New to forum

[Vetman7]

I'm new to the forum and was hoping for some help. I've got a 2002 LB7 with a Kennedy MegaFilter. Recently I'm having hard start issues (long cranking times) and wondered if this is a simple fuel filter issue (15k on most recent Mega filter) or an injector or fuel pressure regulator issue. The injectors were replaced at 90,000 miles and I currently have 130,000. The Tech 2 shows no codes, and the only engine data parameter that looks unusual is a FPR pressure below recommended value in the service manual. Any guidance for me??



I appreciate any help you can give!

[More Power]

Welcome to the forums!

Is the long crank problem when cold or hot?

Jim

[Vetman7]

The problem started last week after a hot re-start and now even when cold, takes about 20 seconds of cranking to get it to run.

[rapidoxidationman]

My first thought is you've got an air leak somewhere in the vacuum portion of the fuel system (before the high pressure fuel pump) that is causing you to lose your prime. Cranking eventually sucks the fuel back up allowing you to start. Just after turning the truck off, maybe try GENTLY pressurizing the fuel system (a rag wrapped around an air chuck put into the filler hose) and see where fuel comes out of the lines. Might need two people: one to operate the air line and one to look for leaks. A couple of PSI would show it. When/if you find it, and fix it, the next step for prevention might be a lift pump to PUSH fuel to the fuel filter instead of sucking it there.

[bmoeller]

Had a similar problem on my LB7. Turned out to be leak at the primer pump. New seals, problem solved.

[Vetman7]

Thanks for the suggestions... hadn't even considered that I might have an air leak. I need to look into that lift pump.

[More Power]

The fuel tank caps should vent when there is in excess of 2-psi positive pressure and 1" vacuum present in the fuel tank. So.... a bad vent can produce excessive vacuum in the tank, which can produce an air leak in the fuel system that might not appear otherwise.

Try running for a day with the fuel tank loose to see if that changes anything.

[Kennedy]

Definitely need a lift pump.

Background info:
http://www.kennedydiesel.com/docs/Duramax%20lift%20pump.pdf

I would recommend the twin pump deluxe kit.