Very Intermittent Crank No Start

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May 26, 2022
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I have this weird problem with my 2002 Avalanche 2500 with the 8.1L. It starts and runs like a top 95 percent of the time. No lag, no hesitation while driving, full power, just turn the key and go. However occasionally, like maybe one out of 50 starts (just a guess, I have no idea) it just cranks and won't fire, like it's not getting gas. This only happens after it's warmed up, never has on a cold start.

Now of course, this usually happens in a crowded parking lot so the embarrassment level is at its peak. But it does start after a bit, I prime the pump a few times and I hear the pump whirl away. Once it was being real bitchy, and only started after I hit the fuel rail Schrader valve to see if gas was in there and it started right up after that. No idea if that's what fixed it. I plan on buying a fuel pressure gauge next pay day, so maybe I'm a bit premature asking here, but since it happens so rarely I'm guessing pressure is good.

So you know, I had rust issues when I got it, so all fuel lines are new, filter is new, both pumps are new, evap canisters and purge valve are new. The only component I had not touched was the fuel rail. I did put a new Ac Delco regulator in a few days ago, but all injectors are the same. I haven't had the issue again, but I haven't driven it much since then.

Maybe the regulator fixed it, I thought perhaps it had been sticky and once in a while wouldn't let fuel in or something weird like that. I have no idea what else it could be so figured I'd ask.
 
Dumb thing to say here, but have you changed your fuel filter?
Another dumb thing is check your battery connections to make sure they are tight and there is no corrosion.
Could this be a Throttle Position Sensor that is on its way out?
 
Not dumb questions. Filter is new, replaced when I did the fuel lines. Battery is good and clean.
TPS? Didn't think of that, maybe. Thank you for the suggestion.
 
I was going to mention the fuel pressure regulator but then saw that you said you had replaced it. I would definitely get a fuel pressure gauge and see what your pressure is key on with engine off and then again with the engine running and then revving it up. I'm not sure what the pressure specs are for that truck but would imagine it's somewhere in the 55-62 psi range.
 
Not dumb questions. Filter is new, replaced when I did the fuel lines. Battery is good and clean.
TPS? Didn't think of that, maybe. Thank you for the suggestion.

No problem. the only other thing I could suggest is to get the codes read on this vehicle. The other thing is the fuel pump, is this the original fuel pump? Are you the original owner of this vehicle?
 
No problem. the only other thing I could suggest is to get the codes read on this vehicle. The other thing is the fuel pump, is this the original fuel pump? Are you the original owner of this vehicle?

It hasn't thrown any codes. I replaced both fuel pump assemblies. This thing has two tanks, main one supplies to the engine and a little one in the back that feeds the main tank. I am not the original owner, I bought it a year ago with 68000 miles, and was a mess underneath.
 
I was going to mention the fuel pressure regulator but then saw that you said you had replaced it. I would definitely get a fuel pressure gauge and see what your pressure is key on with engine off and then again with the engine running and then revving it up. I'm not sure what the pressure specs are for that truck but would imagine it's somewhere in the 55-62 psi range.

Yea, I'm going to buy a gauge next time I go to town. I believe 55-62 is about right.
 
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Have you tried giving it a small amount of throttle when it does this?
I did the one time it was most stubborn, no difference. Didn't even smell gas, that's why I got to thinking the regulator wasn't letting fuel in, and I could hear the pump working.
 
Crankshaft position sensor starting to go bad ?
Very possible, I am redoing the intake gasket at some point this winter. The CPS is hard to get to, should be easier without the intake in the way. I bought a new ac Delco one and will swap it out then.
 
I suggest you get the OBDFusion app for your smartphone or tablet. This app allows you to log a ton of data streams which can be checked in Excel. Go to E46Fanatics (https://www.e46fanatics.com/) to find a threads on the app. You'll need to buy a communications adapter that plugs into the IBD2 port under the dash. The threads will tell which adapter to buy and how to set up the app. I've been using it for years.
 
It could be the immobilizer system. Watch for the anti-theft light when it won't start.
 
I think you’re on the right track with checking fuel pressure…that’s what I would do.
 
I have this weird problem with my 2002 Avalanche 2500 with the 8.1L. It starts and runs like a top 95 percent of the time. No lag, no hesitation while driving, full power, just turn the key and go. However occasionally, like maybe one out of 50 starts (just a guess, I have no idea) it just cranks and won't fire, like it's not getting gas. This only happens after it's warmed up, never has on a cold start.

Now of course, this usually happens in a crowded parking lot so the embarrassment level is at its peak. But it does start after a bit, I prime the pump a few times and I hear the pump whirl away. Once it was being real bitchy, and only started after I hit the fuel rail Schrader valve to see if gas was in there and it started right up after that. No idea if that's what fixed it. I plan on buying a fuel pressure gauge next pay day, so maybe I'm a bit premature asking here, but since it happens so rarely I'm guessing pressure is good.

So you know, I had rust issues when I got it, so all fuel lines are new, filter is new, both pumps are new, evap canisters and purge valve are new. The only component I had not touched was the fuel rail. I did put a new Ac Delco regulator in a few days ago, but all injectors are the same. I haven't had the issue again, but I haven't driven it much since then.

Maybe the regulator fixed it, I thought perhaps it had been sticky and once in a while wouldn't let fuel in or something weird like that. I have no idea what else it could be so figured I'd ask.
Check your grounds. Costs nothing, too
 
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