No power to fuel pump

[Witty]

First off, I'd like to say that I've been fighting with the fuel system since I got this Ranger back in October. I've always had to wait for several minutes before the fuel pump would kick off. Now to my new problem.

I'm not getting any power to my fuel pump. I've checked and I'm getting power at the inertia switch and back. I've tried jumping the connector, taking a new wire from the power side of the connector to the pump, but nothing turns the pump on. Jumping straight from the battery starts it though.

I noticed when I was looking around that there is water getting in the passenger side. The foam on the firewall is soaked, there was moisture on top of the computer behind the kick panel. Could it have screwed the computer up?

This started a week ago after we got a bunch of rain. Parking lot at work was flooded, streets were flooded, heavy rain on the way home, ect.

 

[RonD]

1988 Ranger has two fuel pumps, one in the tank(lift pump) and one in the frame rail(high pressure pump)

Computer only turns on fuel pumps for 2 seconds each time key is turned on, when engine RPMs are above 400(engine is started) computer will turn on pumps full time.


If you have power at the inertia switch the fuel pump fuse and fuel pump relay are OK
There should only be power(12volts) for 2 second though, after that you might see 5-7volts at inertia switch, that is "monitor power" no amps just a few volts, so can't start pumps, it is from the computer, it monitors if fuel pump is getting power when it should and no power when it shouldn't.

The original wiring just went to the fuel pump in the tank, when Ford added Fuel Injection they needed to add a high pressure pump, so they Spliced a wire into the original harness power wire, near where the high pressure pump is located in the frame rail.
That splice often fails and needs to be redone.

Hard to check if the in tank pump is working, but try.

Water won't hurt computer but will hurt the connections on the computer

 

[Witty]

I haven't looked at the spliced wires for the HP pump, but I did put my hand on the in tank pump but couldn't feel it kick on. And as for the volts at the inertia switch, once the relay kicks off, the volts drop to 0.

 

[RonD]

The monitor circuit may not be on the '88 computer, '95 and up for sure had it.
So 0volts can be normal with relay OFF

No vibration from tank means low pressure fuel pump isn't working.
Does HP pump work?

 

[Witty]

Nope. The only time it works is when I jump straight off the battery. I tried jumping the pump off of any connector to see if I could find the problem. The inertia connector didn't work, even tried the relay.

 

[tomw]

You should re-read the posts. You will not, repeat NOT, find power at the fuel pump unless the engine is RUNNING, or the 3-5 second 'prime' run when the key is first turned to ON.
The computer controls the pump power, and will NOT provide pump power until the engine is running, as posted above.
If you have power for the short time referenced, the pump should make noise. The pump in the tank, and the pump on the frame about under the drivers seat.
A gauge on the fuel rail where the injectors plug in would tell you if you have fuel pressure.
If you jump straight from power to the fuel pump, it should run. Both pumps should run when power is applied at the inertia switch terminal. Likely a PK/BK h colored insulation.(pink/black hash markings). The power in to the inertia switch might be Yellow.
If you apply power to the 'output' side of the inertia switch, the pumps should run.
If they do not, pump time. If they do, computer or relay time.
The computer is in the kick panel on the passenger side, I believe, and if you had a delude, you may have a damaged computer.
I don't have an 88 pinout, but the wire to the relay might come from pin 22 and be T/LG D, tan with light green dashes. It would provide ground to the relay 'enable' winding, closing the relay, and sending power to the pumps. (Likely O/LB orange light blue)
The relay has power to the 'switched' power side from a fusible link, 20G blue in 85.
tom

 

[Benjamin.jacob]

I just had this same problem in my 87 2.3 ranger, turns out a passenger kicked and broke the clip to the inertia switch and it was just unplugged a little. Try to give the plug a little push back in