Fuel pump not activating

[C.Fuller305]

I have a 1994 ford ranger with a V6 4.0. I just replaced the fuel pump, filter, pressure regulator, and computer in it now my fuel pump won’t activate. I have good connections on ground and I am receiving 12 bolts on power wire. The inertia switch is hot wired so no problem there. I’m at a loss any ideas?

 

[RonD]

In the engine bay is the Fuel Pump Relay, should be in the engine bay fuse box
The Computer controls this relay..............by grounding its coil

On the main wiring harness from computer to Engine fuse box is the OBD1 plug in, may have a Cap on it with "EEC" embedded

Find it, then look here: https://www.therangerstation.com/tech_library/OBD_I.shtml

You will see a drawing in above link of OBD1 connector with Fuel Pump slot labelled
That slot is connected to both the computer pin 22(fuel pump control) and the Fuel Pump relay's coil Ground

With Key ON, use a jumper wire from battery negative(or any ground) to that slot
When slot is grounded you should HEAR the fuel pump relay "Click" Closed, and fuel pump should come on
If you don't hear the relay click then relay could be bad
If you do hear it click but no fuel pump then fuel pump Fuse may be bad

You can leave the jumper in place if fuel pump comes on, and start the engine, won't hurt anything, computer grounds that slot/fuel pump relay full time when engine is running
You can also leave it in place, key ON, to test fuel pump wiring back at the tank, see if the 12volts is making to inertia switch and then back to the tank

With key OFF pull out fuel pump relay and test each slot for 12volts, only one should have 12volts with key off, that's from the fuel pump fuse, 20amp in this same fuse box
With key ON a 2nd slot should now have 12volts, that's from EEC relay, this is for the relays coil, needs this so the Ground can activate this relay

 

[C.Fuller305]

In the engine bay is the Fuel Pump Relay, should be in the engine bay fuse box
The Computer controls this relay..............by grounding its coil

On the main wiring harness from computer to Engine fuse box is the OBD1 plug in, may have a Cap on it with "EEC" embedded

Find it, then look here: https://www.therangerstation.com/tech_library/OBD_I.shtml

You will see a drawing in above link of OBD1 connector with Fuel Pump slot labelled
That slot is connected to both the computer pin 22(fuel pump control) and the Fuel Pump relay's coil Ground

With Key ON, use a jumper wire from battery negative(or any ground) to that slot
When slot is grounded you should HEAR the fuel pump relay "Click" Closed, and fuel pump should come on
If you don't hear the relay click then relay could be bad
If you do hear it click but no fuel pump then fuel pump Fuse may be bad

You can leave the jumper in place if fuel pump comes on, and start the engine, won't hurt anything, computer grounds that slot/fuel pump relay full time when engine is running
You can also leave it in place, key ON, to test fuel pump wiring back at the tank, see if the 12volts is making to inertia switch and then back to the tank

With key OFF pull out fuel pump relay and test each slot for 12volts, only one should have 12volts with key off, that's from the fuel pump fuse, 20amp in this same fuse box
With key ON a 2nd slot should now have 12volts, that's from EEC relay, this is for the relays coil, needs this so the Ground can activate this relay

I checked everything at the very end when I was checking the relay slots I was reading 12.84 volts on two of them and 11.64 on a third slot. I had the key off following your instructions exactly and double checking the steps

 

[RonD]

Should only be 1 slot with 12volt and key off so you have some wiring issues, or you were testing the wrong relay base
Although I can't think of any relay base that would show those voltages with key off

You should probably disconnect battery cable and pull up the fuse box to look at the wiring to the relays bases

Wiring and colors below
Also 1993 engine fuse box layout which is the same as 1994

 

[C.Fuller305]

Should only be 1 slot with 12volt and key off so you have some wiring issues, or you were testing the wrong relay base
Although I can't think of any relay base that would show those voltages with key off

You should probably disconnect battery cable and pull up the fuse box to look at the wiring to the relays bases

Wiring and colors below
Also 1993 engine fuse box layout which is the same as 1994

So I made a rookie mistake and had reversed the wires on my multi meter every thing you said is working now grounding pin 22 I tried sticking the fuel pump relay back in while the jumper was hooked up and I blew the 20 amp fuse not sure why to do now

 

[RonD]

Wire from relay to inertia switch or from inertia switch to fuel pump may be shorted to ground

Leave fuel pump fuse out
And test if relay works, plug it into its base
Turn on the key
Ground the slot/pin22 and relay should click close, then click open when unGrounded, repeat a few times

You may have shorted it out plugging in the relay

So if relay is working/clicking, then put in another 20amp fuse, key OFF
Unhook pin22 jumper, then turn key ON
See if fuse blows, computer will ground pin 22 for 2 seconds with key on, but only for 2 seconds
If fuse is OK, the hook up jumper again and fuel pump should come on and stay on
If it blows fuse again then new pump could be bad or there is a short to ground on a wire going to the back/fuel pump

You said you jumped the inertia switch, those are 12volt wires, no grounds, so make SURE they can't short to metal