Lost fuel pressure when shutting off engine - 4 fuel pumps + Injectors replaced

[bitterdog]

im at my wits end with this money pit

2006 GMC envoy Denali 5.3L

I've changed the fuel pump 4 - YES 4 times - Delphi PUMPS
I bought and installed new injectors

Engine will not start on first turn. Starts on the key turn of the 2nd try immediately

if its the line wouldn't I smell gas or see a gas drip?

Its a return less system with the regulator / filter built into the pump.... chances of 4 Delphi pumps bad... Very low

Fuel Pressure is 60psi running.. kill the engine and it drops to zero in about 10 seconds

I don't know what else it can be.

Any suggestions? Thanks

 

[m.mcmillen]

Why did you replace the pump in the first place? Was it because of this same issue?

 

[bitterdog]

Why did you replace the pump in the first place? Was it because of this same issue?

Yep same issue... now into this 4 fuel pumps and injectors.

 

[mrrsm]

What Diagnostic Procedures did you use to arrive at the same conclusion ...(4) Times in a Row? The chances of having Four Delphi Fuel Pumps and ALL of the Electronic Fuel Injectors Failing back-to-back... borders on having Astronomical Odds of this ever occurring. Once the Motor Starts... Does the Engine ever Stop Running during normal operations thereafter? In a Returnless Fuel Delivery System... there is usually a dedicated Module that plays a game of "Red Light... Green Light" for feeding the demand coming from the Engine for greater or lesser amounts of Fuel.

Chances are... if you run down the Fuel System-Fuel Pump Diagrams and ALL of the Electronic Control Modules in between.... at least ONE of them... Probably the one closest to the Fuel Tank (Near to or on Top Perhaps) has either been compromised by Road Salt-Saline invasion and/or the Fuel Delivery Circuit may be shorting out from a Broken Wire in the associated Electrical Connectors as a result.

If you have previously considered that the problem might have originated INSIDE of a Bad Ignition Switch and replaced this item as well ... then the symptom(s) you describe of having a Failed First Try at Starting the Vehicle... followed by the Successful Start after the Second Try... is emblematic for starting your investigation using a Diagram of the Fuel System Modules... and Please... Refrain from replacing any more Fuel Pumps until you can dope out these other possible locations for the ACTUAL cause of this problem.

Your Best Friend here is a "Scope on a Rope" Lighted Probe and a Decent Digital Multi-Meter to run this to Ground. Visit any Post from @Mooseman and Download a Digital Manual for your Specific Vehicle and research that as a source for the exact Electrical Wiring Diagram you WILL need to sort this out.


"Doing the Same Thing, The Same Way ... Over and Over ...and Expecting a Different Result... Is the First Sign of Insanity..." Albert Einstein

 

[bitterdog]

Once its running it does not die.. in fact those new injectors gave it a lot more power it seems like. this engine has 190k on it.. so it probably needed to be done anyways

this is everything that's been done... only other thing I think would be possible might be ignition switch or fuel line. Ill take a look at your suggested reading to follow the trail.

heres 100% of what I have done:

1. Fuel pressure test. - Zero pressure with switch off. Turn the key it jumps to 60ish psi after 2nd key turn it starts 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 all 8 injectors

5. Replaced the Delphi Fuel Pump 4 times 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.

 

[mrrsm]

NP... Brother... But if I may suggest... Even though this One Hour Long Video Involves a Different GM Truck... it covers THE DIAGNOSTIC PROCESSES that you need to observe and learn from in how to approach this problem in an Organized, Logical Manner...using the Tools I mentioned above... and follow along with what is required when chasing down such an elusive problem with the Fuel System.

THIS Eye-Opener is well worth Downloading, Saving and Watching as often as needed... and you will become a Better Mechanic by observing what the Hero in this 'Epic Solve' goes through to Fix The Problem. Please note that his Customer's Vehicle is ALSO using a Return-less Fuel Delivery System and it is THAT very Module that winds up being the cause of all this trouble:

 

[bitterdog]

Thank you my friend.. I will watch this now
lol a lot cheaper then throwing more parts at the problem

 

[Mooseman]

Our trucks don't have a FPCM, I6 nor V8, so don't waste your time watching that video.

With what you have done so far, this is what I suggest. Pull the fuel pump relay, then pull the fuel rail with injectors, line and connectors connected (or reconnect them after) and leave it dangling over the engine. You may also hook up the fuel pressure tester as well. Using a wire, jump the relay to run the pump momentarily. Check each injector for leaking fuel and check the fuel pressure if it drops.

The other question would be, are you sure you got the proper fuel pump for a returnless system? No extra unused bung on the fuel pump?

Next, maybe drop the tank enough so you can observe the fuel lines with a good light to be sure it is really not leaking with the pump running. Sometimes you can't just go with one sense (smell) and have to confirm with a second (vision).

 

[budwich]

part number of the pump(s) that you have used / are using might help. Further, as you have spent a lot of time on this, more might still be worthwhile even if your truck runs on "second start attempt"... your time mileage may vary... but potentially you can try rigging up a "spigot" at the fuel pump line with a hose fitting for an air compressor that will allow you to input air into the line and watch the pressure with your fuel pressure gages at the other end. This may help you resolve that the problem is or isn't at the fuel pump. Of course, you need to keep the air pressure below 50 or so but since the injectors will not be energized, no fuel / pressure should be lost in the remaining system. It might hard to do depending on what connectors are available but perhaps you have already experienced the "connector type availability". Anyway, just a thought.

:-( forget it, its holding pressure when there is pressure so the problem has got to be some where near the pump end... probably.

But... maybe the idea still has some merit. Maybe you can fashion a "short test fuel line", attach it to the fuel pump and see what happens there after.

 

[bitterdog]

heres the fuel pump.. I made sure to buy lifetime warranty product.. Yes I have the denali XL

https://www.autozone.com/external-engine/fuel-pump/delphi-fuel-pump/556661_141223_20966_187006

I did replace the quick connect on the fuel line at the fuel pump.. Maybe I can get someone to turn the key as I push the line inward and see … but theres no leaking gas. wouldn't there be leaking gas if it was the connector or a o-ring?

 

[budwich]

hmmm... as someone asked, are you sure that pump is for a "returnless system"? It indicates "2 outlets"... not sure what that means as I have never had my "returnless system" apart.

 

[budwich]

Another question: how were you measuring your "running pressure" and your "stopped pressure"? Lastly, so, when you just turn your key to ON, what is the pressure?

 

[mrrsm]

I'm taking a Very Wild Swing here... But... Just in case You are NOT the original Owner of this GMC Envoy... and the Prior Owner swapped in an Early Model 5.3L Engine without mentioning this... take a look at this video of a FPR replacement on the 2003-2004 GMC Envoy XL ...and then JFTHOI ...look over your own Engine for the presence of this same component.. obviously not required for the 2006 Denali vehicles with the 5.3L V8s with that FPR feature being built into the Fuel Pumps to prevent such an EZ Owner R&R:

 

[bitterdog]

hmmm... as someone asked, are you sure that pump is for a "returnless system"? It indicates "2 outlets"... not sure what that means as I have never had my "returnless system" apart.

Ya its returnless.. one line is for the fuel line. the second line is evap

Another question: how were you measuring your "running pressure" and your "stopped pressure"? Lastly, so, when you just turn your key to ON, what is the pressure?

I start the motor.. pull the fuel pump relay to remove any pressure on the rail. Hook up my guage to the Schrader valve. Put the relay back in and turn the key. Zero pressure built up on first turn of key. Turn key again.. Jumps to 60PSI immediately

Turn off the key the pressure bleeds to zero in about 10 seconds

I'm taking a Very Wild Swing here... But... Just in case You are NOT the original Owner of this GMC Envoy... and the Prior Owner swapped in an Early Model 5.3L Engine without mentioning this... take a look at this video of a FPR replacement on the 2003-2004 GMC Envoy XL ...and then JFTHOI ...look over your own Engine for the presence of this same component.. obviously not required for the 2006 Denali vehicles with the 5.3L V8s with that FPR feature being built into the Fuel Pumps to prevent such an EZ Owner R&R:

Original motor in it. FPR is in built into the fuel pump in the tank

 

[mrrsm]

Damn... Strike One...

Sets in the Box for another Pitch... and offers another Wild Swing...

On the remote chance that the "Security Light" comes on during your First Start Attempts... perhaps a "Security Re-Learn" would tidy things up:

Security relearn procedure:

1. Attempt to start the truck by turning the key to the Start/Run position. Try to crank the vehicle.
2. Observe that the vehicle fails to start and the security light is illuminated.
3. Release key to the ON/RUN position (not the ACC position or OFF)
4. Allow the vehicle to sit with key in the ON/RUN position for no less than 11
minutes. Security light will turn off after this.
5. When the light goes off, turn key to OFF position and allow the vehicle to
remain in the OFF position for no less than 30 seconds.
6. Repeat #1-#5 for four cycles or until vehicle starts.

 

[budwich]

I start the motor.. pull the fuel pump relay to remove any pressure on the rail. Hook up my guage to the Schrader valve. Put the relay back in and turn the key. Zero pressure built up on first turn of key. Turn key again.. Jumps to 60PSI immediately

Turn off the key the pressure bleeds to zero in about 10 seconds

hmmm... rather interesting.... there is zero pressure build... ??? does the pump actually run? not sure the system would directly know about the zero pressure... but maybe since the "returnless" has to monitor is some how to dump.

I guess the question is: after shut down (watch the pressure disappear), if you jump the pump instead of the PCM doing the work, do you see any difference?

 

[Mike534x]

Not sure if this helps, but I came across a post on the old site. It was last year, but a user with an 07 Denali had an issue with theirs not turning over on the first attempt but would on the second. Here is the Link , it would at least maybe have some clues?

Though I am wondering, if its losing fuel pressure that quickly if maybe the FPR is faulty on the new pumps and it's just a matter of Delphi having a bad batch. If there was a leak in the lines there should be an indicator or smell at least. Maybe its something electrical, like the pins not making good contact with the connector on the pump?

 

[Mooseman]

Damn... Strike One...

Sets in the Box for another Pitch... and offers another Wild Swing...

On the remote chance that the "Security Light" comes on during your First Start Attempts... perhaps a "Security Re-Learn" would tidy things up:

No, just no. It's NOT a VATS issue. It starts fine with built up pressure so the pump is being energized and pressure is bleeding somewhere.

Try this. Using the same method you are currently using to hook up the fuel pressure gauge, turn the key to RUN and bleed the air from the gauge (it should have a bleeder with a hose at the gauge), turn the key a couple of times to rebuild pressure and leave the key in RUN, pull the pump relay. Does it hold pressure? if NO, go to **. If YES, turn off the key. Does it still hold? If NO now, then I suspect an injector(s) is being energized with the key off. Unplug all the injectors to confirm and plug in one injector at a time to find the offending injector(s) and to troubleshoot further.

** If not, unplug injectors and repeat. Now does it hold? If the answer is YES, then something is energizing an injector(s). Unplug all the injectors to confirm and plug in one injector at a time to find the offending injector(s) and to troubleshoot further.

If pressure is NEVER holding, it's either a leaking injector or something else upstream all the way to the pump. Since you replaced all the injectors (with new I hope), then I would suspect something upstream. To find a leak, jump the relay socket to run the pump constantly and go over the entire line from the rails to the pump. Then, in the absolute failure of finding a leak, replace the pump with another brand (I would suggest Bosch or ACDelco, both the same). It is quite possible that Delphi are just junk since the time they went bankrupt and were bought out a few years ago.

 

[budwich]

Although the loss of pressure at shutdown might be an issue, I am not sure that is the cause of no pressure build with key ON. I think you might be focusing on the wrong symptom for "no start, engine turn over".

 

[Mooseman]

He's losing pressure somewhere. On first prime, it's not enough because the pump shuts off after a couple of seconds. When you crank, the pump comes back on full time but still has to build up pressure again, hence the longer crank time to start. I know this because I had these exact same symptoms when I had a leak at the pump outlet that rusted through on my '06 Saab. My process above eliminates the injectors as the source of the pressure loss or confirms them as the source.

 

[Denali123]

My 2005 denali is doing the same thing. I have limited funds a day was wo during if you were figured out the issue? Please respond

 

[mrrsm]

Welcome to GMT Nation...

Stop over at THIS Link and see if there are any suggestions that are NEW that might help out (...Talking about Checking on the Engine GROUNDS here...)

NEED HELP - Start-Stall on a 2003 Chevy 5.3

Hey everyone, I'm having an issue with my 2003 Silverado 1500 LS where it turns over just fine, then immediately stalls out. I've searched all over and cannot find a solution. The fuel pump is less than a year old and I've tried the security system re set. It also doesn't do it all the time, it...

gmtnation.com

 

[Mooseman]

The testing procedure I enumerated above will tell you what's going on if it's a fuel pressure issue

 

[blinebrown]

Did you ever find a fix for the pressure dropping to zero? I'm having the same issue after I changed my pump and want to be sure before changing the pump again. The previous pump had no issue holding pressure. My new pump also makes no sound when the key is in the on position.

 

[Mooseman]

If your pump doesn't prime, it's something else. Did you check your fuses? Try jumping the fuel pump relay? See if you get the relay signal from the PCM? If the PCM is not sending the signal, is your security light on? Anything else done that might have disturbed the VATS?

 

[blinebrown]

I’ve swapped my relay with others. I typically have to try to start twice. I hooked up a fuel pressure gauge and I drop to zero after turning off my engine. I have no lights at all. I drive it everyday with no problem. Just bothers me having to start it twice, something obviously isn’t right.

 

[Mooseman]

Oh so the pump is running, it's just bleeding pressure. I would guess that either the pressure regulator or one way valve in the pump module is defective, there's a leak in a line somewhere or an injector is leaking.

 

[blinebrown]

I’ll exchange my fuel pump to rule it out for sure. Would leaks show signs? Fuel on the ground or something? I’ve not had any sign of leaks on no smells of gas so far.

 

[Mooseman]

There would be signs, especially smell and streaks. These fuel pumps usually leak on the top of the tank and there would be evidence. Since you're in a rust belt state, this is a common occurrence. And there's also the steel line going from the plastic line in front of the tank up the side of the frame to the engine bay. However, if it's bleeding fuel pressure even without any leaks, then I would highly suspect the pump module.

If you want to dispel the injectors as the possible source of the leak, what you could do with the engine off, have the pressure gauge connected to the fuel rail and jump the fuel pump relay to run the pump constantly, pinch off the rubber line going into the fuel rail (use an actual hose pincher to avoid damaging it), stop the fuel pump and observe the pressure. If the pressure holds, then it's definitely the pump. If it drops like before, an injector is leaking.

And BE CAREFUL with the schrader valve on the fuel rail when connecting/disconnecting the pressure gauge. It's in a weird angle and I have cracked the fuel rail in the past.

 

[Sailor Mo]

I have not had a problem on my Sierra with fuel so I am not totally aware of the System on your vehicle however I did have a 95 Chrysler LHS that was bought new and It would never start the first time I would have to crank it several times. The dealer could not find the problem After troubleshooting the system I found that the mechanical regulator when assembled at the factory they had pinched an O ring and that when the car set overnight the pressure would bleed off and when you tried to start it in the morning I would have to crank it at least twice and build the pressure up to activate the injectors. I changed the O ring and never had a problem again.

 

[mrrsm]

Review THIS Thread (Post #5)

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While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...

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