NEED HELP Possible bad fuel pump (confirmation needed)

[ghost_leader07]

Hi everyone,

I had my 04 trailblazer i6 parked for almost a year doing some repairs and few modifications in that period it had almost a full tank and i kept starting it up regularly to warm up but didn't drive it (seats were out) it took me a while to realize that fuel can go bad sitting in the tank so after about 7 months i siphoned out as much as i could from the tank and putted about a two gallon of fresh fuel in and crank it but i won't start at first but starts after 2nd or 3rd timet It'll rough idle for awhile then it runs better, there's one time it was idling very rough until it shut off by itself.

I was suspecting a low fuel pressure so i did a fuel pressure test and here's my findings:

Turning the key to ON i see 0psi but i can here the pump turn it OFF and ON again i get a little pressure but it drops down rapidly it doesn't hold pressure not even for a second.



When trying to crank it i see the fuel pressure rising but it won't start it'll start after second or third attempt but with fairly low pressure around 40-35psi but it stays in that range idling.


Once i turn it off pressure drops immediately.


In this video i cycled the key ON and OFF few times to show its behavior.

I'm guessing this is either a bad fuel pump or a major leak somewhere so i did a visual inspection for any leaks and i couldn't find anything.

To isolate the pump and fuel injectors first i pinched the main fuel line near the fuel rail and nothing changed, Since all points to an issue with the pump so just to be sure i disconnected the main fuel line and put it inside of a bottle as shown in the video below, i turned the key ON i can hear the fuel pump but nothing is coming off the fuel line, second try i get a little bit of fuel but no pressure coming off the fuel line tried it few times same thing, the fuel smells awful and it has a bright yellow color and feels a bit oily definitely bad.

My conclusion i have a bad fuel pump that needs to be replaced alongside the fuel filter and cleaning the fuel injectors as well.

Was my testing method and conclusion sound?
I'd appreciate any input. Cheers!

 

[Mooseman]

Try jumping the fuel pump relay and see if the pressure holds better. Also try pinching the return line hose. If pressure really shoots up and holds, then I would suspect the fuel pressure regulator.

Otherwise, I would suspect the fuel pump.

 

[ghost_leader07]

Try jumping the fuel pump relay and see if the pressure holds better.

Jumping pin 30 and 87 correct?

Also try pinching the return line hose. If pressure really shoots up and holds, then I would suspect the fuel pressure regulator.

I'll try that although I've replaced the FPR just recently chasing P0171 but not no harm in making sure.

Do you think a bad fuel would clog the fuel filter and damage the pump by just warming it up for 15 mins periodically? Or it's just weak fuel pump that gave out? Just trying to understand the reason for it dying.

 

[ghost_leader07]

Hey @Mooseman
So i did more tests as you suggested and here's what I did:

I pinched the return hose and jumped the fuel pump and pressure read around 32psi i kept running for about 30 seconds then removed the jumper and pressure dropped to 0psi immediately.


*Picture showing the fuel pressure with a jumper wire running it continuously for about 30secs.

I did another run but i disconnected the main fuel hose and pinched both (main and return) and got exactly the same fuel pressure reading.



Is this enough testing to condemn the fuel pump as weak/bad?

I ready took the fuel tank skid plate in case I'd have to do more testing, I'm thinking maybe I'd disconnect the main hose going to the fuel filter to read another pressure test but not sure if it is a valid test.

 

[ghost_leader07]

I've removed the fuel filter but there's no obvious way to test the pressure once it's removed.

Do you know of a way to hook the fuel tester gauge to the plastic connector from the tank?

Is it even necessary to test pressure without the fuel filter?

 

[mrrsm]

You could try to avoid the Fuel Pump R&R by replacing the In-Line Fuel Filter AND the Fuel Pressure Regulator mounted into the front of the Fuel Rail since both are fairly accessible and relatively inexpensive and then determine the Rate and Volume of the KOEO Pump Fuel flowing into that Collection Bottle during a Re-Test and see if anything promising occurs in the Brief Fuel Pump Priming period with KOEO.

Nominal Fuel Pressure on a Return Fuel System for the GMT360s should be around 54 PSI as demonstrated by @MAY03LT during this Fuel Pressure Test Video on his 2004 Chevrolet Trailblazer LL8 4.2L. The Fuel Pressure you were reading is very well below this Threshold when compared to this Screen Print of YOUR FPG Reading while the Engine was Running briefly at High Idle at just under 40 PSI.



... and so, replacing the Fuel Pump with either an ACDelco OEM Brand or a Bosch OEM Brand Fuel Pump and avoiding using ANY After-Market, Non-OEM Fuel Pump is always the standing recommendation:

Although this Training Video is being performed by an Airtex After-Market Parts Supplier Technician... His Instructions are Totally Valid and Worth Watching for this PITA Fuel Pump R&R:

And here again, Drew shows this process on a 2003 Trailblazer worth watching as well:

This is IMPORTANT:

With the bewildering array of Plastic Fuel Line and Vapor Control Lines... comes the equally baffling array of their Connectors. THIS Video is your means to escape from the Purgatory of NOT being able to easily R&R such Fittings. Please... Watch the Entire Film:

 

[ghost_leader07]

You could try to avoid the Fuel Pump R&R by replacing the In-Line Fuel Filter AND the Fuel Pressure Regulator mounted into the front of the Fuel Rail since both are fairly accessible and relatively inexpensive and then determine the Rate and Volume of the KOEO Pump Fuel flowing into that Collection Bottle during a Re-Test and see if anything promising occurs.

I have replaced the fuel filter and FPR a while ago and i less than 2000 miles on both so they're fairly new, if you read above about the process i did to test the FPR, i did isolate the pump by disconnecting the main fuel line hose then pinched it and fuel pressure didn't change (around 32psi) and drops in seconds keep in mind that the test was done while jumping the fuel pump relay and it has constant power throughout the test.

I've also disconnected the main fuel hose coming from the tank into the fuel filter to see the amount of pressure coming out of the pump and it was pretty low, I'll upload a video show it later.

Nominal Fuel Pressure on a Return Fuel System for the GMT360s should be around 54 PSI as demonstrated by @MAY03LT during this Fuel Pressure Test Video on his 2004 Chevrolet Trailblazer LL8 4.2L. The Fuel Pressure you were reading is very well below this Threshold when compared to this Screen Print of YOUR FPG Reading while the Engine was Running briefly at High Idle at just under 40 PSI.

So we can conclude that i have a bad fuel pump?

Although this Training Video is being performed by an Airtex After-Market Parts Supplier Technician... His Instructions are Totally Valid and Worth Watching for this PITA Fuel Pump R&R:

Thanks for the vids, i already took the tank off the truck to save time while confirming that the fuel pump is bad.

 

[mrrsm]

Right... But since there is no sense in wasting a Good Thread like yours that others can also benefit from during later searches for similar problems... I like to be as comprehensive as possible with these explanations. And thus, everything being mentioned follows a logical order and is always included in my responses. You now have enough information from your empirical testing and have made enough preparatory progress now that the Tank... has been Yanked.

So... Choose your Replacement Pump wisely... and mind any issues that may crop up with the Bosch Pump's Green Round "O" Ring Seal that can get a little tricky to install whenever pushing the *Springy* New Fuel Pump back down inside of the Tank while trying to re-seat the New Outer Locking Ring with a Brass Punch and Mallet.

I would prefer using the Original Black Rubber Seal if the Tank should leak after performing the complete installation and Start Up. If you don't smell any Fuel Vapors around the Tank...everything should be good to go...otherwise... THIS is the OEM Solution to that problem:

Amazon.com

Amazon.com

 

[ghost_leader07]

Right... But since there is no sense in wasting a Good Thread like yours that others can also benefit from during later searches for similar problems... I like to be as comprehensive as possible with these explanations. And thus, everything being mentioned follows a logical order and is always included in my responses. You now have enough information from your empirical testing and have made enough preparatory progress now that the Tank... has been Yanked.

Of course! this is one of the many reasons that makes the GMT community great. Having knowledgeable and competent people such yourself has helped a lot of people throughout the years, much appreciation for your help.

So... Choose your Replacement Pump wisely... and mind any issues that may crop up with the Bosch Pump's Green Round "O" Ring Seal that can get a little tricky to install whenever pushing the *Springy* New Fuel Pump back down inside of the Tank while trying to re-seat the New Outer Locking Ring with a Brass Punch and Mallet.

Yes I'm going with Bosch and I'll keep that in mind.

I would prefer using the Original Black Rubber Seal if the Tank should leak after performing the complete installation and Start Up. If you don't smell any Fuel Vapors around the Tank...everything should be good to go...otherwise... THIS is the OEM Solution to that problem:

Do you recommend using the original used one if it's in a good condition or buy a new one from the link you've provided?

 

[mrrsm]

That Black Rubber Ring is virtually Bullet-Proof... but I am always in the "Replace the Old OEM Parts with New OEM Parts whenever it is easily accessed" Camp. And since it is presently 46% OFF the ordinary GM Price... for less than $12.00 now... it would be a thoughtful "Peace Of Mind" investment for all of the work you are doing.

 

[ghost_leader07]

@mrrsm i need your advice on this, i was scrolling through eBay for a fuel pump, i decided to go with Bosch since it appears to be the OE manufacturer for either GM or ACDelco parts,

It currently sales for $169.99 but i found a listing by what it seems a reputable seller for $74.50 which is a massive price drop, the seller listing iy as a genuine Bosch with a stock image. I message the seller asking for actual photos but haven't gotten any response yet.

It seems too good to be true but my reason for asking is i remember finding the same fuel pump on Amazon at retail price ($169.99) but it had a sale for under $80 so I'm not sure anymore and i really don't wanna end up with a fake product as well.

Here's the listing:

Bosch 67415 Fuel Pump for 2002-2004 Ascender Bravada Envoy Rainer Trailblazer | eBay

<li> Vehicle Fitment Compatibility</li> <li> Make</li> <li> Model</li> <li> Engine</li> <li> Year</li> <li> Notes</li> <li> Buick</li> <li> Rainer</li> <li> L6 4.2L</li> <li> 2004</li> <li> Vin Code - S</li> <li> Buick</li> <li> Rainer</li> <li> V8 5.3L</li> <li> 2004</li> <li> Vin Code - P</li>...

www.ebay.com

 

[Mooseman]

I would be very leery of eBay and Amazon supposedly OEM or name brand parts at a "too good to be true" price. Just watched a YT video regarding fake OEM Toyota parts and it was just that, too good to be true.

 

[mrrsm]

Concur... If you look at the Amazon Offer from Bosch below...their listing has a Link to the Bosch Company as verification of IT being an OEM Product:

Amazon.com

 

[Mooseman]

And it's from the Bosch Automotive Store, not some unknown wholesale warehouse, who might be duped themselves, thinking it's an authentic part.

 

[ghost_leader07]

And it's from the Bosch Automotive Store, not some unknown wholesale warehouse, who might be duped themselves, thinking it's an authentic part.

I'll definitely make my purchase from the Bosch store at Amazon. Better safe than sorry.

 

[JayArr]

Just to throw in one final check before you spend $$.

How is the state of your battery?

Your testing a fuel pump with the engine off by jumping the connections at the fuse box right?

An the car has been sitting for months and months with only the occasional start up?

Throw a voltmeter on the battery and then jump the fuel pump and make sure your battery isn't failing. If the voltage on the battery drops below 13.6V with the pump on then the pressure from the pump will also drop. If the battery is weak get a good charger and charge the battery for a day or so and then try again. The pressure may rise from 35 to 55 with nothing more than a good charge.

7 months is short for gas to go bad in my experience. I've got cars that I don't drive in the winter months and I've never had to worry about the gas in the spring.

 

[ghost_leader07]

How is the state of your battery?

I believe it's good, it shows 12.70V and 14.60V with alternator charge.

An the car has been sitting for months and months with only the occasional start up?

Throw a voltmeter on the battery and then jump the fuel pump and make sure your battery isn't failing. If the voltage on the battery drops below 13.6V with the pump on then the pressure from the pump will also drop. If the battery is weak get a good charger and charge the battery for a day or so and then try again.

I've eliminated all of the variants by jumping the pump directly and disconnected the main fuel hose and pinched it then tested the fuel pressure i was getting about 32psi with continuous power for 20-30secs once i took the jumper off the pressure drops immediately so i believe this is has nothing to do with the battery if pump can't hold pressure.

7 months is short for gas to go bad in my experience. I've got cars that I don't drive in the winter months and I've never had to worry about the gas in the spring.

The fuel in my country isn't the best quality so that might be a factor?

 

[mrrsm]

Nope... All Liquids are In-compressible.... so regardless of whether you are using one type of fuel or another (say... Normal Heptane vs. Iso-Octane) then the Volume of Fuel per Minute being delivered during the pumping action should NOT be any different ...as long as their viscosity is similar.

 

[budwich]

Have you actually pulled the pump yet? It maybe that the pump is "starved" because its intake is plugged.

 

[ghost_leader07]

Have you actually pulled the pump yet? It maybe that the pump is "starved" because its intake is plugged.

Yes i pulled it out and the bottom filter has completely disintegrated check the photos below:

 

[mrrsm]

Hmmm... Be very curious to know if the United Arab Emirates has an issue with Very Fine Grain-Particles of Desert Sand getting in everywhere ...and into everything... in particular ...at the Fuel Pump locations.

 

[ghost_leader07]

Hmmm... Be very curious to know if the United Arab Emirates has an issue with Very Fine Grain-Particles of Desert Sand getting in everywhere ...and into everything... in particular ...at the Fuel Pump locations.

There was no apparent sand or particles other than ones from the filter, it looked clean.

 

[budwich]

Yes i pulled it out and the bottom filter has completely disintegrated check the photos below:

View attachment 110377

View attachment 110376

well that is certainly not going to help flows...

 

[TJBaker57]

Yes i pulled it out and the bottom filter has completely disintegrated check the photos below:

View attachment 110377

View attachment 110376

Yes indeed, that is what I have seen when fuel "goes bad". I once purchased a vehicle that had sat for 7 years. That looks like what I found with various parts of the fuel pump/filter.

Like most chemical reactions heat is a factor. Perhaps 7 months at your ambient temperatures is long enough for fuel to "go bad".

 

[ghost_leader07]

well that is certainly not going to help flows...

Yeah i thought so, I've also tested the pump in a bucket and there's a flow i don't if it's good or weak but my main issue is it doesn't hold pressure at all, possibly a bad check valve?

 

[ghost_leader07]

Yes indeed, that is what I have seen when fuel "goes bad". I once purchased a vehicle that had sat for 7 years. That looks like what I found with various parts of the fuel pump/filter.

Like most chemical reactions heat is a factor. Perhaps 7 months at your ambient temperatures is long enough for fuel to "go bad".

I believe my fuel going bad has destroyed the bottom filter and i also think my pump was weak long before parking the truck since I've been fighting with the P0171 code for years now and I've exhausted almost every possible cause but the fuel pump, hopefully replacing the fuel pump would help with both issues.

 

[TJBaker57]

Yeah i thought so, I've also tested the pump in a bucket and there's a flow i don't if it's good or weak but my main issue is it doesn't hold pressure at all, possibly a bad check valve?

I would suspect that any or all non-metalic parts of the fuel pump module could be degraded/damaged by the old fuel.

 

[ghost_leader07]

I would suspect that any or all non-metalic parts of the fuel pump module could be degraded/damaged by the old fuel.

I'm going to replace the fuel filter and clean the injectors, I've replaced the FPR less than 2000 mile ago would it be damaged as well?

 

[mrrsm]

After performing the New Bosch Fuel Pump R&R... Run some of the Tank Fuel through the Line at the EFI Rail into a Catch Bucket ...and eyeball what comes out of it to be sure you don't find any more of that "Gnarly Nylon" Filtration Material stuck down inside of the small filtration screen inside of the FPR. If so, flushing and cleaning out the Fuel Rail too right after the EFIs are removed will keep things running trouble free again for many more miles ahead.