Disconnected the main line to the fuel rail, cranked, and no fuel came out. Cranked for a good 30-40 seconds. Checked inertia switch, not tripped. Have ~11v going to the switch. Unplugged it and tested continuity, and that was good. Tried testing what i think is the fuel pump harness (middle of the tank in the rear, 6 pin connector?) But wasnt getting power at the pins. Read that i was only supposed to have power at the inertia switch for 2-3 seconds but it was constant, stayed constant until i turned key off. Is that an issue? Also, to the left of the gas tank (drivers side) what is the cylinder thing with a 2 wire harness hidden in the frame? Car in question is an 04 gt 5spd, 63k miles and has been sitting for a year. Had 1/4 tank, filled with new fuel amd octane booster and replaced filter. Was parked cause intake manifold disintigrated at the crossover. Im leaning towards the pump being bad, but id like to test and be sure. Also dont hear pump with key forward.
Fuel No Fuel Pressure At Fuel Rail
- Thread starter xking_conquerx
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TechnicallyMasterful
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- Oct 16, 2016
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Fuel pumps fail on those cars a bit. I say get a dead blow and hit the hell out of the gas tank while someone else cranks it over. If it fires up it's a bad pump. Is the car cranking and not starting or no crank no start. 11v seems weak for a battery.
Even at 63k miles? Im sure lettin it sit for a year didnt do any good. And yes it cranks but no start. Seems low cause i was constantly cranking it every minute or so. Probably took a good year off the starter with how much ive been cranking it. I could just replace the pump part, and not the whole assembly right?
wmburns
SN Certified Technician
Just wondering.......What model year Mustang are we dealing with?
Why is this important? Because it makes a difference in what is "normal" at the trunk IFS switch. But in general for the 1996+ model year there should be voltage at the IFS switch anytime the key is on.
Why is this important? Because it makes a difference in what is "normal" at the trunk IFS switch. But in general for the 1996+ model year there should be voltage at the IFS switch anytime the key is on.
TechnicallyMasterful
Member
- Oct 16, 2016
- 13
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I'm not sure about the electrical part as I have no wiring diagrams. Could just give the pump a generic power and ground with a 9v and some extra wires. As for vehicle mileage. Parts can fail at any time so I wouldn't dwell on mileage. I'm not sure about the pump parts. It's been a while since I replaced it on my old gt. I think I just bought the entire unit from pep boys.
wmburns
SN Certified Technician
For the 1999-2004 Model year the fuel pump on runs for 3-4 seconds at initial key on but there's MUST be +12 volts (battery voltage) at the trunk IFS switch anytime the key is on.
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wmburns
SN Certified Technician
Didn't say that. IF the voltage at the trunk IFS is 11 volts likely it will will work. Use your head and factor in what is going on with the car at the time. IF the battery voltage is 12 volts AND the trunk IFS is 9 volts, THEN likely there's a problem. On the other hand if the battery voltage is 11 volts and the trunk IFS is 10.5 volts then the wiring isn't likely a problem.
Finally if the voltage is 6 volts THEN likely there is a problem.
Here's where the model year is important as for example for the 98 model year with a two speed fuel pump relay, 6 volts at the IFS switch is likely OK.
Again. Use your head.
Alright just clarifying. Im not familiar with electric pumps, so wasnt sure if it needed 12v to kick on or if itd kick on with lower but not work as intended (ie. My truck needs 11.5v for the pcm to fire the injectors, anything lower and itll crank but never fire) ill double check my readings this afternoon and give the gas tank some persuasion and see if it starts. Like i said, just trying to get a without a doubt reasoning that the fuel pump is the issue and not something else, not a fan of part swapping to fix the issue.
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