Fuel Pump??
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Joined: Aug 2011
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From: Seaford VA
Fuel Pump??
I have 1987 f150 WITH A 5.0 EFI AND dual tanks. the truck has an intermittant starting problem. it will often just crank until it kills the battery. sometimes when it is running it will stall when put in gear. The fuel pressure reading showed it was on the low side of normal at idle and when revved up, however as soon as the engine is turned off the pressure drops very rapidly. I dont know what wld cause this pressure loss. the injectors have been checked and are not leaking. also the electric primer is working. any ideas where to look next?? I can answer most other questions as to what has been done so far.
Last edited by CowboyMike38; Aug 12, 2011 at 02:26 PM. Reason: added info
Freshman User
Joined: Jun 2011
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i just had a huge problem with my trucks fuel system. both pumps were working but were acting up and also the cross flow problem plagued me. also my truck was running rough like it had low fuel pressure and it smelled of gasoline and would die on me and was gradually becoming harder and harder to start. i finally just replaced the pump in one tank and use it exclusively and that fuel pump seemed to fix most my issues. the trucks starts great, idles wonderful and also doesnt hesitate after initial gear selection. I know its alot of work to replace the pump but it was worth it in my case
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
Sounds like you have a bad check valve in the HP fuel pump on the frame.
But you to check to see if the frame pump runs for one second when you turn on the key along with the selected in-tank pump.
Sorry for the bad information that was posted yesterday.
But you to check to see if the frame pump runs for one second when you turn on the key along with the selected in-tank pump.
Sorry for the bad information that was posted yesterday.
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Junior User
Joined: Aug 2009
Posts: 78
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From: Georgia
With it being a 1987 model, you should have a Dual Function Reservoir (DFR) mounted on the frame rail behind the high pressure fuel pump, not in-tank FDMs that were used on newer models.
As for low fuel pressure and losing fuel pressure after turning the truck off, I would look at replacing the fuel pressure regulator.
Here are the specs for checking the fuel pressure for you 1987:
Key On Engine Off -------- 35 - 45 psi
Key On Engine Running -------- 27-37 psi
Engine Running Vacuum Hose Disconnected From Pressure Regulator -------- 40 - 45 psi
Hope this helps!!
As for low fuel pressure and losing fuel pressure after turning the truck off, I would look at replacing the fuel pressure regulator.
Here are the specs for checking the fuel pressure for you 1987:
Key On Engine Off -------- 35 - 45 psi
Key On Engine Running -------- 27-37 psi
Engine Running Vacuum Hose Disconnected From Pressure Regulator -------- 40 - 45 psi
Hope this helps!!
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