Duramax Diesels Forum Truck of the Week
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Old 02-27-2013, 02:18 PM
seesaw seesaw is offline
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Join Date: Feb 2013
Engine: LB7
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Default Not getting fuel problem

Hi All, This is my first post here since up until recently and with exception of routine maintenance my 02 LB7 Dmax has been trouble free. However, my last fuel filter change has provoked some problems which I'm trying to develop a better understanding of so here it goes:

Planning to tow my 10,000 GVW enclosed trailer on over a 500 mile trip in the dead of winter I decided to change the fuel filter /water separator to lessen any fuel issues. I filled the new filter with fuel and primed it by hand until it came out the bleeder and then tightened the bleeder. Went to start the truck and it cranked without firing over. I can't get the hand primer firm when pumping by hand and believe I may have an air leak somewhere. If I prime very aggressively and then immediately run to start, I can usually get the truck started with excessive cranking and after starting it will run, drive, and tow well. My concern is that if I indeed have an air leak somewhere, it may be starving the injector pump pressure which may lead to further problems. Since the truck operates well after starting, I dismissed a faulty tank fuel pump but wondering if the injector pump vacuum is sufficient enough to take over in this case even though the tank fuel pump isn't working. I'm unsure if there are other issues which are coincidental to me changing the fuel filter but this has really been bugging me over the past week.

Helpful thoughts appreciated.
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Old 02-27-2013, 02:32 PM
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coldLBZ coldLBZ is offline
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If your Dmax is stock it does not have a fuel pump in the tank or anywhere under the truck. The injection pump (CP3) pulls fuel from the tank. If these problems started after you changed the fuel filter that is the first place I would look. Maybe pull the filter off again and check your O-rings and your WIF sensor. There may also be an issue with the filter head itself, that can happen as well. Also, I never pre fill the filter, I use the plunger and prime and bleed until there is straight fuel coming out of the bleed screw.
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Old 02-27-2013, 02:51 PM
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I installed a fuel pump sith new filters a few days ago and and couldnt get any fuel to the top side filter at the primer.Switched the water sep and the filter around as they use the same base and the truck primed then. (The water sep is before the filter normally and the filter comes after the pump and they use the same base)Started the truck no problem.Shut the truck back off and switched them back and the truck fired right up and kept on running.Not sure if something was blocking or what the deal was but it sure wouldn't start the way it was.
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You come off as a Timeshare Condo salesman on this site.

If you were helping folk with problems, or asking for input on your problems, it might be different, but from where I see, you are only a little different than the Russian spammers selling iPads that we delete.

Act like more of a human, and less like a spambot, and you'd probably catch less heat. This is "family", and it's our corner bar, and a group of guys with grease all over them leaning over fenders of somebodies truck that ain't making the right boost.

It's also one of few sites with more hardcore wrenches and racers than wannabees.

You're welcome to be a member here, and post about your build, but don't expect people to shower you with roses yet. That comes with seat time on the site, and on the track.
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Old 02-27-2013, 09:36 PM
seesaw seesaw is offline
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Quote:
Originally Posted by coldLBZ View Post
If your Dmax is stock it does not have a fuel pump in the tank or anywhere under the truck. The injection pump (CP3) pulls fuel from the tank. If these problems started after you changed the fuel filter that is the first place I would look. Maybe pull the filter off again and check your O-rings and your WIF sensor. There may also be an issue with the filter head itself, that can happen as well. Also, I never pre fill the filter, I use the plunger and prime and bleed until there is straight fuel coming out of the bleed screw.

Thanks for the info:
Upon pulling the new filter back off again I noticed the fuel/water separator appears it may have a small leak around the threads. It turns freely on the bottom filter threads and then comes to a point of resistance and then turns freely again before it hits the same area of resistance on each turn. This part has been swapped out to every fuel filter I've changed since purchasing the truck new in 02. My guess is that I may have got it out of round when loosening and installing it with channel lock pliers since my adjustable wrench won't open that big. I was going to try Teflon tape on the male thread side but figured it wouldn't be long before the fuel compromised the tape seal. Therefore, I ordered a new sensor at my local NAPA store but it will take 3-4 days to come in and hopeful that it will fix my problem.

I have an edge attitude juice tuner but other than that am not up to speed on other Dmax performance upgrades. I love the truck and understand the newer models are a lot more complicated and don't afford similar economy as my LB7. However, my kids are getting bigger and I need to sell and/or trade it for a crew cab within the next month or two. In the meantime, I'm trying to turn over as many stones as possible so the truck is 100% serviceable for the new owner.
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