The other night i was driving home and my truck started bucking like it was out of gas. I figured my senging unit in my front tank had finally gone out. So i go it to a gas station and put some gas in and it started up. After a mile it does the same thing. I managed to get it home and I've been workin on it all day. I figure ed it was the pump on the rail because it was doing the same thing on whether it was on the front or back tank. The pump in there is good, I replaced it. All connections to the relay and pump have been cleaned and I made them tighter. The coil is good. But even after all this, It is still having the same problem. Maybe the inertia switch? It starts cuttin out after about 5 minutes of driving.

It's an 1989 f150 with a 302. Any help would be appreciated.

Oh and where is the intetia switch at? My haynes manual disappeared.

edit* I also check the regulator on the fuel rail and there are no vacuum leakes on the hose on it.

 

Inertia switch cuts power to fuel pump so it wont start - seems like it is located on driver's side firewall forward above brake pedal (88 reference). Probably need to check fuel pressure with a gauge after it starts to act up. It could be trash in the tank clogging the sock on the fuel pickup; or a plugged fuel filter. Also check for good spark at the same time you check fuel pressure when it is acting up.
Above all assumes you don't have codes showing, check for them first.

 

There are also pumps in the tanks, if those die then the pump on the rail has to work harder and it can't always keep up. But, I would check you ignition module, they usually act up only when hot.

P.S. Some inertia switches were located on the passenger side behind the plastic kick panel, kind of inside the back of the passenger side fender.

 

I found the inertia switch and it hasn't been tripped. I wouldn't think the in tank pumps would go out at the same time though, same with both the pick ups being clogged.. I'll check the voltage at the switch tommarow. I need to get a fuel pressure guage

also I got this code
87
Fuel pump primary circuit failure when the PCM commanded the fuel pump on, voltage was not detected on FPM.

whats the M stand for in fpm? Fuel pump ......

 

Module. I thought it was FDM for Fuel Delivery Module. Oh well, memory is the second thing to go.

 

Have you checked or replaced the fuel pump relay. It is on the right hand side in the engine compartment. Also on the EEC computer test connector there is two leads you can jumper that turns the pumps on. I had a voltage drop that caused something like what you described. It would run fine when jumpered though. I sold the truck before finding the problem.

 

The relay is brand new, I havn't heard of the jumper for the fuel pump on the eec connector. But the definition for code 87 is directly off fordfuelinjection.com

ok so here's the thing, I went out there tonight and let it idle for 10 minutes while i was checkin for power at the intank fuel pumps and power at the switch. I had power at the switch but before i checked the voltage going to the tanks i dropped the mag light and busted my lip. Then it died.

So it will idle/run for 10 minutes then die. any idea on what it could be? MAybe a circuit overheating?

 

"fpm" in this case stands for "fuel pump monitor". The ECM drives the signal "FP" to ground to energize the fuel pump relay. It receives the different signal FPM from the output of the relay, so that it can evaluate whether voltage is going to the pump or not. It sets code 87 when the relay output voltage (FPM) drops below a threshold, at a time when it is pulling the FP (relay coil line) to ground, and it is expecting the fuel pump to get a nice steady 12 volts.

The FP wire also goes to the diagnostic connector. You can ground this diagnostic pin to force the fuel pump to run, regardless of what the computer has to say about it.

If your PCM ground is bad, or the FP line has a high resistance, or the connections at the solenoid or battery are iffy, the relay may be dropping out. Check and clean all your grounds and the battery cables. If the problem continues, try letting her idle with FP grounded. If the problem goes away, there is something iffy with the FP wiring or the computer. If the problem continues, the relay is iffy or there may be an intermittant short circuit somewhere between the relay output and the fuel tanks. Check for chafed insulation.

 

fefarms, any clue on the colors of the ground wire on the diagnostic port?

 

Hold the six pin diagnostic connector in your hand, looking in to the connector. There is a row of four pins and a row of two pins. Hold the connector so the row of two pins is at the top, the row of four pins at the bottom.

The FP wire is the one at the extreme right of the row of 4 pins. The wire should be light blue with an orange tracer. The connector position just to the left should be empty (no wire goes there).

 

check the cat converter...mine did the exact same thing and thats what tex on here told me to try...sure enough that was it...and the cat was less than a year old so just because it is brand new dosent mean a thing...the hotter it got the worst it ran for me

 

ok, so the whole fuel system works, fron what i've seen. I still need to get a guage for the fuel pressure to see if it drops when it dies but everything seems to be working fine. I'll pull off the cat and look at it. I have a 3" single with a high flow on it.

 

When it quits give it a shot of starting fluid right away.That should let you know if it's fuel or spark.Have you checked fuel pressure regulator?

 

how do i check it? The tube that goes to the regulator itself is ok.

 

Pull the vacuum line off and see if there is any gas present.