88 2.9L No Fuel pressure, only 7.5V through the inertia switch

[BillRod]

Ummmm.... No.

I only checked fuse number 18.
The listle list glued to the access panel only showed #18 having to do with the fuel.

I will check #1 this morning.

Bill

 

[BillRod]

Number one is good.
My list on the access panel shows #1 as the Stop/Hazard lamps 15amp.

Number 18 is the only one that refers to fuel.

#18 Seatbelt buzzer; warning indicators; carburetor circuits; tachometer; electric fuel pump control; shift on the fly. 15 amp.

That fuse is good and it does have power going to it.
And the warning bell does ding when I have the key in the ignition and the door open so that must be one of the warning indicators.

Bill

 

[351rangerxxx]

ok i was going by the wiring diagram that was posted above and showed power off number 1 sorry. just tring to help. i'm good with electical but if its the wrong diagram its not going to help

 

[BillRod]

Do you have any other thoughts as to where to look or check?

 

[BillRod]

Also there does seem to be power to everything else.
Headlights, dash lights, starter spins.
I put a timing light on the number one wire and it does blink showing spark as the engine turns.

Seems everything else has power and is good.
Just not the front fuel pump.

I have not looked at the rear pump yet, I will try to get to that Tuesday after work. Hopefully I can get to the wires without dropping the tank?

Any other thoughts or suggestions from anyone?

Thanks
Bill

 

[HndMeDnBroncoII]

try to temporarily bypass the inertia switch and see what ur voltage is then
and the power wire to the pumps<pink and black> i believe ,come from the inertia switch

 

[Area 52]

Also there does seem to be power to everything else.
Headlights, dash lights, starter spins.
I put a timing light on the number one wire and it does blink showing spark as the engine turns.

Seems everything else has power and is good.
Just not the front fuel pump.

I have not looked at the rear pump yet, I will try to get to that Tuesday after work. Hopefully I can get to the wires without dropping the tank?

Any other thoughts or suggestions from anyone?

Thanks
Bill

The only other thing that I didn't see that you checked Bill was the ground for the ECU (passenger kick panel...should be a ground connection below that).

 

[351rangerxxx]

have you tried a jumper wire from the battery to the black/yellow wire on the fuel pump relay?

 

[BillRod]

have you tried a jumper wire from the battery to the black/yellow wire on the fuel pump relay?

On my Fuel pump relay (the green one) I have a sold yellow wire and a Yellow wire with a stripe that actually looks more green.

The one with the stripe goes to terminal #1 on the relay.

Is that the one you mean?

 

[351rangerxxx]

i havent found a wiring diagram that i trust to help you with. you need power to two of the terminals. then one goes to the ecm to gound the relay and send power to the fuel. on the diagnostic connector under the hood there is a pin that you ground that will bypass the ecm and trigger the relay with the key on. send me a email to rickyamagnus@yahoo.com and i'll send you a troubleshooting page that shows the connector

 

[BillRod]

Lets look at this from a different angle.

The diagram the I got from Earl43P shows the red/black wire from the inertia switch going directly to the Fuel pump.
I just now put an ohm meter on the wire at the switch and and wire at the pump. OL open, There is no continuity between the intertia switch wire and the pump.
This is the front pump on the frame by the drivers door I have been looking at.

The Chiltons states this has an intank pump.
I did not think at all about looking at the tank or pump in it.

Does the current go from the inertia switch go to the rear in tank pump first before it goes to the front pump?

Is it possible that the rear pump went out and that simply cut the current to the front pump?

Bill

 

[Area 52]

Bill: Throw a jumper on between the inertia switch to the main pump...or have you done this already? The main pump and tank pump should be on the same circuit and may also be the same color. You are close to nailing this down!

 

[BillRod]

Bill: Throw a jumper on between the inertia switch to the main pump...or have you done this already? The main pump and tank pump should be on the same circuit and may also be the same color. You are close to nailing this down!

Have not had a chance to do that yet.
Looks like it will have to wait for a week or so to get back to it.
Way too many other things gettin in the way right now.


Keep the suggestions coming though!!!

Thanks
Bill

 

[BillRod]

Today I pulled the bed the truck to access the connector for the in tank fuel pump.

I pulled the 4wire connector. I assume the wire colors mean the following:
Black wire = ground.
Red w/Black stripe wire = power to the pump.
Yellow w/white stripe wire and solid Orange wire are for the gas gauge.

On the wire side of the connector I put a voltmeter across the red w/black stripe wire and the chassis. Key on, Nothing, to voltage at all.

I was pretty happy at this point thinking that neither pump was getting power and the inertia switch consistently has 12v for a moment then drops to 7v.
I was thinking that maybe the computer had gone bad and was causing all of this.


That was until I tried to spin each fuel pump independently.
I made a long jumper wire for power that had a 30 amp fuse in it so that I would not blow up anything in case I touched the wrong thing.

Front Pump:
I got the electrical connector for the front pump from a junkyard to allow me to easily put power it.
I hooked my long jumper directly to the positive battery post then to the red w/black stripe wire.
I touched the black wire to the chassis and Nothing, the front pump will not spin with separate power to it.

Rear Pump:
On the tank side of the connector I ran short jumper between the black wire's connector and the chassis to ground that pump.
Then I used my jumper with the fuse to run power to the red w/black stripe connector. Nothing, the in tank pump will not spin with separate power to it.

I tried to spin each pump in this manner to totally remove any other component in the electrical path.
I really though each pump would spin with separate power to it.


I am really stumped now. What am I missing?

 

[351rangerxxx]

sure you got a good ground?