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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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Discussion Starter · #1 ·
Hey all,

I am chasing a rabbit on this one and need some help. Here's some important points.
  • 2002 LB7 with 270k miles.
  • I rebuilt the filter head about 4 years ago when I was seeing the same issue and replaced both short fuel lines.
Using the GM manual for troubleshooting, I don't have any visible signs of diesel leak anywhere. I did a leak-down test on the fuel and sure enough after pumping up the system to 10 psi the pressure slowly dropped to nothing in about 10 minutes. Next, I put a clear 1/2" tube in place of the line between the filter head inlet and the FICM and purged the system. Once I started the engine, I did see a small bubble of air a few times but then nothing. I shut down the engine and after waiting approx. 10 minutes went through the purge/restart process again and saw one little bubble in 2 minutes. I'm thinking about not chasing that rabbit but instead looking at the filter outlet to injector pump to return line system components. Any words of wisdom would be appreciated.
 

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I would focus on the filter head first. That is a known weak spot.

Orings in the filter head can wear down and allow air to enter the fuel stream.
OEM plastic bleed screw can crack and allow air to enter or fuel to leak.
Looks for any cracks in the filter head also
 
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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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There are some components in the fuel filter head that you cannot replace when you rebuild it.

I'm not sure how you did your leak down test, but you can disconnect the supply hose from the filter head and stick your thumb over the inlet. Then pump the primer until you get vacuum on your thumb and see if it stays there. If it drops off the first thing you should do is replace the filter head. There are plenty of aftermarket ones and they are a known weak point.

Most of the problems seen on here are called a loss of prime. And what happens is basically there's a place where air is getting into the fuel line, and when the vehicle sits the fuel just drains from the filter head back into the tank. This could be why you're not seeing any fuel on the ground.
 
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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Well heck, somebody beat me to it
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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46 Posts
Discussion Starter · #5 ·
I would focus on the filter head first. That is a known weak spot.

Orings in the filter head can wear down and allow air to enter the fuel stream.
OEM plastic bleed screw can crack and allow air to enter or fuel to leak.
Looks for any cracks in the filter head also
Thanks, I did rebuild it about 4 years ago and bought a couple of the aluminum bleed screws from Merchant, (one for the toolbox) to eliminate that issue. It never hurts to have another look though. I will post once I find the issue.
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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46 Posts
Discussion Starter · #6 ·
There are some components in the fuel filter head that you cannot replace when you rebuild it.

I'm not sure how you did your leak down test, but you can disconnect the supply hose from the filter head and stick your thumb over the inlet. Then pump the primer until you get vacuum on your thumb and see if it stays there. If it drops off the first thing you should do is replace the filter head. There are plenty of aftermarket ones and they are a known weak point.

Most of the problems seen on here are called a loss of prime. And what happens is basically there's a place where air is getting into the fuel line, and when the vehicle sits the fuel just drains from the filter head back into the tank. This could be why you're not seeing any fuel on the ground.
Indeed, I used a vacuum/pressure gauge first to determine the loss of pressure. I'm going to put my old Mity-Vac on the inlet side next as you suggested. This truck needs to run soon because I'm hauling my neighbors '56 F100 custom to Barrett-Jackson in Scottsdale in about 10 days.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Good deal. One of those parts you can't replace is a flapper valve it's supposed to stop fuel from draining back down into the tank. Mine actually got so much Gunk on it I couldn't even prime it because it wouldn't seal between pumps.
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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Discussion Starter · #8 ·
Good deal. One of those parts you can't replace is a flapper valve it's supposed to stop fuel from draining back down into the tank. Mine actually got so much Gunk on it I couldn't even prime it because it wouldn't seal between pumps.
I appreciate the insight.

More importantly-I am a Wounded Warrior contributor on a monthly basis; one of my values that will never diminish.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Awesome, I am a recipient.

Thank you for your contributions and help. They made a huge difference during a rough time in our life.
 

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Had the same issue! Bought an after market fuel filter and head which worked fine other that the prime pump was sticky. Push it down and had to wait for it to come back up. Then I started losing prime about 3 months after installing the new one. Fought with it for a week in -30 wether then discovered fuel leaking from around the sensor on top! Luckily had the old head still so put it back on and it has worked but it lets air in when pulling hard uphill. So now I have ordered a new filter head with lift pump to cure the issue! Hoping it works!
 

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Hey all,

I am chasing a rabbit on this one and need some help. Here's some important points.
  • 2002 LB7 with 270k miles.
  • I rebuilt the filter head about 4 years ago when I was seeing the same issue and replaced both short fuel lines.
Using the GM manual for troubleshooting, I don't have any visible signs of diesel leak anywhere. I did a leak-down test on the fuel and sure enough after pumping up the system to 10 psi the pressure slowly dropped to nothing in about 10 minutes. Next, I put a clear 1/2" tube in place of the line between the filter head inlet and the FICM and purged the system. Once I started the engine, I did see a small bubble of air a few times but then nothing. I shut down the engine and after waiting approx. 10 minutes went through the purge/restart process again and saw one little bubble in 2 minutes. I'm thinking about not chasing that rabbit but instead looking at the filter outlet to injector pump to return line system components. Any words of wisdom would be appreciated.
A few years ago I had a real smoking problem with my 2003 LB7 about 400 Thousand K. I had replaced the injectors around 60 Kilometers ago. I learned that generation of LB7 had a real problem with the injectors. (after I had purchased it of course). The garage I went to to have new injectors installed (on vacation in Southern California) suggested the best way to correct the deficiencies in the LB& fuel delivery system was to convert to a FASS (fuel air separator system) which filters the air out of the fuel thus saving the injectors and pushes the fuel rather than pulling the fuel to the engine. Check the system out online... worked for me 100,000K later, winter and summer. FASS Fuel System. Good Luck.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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I appreciate the insight.

More importantly-I am a Wounded Warrior contributor on a monthly basis; one of my values that will never diminish.
My hand found this in the closet this morning searching for something warm. Thanks for getting it for me :)
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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Discussion Starter · #13 ·
I have been so busy lately forgot to follow up on my repair.

I found no issues upstream so ended up replacing the filter head (kept the old one to rebuild) with one from XDP, new Racor filter and new short fuel lines. Had a day to test before heading to Barrett-Jackson Auction in Scottsdale, AZ.
 

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On my 06 lbz it was the filter head itself that developed a crack that you couldn't see. Replaced filter head and all was, is good right at 100k more. Been a few years but i think it was throwing a code for low fuel rail pressure.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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I have been so busy lately forgot to follow up on my repair.

I found no issues upstream so ended up replacing the filter head (kept the old one to rebuild) with one from XDP, new Racor filter and new short fuel lines. Had a day to test before heading to Barrett-Jackson Auction in Scottsdale, AZ.
So.... It worked,?
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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46 Posts
Discussion Starter · #16 ·
So.... It worked,?
Yes, this fixed my fuel problem and I made an 1,100 mile trip after this repair. Now I've got another issue after this weekend run to Arizona. P1093 code for #8 injector failure and diesel in my crankcase. I will start working on this after my Kiwanis Club meeting on Saturday. A great service club that gives back to communities all over the world.
 

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Yes, this fixed my fuel problem and I made an 1,100 mile trip after this repair. Now I've got another issue after this weekend run to Arizona. P1093 code for #8 injector failure and diesel in my crankcase. I will start working on this after my Kiwanis Club meeting on Saturday. A great service club that gives back to communities all over the world.
Neat... 72 years ago my brother and I lived at the Kiwanis Home in Edmonton, Alberta. Lived there for around 4 years in total. (The Kiwanis home was a home for children in need of care). The home operated for many years helped many families but was closed when the government decided it had to be operated under government control not the Kiwanis club of Edmonton. In my experience, Kiwanians operated under the radar quietly doing good work in the community.
 

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2002 GMC K2500HD Sierra with DuraMax/Allison drivetrain.
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Discussion Starter · #18 ·
Neat... 72 years ago my brother and I lived at the Kiwanis Home in Edmonton, Alberta. Lived there for around 4 years in total. (The Kiwanis home was a home for children in need of care). The home operated for many years helped many families but was closed when the government decided it had to be operated under government control not the Kiwanis club of Edmonton. In my experience, Kiwanians operated under the radar quietly doing good work in the community.
Thank you for sharing your inspiring story! I really appreciate hearing this and will be passing on your story at our meeting. My father passed away in 2020 and was a 50-year Kiwanian. He was my inspiration and best friend plus a car guy too!
 
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