2006 Envoy 5.3L Fuel pressure drops to 0 AFTER shut off w/ 2 NEW Delphi Fuel Pumps..

[bitterdog]

Hi.. Im at my wits end with this 2006 Enovy Denali 5.3L. Had hard start issues.

Heres whats been done im hopeing someone can chime in with other possibilitys or tests?
We have now replaced the fuel pump 3 times in the last month.. ALL DELPHI Pumps from Autozone w/ lifetime warranty

1. Fuel pressure test. - Zero pressure with switch off. Turn the key it jumps to 60ish psi and drops back to zero. The engine starts .. it sits at a steady 55psi. Turn the key off - Drops to ZERO

2. replaced the fuel quick connect fitting at the tank in case it was somehow damaged

3. Pulled injectors looking for any sort of leak

4. Replaced the Delphi Fuel Pump 3 time in case we got bad ones. Check Valve / Fuel Pressure reg / Filter all built into unit

5. Cleaned MAF Sensor

6. no signs or smells of leaking fuel

7. Replaced the Ignition switch.

Obviously some of these have no bearing on the loss of fuel pressure - However it did resolve the hard start issue. However still will NOT hold fuel pressure once the key is off.

I thought about next to add a aftermarket check valve.. but id like to see if theres something im missing.



Not sure where else to go from here. Any other suggestions besides Drive it off a cliff?

Thanks

 

[Mooseman]

Well, you've done a pretty thorough investigation. When you pull the injectors, how did you check them for leakage? What is leading you to check the fuel pressure?
Are there any codes? Is it running rough? If an injector is leaking, there could be a code for running rich or a misfire. Have you looked at the fuel trims?

 

[bitterdog]

Pull injector banks.
1st inspect for any drippage - none -
Then crank the key looked at pattern nothing unusual about spray pattern . none
Stop cranking no signs of drippage.

The Fuel pressure guage immediately was dropping to zero, would have to be a significant leak I would see with injectors out and cycling.. I saw none

I checked fuel pressure because when I crank the engine it would not start EVER on the 1st turn. but on the second key turn it immediately fired up.

Doesn't run rough

No codes are being thrown with my scanner.. albiet obviously it isn't a Tech2 scanner.

I have not looked at the fuel trims or voltages going to the injectors.

I just find it hard to believe Ive thrown in 3 Brand new Delphi fuel pumps and all 3 are bad.. I have to be missing something

I don't know where else to look - Evap Purge canister or Solenoid?

 

[budwich]

maybe you are chasing a "pressure ghost".... not sure on a "no return system" (if you have that) that pressure will be held with key off... you would thinks so.

You said your "hard start" issue went away, so maybe the pressure is not the issue.

 

[Mounce]

So, no pressure regulator on the driver side fuel rail?

Other than that it seems you've covered the obvious things. Head scratcher.

But no, purge solenoid and canister shouldn't have any effect on your issue as they never see pressurized fuel.

 

[mrrsm]

Small Suggestion. Pull the Fuel Pump Relay and check the pin sockets for indications of excess spreading. Then spray some CRC Electrical Cleaner down into the pin sockets and let it dry well... and finally... install a Brand New, OEM Quality Fuel Pump Relay.

 

[Mooseman]

Are you sure you're getting the right pump? There's no extra bung with nothing connected to it? I checked and it's the same pump between all engines of the same year.

I hear you with the long cranking start. I had that when my fuel line was leaking. Maybe until you find the problem, you can cycle the key twice to prime it. Try listening when it primes and stops for hissing or noises.

If you want to try another brand of pump, get the Bosch. It's the same as ACDelco. It's quite possible that Delphi are just bad now since the bankruptcy and new ownership.

 

[Tdub]

You said that your hard start issue is resolved? Does it fire right up after sitting all night? Check another new pump and see if you can blow air back through the supply line. Heck, you could do that right at the Autozone counter. Then try blowing through a different brand.

Seldom will I stick with the same supplier if the first one bit me. But I'm also one to hold serious grudges when my time is wasted by lack of quality causing me to 2nd guess my diagnosis. I have recently gave up Delphi vortec cap and rotors for this very reason.

 

[Mektek]

What are the odds that three pumps would all be defective?
It can happen. Once I had two defective new evaporators in a row - the third one was good.

When you opened a new pump could you smell and see a residue of a solvent like mineral spirits coming from the pump output line? This would be a sign of a factory test.
Otherwise they may have got a bad batch of check valves at the factory and didn't find out about it until people like you started returning them.
Your idea of installing an inline check valve is interesting - that would isolate the problem to the pump if you still had the pressure drop. A bad valve would leak back into the tank so you would have no detectable odor or visible leakage. It would be a bit of work to get the plumbing done.

You're probably sick of changing pumps, but maybe you should try a cheap pump. If it performed identically to the delphi you could be sure it's not a pump related issue.
I\

 

[budwich]

odds are slim that it is a pump problem... :-(
I am guessing a "finger problem" as how did you do your test? How did you "prime" your tester?
You know that air can do bad things to pressures...

As a check, after you have "instructed pump on" (key on), and watched the pressure then see its drop thereafter, disconnect the pressure tester.... does gas shoot out or just dribble?

needed to add... do the check carefully!

 

[coolasice]

Could be a bad pressure tester?