Hello, I am hoping I can get some help as I've been scratching my head trying to avoid throwing parts at it. I recently bought a 04 LB7 and decided to change the fluids and filters to get fresh fluids everywhere. One of the things I replaced was the fuel filter. I followed the procedure as far as bleeding the system after the install and the truck fired up no issues. The next day however, after I drove the truck to class, I went to start the truck and it fired up then died about 10 seconds later. Thinking the fuel system had not been purged completely I rebled the fuel system and went about my day thinking the problem had been fixed. However the next day I had the same issue and decided to start doing some research. Found that the filter head has a tendency to leak, so bought a rebuild kit from napa and rebuilt the head and replaced the bleeder screw. The truck does have an adapter on it to run the cat fuel filter, I forgot to take note of the brand when I took the housing off to rebuild it. The same day I had a prime issue once again, so I decided to pressurize the fuel tank and look for leaks. I had the tank under about 10psi for a little over 20 min and could not find any evidence of any leaks. This has been going on for a week or so and I have been able to duplicate the issue without fail by driving the truck until everything is up to temperature and then letting it sit for at least an hour. If I do this the truck will not stay running and will loose it's prime. If the truck sits overnight and cools completely or does not sit for more than an hour once warmed up it will start and run fine.
I am leaning towards replacing the entire filter head and potentially running the factory fuel filter rather than the cat adapter. To me, it seems that the vacuum leak must be between the filter housing and the cp3 because the bleeder screw does not need to be cracked to reprime the truck, and it only takes 5-10 pumps for the primer to get hard. I do not know if this logic tracks though. Sorry for the long post, wanted to show what I have done before immediately asking for help. Is there anything else I should check or do before replacing the filter housing? The loosing prime when hot leads me to believe the housing is cracked, and only once the metal warms up and expand does it begin to let air in but it seems odd this issue starting happening right after I changed the fuel filter and having it not be user error, but after having bled the system multiple times, and reinstalling the filter, I am confident that was done correctly. Any input would be greatly appreciated.
I am leaning towards replacing the entire filter head and potentially running the factory fuel filter rather than the cat adapter. To me, it seems that the vacuum leak must be between the filter housing and the cp3 because the bleeder screw does not need to be cracked to reprime the truck, and it only takes 5-10 pumps for the primer to get hard. I do not know if this logic tracks though. Sorry for the long post, wanted to show what I have done before immediately asking for help. Is there anything else I should check or do before replacing the filter housing? The loosing prime when hot leads me to believe the housing is cracked, and only once the metal warms up and expand does it begin to let air in but it seems odd this issue starting happening right after I changed the fuel filter and having it not be user error, but after having bled the system multiple times, and reinstalling the filter, I am confident that was done correctly. Any input would be greatly appreciated.
