How, Exactly is the power wire routed from the Inertia switch to the fuel pumps?

[BillRod]

I put my ohm meter between the red and black wire on the intertia switch connector and the red an black wire on the rear pump conector. Nothing, no continuity.

Tried the same between the Inertia switch and the front pump connector, same result.

Then tried the same between the 2 pumps, same result.

So now I am wondering what the connection is between the inertia switch and the Fuel pumps.

 

[901wd]

relay, inertia sw, then pump.

cut the fawker out and solder the wires. they are more trouble than they are worth. imo

 

[BillRod]

Doh!!!

I did not mean for this to be a seperate thread, I meant for this to be part of my other thread about the voltage through the inertia switch.

Sorry about that.
Bill

 

[Psychopete]

Inspect the small plug on the drivers side, I want to say it was PK/BK on my '88, but it's a single wire that is the power for the pumps. Just a small single plug, not documented in the Helm Inc. EVTM. The wire is the same color as the +12 on the high pressure frame rail pump. You could put +12 volts there (at the small plug) to turn on the pumps to verify that part of the circuit is working. Have you also tried to temporarily bypass the inertia switch?

I would be tempted to test with an analog meter or test light on the relay side (IN) of the inertia switch to verify that the computer is trying to prime the fuel pumps when the key is put on run (it doesn't run constantly until the computer knows that the engine is running).

Pete

 

[BillRod]

Inspect the small plug on the drivers side, I want to say it was PK/BK on my '88, but it's a single wire that is the power for the pumps. Just a small single plug, not documented in the Helm Inc. EVTM. The wire is the same color as the +12 on the high pressure frame rail pump. You could put +12 volts there (at the small plug) to turn on the pumps to verify that part of the circuit is working. Have you also tried to temporarily bypass the inertia switch?

I would be tempted to test with an analog meter or test light on the relay side (IN) of the inertia switch to verify that the computer is trying to prime the fuel pumps when the key is put on run (it doesn't run constantly until the computer knows that the engine is running).

Pete

I did bypass the intertia switch. no change.

I also put the voltmeter on the intertia switch.
I shows 12v for a second or so then drops to ~7v.
Is that what it is supposed to do?

But even for that brief second or two of 12v I do not hear either pump run.
I have good ground all around the truck and to the frame, I assume they each have seperate ground connections to the frame so the ground seems ok.

I want to say it was PK/BK on my '88
I don't understand, what does PK/BK mean?


Bill

 

[Nailzs]

bill, pete is refering to the wire colors. pink/black

as to your fuel problem, i had an earily similiar problem on my bronco ii recently. no fuel pressure, high pressure pump would not run, crappy continuity, and i had 12v that would drop to a constant 6v.

i never did figure out what was wrong with the wiring, if there in fact was a problem. what i can tell you is that after 2 napa high pressure pumps,and finally putting in a ford high pressure pump, my bronco starts up and runs fine(as far as the fuel pressure goes) now.

im trying to find that thread...
here it is
http://www.therangerstation.com/forums/showthread.php?t=52330

 

[HndMeDnBroncoII]

the ecu automatically builds up pressure when u turn the key on this way good pressure is there when it starts.thats why the voltage drops i believe i could be wrong if can get the motor running check the voltage while its running. and i used to hear my pumps all time like normal now i dont hear them at all but the mototr still runs though

 

[holyford86]

I had a similar problem, I was getting voltage to the pumps but no pumps running. It turned out I had a faulty ground to the pumps, adding a ground wire from the high pressure pump to the frame seemed to remedy this issue.

 

[Mysticcook]

Since my box is off! and fuel pump out i applied 10 volts very briefly(using battery charger prolly not smart) to the left two pins red wire to pos black to ground spins. The first pin is black then red.if you run power to this and still nothing I would guess a fuel pump. The 3rd pin is your gas gauge the next pin goes nowhere. ground I dont know.
You can hook it up either way just pushes or pulls pump. My pump was out of truck using a old one that was "extra" so wasnt worried about sparks etc.

This would elimate fuel pump I would think. I got just pump from RockAuto much cheaper. thougtht that was problem turns out previos owner had put in electric fan and ran power wire under the battery (kids) so yea it had worn down the insulation causing me a whole lot of scratching my head moments!.

This is from a dual tank ranger but dont see how that would affect anything.

The twelve volts you see then dropping is prolly the pump priming before you start then computer kicks in when running and gives the full 12v.

 

[Psychopete]

I'd be real tempted to apply the 12 volts to the connector that runs to the fuel pumps on the driver's side to see if the pumps turn on. That would narrow it down to it being a bad ground / broken connection / pump (that intank is hard to hear), or if there's an issue with the relay / fuel pump circuit if continuity is good between the legs of the inertia swtich. There is also a way to test the whole circuit from the diagnostic connector, IIRC it acts as the ground from pin-22 from the computer, which ultimately controls when the fuel pump is running or not. FWIW, The ECC relay and computer have to be functioning for the fuel pump circuit to work.

Pete