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Engine starts on second key turn and one more issue

M

mdovenmuehler

Full Member
Joined
Sep 18, 2018
Messages
54
Location
Twin Falls, Idaho
Not everytime but it happens more often than id like. Truck runs great when its running, no stales etc. I had the fuel pump changed about two months ago and it seemed to happen then, by chance whomever installed the new pump forget to hook the low level line up to it on the inside of the tank?

Also Im still getting the ridicular p0455 code x_X. Changed the Vapor Purge Valve and the Vapor Canister and still no luck, I have not changed the actual Charcoal Canister yet which is last on my list. Im not quite sure what else the problem might be. By chance would the vapor purge valve be faulty or?


Thanks guys
 
When I bought my 2003 Z-66 back in February 2020, it was having similar issues when starting.

Since the truck had 243K miles on it with no indication of ever having had the fuel pump changed, I opted to go ahead and have that done.

I figured it was probably due.

I had already changed the frame mounted fuel filter and the fuel rail mounted fuel pressure regulator with no improvement.

The problem was the fuel pump, or rather the check valve in the fuel pump that allowed the fuel system to maintain pressure after the truck was turned off.

When I put my fuel pressure tester on the engine, I found the fuel pump would pressurize the fuel system from zero when I turned on the key, but the fuel pressure would instantly drop back to zero once the key was turned off.

Anytime the key was on, the fuel pressure was normal, allowing the engine to run normally.

But, since the fuel pressure went to zero once the key was turned off, there was sometimes a delay in the engine starting as there was no pressure in the system at the moment I first turned on the key.

I suggest testing your fuel pressure before proceeding.

When you had the fuel pump changed, did you have an ACDelco OEM fuel pump installed and not an aftermarket unit?

Some aftermarket pumps have been reported to have problems and that is why I always install OEM parts for this repair.
 
EXT4ME said:
But, since the fuel pressure went to zero once the key was turned off, there was sometimes a delay in the engine starting as there was no pressure in the system at the moment I first turned on the key.
Click to expand...

Could the OP rule this out by simply turning the key to on for a second, then start the truck? (Sort of like having glow plugs in a diesel)
 
Navigatin1 said:
Could the OP rule this out by simply turning the key to on for a second, then start the truck? (Sort of like having glow plugs in a diesel)
Click to expand...

Normally I would agree.

Except mine did not always start using the method you describe.

If you watched the fuel pressure, mine would start at zero with the key off, then build to full pressure when the key was turned on.

BUT, if you did not start the engine as soon as the full pressure was there, SOMETIMES the pressure would drop within several seconds and would come back up shortly and the engine would start.

MOST of the time, it would behave as you described.

All of the time, once the engine was started, it would continue to run.

You could never count on it doing what you described and I wasn't going to let it strand me when mine decided to finally give up the ghost.

I still say a fuel pressure test might yield some answers.

Can't hurt.
 
Thanks guys for the info, Im gonna give the pressure test a shot and go from there. It was an aftermarket, according to my mechanic who helped me said he couldnt get an oem soon enough for how fast I needed one. Said the one he got should work fine, was only 80 bucks as well. Thanks again
 
Long delay on this. So after using a fuel pressure gauge and just doing various things as everyone suggested Im pointing at the Fuel Pump as the problem, it was an aftermarket as well. I went and got an oem made by delphi at advancedauto, they told me should be just as good as the acdelco so hopefully this does the trick. I didnt see any black smoke etc or any of those signs of fuel leaking. It does it everytime as well, sometimes if Im lucky it would start right away.
The PG would go to 54 give or take and hold for a second or two and than immediately drop to 0 almost immediately. I tried waiting for 20 seconds up to a couple minutes with the key on and still would not hold pressure or come back up. Chevy told me it was a faulty check valve in the pump itself, that alot of aftermarkets just do not hold of up to spec on the 8.1 engines and how the gas rail system works, I have no idea really what he means but he sounded like he knew what he was talking about, he did mention if I had any exhaust leaks in the line as well, major ones. I did manage to crawl under the truck and find a hole in the exhaust line that goes to the aux pump, which I am replacing the lines this weekend. He said possibility pressure just wont hold unless the engine is running if there is any leaks in the fuel lines or fuel exhaust lines period. So yeah sounds great to me.... Thanks for the info guys. If anyone has any other ideas or this sounds possible let me know.
 
Nope, if the pressure drops off like that it will cause problems like you have
 
The pressure drops you describe is exactly what I was seeing.

Replacing the fuel pump solved this problem for me instantly.

Bad check valve.
 
Glad you got it fixed. (y)
 
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