassis that you can find. Watch for any green corrosion on any connectors or any ground circuits that might be attached to the block or the chassis. And just because the ground looks good doesn't mean that it's making actual good contact to the chassis so really try to be thorough. And let me know what you find. Have a good evening.
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Thursday, December 5th, 2019 AT 4:15 PM

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