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96 crown victoria not getting fuel ......please help!!!!


aerodude_66
11-24-2005, 05:10 AM
I drove my car home from work one day and it ran fine all the way home. A few hours later I was going to run an errand and it wouldn't start. It is not getting fuel , I have checked all fuses and they are fine. Checked relays and they seem fine, I even jumped the fuel relay and the fuel pump wouldnt run. I have a solid 12 volts to the supply of the fuel relay but back at the inertia switch I am only reading 6 volts. This is also an old police interceptor, and have had zero problems with it till now. Any and all suggestions welcome................Thanx!!!

dzus
11-24-2005, 12:25 PM
>The pcm controls the fp and sound like it is grounding the power thru the pcm. To check this unplug the pcm and jump the fp relay and you should get 12v at inertia switch & pump should run if working. The pcm will not let the fp run if it doesn't get a crank signal,so if the pcm is causing the problem check the crank position sensor for good connection etc...

aerodude_66
11-24-2005, 04:16 PM
Thanks for the suggestion, I had completely forgot about the pcm in the circuit. As soon as this weather breaks I will try it out. You have been a big help...............Thanx a million

Gandolf
11-26-2005, 06:47 AM
Pcm controls the relay that controls the pump. Sounds like you have a open circuit somewhere between the relay and the pump? Pump should run for about 1 second when the key is first turned on regardless of any other engine controls.

aerodude_66
11-26-2005, 04:49 PM
If the pcm were malfunctioning, couldn't it ground out or partially ground out the fuel pump??

ModMech
11-26-2005, 04:55 PM
A few hours later I was going to run an errand and it wouldn't start. It is not getting fuel , I have checked all fuses and they are fine. Checked relays and they seem fine, I even jumped the fuel relay and the fuel pump wouldnt run. I have a solid 12 volts to the supply of the fuel relay but back at the inertia switch I am only reading 6 volts. This is also an old police interceptor, and have had zero problems with it till now. Any and all suggestions welcome................Thanx!!!

You have done an EXCELLANT job of troubleshooting so far, and you have found the problem, low voltage to the Inertia Switch (IS).

The fuel pump power circuit looks like this:

Battery> FP Relay (PCM controlled)> Inertia Switch > Pump.

Since you have battery voltage at the relay (you jumped it), the problem is somewhere between the relay and the inertia switch. I would bet $$$ that the female terminal at the relay box is badly corroded which is causing the low voltage condition.

Jumper the relay, and check every connector for voltage, when you find a voltage loss (Voltage drop) you have found a problem.

Let's say that with the relay jumpered, you have 12.6V at the BATT terminal of the relay, and 12.58V at the TOP of the FP feed terminal, but only 7.1V at the bottom (or next connector in the circuit), then that terminal or crimp is bad (most likely badly corroded as in GREEN).

Just remember to check the WIRE and the TERMINAL seperately for voltage, and you WILL find the problem.

aerodude_66
11-26-2005, 10:32 PM
I am very appreciative of all the help I am receiving. Does anyone know if the pcm is connected to the fuel pump circuit though and could cause this symptom??

aerodude_66
11-27-2005, 06:03 PM
I am not able to continue troubleshooting today, as my car is locked in my buddy's garage and he will not be back until monday from thanksgiving holiday. I look at the mediocre schematic of the fuel system in my haynes manual and it shows a wire going into the pcm after the fuel relay . That is why I wonder if it could possibly be a malfunctioning pcm.........would anyone happen to know this for sure??? As always any help would be appreciated.

dzus
11-27-2005, 07:29 PM
I am not able to continue troubleshooting today, as my car is locked in my buddy's garage and he will not be back until monday from thanksgiving holiday. I look at the mediocre schematic of the fuel system in my haynes manual and it shows a wire going into the pcm after the fuel relay . That is why I wonder if it could possibly be a malfunctioning pcm.........would anyone happen to know this for sure??? As always any help would be appreciated.
> The pcm has 3 wires in the fuel pump circuit. One wire goes directly to f/p relay. One wire goes to the fuel sender/instrument cluster. One wire that is spliced into circuit that goes to the inertia switch and on to the f/p.
That is why I said earlier too disconnect the pcm so you can isolate the problem by removing the pcm from the f/p circuit. Then when you jump the f/p relay and still have 6v at inertia switch you'll know the problem is between the fuse box and inertia switch which will rule out the pcm as the problem.

ModMech
11-27-2005, 09:31 PM
If you have ONLY 6V at the inertia switch, it is ABSOLUTELY IMPOSSIBLE for the PCM to be any part of the problem, it IS in the wiring or connectors between the FP relay and inertia switch, period.

aerodude_66
11-28-2005, 07:42 PM
It looks as if I was incorrect, what is going on is that I dont have 12 volts to the supply of the fuel pump relay. If I supply 12 volts to the relay, it starts right up. So obviously I am losing voltage somewhere between the distribution box and the relay panel. Does anyone know if there are any connectors to check or obvious places I should be looking.........thanks for all your help.

aerodude_66
11-30-2005, 05:55 AM
Is anyone familiar with the wiring harness between the power distribution box and the fuel pump relay center? This is where my voltage drop is occurring.

way2old
11-30-2005, 07:06 PM
Look at the wiring that runs across the front of the car. It goes from the Power Distribution, down under the battery, across the inside of the front bumper(on the support tray) then up the left fender to the connections at the rear of the left inner fender. Look closely at the wiring under the battery and the front of right fender well. There is a bend in the wiring loom that collects water and allows the "green death" to corrode the wires. You need to open the loom cover to find the area. If you see no obvious concerns, look at the wiring connectors for corrosion at the rear of the lefr front fender. There are 3 connectors there and one of those runs the wire to the F/P relay. It is a matter of opening the wiring and looking for the problem. Happy hunting.

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