1988 F150 Not running need advice
10-21-2013, 09:10 PM
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1988 F150 Not running need advice
So ive gone through a lot to get this truck running to no avail. it's a 1988 f150 with the 4.9 six. I bought it from a friend of mine who gave up on it.
-had low fuel pressure to begin with
-replaced in tank pump
-replaced high pressure pump
-replaced fuel filter
That fixed the pressure problems, has 55 psi at rail.
Still not running, Has spark, fuel pressure and compression.
-took out the injectors and tested them they are fine (good flow)
-tried another known good computer (no change)
-discovered that the fuel pumps are hard wired to the igintion so the relay is non functional. (truck did run like this before, so shouldnt be a problem)
-discovered a rigged jumper wire that connects the Inertia switch to the fuse box (looks to still function)
So it still wont run. I can pour gas in the intake and it it will run fine till it runs out. I can just barely keep it going by pumping the Throttle as soon as I quit it dies.
So now im thinking the throttle position sensor? For some reason the injectors arent getting fuel to the cylinders. I cant test the sensor till I put the intake and everything back on. is there anything else I should check before I do? I dont want to take that intake off again.
I am also thinking maybe the rigged inertia switch may have something to do with it?
Thanks in advance
-had low fuel pressure to begin with
-replaced in tank pump
-replaced high pressure pump
-replaced fuel filter
That fixed the pressure problems, has 55 psi at rail.
Still not running, Has spark, fuel pressure and compression.
-took out the injectors and tested them they are fine (good flow)
-tried another known good computer (no change)
-discovered that the fuel pumps are hard wired to the igintion so the relay is non functional. (truck did run like this before, so shouldnt be a problem)
-discovered a rigged jumper wire that connects the Inertia switch to the fuse box (looks to still function)
So it still wont run. I can pour gas in the intake and it it will run fine till it runs out. I can just barely keep it going by pumping the Throttle as soon as I quit it dies.
So now im thinking the throttle position sensor? For some reason the injectors arent getting fuel to the cylinders. I cant test the sensor till I put the intake and everything back on. is there anything else I should check before I do? I dont want to take that intake off again.
I am also thinking maybe the rigged inertia switch may have something to do with it?
Thanks in advance
10-24-2013, 09:50 PM
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Did you check the cut off swith located on passenger side kick panel? This is the swith that is supposed to kill the fuel in the event of a rollover and can sometimes go bad.....I had an 88' F150
10-25-2013, 12:26 AM
#3
Auggie the cut off switch is the inertia switch.
if the pump runs the wiring should be ok for the inertia switch. if im not mistaken, the fuel pump power wires go from the relay through the inertia switch then to the pump.
what it sounds like to me is that the injectors are not working. since you can pour fuel and it runs. see if you can get a noid light ( borrow or get from harborfreight) hook it up to injector wiring harness and see if it flashes. check them all. you might have a wiring issue.
also check your grounds around the radiator area. they have been know to go bad.
if the pump runs the wiring should be ok for the inertia switch. if im not mistaken, the fuel pump power wires go from the relay through the inertia switch then to the pump.
what it sounds like to me is that the injectors are not working. since you can pour fuel and it runs. see if you can get a noid light ( borrow or get from harborfreight) hook it up to injector wiring harness and see if it flashes. check them all. you might have a wiring issue.
also check your grounds around the radiator area. they have been know to go bad.