Fuel Pump cut out- electrical help - Ford Powerstroke Diesel Forum
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Old 04-11-2013, 10:45 AM
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Fuel Pump cut out- electrical help

2002 7.3 excursion
Lost fuel pressure close to home. limped to the driveway and began to trouble shoot. I thought the pump was shot so I got a new one. I have found the following:
Only 6-8 volts to pump.
Only 6-8 volts at inertia switch on pass side
12 volts at fuse #40


I am lost as to where I am losing power to the pump. I need a wiring diagram and someone to talk me through this like the dummy that I am with electrical. I think there is a relay behind the radio but I could not find it and thought a relay will give me on or off power anyways.

To top it off I broke the rear quick connect to the fuel pump so I will also need a little advice on that when I can figure out the electrical side.

I do not want to take this to the dealership if at all possible so if anyone can help I would appreciate it.
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2002 Excursion Limited 7.3 PSD 170k and counting
AFE Intake, Edge PHP Gryphon, rancho 9000 front shocks, V& Modded B code spring upgrade DFA V3, upped tire size 285/75/16 nitto dura grapplers.
4" Diamond Eye turbo back, 6.0 tranny cooler upgrade.
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Old 04-11-2013, 06:29 PM
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ok. I'm considering wiring my d2 pump directly to a keyed source with a switch in the cab for safety. anyone see any issues with this? I am seeking a wiring diagram for 2002 excursion also so I can eventually chase this thing down. I may tap directly to the #40 fuse that is currently supposed to supply the d2 pump since the problem seems to be down stream.
[fuse--switch--d2 pump]

Any input or wiring diagram would be greatly appreciated. Unless I'm missing something, this seems to be a workable solution to get me running again until I can find my gremlin.

didn't someone already do a switch for the d2 pump?? If you did please chime in.
Thanks
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Old 04-11-2013, 07:39 PM
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Fuel pump voltage comes from pin 40 on the PCM (Located on the lower right firewall if your facing the truck)
now that you say the inertia switch and pump only have 6-8 volts. The power for both of those splice off the same wire from the PCM. It is a Pink wire with a black tracer. which means you have resistance from somewhere behind that splice to the PCM inspect the wires and see if you can find any corrosion and perform voltage drops to find your problem.

if you want a wiring diagram i can get a picture for you
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Old 04-12-2013, 06:11 PM
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Quote:
Originally Posted by mcyrana View Post
Fuel pump voltage comes from pin 40 on the PCM (Located on the lower right firewall if your facing the truck)
now that you say the inertia switch and pump only have 6-8 volts. The power for both of those splice off the same wire from the PCM. It is a Pink wire with a black tracer. which means you have resistance from somewhere behind that splice to the PCM inspect the wires and see if you can find any corrosion and perform voltage drops to find your problem.

if you want a wiring diagram i can get a picture for you
I rechecked -voltage to the inertia is ok. the drop is between the inertia and pump. still searching for a solution. the pcm monitors pump after the inertia so I wonder if it can suck my voltage down. Hand tracing the wires from the inertia switch is going to suck. I'll start ripping into things tomorrow.
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Old 04-13-2013, 05:30 AM
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Keep in mind, the reason the fuel pump is controlled by the PCM is for safety. After a crash, the PCM would not allow it to continue to pump fuel without the engine running for too long...

Simply connecting it to a keyed source would defeat that, might be worth taking some time to solve the issue. Alternatively, you might also use that 6-8v to trip an added relay and run the pump on 12v with it
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Old 04-14-2013, 08:21 AM
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I have tried to trace the best I could and have failed. What I found was the voltage at the 40 fuse is good. The green/yellow stripe wire going to the inertia switch is 12v. The pink/black stripe going to the inertia switch is 6v. everything down stream to the pump is reading 6v on the pink/black stripe wire. If the inertia switch is plugged in, unplugged, or bridged with a wire I get the same voltage reading down stream. It's almost like the pcm is putting out 6v. When I run a 12v source directly to the pump on a switch I get good pressure and the truck starts. I get an abs light and a pump circ failure.

I may use this setup to tuck my tail and drive it to the dealership. Unless anyone has any last minute advice I think I've chased this as far as I can.
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Old 04-15-2013, 06:16 PM
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I took the ex in to the dealership expecting the worst like a bad PCM. After 2 hrs they found that pink/black stripe wire pierced and coroded just below the brake fluid resivor near the steering linkage. I was at this for a lot of hours and I'm just glad they found it. Not thrilled that I didn't find it myself after all that searching and troubleshooting but glad it's over and fixed. Thanks to all that offered thoughts and advice.
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