Fuel Pump Problems

Discussion in 'SN95 4.6L Mustang Tech' started by power1, Nov 14, 2013.


  1. power1

    power1 New Member

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    Hello im new to this stuff but i need help please! My problem is with no fuel to the rails. last week my ac blower resistor was burning up i could smell it in my vents. I turn my ac off and drove home about 5 miles. I pulled out the resistor and it was fried. The I drove it for a couple of day with it out, i didnt try to turn on the ac fan at all. Then I went to autozone and bought one, installed it in the parking lot. I started up my car turn on my heat and started to drive. About 100 yards down the road the blower began to surge. I shut off the fan and was headed back to the store. Just then my car began to buck. driving 25 to 30 mph i went about 25 yard before it stalled and would not start. I turn the key off and back on and could not hear the pump priming. pop the hood pushed the fuel valve with my key and nothing. I figured my ccrm went back from the ac relay over heating and damaged the pump relay in the process.Pump fuse is good. I try to follow the wire diagram ccrm to kill switch to fpdm to pump. i have no one to help turn the key as im checking fpdm and cutoff switch in the trunk. in a rush a bought and ccrm for the dealer ($322) didnt work. Do wont to waste any more more that does not help the problem. i read at the fpdm pin 3 to 10 if it has more then 10.5v then its bad. I have 12.5v, i was looking for and explanation why this is so, before i by a fpdm. thanks for the help.... 2001 mustang gt (stock) "for now"
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  2. COramprat

    COramprat Drone Driver Mod Dude

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    I'd go back to looking at what caused the resistor to go bad. Sound like you have a wiring issue somewhere.
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  3. power1

    power1 New Member

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    thanks for responding coramprat. That would be my first thought, too. But when i pull it out its was obviously corroded and one of the terminals was broke at the bottom and the spring was pushing down just hard enough too still barely make contact instead of making an air gap. I live in florida not close enough to the beach for salt spray but i think the humidity did it in plus about 150k miles of use. My car ran fine for a day or so while the resistor was out. But immediately after putting the new one in, it was almost like the a/c relay was now drawing amps again after being overheated and then it heated up the circuit board more, effecting my fuel pump relay. That's why i change the constant control relay module. I dont believe the it needs to be programed. But if so I surly didnt do it. Thanks again for the help
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  4. wmburns

    wmburns SN Certified Technician

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    IMO this is an example of what may happen if a diagnostic tree is entered without following all of the steps that proceed. The quoted FPDM test is totally useless unless the tests are followed in order.

    IMO2, in general a fuel pump will fail 10-20 times more frequently than a FPDM. However, often a good FPDM is replaced first. Why? Because it's easier to swap a FPDM than a fuel pump.

    I have always been a test first and then make your best guess before replacing parts.

    Always confirm +12 volts at the trunk IFS switch with the key on. IF there isn't any voltage, then the problem is upstream towards the CCRM, fuse, ignition switch, ground, or wiring.

    IF there is voltage at the IFS, then y suggestion is to remove the FPDM and inject 12 volts on FPDM #5 and #10. THEN listen for the fuel pump to run.

    IF the fuel pump doesn't run, then the fuel pump has to be bad (assuming the tests have been done correctly).

    IF the fuel pump does run, then likely the FPDM is bad.

    IMO3, following a methodical approach greatly improves your chances of fixing it right with a minimum of "part swapping".

    IMO4, the failed blower resister has nothing to do with the current problem.
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  5. power1

    power1 New Member

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    problem solved, Thank you very much wmburns and coramprat for all the help. I have to admit I broke down and went to the dealer. Bad Fpdm. I went ahead and had them change it out, way over priced, but the mech need to make a living, too. When I picked it up got to thinking about the posts i received. So I brought the old ccrm in, in hope that i would be able to send the new one back and maybe put the $322 towards the bill. I asked first and he said that would be fine. Well to his credit not in anyway mine. He took it from me and flip it over and said it was bad. A small little black spot on the back where the bottom meets the lid , so he took it over and drill out the rivets popped the top off and it look like a bomb went off inside. The a/c relay was toast the plastic top was melted off. He told me the short must have when back to the fpdm and grounded out the terminal. idk? It didnt smell to bad and i never even saw the burn mark. But at the end of it all i'm up and running. ccrm, fpdm, and about $700 later. I hope this help anyone else out. A thanks again for all the tips.
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