Truck has run fine for the two years I've owned it. Two weeks ago, I started it to move it and it ran for about 5 minutes and just died. Seemed to me like it ran out of gas. It had 1/2 tank so I checked the Schrader valve and no gas even dripped out. I checked for the fuel pump prime and heard nothing. I swapped relays and checked fuses, to no avail. Fuel pump safety switch was intact and I did cycle it several times to make sure it was set properly. The truck does run on starting fluid, so it's not an ignition issue.

I needed to replace the filler neck anyway so I replaced it and the pump. It still doesn't cycle on. No fuel pressure. I have checked voltage at the relay and I have 12v, there. When shorting across pin30 and pin87, I still get no fuel pump.

What are the next points in the pump circuit to check?I'm certain that I'm going to need to pull the bed back off to complete testing. That's ok. It's a simple process, now that I've replaced the old rotted bed hardware. 😉

 

Welcome to the forum and Good work so far, nice diagnostics

Here is the 12v power pathway to fuel pump

Battery Positive------Maxi Fuse #12-------fuel pump relay---(dark green wire)-------inertia switch-------(pink wire)--------fuel pump

Battery power runs to engine fuse box bus
#12 maxi fuse is in engine fuse box, it is 20amp, and supplies power all the time to slot 30 in fuel pump relay socket, not key on/off power

Slot 85 or 86 in relay socket should have 12volts when key is on, the "other" one is the Ground wire to the Computer, Computer Grounds this relay to turn fuel pump on(30 and 87 connected)

The inertia switch will be in the cab, passenger's foot area, can be just above carpet under glove box or in kick panel up high
It looks like this: http://www.explorerforum.com/photopo...ut_off_WEB.jpg

Inertia switch cuts fuel pump power if vehicle stops suddenly or rolls over, i.e. accidents

1997 should have a Warning light on dash that will come on if Inertia switch is tripped
Inertia switch has reset button on the top but once it has been tripped once it will trip much easier after that so replacement is recommended.

On vehicles that have been in accidents and rebuilt these are often not replaced so can cause issues down the road.
i.e. slamming a door or going off a curb(sharp bump) will trip it

Pink/black stripe wire runs from inertia switch to the fuel pump.
Fuel pumps Black Ground wire may also be near inertia switch, although Ford moved it around over the years, follow pink wire to where it exits the cab and see if it is joined by a Black wire, that should be fuel pump ground wire.

 

Thanks, RonD. I'm getting close to getting it running again. (Not much left to check. Lol.)

Since the fuel pump circuit will only get power for two-seconds every time the key is turned, would it be wise to 'jumper' across pin30 and pin87 for the purpose of troubleshooting? I can put a fuse in the jumper to be sure I don't burn the truck to the ground. Lol.

 

It already has its own fuse in engine fuse box with the relay, Fuse #12 20amp


With key on it will have 12volts for 2 seconds but then it will show 5 to 7 volts after that, that lower voltage has no AMPs it is Monitor Voltage from the Computer(PCM)

 

I would build or buy a test light that could be attached/probed into the relay coil contacts in the power distribution box. Or have someone listen for the relay contacts to click when the key is first turned to ON. If the computer is doing its job, a light would turn on in place of the relay coil closing the relay contacts when the key is turned to ON.
If you don't get that, you can do an 'emergency' jumper of the power contacts in the PDB to energize the fuel pump. That should confirm the power path to the pump.
If you have a question about the rollover switch(never heard of replacing them after pushing the reset button, it's just a steel ball bearing sitting on two contact fingers), you can put the test light across the two wires. If the switch is not conducting, the light will come on for a few seconds as you turn the key to ON, as the light will take the place of the switch, sending power on to the pump. A load test using a light will better inform of amp capacity than a VOM.
Have you ever heard the new pump run? It could be defective right out of the box.
If you follow the wires RonD noted, you should be able to see power(test light once again) by probing the connectors from the 'backside', and grounding the other wire of the test light to clean metal.(chassis bolts/screw heads)
tom

Dublin Eire, CA or GA?

 

I got a chance to tinker with it today. I pulled the bed and checked for power at the terminal. Had both 12v for "prime" and good ground.

Pulled the pump and (eventually) checked continuity from the terminal to the pump and discovered a problem with the Ground connection. Did the "wiggle test" and the swaged end of the wire (on the harness connector end) and it popped right off.

I ended-up buying a NAPA hanger and pump assembly and installing it. Truck started right up after 3-4 cycles of the key to prime the system.

Drive it around all day today with zero issues.

Thanks for all of your help, guys. Awesome bunch, here.

Rob

 

Good work

Thank for the update and fix