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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Chevy
Satisfied Customers: 44516
Experience:  16 years of experience
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03 lb7 duramax losing prime if fuel is under half a tank.

Customer Question

03 lb7 duramax losing prime if fuel is under half a tank. Over half a tank starts with no issue. Under half a tank you have to prime before you can start or it just dies after a few seconds. Once started it runs good till you Shut it off again. Has cat filter adapter.
Submitted: 3 months ago.
Category: Chevy
Expert:  Chris (aka-Moose) replied 3 months ago.

Welcome, I'm Chris (aka Moose) I prefer to work when others don't, I am here around lunch and after dinner till after midnight.working after noon till just after midnight.

  • Sorry no one has helped yet.
  • Yes, you have been charged already.
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  • I will be online a couple more hours after this post.
  • This is not an answer to your question, just an inquiry if your still needing/wanting help. Because I believe I can help.
Customer: replied 3 months ago.
Need an answer to my question from Chevy tech
Expert:  Chris (aka-Moose) replied 3 months ago.

Is the fuel filter housing empty prior to you priming it?

Customer: replied 3 months ago.
No. It still has fuel there. Takes about 12 pumps to pump it back to ready to start. Only after half a tank though. I rebuilt fuel filter head recently. It didn't do it till after I put new filter a new filter on. Took it back off and rechecked seals and everything looked good. No visible leaks.
Expert:  Chris (aka-Moose) replied 3 months ago.

This new filter system you installed is it mounted in the same place or somewhere else on the vehicle?

Customer: replied 3 months ago.
It's just a cat filter adapter. Same one everyone uses. Mounts in same spot. Adapter has been working great till last filter change
Expert:  Chris (aka-Moose) replied 3 months ago.

Thanks, ***** ***** the one way valve in your filter is bad. When you shut the engine off the fuel supply line is pulling a vacuum on the supply line at half or below half tank and drawing fuel out of the line from the injector pump and filter housing.

This is my 1st answer, but does not have to be my only answer. You the website and myself expect you to have a great experience with my help. Please let me know if you are pleased by selecting a star rating above or by replying and saying your pleased. Not rating or rating 1-2 stars does not benefit you nor me in any way. Follow up and reply as often and when needed, there is no extra charge to do so.

Thanks Moose.

Customer: replied 3 months ago.
There's a valve inside the filter ?
Expert:  Chris (aka-Moose) replied 3 months ago.

The fuel filter housing has a valve to prevent fuel from gravity flowing back to the tank.

Customer: replied 3 months ago.
When you put the cat adapter on you take the check ball valve out. Been running like that for couple years
Expert:  Chris (aka-Moose) replied 3 months ago.

I am sorry but I'm seeing no progress in your and my communications. I am going to opt out and let you wait on the list for another to help.

Best of luck.