Fuel Pump Issue 87 B2 2.9L

[johndough]

Can’t get any power down to the high pressure pump. Tried new fuel pump relay, bypassed the inertia switch. Now what? I’m lost and would really like to fix this because I just got this thing running for the first time in 10 years and was just driving it around like it was nothing.

 

[Rimjam]

Have you tried putting 12v to the output wire of the inertia switch just as a test? Pretty sure I've read about this problem in the 2.9 forum. RonD explained how to trouble shoot this issue step-by-step.

 

[RonD]

Because there is only 2 seconds of 12volts for the fuel pumps with key on it can be a pain to test the wires

Locate the OBD1 test port in the engine bay, it will be on main harness, looks like this: https://www.therangerstation.com/tech_library/images/eec-iv_testing2.gif
Odd shape

Fuel pump slot is labelled on the drawing
That is the GROUND for the fuel pump relay, the computer grounds this slot(an relay) for 2 seconds when key is turned from off to on, and only for 2 seconds, its a safety thing

If YOU ground this slot then fuel pump relay will activate with Key On and it will stay activated until Key is Off or you remove the ground wire

So great for testing for 12volt on the fuel pump wires, also for draining the tank or ???
Doesn't hurt anything, it is what the computer does when engine is running, but not UNTIL its running

1986-1988 Rangers and B2s have two fuel pumps
One in the gas tank
One in the frame rail under drivers seat area
They share one 12volt wire, it comes from inertia switch in the cab, and runs to frame rail pump first, there is a splice there, then wire continues on to the top of the gas tank

The splice by the frame rail pump was a common failure point, it would get corroded

 

[johndough]

Because there is only 2 seconds of 12volts for the fuel pumps with key on it can be a pain to test the wires

Locate the OBD1 test port in the engine bay, it will be on main harness, looks like this: https://www.therangerstation.com/tech_library/images/eec-iv_testing2.gif
Odd shape

Fuel pump slot is labelled on the drawing
That is the GROUND for the fuel pump relay, the computer grounds this slot(an relay) for 2 seconds when key is turned from off to on, and only for 2 seconds, its a safety thing

If YOU ground this slot then fuel pump relay will activate with Key On and it will stay activated until Key is Off or you remove the ground wire

So great for testing for 12volt on the fuel pump wires, also for draining the tank or ???
Doesn't hurt anything, it is what the computer does when engine is running, but not UNTIL its running

1986-1988 Rangers and B2s have two fuel pumps
One in the gas tank
One in the frame rail under drivers seat area
They share one 12volt wire, it comes from inertia switch in the cab, and runs to frame rail pump first, there is a splice there, then wire continues on to the top of the gas tank

The splice by the frame rail pump was a common failure point, it would get corroded

So I should use something and put it inside of that slot to ground the relay, then take a multimeter down to the fuel pump wires?

 

[RonD]

Yes, but turn the key on after grounding that slot or no 12volts and turn key off after you are done because fuel pump being left on will drain the battery, I know DUH, but I have forgotten, kinda like leaving the heads lights on