wont hold prime lly duramax

[MysteryMax]

so it first started with my truck not starting so I primed the hell out of it and it fired up came back later and nothing. So I ordered a new fuel filter head from the Dmax store because it was leaking put on the new one and it wont prime I have a lift pump Fass I was wondering if I could just connect the hoses with a coupler and delete the head to see if it will run or will I mess something up doing it. Any input would be helpful thanx in advance

[Mike D]

So if you have a lift pump (Fass) you should be able to just turn the key, hear the pump come on and open the bleeder screw on the filter head. The truck should push fuel out the filter head and stay primed.
However the Fass pump are known to have a fuel delivery issue if the truck has under 1/3 of a tank. Make sure you have fuel in the truck.
Also it is better to keep the under hood factory filter. Some people bypass it but it is not a good idea.


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[MysteryMax]

so I bypassed the fuel primer head and just ran it straight and it still wont start I can see fuel pushing from the lift pump and the tank is 3/4 full

[Mike D]

So what was the reason for adding the Fass? Have you been having starting or fuel rail issues previously?
Give us some history on the truck.

[MysteryMax]

no problems with the truck at all I just tuned it and the guy didi a lift pump install for 600 so I couldn't pass it up

[Mike D]

Ok so when did this no start problem begin?

[MysteryMax]

about a week ago went out to jump in it and go and it wouldn't start so I reprimed it and it started took off came back and came out later to leave again and it lost prime the filter head was leaking so I ordered a new one and put it on and its still losing prime and wont start

[Mike D]

Its normal for a filter head to leak a little bit after installing a lift pump.
However the no start is unusual. Do you have a way to see desired and actual fuel pressure? An Egde insight would be great for this.

[MysteryMax]

ive got a rail pressure gauge and it says 10 and that's where its always said its been. would a battery going bad not let it start?

[Mike D]

Fuel rail pressure during start or cranking is important to know. You will need a scan tool or Edge insight to view desired and actual fuel pressure. You should also scan the computer for DTC codes. That is going to be a big help. Once you have the stored DTC’s please post them here.

[MysteryMax]

ive checked there are no codes at all

[Mike D]

Ok so what is the ECM demanding for fuel pressure when your cranking the truck?

[MysteryMax]

my gauge says 10

[Mike D]

What gauge? Vacuum?
You need to know what the actual fuel rail pressure is during cranking while the motor is trying to fire. Can you get a scan tool or Edge insight or equivalent?

[NReckDMAX]

Was anything ever found with this? I am having the same issue with my dads 05. AirDog 165 lift pump, EFI, Stage 1 turbo, y-bridge, PPE race plug, and head gaskets just being done. I have the fuel filter head out of the system, but it won't hold prime and the actual fuel pressure will drop from 16k to like 4k psi while accelerating