2.3L ('83-'97) Fuel pump relay signal/trigger

[b1pig]

Someone help me out here.... 88 2.3 manual.

The red wire on the fuel pump relay is the trigger (12v) to close the relay and send power to the pump. I can't reliably get 12v on that wire. I poked a jumper into the relay, relay close, pump came on. I checked and found fuel at the fuel rail. Pulled the jumper off, and the relay stayed closed. Checked again... and NOW had 12v on the trigger wire..

Turned the ignition off. Turned it back on. Right back where I was. No power (actually, 1-2mv, but not the 12v needed).

I'm guessing that the computer will be the source of the 12v power to trigger the relay. Any way I can possibly fix this without hunting for another computer?

 

[RonD]

No

The fuel pump relay gets 12v with key on from the EEC relay(brown base) full time when key is on
The computer GROUNDS the fuel pump relay to activate it, but only for 2 seconds, computer won't ground it full time until engine RPMs are above 400, cranking speed is 200rpm

But computer will ground it for 2 seconds EACH TIME key is turned from off to on

1988 most likely uses a micro-relay for fuel pump in a Green Base, slots look like this: https://www.gtsparkplugs.com/images/micro-automotive-relay-wiring.jpg

85 and 86 are to activate the relay, one will have the red wire from EEC relay
Other will have a Tan/green(?) wire from computer pin 22
(there is no need for assigned polarity on these relays so Ford could have wired it either way)

This Ground wire runs thru the OBD1 connector in engine bay so you can use that to ground the relay full time, for testing

Have a look here, second drawing down: https://www.therangerstation.com/tech/testing-eec-iv-equipped-engines/
OBD1 connector is labelled
Fuel Pump slot is the ground wire pass thru from computer pin 22 to the fuel pump relay base
With key on that slot should show 12v, after 2 seconds, that's the 12v passing thru the relay's coil
Insert a jumper wire in that slot and ground it
Fuel pump relay should click closed and, if its working, fuel pump should come on and stay on until key is turned off

 

[b1pig]

For what it's worth, I found and fixed my issue today.

I stripped back the wiring harness from the flexloom. I was getting very low voltage on both the 12v and ground wires on the fuel pump trigger wires. The voltage was good on the main power feed to the relay. I borrowed a Maestro tool from work to test the thing this weekend. Spent all day chasing this mess.

Fuel pump ran when I fed 12v on the outbound side of the relay. I put my fuel pressure gauge on the rail to watch it. Also to flush some of the old fuel out of the lines while I was at it. Trying to trigger the relay by feeding 12v on the positive side and triggering ground on the ground side just would not work for some reason. I decided to leave the ignition on and the battery connected while I stripped back the harness. Pulled the air filter box as well.

As I was lifting and moving the harness, I heard a relay click under the hood somewhere and the tester showed pressure on the rail. I started manipulating parts of the harness, which resulted in me chasing the problem until it literally quit clicking completely. Got to digging around and found a wire coming out of the harness loom right behind the battery. The wire was hanging out of the ground terminal off the battery, was burned and pitted from arcing. I touched it to the battery and the relays clicked the fuel pressure shot up to 40.

I stripped back and replaced the ground wire, reset the ground terminal (one of those cheapy replacements, but it still works) .... and while I was in there, I went ahead and replaced a bunch of sketchy butt terminal connections that my wife's uncle had done some years ago... obviously making quick fixes of broken wires, replaced relay plugs... and such. Who knows. Rewrapped the harness with tape, put the flexloom back on and put it back together.

Put the bed back on and went for a drive. Runs better on 1 year old gas than it did when we parked it over a year ago. A/C still kicks butt.

Tomorrow, I've got to wash it off a bit and put it on FB.....
Since the wife's parents passed away last year, we ended up taking on a lot of other financial junk..... to include her dad's F-150. Yep. Another Ford. I picked up an old SN95 Mustang last year right before her dad died. Didn't expect we'd be taking on his truck. So, her uncle Tommy's truck has to go. Ironically, it seems like its the one vehicle on our insurance that has a premium higher than it should be for such and old truck.

Problem solved.

Thanks for the help.