Hi everyone. I have a 1991 Ford Ranger Sport 2.3L 2wd. The truck was running well until i had my clutch replaced. After test driving it, I camw to an abrupt stop and the car broke down. What I now realize is this could have been caused by the inertia switch. However, I just installed a new fuel pump after a mechanic told me the fuel pump was bad. The truck still wouldn't start even after resetting the inertia switch. After replacing the pump, I have also replaced the fuel pump relay switch and EEC switch. I even bought a second new fuel pump which also did not work, so I know it is an electrical problem. I decided to bypass the inertia switch and in doing so tested all of the voltages with a multi-meter. It seems that the fuel relay switch is getting 12V, but at the inertia switch I am only receiving 6.7V. I am also receiving 6.7V at the fuel pump connector which means there is not problem in the electrical system from the inertia switch to the fuel pump.

My questions are, I have read on another forum that the fuel pump relay switch should have one pin that is 12V constantly, and one that is 12V when the truck is turned on and then turns off after 2 seconds, which pin should have the constant 12, and if there is not that voltage, what could be causing this? I've checked the fuses which are all fine.
What voltage should the intertia switch have? Should it have 12V as well? I have seen varying opinions, some saying it should be 12v for 2 seconds when turned on and then it should go down to 5-8V, mine stays at 6.7V.
Could bypassing the inertia switch mess with the computer? The voltage?
What voltage should the fuel pump have? I assume 12v but also have heard varying opinions.

Also want to add I tested continuity for the green and yellow striped wire from the fuel relay to the inertia switch and it had continuity. Also I have bypassed the clutch safety system in order to get the engine cranking, in case that could somehow be messing with the voltage? Lastly this all happened after my clutch was replaced, in case anyone else had a similar experience.
Thanks for the help! Happy to be a part of the forum and will gladly include any more info needed or pictures to help

 

Yes, you will read between 5 and 8volts at inertia switch when key is on, its the monitor voltage NO AMPS so can't power fuel pump, so 6.7volts is correct, but its from the computer not the relay

Yes, with key off one of the Fuel Pump Relay slots will have 12volts all the time from the Fuel Pump fuse, the slot changes yearly so no record exists as to which slot it might be but there is only 1 with 12volts
If no slot has 12v key OFF then FP fuse is blown, in a 1991 its usually fuse #1, 30 amp, its in the engine fuse box, pull it out and test if fuse holder has 12v, and then test fuse with OHM meter

Another slot in FP relay will have 12volt with key on, not for 2 seconds, for as long as key is on

Yes the inertia switch would only show 12volts from relay for 2 seconds just when key is turned on, then show, 6.7v in your case

The computer GROUNDS the FP relay to turn it on, most relays in cars work that way, they get 12v with key on but are not grounded, so they don't do anything, until they are grounded

You can ground the FP relay full time for testing purposes
In the engine bay there will be an OBD1 connector, looks like this: https://www.therangerstation.com/tec...ry/OBD_I.shtml

In the drawing the Fuel Pump slot is labelled
Thats the GROUND for the fuel pump relay, use a jumper wire to ground that slot
When you turn on the key the FP relay should "click" closed, and you should have 12v at inertia switch full time assuming fuse is good

 

Thank you Ron D!

After realizing the Fuel Relay Switch should constantly have 12V, your answer helped me deduce it HAD to be a fuse problem. Although I had checked the fuses multiple times before, I now realized the stock fuses have multiple break points and finally saw a small hairline break in the fuse. Replaced the fuse and the truck started back up! Finally. For anyone else experiencing a similar problem, always triple check those fuses!!

 

Good work

Thanks for the update and THE FIX