Please help no power at fuel pump.

[ericarnold5010]

My 2004 mustang gt cranks and cranks and cranks with no sign of starting. Checked for power at fuel pump and there is none. I seem to have power at the inertia switch but when I check the fuel pump connector I get nothing from pins 6 and 7, is my inertia switch faulty? Am i testing at the wrong pins or doing something wrong? Any help would be much appreciated as I'm trying to get my car out to enjoy the summer

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[5.4MarkVIII]

can you by pass the inertia switch?

would be the easiest way to test

[Ponyryd]

I can’t say which pins are which, but when you look at the connector there will be two big wires, those are your pump wires, one will be ground and the other is the feed, you need to check which you are missing, usually what I do is backprobe the connector with t-pins and clip the test light across the two wires, key on it should light for a couple seconds, cranking it should light solid. If it does not you need to see what you’re missing, power or ground. If neither is there you’ll need some further diag, likely starting at the module in the trunk, I believe it’s in the drivers side, just around the back of the wheelwell.

Was the car running and then died, or is this a new issue from coming out of storage?

[ericarnold5010]

can you by pass the inertia switch?

would be the easiest way to testI'm actually not sure there's 8 pins in the connector at the fuel pump, this might be a dumb question but by looking at this connector view would you think I just need to hook up to 6 and 7 to jump the fuel pump or should I hook up to 5 6 7 and 8https://uploads.tapatalk-cdn.com/20180501/ece2c8378229a45776e215b81254faaf.jpg

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[ericarnold5010]

I can’t say which pins are which, but when you look at the connector there will be two big wires, those are your pump wires, one will be ground and the other is the feed, you need to check which you are missing, usually what I do is backprobe the connector with t-pins and clip the test light across the two wires, key on it should light for a couple seconds, cranking it should light solid. If it does not you need to see what you’re missing, power or ground. If neither is there you’ll need some further diag, likely starting at the module in the trunk, I believe it’s in the drivers side, just around the back of the wheelwell.

Was the car running and then died, or is this a new issue from coming out of storage?Thank you very much and this is a new issue since coming out of storage, and if I'm testing correctly then at this point I'm seeing that I have no power at the fuel pump but I do have power at the inertia switch, my wiring diagram looks like its saying the inertia switch is the last thing before the fuel pump, I don't think the inertia switch is a common failure on these cars but I'm not sure, maybe I just have a broken wire like a mouse or something got in while I had it stored?

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[ericarnold5010]

I can’t say which pins are which, but when you look at the connector there will be two big wires, those are your pump wires, one will be ground and the other is the feed, you need to check which you are missing, usually what I do is backprobe the connector with t-pins and clip the test light across the two wires, key on it should light for a couple seconds, cranking it should light solid. If it does not you need to see what you’re missing, power or ground. If neither is there you’ll need some further diag, likely starting at the module in the trunk, I believe it’s in the drivers side, just around the back of the wheelwell.

Was the car running and then died, or is this a new issue from coming out of storage?Thank you, unless I'm testing wrong I'm seeing that I have no power at fuel pump but I do have power at the inertia switch, I don't think the inertia switch is very likely to fail but I'm not sure, maybe I just have a broken wire or something? Yes this problem started while the car was in storage

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[ZR]

If it's not starting after being stored, super common for pump not to fire back up.
With car in neutral, parking brake on, take flat piece of 2x4 and give the tank a good repeated smack on the bottom of the tank closer to pass side while someone else cranks the engine over (must be done while engine being turned over).

[5.4MarkVIII]

8 is the signal for the gauge.
do as ponyryd said or if you want to test just the pump # 7 to ground and then #6 to 12 volt source. use to use a drill battery for quick easy issolation tests. battery will be marked + and - just use jumper leads to connect and see if the pump comes on


but try as Rick said first
he is the dr

[ericarnold5010]

If it's not starting after being stored, super common for pump not to fire back up.
With car in neutral, parking brake on, take flat piece of 2x4 and give the tank a good repeated smack on the bottom of the tank closer to pass side while someone else cranks the engine over (must be done while engine being turned over).I tried this, was sure it was gonna work cause it did last time but now I have no power at the pump and it seems I'm losing it either at the inertia switch or somewhere between that and the pump, but I feel like its unlikely for the switch to fail over the winter in a warm garage especially since it was never in the tripped position. Starting to wonder if a mouse got to it or something

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[ZR]

So pump had previously done it? Really should have replaced then as it was first sign of being on the way out. Pretty easy to follow / trace wires from the inertia switch across the rear panel n down to the tank junction. Could be a FPDM issue but yet to see one fail like that but anything is possible I guess. Pull tank connector, hook test light to fuel pump ground n power, crank it over. If no light, need to figure out if your missing power or ground.
I'm assuming you pushed the inertia switch regardless?

[ZR]

Inertia switch, are you positive you get power to both pins?
Unless being cranked over, only see power there for a couple of seconds.

[Laffs]

Is the system stock or modified? Verified no issue with PATS?

[ZR]

^ Great thought?

[Laffs]

Ya have had that PATS bite a few friends in the ass over a winter. Take the battery off in Fall and hook it back up in winter to find low and behold it's not recognizing one or both keys. Also seen the wiring under the dash fail which results in a full fail with any key.

If OP is running a heavily modded fuel system the FPDM checks would be my next call of port after verifying PATS. That aside there's always the rodent induced wiring damage angle.

[maxwell6]

Try dropping the back seat down and turn key to on position not start and see if you hear the fuel pumps prime. Just listen carefully i can deff hear mine. Verify that first.

[ericarnold5010]

So pump had previously done it? Really should have replaced then as it was first sign of being on the way out. Pretty easy to follow / trace wires from the inertia switch across the rear panel n down to the tank junction. Could be a FPDM issue but yet to see one fail like that but anything is possible I guess. Pull tank connector, hook test light to fuel pump ground n power, crank it over. If no light, need to figure out if your missing power or ground.
I'm assuming you pushed the inertia switch regardless?Sorry guys I was out of town for a couple days and haven't had time to post. Something weird happened today when I went to test at the inertia switch again I saw 10-11v at middle pin when cranking and a constant 1v at the other pin even without cranking, the weird part is when I went to test the second time the car started.. with the inertia switch unplugged. I now have 2 codes p1233 fpdm disabled or off line and p1237 fuel pump secondary circuit (fpdm) do you think the driver module is bad or did I set these codes because the car started up while the inertia switch was unplugged

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[ericarnold5010]

So pump had previously done it? Really should have replaced then as it was first sign of being on the way out. Pretty easy to follow / trace wires from the inertia switch across the rear panel n down to the tank junction. Could be a FPDM issue but yet to see one fail like that but anything is possible I guess. Pull tank connector, hook test light to fuel pump ground n power, crank it over. If no light, need to figure out if your missing power or ground.
I'm assuming you pushed the inertia switch regardless?Didn't consider this at first but is it possible the car just started from residual pressure in the lines since I haven't touched it in a few days? It has gotten much warmer recently

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[ericarnold5010]

Didn't consider this at first but is it possible the car just started from residual pressure in the lines since I haven't touched it in a few days? It has gotten much warmer recently

Sent from my SM-G950W using TapatalkOkay and now the car started and is running absolutely fine and I could not be more confused

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[ZR]

You'll need it to quit again to know for sure.

[ericarnold5010]

You'll need it to quit again to know for sure.That's what I thought, I'll keep checking for the next couple days and if it doesnt start I'll test it then. Thanks alot for your help I really appreciate it.

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[Laffs]

I'd lean towards bad FPDM driver issues but as stated will need another failure to confirm.

[ZR]

I'm hovering between it or CCRM (or wire between the two)