2003 GT fueul pump issue

[beerman1378]

I have an 03 GT and all of a sudden the car wouldn't start. Kept cranking...no fuel. I brought it to a guy I work with that is a mech and he said my fuel pump is more or less bad. I bought a new pump, he installed it and the car "ran", but "ran" ****ty. I pulled it back into his bay and noticed service engine soon light. he hooked it up to the OBD* and got a fuel/air code. Put the car up on the lift and the pump was going on then off when the car was started(sputtering/starving bad). Then the car wouldn't start. Then it would start bad. then all of a sudden it would start and be NORMAL! Then back and forth. He said the pump I bought must be defective because he checked the power near the tank and there was power with the test light. So, I buy the OEM Motorcraft pump and they install it, but I get a call back saying the relay is gone. The question I'm asking is does anybody think the relay could have been the initial problem and not the pump?? Am I getting soaked here or what?

 

[Modular2v]

if its kicking on and off...its probably the relay!

 

[trinity_gt]

Find another mechanic. There isn't a fuel pump "relay" in that car. The fuel pump is driven by a PCM-controlled module called the FPDM - fuel pump driver module. Because the system is returnless, the PCM adjusts fuel pressure by adjusting the power delivered to the fuel pump via the FPDM.

If the mechanic throwing parts and making guesses doesn't know the difference between a simple relay and the way the returnless GT fuel system operates, find a new one.

 

[beerman1378]

I think I screwed up when he told me quickly what it was. It is the FPDM! Its located under the plastic fenderwall. I think ford calls it the constant control module or something like that. I guess there is some sort of relay or something in that module. From my understanding, he bypassed that somehow and ran constant power to the pump and it ran fine. Sooooo I just ordered a new one and it will be in tomorrow. Lets hope this is the issue or I'm gonna turn into the anti-christ when I go to pick it up tomorrow!

**I just did some looking around and found that its actually the "CONSTANT CONTROL RELAY MODULE CCRM". Not the FPDM.**

 

[wmburns]

+1 on what trinity_gt said.

Would be nice to know what the DTC code was exactly.

What is the theft light doing? Remember for the 1999-2004 MY the theft system (PATS) disables the fuel injectors. Note, PATS will not affect a car once it starts.

The constant control relay module (CCRM) turns the power on to the fuel pump driver module (FPDM). The power passes through the trunk mounted IFS switch which is a great spot to test for power. The FPDM uses commands from the PCM to rapidly turn the power on/off to the pump to achieve the desired fuel pressure.

This could be anything from a bad fuel pressure sender, leaky fuel injector, dirty MAF, or a common misfire. Suggesting starting by getting the full DTC code and post.

Note: it is normal for a car to run poorly after the battery is disconnected. The PCM needs time to re-learn idle trim values.

 

[beerman1378]

OK..just got back from the mech. After a new pump and CCRM(multi relay module) the car starts if he bypasses something in the trunk. Sorry if I'm real vague....I'm definitely not knowledgeable on this issue. But once he takes that bypass off, the module kicks on and off therefore not getting fuel. Maybe a loose connection or ground?? Any ideas on where you'd start here? I just want to have this knowledge so the mech doesn't speak another language to me!

 

[wmburns]

FPDM

The "thing" in the trunk is the fuel pump driver module (FPDM). The FPDM takes a signal from the PCM which tells the FPDM know how much fuel is wanted.

The FPDM rapidly turns on/off the power to the fuel pump. By varying the duty cycle, the fuel pump will supply the correct amount of fuel. The greater the duty cycle, the greater the time the pump is on vs off and the greater the amount of fuel supplied to the motor.

The trick here is to determine where the problem is (PCM or FPDM). For example, if the PCM is not calling for fuel, then it would be expected for the FPDM to not power the Fuel Pump (RD/BK BN/PK).

If on the other hand, the PCM is calling for fuel (LB/OG WH/RD) and the FPRM is not powering the FP, then the FPDM is likely bad.

Sounds like your mechanic ASSUMED that no power to the FP means a bad CCRM. As stated previously, the CCRM powers the FPDM. The FPDM powers the FP. This is necessary because of the return-less fuel system.

Is it likely that the CCRM was good as well as the original fuel pump. Maybe find someone that understand how the Mustang's fuel system works.....

Not wanting to sound like a broken record, but the Theft system (PATS) if tripped will disable fuel. The PCM withholds the signal to the fuel injectors thus preventing the motor from getting any fuel.

 

[ToplessStang]

Can we start from square one ???? With everything reconnected correctly does the car start ????

 

[classic02]

ok been reading on this thread and I am having a fuel issue with my 02 mustang gt. I have replaced the fuel relay ( on the fuel rail) I also changed the fpdm, I have voltage coming out of the relay, switch, and fpdm but I have nothing going to the fuel pump.. I don't know what else it could be.

 

[wmburns]

Let's start over. To correctly trouble shoot a fuel pump problem we need to start by confirming IF the fuel pump runs for 3-5 seconds at every initial key on.

IF the fuel pump does not run, THEN confirm power in and out of Fuse F2.34, F2.2, and F2.8. Use a KNOWN good ground. Best to use a test light that will "load" the circuit. Also not a bad idea to confirm key on +12 volts to the trunk mounted IFS switch.

IF no power into F2.34, THEN suspect a bad ignition switch.

IF no power into fuse F2.2 and F2.8, THEN suspect a bad CCRM.

Here's some more information.

1999-2004 BJB CJB fuse panel layout:
https://www.allfordmustangs.com/for...r-swap-wont-fire-please-help.html#post2669271

1996+ Crank with no start check list
https://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html

 

[classic02]

thanks for the reply. I will check again the fuses, I have checked the one for fuel pump and pcm.. I have 12 volts at the switch in the trunk. and no the pump never turns on when I turn the key on. I get nothing.

 

[wmburns]

With verified key on voltage at the trunk IFS switch the "proves" that the CCRM is supply power to the FPDM. That leaves:

• A bad fuel pump.
• a bad FPDM
• a bad trunk ground
• wiring fault
• a bad PCM

If this were my car with the test results posted so far (key on 12 volts at IFS switch with no running fuel pump), I would be thinking bad fuel pump.

 

[classic02]

well with the fuel pump out of car and direct power to it, pump works. no votage reading out of pump connection.
and the ccrm isn't that inside the pcm?

 

[wmburns]

well with the fuel pump out of car and direct power to it, pump works. no votage reading out of pump connection.

Please go back to my previous reply regarding other "possibilities".

• A bad fuel pump.
• a bad FPDM
• a bad trunk ground
• Wiring fault
• a bad PCM

Note, it would be expected to not see a voltage out of the FPDM if the PCM is not calling for the fuel pump to run. Remember that the fuel pump only runs for 3-5 seconds at initial key on. The fuel pump will stay off until the PCM has detected that the motor is running. So if trying to confirm the voltage out of the FPDM it will be necessary to check while cycling the key.

Also not every VOM can correctly measure a pulsed duty cycle power source. To test the output of the FPDM, use a test light. This will "load" the circuit and the test light will "process" the duty cycle output of the FPDM and indicate the duty cycle in the relative brightness of the test light.

and the ccrm isn't that inside the pcm?

No! CCRM is located inside the right hand front passenger fender well. PCM is located in the passenger's right hand kick panel.

Other "far out" possibilities could be something like the incorrect fuel pump for this application has been used. It is a different fuel pump to use on a return system verses a return-less system.

FWIIW, I would still replace the fuel pump now that the gas tank is down. This goes double if the car is high mileage.

 

[classic02]

the car only has 78000 and also we has car running with what gas that was in the rails, system, had fuel filter off and we still had no gas coming out of the tank. Through the fuel pump. I will check wires again. again I already replaced the fpdm and I have nothing. also when I turn the key on I don't get the 3-5 second pump run. I thank you for all you advise and thoughts

 

[classic02]

help here is the low down now... I have power to the cut off switch with the fpdm unplugged tested the power going out of switch at the plug. have power. when i plug fpdm in to check voltage out I only 1.5 volts. with module plugged in I rechecked power going into the cutoff switch and now it only reads 1.5 volts.. why is it that I lose my voltage when I plug the fpdm in if I don't have it plugged in I have normal volts though the switch to plug in at fpdm?

 

[wmburns]

why is it that I lose my voltage when I plug the fpdm in if I don't have it plugged in I have normal volts though the switch to plug in at fpdm?

IF what you say is true THEN I have to tell you that there really isn't 12 volts at the IFS switch. The problem is that a Volt-Ohm meter doesn't "load" the circuit like a real device does. Please review the following on voltage drop testing.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

^^This is why testing with a test light can be so much more reliable than testing with a VOM.

Likely there's a high resistance connection somewhere in the system. The most logical point for the poor connection might be the relay contacts at the CCRM. But if this were my car I would visually inspect the CCRM connector. Look for evidence of over heating, corrosion, rodent activity, water intrusion. Confirm with a test light power into the CCRM pin #11 (LB/OG).

Then confirm key on power out of the CCRM pin #5 (DG/YE). Note this pin the power source for the fuel pump IFS switch.

If no power out of CCRM pin #5 test for key on power in and out of fuse F2.34, F2.2 and F2.8 before blindly replacing the CCRM. Why? Because if there's no key on power into fuse F2.34 then it would be expected there would not be power out of the CCRM.

 

[classic02]

wmburns. I get 12volts from switch the gr/ye wire. and I get 12 volts out, but as soon as I plug in the module that's when i lose my voltage. my voltage going in the switch drops to 1.5. if I unplug the module my voltage goes back up to normal. I have plugged in 2 different modules and get the same results. i am not understanding why I lose voltage when I plug the module in.
also cant run the voltage drop test because I cant get the car to start

 

[wmburns]

also cant run the voltage drop test because I cant get the car to start

You are using the information too literally and too specifically with regards to alternator testing. It is the CONCEPT of how to perform a voltage drop test. For this example you would put one lead at the CCRM pin #11 and the other on CCRM pin #5. With the key on the voltage drop through the CCRM should be very low. IF it's above 0.250 volt this indicates there's a high resistance connection inside the CCRM. This would confirm the diagnosis.

IF the voltage drop is low through the CCRM then move the test point back until the spot where the voltage drop increases is found.

To correctly trouble shoot this problem it's important to understand the CONCEPT behind a high resistance connection and why this creates a voltage drop in response to current flow.

wmburns. I get 12volts from switch the gr/ye wire. and I get 12 volts out, but as soon as I plug in the module that's when i lose my voltage. my voltage going in the switch drops to 1.5. if I unplug the module my voltage goes back up to normal. I have plugged in 2 different modules and get the same results. i am not understanding why I lose voltage when I plug the module in.
also cant run the voltage drop test because I cant get the car to start

Again the problem is NOT the FPDM (the load). The problem is upstream of the FPDM (the load).

There are multiple ways to track this down. One way is with a test light. The reason why a test light is a better testing device is it applies a load to the circuit. For example if we touch the probe to CCRM pin #11 (LB/OG) and the light is bright this confirms a solid 12 volts coming into the CCRM. Then move to CCRM pin #5 (DG/YE). With the key on the test light should also be bright.

Again this is a process to use to narrow down where the high resistance connection is.

 

[classic02]

ok with a test light I went to lb/or wire at ccrm. and with key on I get no light to come on nor do I have a light at the dg/ye.
please advise what it could be or what I should noe=w check I am at a loss...
and thank you for your time and advise