2001 Yukon XL has problem starting

[bungnati]

Hi, I have a 2001 Yukon XL 5.3L. When I try to start the truck sometimes it starts fine. Other times it will crank for 5-10 seconds with sputtering, turn key off and try again - perfect. Also intermitently I will start the truck, rpms goto 1500 and then dies when trys to go to idle (all in about 2 seconds). It will do this 2-3 times and then run but with low (200-400) rpm's. Then I will park the truck and return 5 min later and runs fine.
Also I have looked at the computer data and it seems the computer is resetting itself randomly as it will say that the onboard rediness tests arent complete.
I replace the fuel pump about 3-4 months ago (whining losing power) and the Intake man gasket (leaky gasket, rough idle at cold startups) about 6 months ago.
Let me know what you guys think I should check.
Thanks

[bungnati]

I just checked the fuel pressure and it reads 60 psi when the fuel pump running but quickly drops to 0 within 2-3 seconds. Im guessing that is the problem. What could be causing this, fuel pressure regulator, fuel pump??
Dunno please help in any way you can. Thanks.

btw when engine is running pressure is at 48-49 psi which i beleive? sounds correct.

Thanks guys

[maxwedge]

Pressure running is low, I would suspect the regulator here. Both the pump and regulator have been problematic on these trucks, get the plenum off and look for leaks around the spider and regulator.

[2000CAYukon]

Originally Posted by maxwedge

Pressure running is low, I would suspect the regulator here. Both the pump and regulator have been problematic on these trucks, get the plenum off and look for leaks around the spider and regulator.

On my 2000 5.3L Yukon, the regulator is on the driver's side fuel rail and it does not have a spider. I though the spider was only on the 96-00 5.7L Vortec.

Did the 5.3 come with a spider in some years?

//2000CAYukon

[maxwedge]

You may be correct,I will check further and repost. You are correct, the 5.3 has an external on the rail regulator. Pressure should not drop to 0 here, he must look into that.

[bungnati]

Hi again. I replaced the FPR but didn't correct the fuel pressure dropping off after fuel pump shuts off. it still drops to about 5 to 10 psi in about 3 seconds. Does the fuel pump have a check valve that could be stuck? or should I pull the fuel rails and look for a leaking injector. would a leaking injector cause the pressure to drop that fast? .
thanks guys for the help so far.

[2000CAYukon]

The pump does have a check ball. You could pull the plugs to see if an injector is leaking but I doubt that would cause the drop to 5 or 10 PSI (unless multiple injectors are leaking really bad).

This sounds more like a bad fuel pump to me.

//2000CAYukon

[bungnati]

The pump "seems" good as it pressurizes to 60 psi. . Ill put a valve inline with the fuel send line and quickly shut it off then the fuel pump shuts off and see if the pressure still drops.
Thats what I get for buying a discount fuel pump.
Thanks guys.

[bungnati]

Hi guys,
Just replaced the fuel pump, Twice. The first one was defective. When the system pressurizes I get 59 PSI at the rail and running is still 49 PSI. The pressure holds between 52-49 PSI for atleast 10 min. I have no problems starting now. When I pull the vacuum tube off the regulator the pressure is at 59 PSI when running.
Let me know if anything still sounds off and I will check into it.
As for now Im gonna run some injector cleaner to clean any dirty ones.
BTW as a side note the float arm must have been bent because a full tank now registers at 7/8 of a tank and is on E with 10 gallons left.
Im not dropping the tank again.
Thanks Guys.

[2000CAYukon]

My 2000 5.3 Yukon runs at 50 PSI at idle. Always has since new.

//2000CAYukon

[bungnati]

Originally Posted by 2000CAYukon

My 2000 5.3 Yukon runs at 50 PSI at idle. Always has since new.

//2000CAYukon

Thansk for letting me know.

[bungnati]

The Computer resetting problem was being caused by a VERY corroded positive terminal. I replaced the ring and cleaned up the battery and havent had a problem since.
The truck would try to start then no power to anything, lights not even dim, then all of the sudden about 1 min later everything came on. Wierd symptoms, I thought it was a time reset breaker but didnt think the truck would have that.
After the 3rd time of this happenenig I looked at the terminals and didnt see a problem then I removed both and as i was removing the + I saw like an ounce or two of corrosion flake out from under the rubber sleeve.

Thanks Guys For all Your help especially maxwedge and 2000CAYukon.

You guys saved me a lot of money . Got my parts at dealer cost and free labor(not really, Im friggin sore from dropping the tank 2 times by myself).

[svroom]

Did you have any luck? I have a similar problem 1998 GMC K2500 7.2L EFI but the fuel pressure runs at 55 PSI, which is a little low. When I shut the key off, it goes to 40 PSI then slowly drops to 20. 55 PSI during operation as well, this is a replacement fuel pump. Engine cranks hard to start but does start. The pressure regulator is under the intake plenum so I want to be certain before I take things apart.