1988 Ford F250 no power to fuel pump
#1
02-22-2017, 07:30 PM
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1988 Ford F250 no power to fuel pump
Hey guys, just received a 1988 ford 4x4 with a 351 windsor with just over a 100,000 miles. very clean and not all hacked up, the previous owner which is a good friend of mine last drove it about 4 weeks ago with no issues then parked it until last Saturday when he went to try and start it but got nothing. he noticed it wasnt getting fuel so if starting fluid is sprayed into the intake she fires up no problem but just no fuel is being delivered, trusting his word and thinking it was something as simple as a bad relay i towed the truck on home and have been diving in.
first thing i did was replace the relay with part #913157 from my local auto parts store and double check that there actually was gas in the tank which there was but still no start. i got up underneath the truck and began pulling the fuel lines going to the in line pump on the frame. now both the in tank pumps have been replaced by the previous owner but the inline wasnt so i pulled the fuel line going to it and got a good flow of gas but nothing coming out the side heading to the engine so i figured bad pump, replaced that with a new unit and still no luck so i pulled out the volt meter and began checking. the yellow wire going into the relay gives me a constant 12v, i get 12v with the key on at the red wire but only 6-7 volts going into the brown one. i followed that back to the inertia switch and only got 6 volts there and followed that to the in line pump where i only got 7v and 9v while turning the engine over, not enough to run the pump.
today i was messing with it still and i noticed the buzzing sound coming from the dash no longer comes on, could be unrelated i have no idea?i tried turning it over again with the old relay just as a last ditch effort to see if i could fix it and now i have no power to the brown wire at all but still 12v to the yellow and red wires at the relay so im lost now. in 18 and this my only car, ive had a few before and am no stranger to electrical but i just cant figure this out.
Any help you guys could give would be beyond appreciated. thank you in advance!!!
first thing i did was replace the relay with part #913157 from my local auto parts store and double check that there actually was gas in the tank which there was but still no start. i got up underneath the truck and began pulling the fuel lines going to the in line pump on the frame. now both the in tank pumps have been replaced by the previous owner but the inline wasnt so i pulled the fuel line going to it and got a good flow of gas but nothing coming out the side heading to the engine so i figured bad pump, replaced that with a new unit and still no luck so i pulled out the volt meter and began checking. the yellow wire going into the relay gives me a constant 12v, i get 12v with the key on at the red wire but only 6-7 volts going into the brown one. i followed that back to the inertia switch and only got 6 volts there and followed that to the in line pump where i only got 7v and 9v while turning the engine over, not enough to run the pump.
today i was messing with it still and i noticed the buzzing sound coming from the dash no longer comes on, could be unrelated i have no idea?i tried turning it over again with the old relay just as a last ditch effort to see if i could fix it and now i have no power to the brown wire at all but still 12v to the yellow and red wires at the relay so im lost now. in 18 and this my only car, ive had a few before and am no stranger to electrical but i just cant figure this out.
Any help you guys could give would be beyond appreciated. thank you in advance!!!
#2
02-23-2017, 08:17 AM
Hotshot
The fuel pump relay is energized for 1-2 seconds when cycling the key from Off to Run. This is controlled by the computer (PCM). When cranking the engine (key in the Start position) the PIP signal from the distributor triggers the computer to pull in the fuel pump relay.
The 6-9VDC you are measuring is an open circuit because the fuel pump relay is no longer energized. The best way to troubleshoot your issue is placing a jumper between Pins 2 & 6 on the diagnostic link then turning the key to the Run position. Use an incandescent test lamp to check for voltage along the circuit. A high impedance DVM will lie to you.
Based on your statement "i only got 7v and 9v while turning the engine over" I suspect an issue with the PIP signal operation. But I highly advise you to do a few simple tests before throwing parts at the problem.
The 6-9VDC you are measuring is an open circuit because the fuel pump relay is no longer energized. The best way to troubleshoot your issue is placing a jumper between Pins 2 & 6 on the diagnostic link then turning the key to the Run position. Use an incandescent test lamp to check for voltage along the circuit. A high impedance DVM will lie to you.
Based on your statement "i only got 7v and 9v while turning the engine over" I suspect an issue with the PIP signal operation. But I highly advise you to do a few simple tests before throwing parts at the problem.
#3
02-24-2017, 04:44 AM
Check the "bump switch" which trips if the vehicle is hit or hits something. Check the owner's manual for exact location, but usually on the left floorboard area- There is a little tit which pops up when it actuates, and this deactivates the fuel system... Just press it back down... I think the proper name is the "Emergency Fuel Shutoff" or something...
Scott
Scott
#4
02-24-2017, 07:20 AM
Hotshot
Check the "bump switch" which trips if the vehicle is hit or hits something. Check the owner's manual for exact location, but usually on the left floorboard area- There is a little tit which pops up when it actuates, and this deactivates the fuel system... Just press it back down... I think the proper name is the "Emergency Fuel Shutoff" or something...
Scott
Scott
On the other hand the OP needs to jumper Pins 2 & 6 on the diagnostic port to keep the fuel pump relay energized so they can verify power is getting through that inertia switch.
#5
02-24-2017, 07:33 AM
Scott you are referring to the inertia switch. The OP already stated the voltage is "6-7VDC" before that component. Whether that switch is closed or open would not affect upstream readings.
On the other hand the OP needs to jumper Pins 2 & 6 on the diagnostic port to keep the fuel pump relay energized so they can verify power is getting through that inertia switch.
On the other hand the OP needs to jumper Pins 2 & 6 on the diagnostic port to keep the fuel pump relay energized so they can verify power is getting through that inertia switch.
Scott
#6
03-05-2017, 10:54 AM
Hey guys, just received a 1988 ford 4x4 with a 351 windsor with just over a 100,000 miles. very clean and not all hacked up, the previous owner which is a good friend of mine last drove it about 4 weeks ago with no issues then parked it until last Saturday when he went to try and start it but got nothing. he noticed it wasnt getting fuel so if starting fluid is sprayed into the intake she fires up no problem but just no fuel is being delivered, trusting his word and thinking it was something as simple as a bad relay i towed the truck on home and have been diving in.
first thing i did was replace the relay with part #913157 from my local auto parts store and double check that there actually was gas in the tank which there was but still no start. i got up underneath the truck and began pulling the fuel lines going to the in line pump on the frame. now both the in tank pumps have been replaced by the previous owner but the inline wasnt so i pulled the fuel line going to it and got a good flow of gas but nothing coming out the side heading to the engine so i figured bad pump, replaced that with a new unit and still no luck so i pulled out the volt meter and began checking. the yellow wire going into the relay gives me a constant 12v, i get 12v with the key on at the red wire but only 6-7 volts going into the brown one. i followed that back to the inertia switch and only got 6 volts there and followed that to the in line pump where i only got 7v and 9v while turning the engine over, not enough to run the pump.
today i was messing with it still and i noticed the buzzing sound coming from the dash no longer comes on, could be unrelated i have no idea?i tried turning it over again with the old relay just as a last ditch effort to see if i could fix it and now i have no power to the brown wire at all but still 12v to the yellow and red wires at the relay so im lost now. in 18 and this my only car, ive had a few before and am no stranger to electrical but i just cant figure this out.
Any help you guys could give would be beyond appreciated. thank you in advance!!!
first thing i did was replace the relay with part #913157 from my local auto parts store and double check that there actually was gas in the tank which there was but still no start. i got up underneath the truck and began pulling the fuel lines going to the in line pump on the frame. now both the in tank pumps have been replaced by the previous owner but the inline wasnt so i pulled the fuel line going to it and got a good flow of gas but nothing coming out the side heading to the engine so i figured bad pump, replaced that with a new unit and still no luck so i pulled out the volt meter and began checking. the yellow wire going into the relay gives me a constant 12v, i get 12v with the key on at the red wire but only 6-7 volts going into the brown one. i followed that back to the inertia switch and only got 6 volts there and followed that to the in line pump where i only got 7v and 9v while turning the engine over, not enough to run the pump.
today i was messing with it still and i noticed the buzzing sound coming from the dash no longer comes on, could be unrelated i have no idea?i tried turning it over again with the old relay just as a last ditch effort to see if i could fix it and now i have no power to the brown wire at all but still 12v to the yellow and red wires at the relay so im lost now. in 18 and this my only car, ive had a few before and am no stranger to electrical but i just cant figure this out.
Any help you guys could give would be beyond appreciated. thank you in advance!!!
#7
03-08-2017, 09:12 PM
I had a relay issue with my truck, 1990 f350. With some knowledgeable help (a neighbor) I was able to bypass the fuel pump relay, and then test the fuel rail had pressure...but still wouldn't start. Then checked and the plugs were still arcing, turned out it was another relay right next to the FP relay, I am actually not sure which one, but when I jumped that one as well she fired right up. Not sure if that helps but felt lucky to realize it was BOTH relays. Water had got into them. Good luck!
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