Computer Question?

[danger87ranger]

Ive got a 87 ford ranger 4wd 2.9l 5spd. Ive been working on it for awhile now and still cant get it running. I cannot get my fuel pumps to get power and its like i cannot get power to my computer cause it will not self test i have switched the computers out 3 different times and they all are the same way. i have changed both fuel pumps and the fuel pressure regulator, the computer relay, fuel pump relay, idle air control valve, fuel filter. My injectors will not work if i spray something into the intake it will run. WHAT CAN I DO NEXT? to try and get it running i can use all of the help i can get

 

[holyford86]

have you checked for power at the fuel pump relay and at the pumps? Are the grounds for the pumps good? Have you checked the inertia switch under the passenger side of the dash near the passenger's feet to see if it is set? if the engine will fire on starting fluid the computer is working, as the spark is controlled by the computer.

 

[danger87ranger]

Question

I have changed the inertia switch under the dash. I havent checked the power to the relays though.I also havent checked the grounds at the pumps. Ive checked the power at the pumps and their is none.My fuel injectors will not work either. What could cause that? Thats im gonna try and do what you said today

 

[shadetree]

Do this from another post:

Heres how it works:

Ignition on - 12vdc thru rd/lt grn wire to EEC relay energizing relay coil.

Coil energizes closing EEC relay contacts sending 12vdc from yellow wire thru red wire to wiring junction sending voltage to fuel pump relay, and several sensors and part of computer.

The yellow wires to the EEC relay and the fuel pump relay come from the terminal on the starter fender relay thru fuse links. Each relay is on a separate link, so check voltage from all links.

The computer senses voltage, and temporarily grounds pin 22 of the computer thru tan/lt grn wire. This energizes the fuel pump relay coil closing relay contacts sending 12vdc to the inertia switch thru or/lt blu wire and also pin 94 of the computer.

After a couple of seconds, the computer releases pin 22 shutting off the fuel pump relay, then waits for ignition pulses from the TFI module.

When the starter is engaged and the TFI module starts sending ignition pulses, the computer then re-grounds pin 22 closing the fuel pump relay supplying gasoline for engine start.

To test the pump, ground the tan/lt grn wire going to pin 22. With the ignition switch turned on, the pump will run as long as the jumper is in place.

If the pump starts, relays are good as is all wiring and fuses. If the pump doesn't start, you can diagnose back and see where the problem lies.shady

Quote:
Originally Posted by equalXlength
I have no spark, what could cause this. I have replaced the tfi and i still get nothing. if i can get spark and bypass the fuel pump relay i think it should run???[/QUOTE]

One thing at a time. You are jumping all over the place replacing parts.
Check the EEC relay circuit. EEC stands for electronic engine control. This relay operates the computer. If the computer is not working, you are not going to have any spark or fuel output.

Use a test light, or meter and check the voltage path outlined in my post above.shady

 

[danger87ranger]

If i put a jumper wire from the hot post on the battery to the inertia switch the fuel pumps will come on and run. what does this mean?

 

[Cyberbeer]

heh could also bypass the switch. I think you connect the red and orange wire. Dont quote me on that. I had to do the same thing.

 

[holyford86]

it could mean that the relay is shot or the fusible link is bad. Pull the relay out of the socket and look at the connector, there should be 2 terminals bigger than the rest, if you trace the wire from one of them it will lead back to the fender mounted starter relay and there will be a fusible link in it. the other large terminal on the relay plug is the power to the pumps, jump the two big terminals together and see if the pumps run. If the pumps dont run, jump the pump power terminal to the battery, if they run then then your fusible link is shot, if they dont, jump the terminals at the inertia switch and see if they run. If they don't run leave all the jumpers hooked up and test for voltage at the fuel pump, if there is power there then your pump ground is bad.

 

[mjonesjr]

There is a ground off somewhere.

I had the same problem 2 weeks ago and come to find out there was a ground wire broke off about 6" from the battery. Check there.