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Discussion Starter · #1 ·
Hey guys new to the 12 valve world, I recently bought a 1994 12 valve bone stock truck as a winter project. When I purchased this truck it ran very poor and you could not rev the motor past 2500 RPM it would just stay there, when trying to move in and out of the garage it would stall. So I purchased a new fuel filter deleted the fuel heater, cleaned pre filter, installed new overflow valve and Larry b's fuel pressure gauge. Primed the fuel filter by adding air into the fuel tank. have fuel at the low pressure side of injection pump. Cracked 3 injector lines was unable to get fuel when cranking motor over. Did not get any pressure on my gauge what is the proper psi at cranking over 10? Well I have 0. My question is it the lift pump is bad why did it run and start before? Do you guys think its a lift pump or plugged sock in the tank?
 

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And go ahead and bleed all 6. It helps the process if you have a buddy. Call me OCD I don't care. And shoot some WD-40 into the turbo to see if it'll bust off long enough to get a drink.


Sent from AutoGuide.com App
 

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Discussion Starter · #6 ·
i have a fuel gauge which i ordered from larry b's i have zero fuel psi when cranking the motor. am i overlooking something? the fuel gauge is installed on top of the fuel filter. when i back off the banjo fitting on the fuel inlet to the injection pump yes i do have get a steady flow of fuel when pressing the primer. do you think its my lift pump or the sock in the tank?
 

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i have a fuel gauge which i ordered from larry b's i have zero fuel psi when cranking the motor. am i overlooking something? the fuel gauge is installed on top of the fuel filter. when i back off the banjo fitting on the fuel inlet to the injection pump yes i do have get a steady flow of fuel when pressing the primer. do you think its my lift pump or the sock in the tank?
Even with a lift pump that's not pumping on it's own, the truck will still start and run off of the fuel that you manually primed into the filter by hand with the primer button. It'll shut back down when it burns all of that. This is what my 12 valve was doing with a broken lift pump.
 

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Sounds like a bad lift pump. Local cummins dealer has em for IIRC around $75.
 

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Discussion Starter · #10 ·
thanks i priced around and the best price i was able to get local was 200 and up to 350. i live in canada nova scotia the nearest cummins dealer is 5 hours from me. i will be ordering the lift pump for 200 today hope to have it on monday. i could order one from larry b's for a 100 and have to pay 37 for shipping and 47 brokerage fees and the wait would be around 2 weeks.
 

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When I did some fuel work on my truck I had a difficult time getting it started. To check the pump I attached a clear hose to the pump inlet. I then filled it with clean fuel and made sure all air was out. I then tied it up high onto the hood. Pressing the primer button I could see the fuel going down the hose as I worked the primer button. I refilled hose and used starter. Again I could see the fuel going down the hose. As luck would have it, the engine started using this hose.

To attach the fuel feed to the pump, I added air pressure to the tank and held the pump inlet hose until I had a good fuel flow going. I then connected the hose as the fuel was flowing. Engine started right up, closed injector lines and let engine clear itself. All good to go.
 

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Discussion Starter · #12 ·
hey guys,

replaced lift pump today primed fuel system and the truck started up. turns out the lift pump was bad i now have 28 psi fuel pressure at 500 rpm, quick question ran the motor for 30 minutes seems to run well no problem starting when held to the floor in park the engine will not rev past 2500 rpms is this normal?
 
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