5.3L Starting Issue

[ChrisK7UND]

How did you figure out it was the fuel pump? Did the dealer diagnose it?


Chris Underwood

 

[ccapehartusarmyINF.(ret)]

its generally the fuel pump mine started going out at 135k miles and after reading on these forums they tend to become problematic after about 100k miles from what read about other forum members expierence

 

[SGinn722]

Fuel pump was replaced and the problem stopped up until a couple of days ago......Then it starts again... when the new pump was installed the fuel pressure was holding but maybe it's the regulator going out? I don't understand it. If the engine is cold it cranks fine but once it's hot it likes to spin and spin and barely crank. Any thoughts before I spend more money with my mechanic?

 

[992dr]

Turns out it's the fuel pump....Does anyone know the AC Delco part number? There appears to be several options. Mine is Vehicle VIN 0

How did you determine it was the fuel pump?

How does it idle once started? Smooth?

 

[db0353]

My experience with hard starting in a way similar to yours was fuel and vapor from the tank dumping into the intake and flooding the engine. This generally happened when I filled the tank, but not always. It led to very long crank times but the engine would finally start. It would run raggedly for a few seconds until the excess fuel was cleared from the system. No warning lights or messages. The one time the check engine light came on the code was for a large evap leak(P0496 I think it was). The evap valve on the engine was stuck open. I replaced the valve and have had no problem since. I have over 163k on original pump. The should open with 12v signal and default to a closed position with no voltage present. You can check it by removing it from the engine and blowing through it. If you can blow through it, it's bad. Replace it. Mine was around $50. Don't change it on a hunch, check it out.
I don't believe the problem is the fuel pump because it does start and run. Those pumps generally pump enough or they don't. If you want to know, have a tech check it out.

 

[SGinn722]

How did you determine it was the fuel pump?

How does it idle once started? Smooth?

I had a mechanic diagnose it based primarily on the fact that once I fill it up and crank it, it starts perfectly. He said that it sounds like the pump is too hot and once cold fuel it dumped on it, it acts normally. So I went ahead and changed it out and the problems stopped until a few days ago. Also, once it cranks it always runs normally.

---------- Post added at 03:53 PM ---------- Previous post was at 03:51 PM ----------

My experience with hard starting in a way similar to yours was fuel and vapor from the tank dumping into the intake and flooding the engine. This generally happened when I filled the tank, but not always. It led to very long crank times but the engine would finally start. It would run raggedly for a few seconds until the excess fuel was cleared from the system. No warning lights or messages. The one time the check engine light came on the code was for a large evap leak(P0496 I think it was). The evap valve on the engine was stuck open. I replaced the valve and have had no problem since. I have over 163k on original pump. The should open with 12v signal and default to a closed position with no voltage present. You can check it by removing it from the engine and blowing through it. If you can blow through it, it's bad. Replace it. Mine was around $50. Don't change it on a hunch, check it out.
I don't believe the problem is the fuel pump because it does start and run. Those pumps generally pump enough or they don't. If you want to know, have a tech check it out.

Forgive my ignorance but where is the evap valve and what does it look like. Coming from older model vehicles I'm not familiar with all this emissions crap.

 

[db0353]

Check out the thread on this (Tahoe/Yukon)site: Conquering the (NNBS) P0449 Code. You aren't getting the code this fellow had but he shows some good photos with locations for the purge solenoid and canister purge valve. I wouldn't change them without checking their functionality. I like to work on my own vehicles but often it's less expensive to have it checked out by a qualified tech who really understands the system and how it work. That way I don't have a garage full of "known good test parts."

---------- Post added at 08:37 PM ---------- Previous post was at 08:22 PM ----------

A quick set of checks:
1. Have a fuel gauge attached to the port on the engine. Crank the engine and check fuel pressure. Running or not doesn't matter. Just pressure the system. Turn the key off and watch the gauge. It should hold between 56-62 psi. If it does, your pump is good. If the pressure hold but it's low, the pump is going south. If it drops to zero or very low, look for a regulator. The regulator is part of the fuel injection unit under the air plenum.
The fact your engine runs well once it starts argues very strongly against a fuel pump. Did the mechanic check the pressure or shoot from the hip?
A good tech with a top notch scan tool who specializes in drivability issues can check the fuel trim, both long and short term as well as other fuel and ignition parameters. He/she can usually pinpoint the problem in short order. You can decide whether to replace the parts yourself yourself or pay to have it done.

 

[ccapehartusarmyINF.(ret)]

yeah it seems the fuel pump in these tahoes are notorious for failing after about 100k
when mine was going out about every other time i started it it wouldnt start on the first turn of the key it would start on the second turn

 

[SGinn722]

Check out the thread on this (Tahoe/Yukon)site: Conquering the (NNBS) P0449 Code. You aren't getting the code this fellow had but he shows some good photos with locations for the purge solenoid and canister purge valve. I wouldn't change them without checking their functionality. I like to work on my own vehicles but often it's less expensive to have it checked out by a qualified tech who really understands the system and how it work. That way I don't have a garage full of "known good test parts."

---------- Post added at 08:37 PM ---------- Previous post was at 08:22 PM ----------

A quick set of checks:
1. Have a fuel gauge attached to the port on the engine. Crank the engine and check fuel pressure. Running or not doesn't matter. Just pressure the system. Turn the key off and watch the gauge. It should hold between 56-62 psi. If it does, your pump is good. If the pressure hold but it's low, the pump is going south. If it drops to zero or very low, look for a regulator. The regulator is part of the fuel injection unit under the air plenum.
The fact your engine runs well once it starts argues very strongly against a fuel pump. Did the mechanic check the pressure or shoot from the hip?
A good tech with a top notch scan tool who specializes in drivability issues can check the fuel trim, both long and short term as well as other fuel and ignition parameters. He/she can usually pinpoint the problem in short order. You can decide whether to replace the parts yourself yourself or pay to have it done.

Unfortunately I've already wasted the $20 on purge valve solenoid which did NOT fix the problem. The canister vent valve is only $23 from Autozone and I'm willing to try that before I tuck my tail and head to the shop. Fuel pressure holds around 55-56 so I don't think its a fuel pump.

 

[mactexas]

I just joined this forum because I have the exact same problem with my 2007 Yukon. It has been an intermittent problem for the past 3 years. Right now I have 79,000 miles, it started with just over 50,000. I have not taken it to a dealer because some days I have the problem and other days it starts with one "crank" of the starter. It happens when the engine is cold and when it is hot.

Very frustrating. I will be watching this thread and hope there is a solution.

Thank you