Ive got a 88 ranger 4x4, ive replaced the in tank fuel pump, both fuel filters, the fuel pump relay, bypassed the inertia switch and still no power to the pump. When i bypass the wiring harness to the pump i can get power yet it will not start up. It will turn over fine and has fuel on the fuel rail yet will not fire. And advice will be helpful.

 

Welcome to the forum

First the No Start issue
50/50 test
Spray gasoline or Quick Start(ether) into the intake
Then try to start

If it starts and then dies you have Spark but no fuel from the injectors
If it doesn't start then you have No Spark or Low compression
50/50, quick and easy


In 1988 Fuel Pump power comes from a Fusible link most likely.
A Fusible link is a short wire connected to Starter Relay(battery post), it acts as a slow blow fuse, and it's other end connects to Fuel Pump Relay

Fuel pump Relay base will be Green, it will have 4 or 5 slots
1 slot will have power power(12v) all the time, that is the Fusible Link Power
So key off, test each slot for 12v, if no 12v then you will need to find and replace that fusible link

Starter relay(wrongly called starter solenoid) is mounted on inner fender, it is the Power distribution point for the vehicle.
Battery Positive cable is hooked up on one post of this relay, fuse box, several fusible links for alternator and fuel pump power are all on that 1 post.
Other larger post in this relay will just have 1 cable, to start motor, NO OTHER CABLES/WIRES should be on that post, just starter motor cable.

So pretty simple wiring, Everything on 1 post, starter motor on the other, lol, and doesn't matter which post they are reverse-able
Red/blue stripe wire on the small "S" post

If you have 12volts at FP Relay with key off, then you have fuel pump power there.
Turn key on
There should now be another slot in Green FP relay base that now has 12v, test for it, if not EEC relay, Brown Base, may be the problem

If you have a slot 12v key off and another slot with 12v key on then time to check for Ground.

Put FP Relay back in
Have someone turn key on while you touch FP Relay, you should feel it click closed for 2 seconds then click open.
Fuel Pump only gets power for 2 seconds each time key is turned on, a safety feature.
If you don't have a helper, disconnect ground cable on battery
Turn key on
Put finger on FP Relay and then connect the Ground cable to battery, you should feel it click closed and then open, when computer starts up

If it isn't closing then computer's wire to FP Relay or computer itself is bad
Pin 22 on computer is the ground for FP Relay

There is a Grounding wire available for FP Relay
You need to find the OBD1 plug in, it is in the engine bay.
Drawing of it here: Ford Ranger - Testing EEC-IV Equipped Engines

Fuel Pump slot is labelled in drawing, that slot is the GROUND for fuel pump relay.
So it you put a jumper wire in that slot and ground the other end of the wire the FP relay will close each time key is turned on and it will stay closed, by-passes computer ground.
Doesn't hurt anything.

If everything checks out then test for 12v at inertia switch, only there for 2 seconds unless you have grounded that OBD1 slot

Now in 1988 there are two fuel pumps, in tank and high pressure pump in the frame rail.
They share the 1 power wire from inertia switch, there is a splice in the wire by the high pressure pump.

And then there is the Ground for the pumps, no electrical device works with 1 power wire, gotta have 2 wires, 12v AND Ground, other wise no power can flow thru the device, which is what makes a light bulb light up and a pump spin, power MUST FLOW, so you need a good ground on each pump

Power path
Battery---fusible link-----FP Relay-------inertia switch--------------Fuel Pumps----Grounds

 

auto parts store said fuel pump relay has a gray base. But has power on 2 pins on gray base relay. Will check green base today. Will post if any changes

 

The relay itself can be any color
Ford used these base/socket colors
Brown = EEC Relay
Green = FP Relay
Black = WOT Relay << only for vehicles with AC, turns off AC Compressor when extra power is needed(WOT = Wide Open Throttle)

Not written in stone, depends where vehicle was made and if they had all the correct bases that day

Drawing here of 1988 Ranger relay placement: https://ww2-secure.justanswer.com/up...12_Graphic.gif

Self-test connector is shown, that's the OBD1 connector

 

have power at relay tested computer ground relay works. No power at inertia switch with ground bypassed

 

Then wire from FP Relay to inertia switch has been cut or is corroded.

Look at wire colors at inertia switch
Ford often used a Pink/black stripe wire to Fuel Pump

The other wire goes to FP Relay, there may be two, Dark Green/yellow stripe, usually.
So look at bottom of FP Relay for that color wire

The reason the are 2 wires(3 total) at inertia switch is that computer gets the same 12v as fuel pump when FP relay closes, this tells computer FP Relay is working.

 

not sure what else i can do. Thanks for the input. Ive tried everything youve told me and still nothing.

 

Sorry I couldn't help

Power path
Battery---fusible link-----FP Relay-------inertia switch--------------Fuel Pumps----Grounds

Thats all there is to it