ya you want that thing to be on fumes, lol usually they right after a fill up
Starting issue
- Thread starter dross99_si
- Start date
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swathdiver
Full Access Member
I've got lots of tools and several floor jacks and 4 stands but do not have those tools that easily disconnect those new to me style lines. They're on my list but maybe Harbor Freight will have them, O'Reilly or Autozone should.
Last time we looked, did we check the fuel pressure? I seem to think that we did but cannot remember.
iamdub
Full Access Member
First time seeing this thread and @thompsoj22 said on the first page what I was leaning towards. What module controls the starter- PCM? BCM?
If it never happens when cold, I'm wondering if you have an intermittent open circuit in whatever tells the module to disengage the starter. At first, I understood it as the engine firing up like normal but the starter was still engaged. Then later it was said that it cranks for 5-6 seconds and doesn't start, but then cranks and starts just fine on the second try. Could it be that it's not a starter engagement control issue and it's not firing up so the computer keeps cranking it in an attempt to start it? Sometimes it just doesn't fire at all and other times it fires up almost right away, but it's sputtering as if it's getting too much fuel or not enough fuel so it doesn't reach the RPM the computer wants before it disengages the starter? It's been a long day so maybe I'm mixing up some details.
If it never happens when cold, I'm wondering if you have an intermittent open circuit in whatever tells the module to disengage the starter. At first, I understood it as the engine firing up like normal but the starter was still engaged. Then later it was said that it cranks for 5-6 seconds and doesn't start, but then cranks and starts just fine on the second try. Could it be that it's not a starter engagement control issue and it's not firing up so the computer keeps cranking it in an attempt to start it? Sometimes it just doesn't fire at all and other times it fires up almost right away, but it's sputtering as if it's getting too much fuel or not enough fuel so it doesn't reach the RPM the computer wants before it disengages the starter? It's been a long day so maybe I'm mixing up some details.
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dross99_si
Full Access Member
It's more like the cranks for 5-6 seconds and doesn't start, but then cranks and always starts on the second try, but with a sputter and very brief rough idle that normalizes.
Never happens on a cold start.
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dross99_si
Full Access Member
No we never checked fuel pressure. We were trying to figure out the darn P0442.
iamdub
Full Access Member
So now it seems those other symptoms are issues resulting from a root problem and are not the root problem itself.
Yeah, at this point I'm gonna jump on the fuel supply bandwagon. The symptoms are similar to a faulty prime valve (AKA "check valve"), except that issue happens pretty much ONLY during a cold start.
With the issue presenting after it's run for some time, I'm thinking a fuel pump failing when warm (intermittently).
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dross99_si
Full Access Member
Thanks for your suggestions. So is there a definitive way to distinguish between a failing pump vs faulty injectors just by checking and/or monitoring fuel pressure during different conditions.
iamdub
Full Access Member
Yes. This is what a full and proper fuel pressure test is for. It's why you watch the pressure gauge with Key On/Engine Off, Key On/Engine On, etc. The problem with you performing this test is that your symptoms don't present frequently at all. Everything may pass with flying colors but a few starts after you remove the gauge, it may act up.
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HiHoeSilver
Away!
Yup. But it sounds like it's pretty repeatable at this point. I'd get some baseline numbers cold (pressure at ko/eoff, see if it bleeds down, pressure at idle and driving). Then shut her down, and do it again warm. Ko/eoff might even be your answer right away at that point.
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iamdub
Full Access Member
Lol
I just realized that "KO/EO" could be read as "On" or "Off". Edited post to clarify.
I just realized that "KO/EO" could be read as "On" or "Off". Edited post to clarify.
HiHoeSilver
Away!
Ha! I figured that's why you wrote it twice. I edited mine to be clear. Key on engine off will prove to be the important one in this case, i think. We know the thing runs.
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dross99_si
Full Access Member
So can all this fuel pressure testing simply be done with something like the Tech-2, or do I HAVE to have a pressure gauge connected to the rail?
iamdub
Full Access Member
Gonna need a mechanical gauge hooked to the rail. The PCM reports fuel pressure in the live data stream, but I don't think this is from an actual pressure transducer. It's probably calculated based off an algorithm using input from other sensors. You want an "unbiased, third-party" input in this scenario.
Yes, get as much fuel out of the tank as possible. I had a handheld hand pump that I cranked, till I got an electric one, that had a hose pushed in to the tank and out to gas cans and drained it as dry as I could. Elevation is a good thing and proper toll set. Pay very close attention to all that surrounds the tank and what is on top and if you come to a stopping point with uncertainty of something, get on here and ask and supply pics if possible. In another thread there is a guy that did a fuel pump replacement and when he put it all back together he pinched a vent line and that caused a code on restart. I am very OCD and when I did tanks and pumps I tied everything back as I disconnected so that I could then pull back in to the tank area as needed.
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dross99_si
Full Access Member
Have any of you guys installed a permanent pressure gauge on the rail?
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dross99_si
Full Access Member
Update:
Yesterday swathdiver (James) was nice enough to come over with the Tech 2 to see if we could figure out the P0442 and check fuel pressure to diagnose the starting issue. Unfortunately the fuel system monitoring was not an option listed for my particular vehicle. Not sure if the 2007s support this or not..
On a better note we did some experimenting with the EVAP purge valve. With the engine running, the vent valve closed and the purge valve commanded open (even to 100%) there was never a negative pressure generated in the fuel tank according to the fuel tank pressure sensor. In other words the new purge valve I purchased and installed a while back had to be defective.
The purge valve is a Duralast lifetime part from AutoZone. This was against my better judgement as I usually only purchase OEM replacement parts. This is exactly why.
After James left yesterday afternoon I hopped on Amazon and ordered a Genuine GM EVAP purge valve.
This afternoon the new part arrived and I installed it. The Duralast part was definitely defective because I am able to suck through it with ease. No resistance at all.
Now we wait and see if the code comes back and/or the starting issue persists.
Thanks to all who have been helping me with this
Yesterday swathdiver (James) was nice enough to come over with the Tech 2 to see if we could figure out the P0442 and check fuel pressure to diagnose the starting issue. Unfortunately the fuel system monitoring was not an option listed for my particular vehicle. Not sure if the 2007s support this or not..
On a better note we did some experimenting with the EVAP purge valve. With the engine running, the vent valve closed and the purge valve commanded open (even to 100%) there was never a negative pressure generated in the fuel tank according to the fuel tank pressure sensor. In other words the new purge valve I purchased and installed a while back had to be defective.
The purge valve is a Duralast lifetime part from AutoZone. This was against my better judgement as I usually only purchase OEM replacement parts. This is exactly why.
After James left yesterday afternoon I hopped on Amazon and ordered a Genuine GM EVAP purge valve.
This afternoon the new part arrived and I installed it. The Duralast part was definitely defective because I am able to suck through it with ease. No resistance at all.
Now we wait and see if the code comes back and/or the starting issue persists.
Thanks to all who have been helping me with this
Tell the truth, @dross99_si, one of @swathdiver's kids did the work, right? LOL
TYF Collaboration FTW!Update:
Yesterday swathdiver (James) was nice enough to come over with the Tech 2 to see if we could figure out the P0442 and check fuel pressure to diagnose the starting issue. Unfortunately the fuel system monitoring was not an option listed for my particular vehicle. Not sure if the 2007s support this or not..
On a better note we did some experimenting with the EVAP purge valve. With the engine running, the vent valve closed and the purge valve commanded open (even to 100%) there was never a negative pressure generated in the fuel tank according to the fuel tank pressure sensor. In other words the new purge valve I purchased and installed a while back had to be defective.
The purge valve is a Duralast lifetime part from AutoZone. This was against my better judgement as I usually only purchase OEM replacement parts. This is exactly why.
After James left yesterday afternoon I hopped on Amazon and ordered a Genuine GM EVAP purge valve.
This afternoon the new part arrived and I installed it. The Duralast part was definitely defective because I am able to suck through it with ease. No resistance at all.
Now we wait and see if the code comes back and/or the starting issue persists.
Thanks to all who have been helping me with this
How else are they going to learn?
As a kid, my dad would tell me to go start the grill.
Then he would tell me to spread the coals out and put the meat on.
Then he would tell me to turn the meat.
Then he would tell me to take the meat off.
Then he would tell the neighbor that he grilled for supper.
I now know have a 13 year old son that I tell to go start the grill.......
How often do you tell that son to "Pull my finger"? 
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