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The fuel pump in my 2002 GT Convertible quit last weekend. I'm waiting for the new pump to arrive. I thought I would write some general information that I learned while diagnosing the problem in case it may help other people with fuel problems in the future. All of this pertains to my 2002 Mustang GT Convertible. I do not know how other years/generations may differ from this. Anyone is welcome to correct anything that I have wrong. I am not a service technician. I am just some dude that had a fuel pressure issue. I do not have access to a Rotunda system. I do not have access to a programmer. I only have an Actron code reader (no DTCs present). I do not have a fuel pressure gauge. In my case, I was "lucky" that the fuel pump was a complete failure. With a rag over my hand, I pushed the fuel rail schrader valve pin in. Not one drop of fuel came out after several key on/engine off cycles. If I had a partial fuel pressure issue I would have likely needed a fuel pressure gauge to determine the problem.

Pictures are hotlinked into this post. My apologies for the length of this post, but I wanted to try and communicate as much detailed information as I can remember based on my recent diagnostic experience in case it helps others.


WIRING DIAGRAM

The wiring diagram reveals the general setup of the fuel pump power system. When the key is in RUN or START 12V is applied to activate/close the fuel pump relay located in the right front fenderwell in the Constant Control Relay Module (CCRM). This relay is fed by 12V through the fuel pump fuse in the power distribution box under the hood (yellow mini-atc 20A fuse #14).

Power then flows from the fuel pump relay to the inertial fuel shutoff switch in the trunk area. This switch interrupts the fuel pump power circuit when it detects a high-G-force incident (such as a collision). This is just a switch. It is either closed (normal) or open (when it interrupts the circuit). This switch has a red reset button to close the switch in the event that it has been activated (interrupting the fuel pump power circuit).

After the inertial fuel shutoff switch, power flows to the Fuel Pump Driver Module (FPDM) also located in the trunk area. The FPDM takes care of cycling power to the fuel pump depending on many variables including the current fuel pressure and the fuel pressure desired by the PCM based on various sensor inputs.


COMPONENT LOCATIONS

Here are two pages that helped me with component locations and connector numbers. The connector references (e.g., C433) are the actual Ford connector designations, as far as I know. Likewise, the component designations (e.g., A195a/9D372) are also the actual Ford designations. In the following sections there will be actual photographs of my car showing the locations I was interested in for the fuel pump power delivery system.

Location diagram #1
Location diagram #2


COMPONENTS

I. FUEL PUMP POWER FUSE

The fuel pump power fuse is located in the power distribution box in the engine compartment. It is basically a fuse box under the hood of the car. It is located near the driver side front strut tower upper mounting point. Generally, it is located on the driver side of the engine compartment, right next to the front fender, near the brake master cylinder fluid reservoir. I did not have a picture of this, but it should be easy to find. Removing the plastic cover reveals the fuses. On my car, the fuel pump relay fuse is fuse #14, a yellow mini-atc 20A fuse. The fuse numbering diagram is embossed on the underside of the power distribution box cover.

In my case, the fuse checked out as OK with a multimeter and I did have 12V power at the #14 fuse terminal.


II. FUEL PUMP RELAY (CONSTANT CONTROL RELAY MODULE)

The fuel pump relay is located in a module called the Constant Control Relay Module (CCRM). The CCRM is located in the right fenderwell. It is not actually located in the engine compartment itself. The connector and mounting nuts are visible from the engine compartment. The CCRM has a bolt-secured harness connector, similar to the PCM connector. I have heard of the CCRM being hard to access/remove, but as it turns out I did not even need to bother with it.

General location of CCRM
CCRM Connector visible from engine compartment



III. INERTIAL FUEL SHUTOFF SWITCH

The inertial fuel shutoff switch is located in the trunk on the driver's side. It's sole purpose is to interrupt power to the fuel pump power circuit in the case of a high-G-force incident such as a collision. If the switch is triggered it can be reset by pushing down on the red button. Here is an overview picture of the driver's side of the trunk (with lining removed) showing the general location of the Inertial Fuel Shutoff Switch and the FPDM (the FPDM is not visible in the picture because I had already removed it). And here is a closeup picture of the inertial fuel shutoff switch.

I mentioned above that I didn't bother removing and/or testing the CCRM. With Key On/Engine Off I checked the inertial fuel shutoff switch connector with my multimeter. My meter showed that 12V was present at the inertial fuel shutoff switch indicating to me that the CCRM fuel pump relay was closed and passing current. I also checked the continuity of the inertial fuel shutoff switch pins with my multimeter. There was continuity so I know that 1) power is present at the inertial switch and 2) the inertial switch is passing power through it. This ruled out a CCRM fuel pump relay failure. It also ruled out a failure of the inertial shutoff switch.


IV. FUEL PUMP DRIVER MODULE (FPDM)

As noted in the driver's side trunk overview picture, the FPDM is located on the driver's side of the trunk. In the overview picture the FPDM is not visible because I had already removed it.

I have a picture of the FPDM as installed in the trunk. And here is a closeup picture of the FPDM after removing it from its mounting point.

The wiring harness connector that connects to the FPDM is Connector C433. Here is a pinout diagram for C433.

In addition to the above pinout diagram for the FPDM Connector C433, I have this picture which shows a closeup of the C433 connector including annotated pin descriptions.

The FPDM harness connector (C433) was crucial in my diagnostics for my car. If you can verify 12V power at FPDM C433 pin #9 (PK/BK) then it means that everything upstream is in presumably good shape (Fuel pump power fuse, Fuel Pump Relay in the CCRM & Inertial Shutoff switch). This harness connector (C433) would be a great place to start if I had to diagnose things again (right after checking the fuel pump power fuse). It would have allowed me to immediately eliminate the CCRM and the inertial shutoff switch as problems in my fuel pump power problem.

One other note about the FPDM is that I have seen screenshots and/or scans in posts online of a portion of a diagnostic chart regarding the fuel system. The portion of the chart I've seen a few times basically says to test the FPDM harness connector (C433) for power on pin #9. If power is at pin #9 then the chart says to replace the FPDM. Be very careful here for two reasons:

#1. The screenshots/scans of this diagnostic page are out of context. That is, that particular diagnostic page is the end of a long sequence of elimination tests designed to eliminate other component failures before testing for FPDM power.

#2. I have seen a post, here or elsewhere, by Randy Stinchcomb regarding FPDM failure rate. Randy has a ton of experience in parts and service. I don't have a link handy, but he basically said that FPDMs rarely fail. He has sold a lot of FPDMs, but he has seen only one replaced due to circuit failure. The moral is to assume that the FPDM is good and test around it until there is nothing left to explain the failure other than the FPDM.

If you have 12V on C433 pin #9, assume the FPDM is good for now and use the connector to check for fuel pump issues. Using C433, I used some home audio speaker wire. I cut about 6 inches of two-conductor speaker wire. I separated the wires so I had two insulated wires. I stripped about ¼ inch off of each end of the wires and twisted the exposed stranded ends. I carefully inserted the wire ends into the FPDM module harness connector (C433). I connected pins #2 & #3 together (this grounds the fuel pump). Then, with the Key On/Engine Off, I connected pins #9 & #10. This basically bypasses the PCM and directly supplies power to the fuel pump. Listen for the fuel pump when you make these connections (whirring/whining sound). I did not hear the fuel pump running, so I needed to check one more thing.


V. FUEL PUMP CONNECTOR (C463)

The wiring harness fuel pump connector C463 is located at the rear of the fuel tank. This connector is accessible immediately under the rear of the car without any need to drop the fuel tank to access it. The C463 connector pinouts are shown in this picture. Note that, unlike the FPDM harness connector (C433) which has a female harness connector, the fuel pump connector C463 has a male harness connector. That is, the portion of C463 that has the pins on it is connected to the wiring harness.

On my fuel diagnostic problem, I knew that the FPDM had power. My next step was to test the wiring between the FPDM harness connector C433 and the fuel pump connector C463. With Key On/Engine Off, I jumpered the FPDM pins as mentioned above (#2 & #3 together, #9 & #10 together). I took my multimeter under the rear of the car to check the fuel pump connector C463. Pins #5, 6 & 7 are the pins I was interested in. #5 should be a harness ground. #6 should be the “fuel pump +” voltage from FPDM pin #10 (BN/PK). #7 should be the “fuel pump -” connection from FPDM pin #3 (RD/BK). With my multimeter I checked voltage between pins #5 and #6, which read as 12V (good). I checked continuity between pins #5 and #7 to verify that the “fuel pump -” was grounded. Zero resistance (good).

So I know that, with direct power applied to the fuel pump, it isn't running. This is the point where I assumed that the fuel pump itself is dead. I ordered a new pump and strainers which should arrive in the next 10 days. I may do a video or more pictures detailing what I go through when actually replacing the fuel pump. In addition to the fuel pump and strainers, I ordered a new filler neck grommet and a new fuel filter.

I hope this information helps someone at some point. I will not be at all offended if anyone would like to correct any information that I have incorrect in this writeup.
 
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