Fuel loses prime???

[Classicfordguy]

Truck in my sig has started losing fuel prime. Used to happen after 3 days of sitting or one day sitting on a hill but now its happening after sitting overnight. It starts then sputters and shuts off. I then have to crank for a while to it gets fuel again.

Is this an air leak or maybe bad lift pump?

thanks,

-Rob

 

[jim_22]

Happened to me so I would bet on the lift pump. The ****** is that it can run for a long time like that while you trouble shoot in the wrong place. If that is the case, eventually the vacuum generated fuel filter light will come on indicating low fuel pressure at the IP. The way to check is to measure fuel pressure.

 

[hesutton]

Classic senario for a fuel/air leak. Any smell of diesel under the hood? Any wet return lines/caps on the injectors? You may need a new set of injector o-ring, return lines and caps.

You can test the lift pump. Take the core out of the schrader valve on the fuel filter head. Hook up a pressure guage to that valve and crank the engine. It should be 4-6 psi. For volume, you should get 1/3 of a pint minimum with 10 seconds of cranking.

Heath

 

[Classicfordguy]

Ok thanks for the tips. I would hope its not my return lines, replaced injectors, lines, caps and all that not too long ago but I'll double check them.

I have a fuel pressure tester so Ill check the LP. I have been smelling some diesel but haven't seen any drips. I did see one drip hanging off one of the LP lines.

-Rob