I need some help trying to figure out my 87 F-150. It has a 302EFI and doesn't always start. It was using too much gas and sometimes kinda flooded itself out and then was hard to get running again. I replaced the plugs, fuel filter, fuel pressure regulator, thermostat, and the temp sensor. I don't know if the milage is any better yet b/c I don't dare drive it very far in case it dies on me. When I turn the ignition switch on, the fuel pump doesn't always kick in. Usually when I "need" to use it! I can turn the switch on and off and crank the motor till the battery goes dead. Everything worked and it started fine this morning. It ran for 10 min and then died again. I left the switch on and was so pissed that I opened the hood and started jerking and shaking any bundle of wires I could find. As I was doing that I heard the pump kick in so I jumped it off the solenoid and it started again.

First I thought I had a bad fuel pump, but when it starts, it seems to run fine, except when it sits at an idle for a while, it just dies. If it's been running a long time I can usually get it started again though.

Do you think it is the pump or could there be another electrical explanation? If it helps at all, the ignition switch just hangs from the dash(has to be started with a screwdriver), and the temp guage still doesn't read more than 1/4 inch from the bottom even after a new 195 thermostat and new temp sensor(I have only seen the guage jump to where it's supposed to twice, then right back down is where it stays.) I think this is all related some way or another, BUT HOW?!*$^%@#
P.S.- Sorry for such a long article. Just don't know how to explain it so someone understands. Please help me.

 

There may be more than one coolant temp sensor on your vehicle - one for the guage and one for the computer. Or a bad gauge or a bad connection to the dash panel. Try beating on the dash when the gauge is low, if it jumps - may have to clean the connections on the dash panel.

May have a bad fuel pump relay, a wiring problem, a bad inertia switch, or yes, a bad fuel pump. Shaking the wires as you mentioned would lead me to look at the wiring and the relay a bit closer first. Inertia switches are known to get weak, but I think this problem requires a reset of the switch, not just an intermittent problem.

Intermittent problems are among the toughest to troubleshoot, so hang in there.

 

Check the wiring under the EEC Power relay & the Fuel Pump Relay.

 

I'm not very elecrically inclined and haven't got any wiring books yet, so please don't laugh at me when I ask where is this inertia switch and what exactly does it do?

 

You said you changed the temp sensor, did it have a connector with one wire or 2? If it had 2 wires then is was probably the one for the computer. The one for the guage is in the intake manifold in the front driver's side corner, it will be stubby with one wire on it, it may be hidden behind some mounting brackets (I forget wich ones). to verify you can ground that wire and the gauge should spike.

As for the starting problem, next time you can't get it started, and the fuel pump does not kick in, then jump the fuel pump relay, If the pump runs then replace the relay. if the pump does not run, then jump the relay with a good wire directly from the battery (not the power supply in the relay connector). IF it works then, then you could have a bad EEC relay (EEC relay powers the Fuel pump relay), or bad wiring. These things had a problem with corrosion in the main wiring harness as it went around the nose of the truck to the Relays.

Keep us posted.

 

The inertia switch is in the front pass corner of the cab under the dash. Un an accident, the impact causes the switch to kill power to the fuel pumps to prevent fires.

 

I also vote for the fuel pump relay or the relay wiring. I had the power wire corrode off my pump relay and before it totally let go it produces intermitent pump operation similar to what you describe.

 

Thanks for all the info guys. I will check it out as soon as I find a heated shed to park it in. Shop's full of tracktors now. If I solve it I will surely let you all know.

 

Hey guys, been away from the computer for a while. I found the other temp sensor, changed it and now the guage works like it should. Thanks for reminding me it had two sensors. Also hit the reset on the inertia switch a few times and so far the truck starts and runs great - time will tell. Just put a new u-joint in the front driveshaft and replaced the 0-2 sensor as well. Thanks for all the help to everyone, this Ford community is great. If anything else goes wrong with the truck, I will be sure to update you. Thanks again.