Please help 91 Ranger issues with fuel pump has power all of the time

[XR 50 Racer]

I just purchased a 91 Ranger 4L, 5 speed, 4x4 and I am having some issues. when I bought it they guy said that the batery was bad. after putting a new batery in the ranger and using it for about 3 days the new batery is dead. I checked the voltage going to the batery when it was running and I am getting 14.4 volts all is good there when I was installing the batery agian I could hear a relay clicking. after doing some more research it is the relay for the fuel pump and it was priming the pump each time that I put the cables on the batery with the key off like it primes all day long. I tryed a new relay with no luck. I also tryed a new igniton switch and that too didnt work either. this is my problem where is the non keyed power getting to the relay is there another switch that I am missing or somewhere else that I need to be looking.

 

[410Fortune]

the computer turns on the fuel pump relay I would check the signal from that wire... it may be the PCM itself with the issue

did you replace the relay?

 

[XR 50 Racer]

I did replace the relay all other aspects of the electrical system seem to be good I am not all knowing but how does the computer get power if the key is off?

 

[MrShorty]

Do you have a wiring diagram? Fuel pump running constantly like that almost has to be a problem of some kind with the relay. If you get a wiring diagram, you'll notice that the main power feed to the relay is "hot at all times" (meaning key on or off). If that relay gets stuck closed, then the pump will run continuously. The coil side of the relay gets power from the EEC relay, and the PCM acts as a ground side switch to open and close this relay. The right combination of "shorts" can cause the coil side of the fuel pump relay to be continuously energized.

In short, I'd start diagnosing this at the fuel pump relay. With a wiring diagram and voltmeter I'd figure out why the fuel pump relay is stuck closed (or if someone has bypassed the relay -- it happens sometimes).

 

[XR 50 Racer]

the pump doesnt constantly run or run any diffrent than it should with the key on when you conect the battery with the key off you can hear it prime and then it stops similar to what you would hear when you turn the key on but it does it with the Key off. I have tryed diffrent relays with not luck I have also unpluged the relay when the truck was running and it did die. that prompted me to think it was the igniton switch and when I tryed a new one of thoes and it did the same thing when I hooked the batery back up pump primed and then stoped. I guess I am wondering if it could be or is there a presure switch on the rail that is demanding for the pump to prime with the key off

 

[92exp4x4]

Check the PCM power relay. Check the power dist box and PCM relay terminals. You may have bad corrosion and some shorts.

When you turn the key to on, the circut closes for the PCM relay which powers the PCM. The PCM then provides a ground for the fuel pump relay and it turns on, running the fuel pump.

There should be 3 relays on your truck. One is for the A/C cutout, PCM and fuel pump. They are the same and you can use swap them to help find the bad relay.

Hope this helps, let us know what you find.

 

[92exp4x4]

Also which ignition switch did you look at? The actual electrical switching part is on the top of the steering column under the dash.

I assume you know this but some people mistake the keyswitch for the "Ignition" switch.

 

[XR 50 Racer]

yahtze! the hidden and third relay was the issue I switched that with the one that wasnt doing anything (AC I belived) and no more cycling when I hooked up the battery I left it hooked up tonight we will see if I have won the battle between the truck! Thanks Agian for all of your ideas and support.


PS I did try the lower actual igniton switch I found it was way easier to drop the columb to get to it