Help diagnose crank but no start condition....Fuel Pump or FPDM ?

Discussion in 'SN95 4.6L Mustang Tech' started by Quadgod, Jan 12, 2012.


  1. Quadgod

    Quadgod Member

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    Hi all......I have a 2001 Mustang GT that has been sitting for a long time....roughly a year. I generally try to start it about once a month & let it run for a while or take it out for a drive (I work a lot). I've been reading through these forums recently & there definatley seems to be a correlation with mustangs that sit for a while devleloping fuel / elect. system problems. As expected, the battery went dead & that's when the problem seemed to start. A new battery was recently installed. The car started & ran fine for 15 minutes. I turned it off & it struggled to start a second time. I was able to pedal it a bit to start but it died out. Fast forward a bit....All fuses checked ok. I hear the CCRM click when the key is turned on but the fuel pump does not run. I've tested for power at both the inertia switch plug & FPDM plug. I get the same reading of 11.6v at both locations. I read that if the reading at the FPDM is over 10.5v then it needs to be replaced. Does anyone know why this ? What more can I do to diagnose whether it's a bad fuel pump vs. driver module ? I'm stuck at the moment & would rathed not replace parts that are not necessary. Once repaired, I'd really like to know why my problem seems to parallel other forum members who have had similiar issues with cars that have sat unused for a while. Any feedback would be greatly appreciated. Thanks.
  2. bbayne35

    bbayne35 Member

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    I am going through something similar, although my car had not been sitting. The woltage going in to the FPDM should be the same as what goes in to the inertia switch, ~12V. I believe that the voltage going from the FPDM to the fuel pump will vary between 0V and 12V while the engine is running.

    My suggestion is for you to manually power the fuel pump with a battery charger or by jumpering the connector going to the FPDM while checking the current draw of the fuel pump. If the fuel pump runs and the amps are normal (around 7 amps I believe), then I would think the FPDM needs replacing.

    THAT being said, I was not hearing my fuel pump at every key on. When I powered my fuel pump manually, it ran fine with a normal current draw. So, I replaced the FPDM. I was able to start the car, but the first time I drove it, the fuel pressure steadily dropped, and the car stalled and would not start. So, I will be replacing the fuel pump this weekend. My conclusion is that my fuel pump is starting to fail and is working intermittently. Maybe you are having a similar issue.

    Post your results!
  3. bigbird04

    bigbird04 Active Member

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    Check and make sure you are getting power to your fuel pump. Check for voltage at the wire harness connector at the fuel pump. Have a friend turn the key to on while you check for voltage on the conector that comes from the inertia switch to the fuel pump. It's easy to get to right behind the bumper. If you have power going to the pump. But can't hear the pump priming with key on it's the pump. Had to do this a year ago to mine ( replace fuel pump ) hope this helps diagnose your problem.
  4. wmburns

    wmburns SN Certified Technician

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    +1 on above. Once power has been confirmed to the IFS switch, this proves the circuit upstream from the IFS.

    There is a round connector (C420) located near the center rear bumper area very close to the gas tank. Split C240 and inject 12 volts to the RD/BK and BN/PK wires. This will power the fuel pump directly.

    If the pump does not run, use a rubber hammer and hit the center of the gas tank. This may make the pump run. Regardless, the fuel pump is bad.

    If the fuel pump does run, then check the trunk ground. If good, then focus on a bad FPDM or bad PCM.
  5. bbayne35

    bbayne35 Member

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    wmburns, where is the trunk ground you are referring to? Is it the one next to the FPDM?
  6. Quadgod

    Quadgod Member

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    First off....thanks everyone for taking the time to reply. The diagnosis is a bad fuel pump. The replacement OEM Motorcraft part # I've come up with is PFS-170. It's for a complete module assy & runs in the $300.00 range online. The dealer wants over $500.00. Is it true that a replacement Motorcraft electric pump only is not available ? I see some aftermarket options for just a pump only for less than $100.00 but would prefer to stay OEM. I've seen some people recommend a Focus SVT pump. Would this be a wise choice ? If so, could someome please provide me with the part # ? Thanks.
  7. bbayne35

    bbayne35 Member

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    It looks like the OEM part number for your car is 9H307 which is the same one I just installed in my 2000 GT. I am not sure how that differs from the Motorcraft part (if at all) aside from the fact that the 9H307 should cost a little less (about $480) from the dealer.

    Out of curiousity, how did you conclude that the fuel pump was bad? Did it not run when you powered it directly?
  8. Quadgod

    Quadgod Member

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    I used a battery pack to supply 12v to fuel pump harness connector RD/BK & BN/PK wire terminals per the posts above. I'm planning to order the SVT module PFS-204 & use just the pump only. Does anyone know if there are any modifications required for the proper install or does the PCM require tuning to work properly ? Also, does the SVT assy. come with a pump strainer bag that can be used in place of the stock factory one ?
  9. Quadgod

    Quadgod Member

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    Ok....now I'm frustarted. I replaced the fuel pump with the Focus SVT pump. I turned the ign. on , heard the pump prime & the car started right up. I let it run for about 20 minutes & it seemed to run normal. I turned it off & let sit for about an hour. I started it up again & was running like it had a miss. If I put it in drive (auto trans.) the rpm's were low at about 500 rpm's. Rpm's are normally around 700 in drive. I could hear the fuel pump running but it seemed to change tone intermittently. After a few minutes, I shut it down. When I started it up again the engine sputtered to a stall after a few seconds. It now stalls after starting & running for a few seconds. The fuel pump primes each time the key is turned on. Does it sound like the fuel pump driver module could be bad & not sending proper variable voltage? When tested during troubleshooting, the voltage was 11.6. I've seen it written that the FPDm should be replaced if the voltage is over 10.6. Please help !
  10. wmburns

    wmburns SN Certified Technician

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    First, it's NORMAL for the car to run poorly after a battery disconnect. The low idle could be caused by something as simple as not allowing enough time for the PCM to re-learn new idle trim values.

    Next. Never replace the FPDM until the FRPS and all of the circuits have been verified. DOUBLE check that the intake vacuum reference line is connected and leak free.

    Regarding the post to replace the FPDM if the voltage is over 10.5 volt. I have seen this same bad reference in other places. Please note that the decision/trouble shooting tree in the Ford service manual has several steps before this pinpoint test. The result of the tests DEPENDS upon the PREVIOUS tests being performed IN ORDER. So unless you have perform all of the proceeding pinpoint tests in order, you may be finding yourself replacing a good FPDM.

    Finally, there is a limit to how much larger of a fuel pump can be installed without a tune. There is a table in the PCM that defines what duty cycle to call for for a given fuel volume. A larger than factory pump will result in excessive fuel being delivered and a chronic rich condition. If the pump is too large, it may rupture the membrane in the FRPS.
  11. Quadgod

    Quadgod Member

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    Thanks for the reply Burns. It looks like you're the expert on here for fuel systems & just the guy whose expertise I need to help me save my sanity. I never had a problem with this car until it sat too long & the battery went dead. Was it a mistake to install an SVT focus pump instead of a stock module ? I was told it's plug & play. What diagnostic test should be performed next ?
  12. mikevm78

    mikevm78 Member

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    Gonna sound crazy but how old is your alternator? The 2V alt can have diode failure which will cause it to act like the cam position sensor is bad resulting in hard starts and dying after starting. My alt was still semi charging the car but when taken off for testing it FAILED.

    Just a thought.
  13. evolucion311

    evolucion311 Member

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    Can someone please explain to us how disconnecting the harness from the FPDM and testing the appropriate pins and getting a greater than 10.5v reading means the FPDM needs to be replaced? I'm trying to wrap my head around the logic of it.
  14. Quadgod

    Quadgod Member

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    Mike....thanks for the reply. I checked the alternator & output tested good so it's been ruled out. @ evolucion......I too would like to hear an educated response to your question. If I understand it correctly, the FPDM acts as a voltage regulator by supplying variable voltage to the fuel pump. I suppose if the voltage output is too high then the pump will allow too much volume. My engine is flooding with fuel. The engine will now start but run like crap while blowing thick smoke. Unless I'm missing something, I think installing the Focus SVT pump was a mistake. Although no CEL comes on, I'm getting 2 codes.....P1000 - ODP readiness incomplete & P0190 - Fuel rail pressure sensor. I'd really like to hear some feedback on the SVT pump before I drop the tank again.
  15. Quadgod

    Quadgod Member

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    Anyone else care to chime in ?
  16. mikevm78

    mikevm78 Member

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    FWIW my alt also outputed ok in the car running, it failed when taken to the parts store tester.

    Also I had a similar issu with the FRPS code. Gonna sound dumb but how much gas is in your tank when the symptoms occur?

    When i isntalled the Termi hat in my GT i ran into fuel rail preseure sensor issues, what it wound up being was two small pinhole leaks in the the fuel lines on the pump. When the tank was full, no problems. When the tank got lower to the point of the holes it tripped the sensor. Kinda like when you break your mcdonalds straw and once you get to that point you suck air only in the tank the fuel is being sprayed back in the tank instead of the lines. Resulting in low pressure and tripping the FRPS.

    Just another thought. Hope ya figure it out!
  17. evolucion311

    evolucion311 Member

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    Well, I doubt that my problem and yours are similar but I recently had a P0193 code and chronically high fuel pressure... or at least the computer thought it had high fuel pressure.

    I replaced the FRPS and the P0193 code was cured. I haven't read the fuel pressure PID to verify but 100 miles later the car runs very smoothly.

    +1 how much gas was in the tank? You said that the car has been sitting for a year. I think that's long enough for the gasoline to varnish and go stale. Wait. Stupid me.... you dropped the tank to install the SVT pump. I assume you put fresh gasoline back into the tank?

    I also haven't read anything in this thread about your fuel filter?

    Chasing these problems can be mind numbing and you have to start with the simple stuff first.
  18. Quadgod

    Quadgod Member

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    Thanks for the replies. The fuel filter was replaced at the same time to pump was replaced. I've determined that the engine is getting way too much fuel. Below is my latest correespondence with member wmburns in another forum.....

    wmburns:

    Have you confirmed that the intake vacuum reference line is connected and leak free?

    Have you confirmed there is no raw gas in the intake vacuum reference line?

    What is the fuel pressure as reported by the PCM? An ODB2 scanner will be one of the quickest way to narrow this down. If you don't have one yourself, try your local autoparts store.

    We need to know if the fuel pressure is constant or changing. Is it high or low? If so, by how much.

    If the PCM reported fuel pressure is greater than 40 PSI, this can explain why it runs rich. Now we need to determine if the fuel pressure sensor is faultly or the Fuel pump is too large for the tune.

    If the problem is in the tune, one would expect to see the fuel pressure "spike" as the fuel pump over powers the requirements of the motor.

    My reply:

    1. Vacuum reference line is connetced, leak free & no raw fuel present.
    2. I have a Diablosport Predator tuner & Actron scanner but don't know how to view fuel PSI with engine not running. But what I did tonight was connect a fuel pressure gauge to the fuel rail. First, I disconnected the intertia switch. Started engine to relieve fuel pressure. Surprisingly, the engine ran pretty much normal for almost a minute until fuel was depleted. I reconnected the inertia switch & connected fuel gauge. Turned key on but did not start. The fuel pump primed & the gauge read 45 psi. Started car & fuel gauge bounced between 80-100 psi so I shut it down immediately. This was done with the factory original tune installed (I've tried the diablosport & my customer tune previously but the enigne still ran poor) . I then disconnected the interia switch again & started the car. Surprisingly, the engine ran normal until the fuel supply was depleted. No doubt the engine is getting way to much fuel.
    3. I then scanned for trouble codes. Diablosport read no codes but the Actron read P0190 "fuel rail pressure sensor". The diablosport had previously recorded fault P0190 but it must have cleared when I tried disconnecting the battery yestreday. The battery disconnect had no positive effect.
    4. If the PCM fuel pressure readings are important, please advise how to retrieve the infomation so I can supply you with the data.
    5. Many people have reported installing SVT focus pumps with no problems. Did I make a mistake going this route ? Should I just install the factory OEM pump module?
  19. evolucion311

    evolucion311 Member

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    If you properly back probe the FRPS connector (while connected to the sensor) you can watch for a decrease in voltage to see the fuel pressure drop, or at least the signal the FRPS is sending dropping.

    Please note that my FRPS was sending false high readings. Replacing it fixed the problem but I'd want to rule everything else out before throwing $75 at it. Maybe a mechanical fuel pressure gauge hooked up at the rail to verify true pressure?

    When doing the pinout tests for FRPS I think you get to step 7 and if there aren't any apparent wiring problems the procedure calls for replacing the FRPS.
  20. Quadgod

    Quadgod Member

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    I tested the fuel rail pressure per above post. The engine is flooding with fuel. I'm trying to figure out why. Code P0190 appeard after the engine started to run poor. I'm trying to dtermine if there's an underlying problem that caused the code or is the SVT focus pump just going to work right in my car. Can you provide details on the pinout tests you mentioned above ?

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