2.3L ('83-'97) 1986 fuel pump cycling

[Dan B.]

Been steadily working on the 1986 2.3, 5sp, 2wd project truck. It's been running awesome. We even swapped in a 8.8"/4.10 diff in preparation for a "down the road" 5.0/T5 swap...in the parts accumulation stage. But until then we are having fun rolling around in it.

Anyhow...the other day it wouldn't start. Instead of the fuel pump cycling on for about two seconds then turning off, it's running constantly and you can hear fuel trickling back into the tank. I'm pretty Ranger savvy but hate electrical issues...which I'm guessing this is. Ideas? I tried the search function already and didn't come up with anything.

 

[rusty ol ranger]

Relay stuck on?

 

[RonD]

Does Fuel Pump only run with Key ON?

If so then its not the Fuel pump Relay, but pull it out to make sure pump turns off with Key ON, it should of course
If it does turn off then most likely issue is the ground wire for this relay
Pin 22 on the computer grounds this relay for the 2 seconds with key on
This ground wire runs from pin 22 to the OBD1 port and then to the relay, if this wire is chaffed and grounding out then relay would be activated full time with Key ON
Or its a computer issue
You can test for ground at Fuel Pump slot in OBD1 port, should not show a ground after 2 seconds with key ON

OBD1 slot labels seen here: https://www.therangerstation.com/tech_library/OBD_I.shtml

If you connect test light or volt meter to battery positive and Fuel Pump Slot, Key ON, you shouldn't see voltage
If you do, try moving wiring harness around to see if it unGrounds, no volts, if it does this would mean a ground short in the wiring
If not then you will need to pull off the connector on computer to see if it unGrounds
If so then you will need to "pop the top" off computer and have a look inside for damage


If fuel pump is on with key OFF then yes fuel pump relay may be stuck closed, so bad

 

[Dan B.]

I'll more testing and report back.