So i bought a 1989 f150. It has the inline six with efi. I go to start it and nothing happens. I replaced the battery and only the oil light and that stuff comes on when i turn the key over. If i put power straight to the fuel pump, i jump the starter solenoid, and the turn the key all the way over it will start but then die right away.

Whats my problem???

 

Man, there are so many things it could be. Lets see, where to start. Begin by checking both battery cables, both ends. If that isn't it, you're going to be checking electrical components all over the place. Check the ignition switch, not the key, the electrical switch. Check for power at the computer with the key on. You can check for power on both sides of all relays, in and out. In comes from a fusible link at the solenoid and is hot always, out will be hot with the key on only. The fuel pump out will be hot with the key on only momentarily, until the truck starts and then it will be hot always.
Instead of jumping the fuel pump relay, you can jump the computer relay and then jump the solenoid and see if it starts.
It sounds to me like it's the ignition switch.

 

How do i jump the computer relay?

 

The computer relay is the one with a yellow wire, a white wire with a light blue stripe, a red wire, and a black wire. Hook the red wire to the battery positive. See if it starts. If it doesn't, hook the battery positive to the white wire with the light blue stripe.

The red wire will hot the computer while bypassing the relay, but the coil and ignition module is on a different circuit. Putting hot to the white wire with the light blue stripe will hot the coil and ignition module and energize the computer through the relay.

If it doesn't start either of these ways there is probably a fusible link burnt out. Also check the fuses if you haven't already.

 

Sorry to ask so many questions but if it starts with the red wire what does that tell me?
If it doesnt start with the red but does with the white what does that tell me?
Thanks alot Sean finally i found a site that can help me.

 

If it starts with the red wire then a fusible link is probably burnt out or the computer relay is bad. If it starts with the white wire with the light blue stripe then it could be the ignition switch. If it still doesn't start it could be a different fusible link.

Doing it this way saves some electrical curcuit testing at first but narrows down what you will be testing later. You are just bypassing certain things.

And no problem with the help, you're giving me something to do.

 

Ok then haha i have more for you.. were are these fusible links? How do i pull the wires out and what do i hook them up to so i can bypass this?

Thanks alot bud

 

The starter solenoid has a side with one large wire on it that goes to the starter. The other side has the large wire that goes to the battery and several other smaller wires. The smaller wires are the fusible links. Instead of blowing out like a fuse they melt, you can see where the link ends and it changes into the regular wire. If it's melted you cut it off and put a new one in. The other one I was talking about will be more difficult to find. I believe it's somewhere on the drivers side near the firewall, tangled up in the mess of wires. You don't need to look for it until you figure out if it's the problem.

Don't pull any wires out, leave everything hooked up as it is. Get a length of wire that will reach from the battery positive to the relay. Use something at least 16 gauge or larger. Hook one end to the battery positive and shove the other end into the relay from the under side. I don't think the relay connections are sealed, at least they aren't on my truck. If you look at the relay plug you should be able to see the metal connectors in it from underneath, make sure the wire touches it. Hook up the relay side first and then the battery side so you don't start a fire. When you hook up the battery side you should hear the fuel pump energize like it would when the key is turned.

 

Thanks alot!! You have no idea how much youve helped. I cant work on the truck til sunday. Ill make sure i post my findings after i get done. Thanks again

 

Check voltage across battery. 12v ?/Bat-pos to eng. block. should be very close if not the same. Then check for blown fuses in the fuse panel and while in that area,see if the inertia switch needs reset. Still nada, check voltage from ign. wire going to starter sel. to bat-neg while someone turns the key to the start position. voltage good? return wire to sel.,turn key on & jumper the starter selinoid. See what happens. Any history on the truck ?