This is a continuation of my Previous Thread titled

'Truck drives Like I'm Towing a Battleship' I felt it necessary to make it a new topic.

After establishing that it is not the clutch fan, coil, distributor, plugs, wires, badly grounded intake manifold, blown head gasket, and anything I've forgotten to add here; I've discovered possibly the root of my problems

For those of you first time viewers...

1988

Ford

F-250

VIN H 5.8L

4x4

This truck started out with a simple lagging problem when I stepped on the gas to accelerate hard.

Today, I went through much of the electrical system, not all there’s only so many hours in a day I can work on this as I work a 3rd shift job.

My findings are as follows

Inertia switch is good and checks out, only 20 Ohms of resistance on a continuity test; but no voltage.

Checked the Intake manifold for stray voltage that would cause the truck to not fire up. Zero volts found Zero Ohms of resistance.

Checked continuity of the brown wire that goes from the Computer to the Inertia Switch, to the fuel pump, the continuity checks out only 12 Ohms of resistance.

Checked both relay sockets Green (fuel) and brown (I guess that’s power...?) the sockets are find and both had about 20 Ohms resistance and they both had 12.4 volts both with key off and on...

Replaced the two relays. Here’s where the new trouble begins...

After reconnecting the battery, the In-Line fuel pump turns on I thought nothing of it (maybe I left the key on...) the key was off...

Alright...At least the pump is now on, it wasn't before all this time...so I try starting it, I get a grumble backfire out of the motor and then nothing. I checked the rear fuel tank for the hum of the in tank pump, I hear nothing…

I've given as much data as I have for today, My questions...Why is the fuel pump staying on with the key OFF, Is there another way other than sound, or dropping the tank the check the rear pump?

Might I add, the wiring job in the truck, by the air cleaner and computer was HACKED this morning, I went over it with my Haynes manual and checked the wiring (it checked out) and proceeded to solder everything instead of leaving wire nuts, which was what was there for the wiring. I suspect this truck has had a new motor put in, or something else done with the electric system.

Any help would be mighty appreciated.

Thanks.

 

I wish you would have left this connected to the other thread. it makes it hard to help you when we cant easily see what you have been doing. this is a complicated issue and we need all of the facts.

 

In my opinion...any resistance greater then 1.0 ohms on what is supposed to be a "solid" connection....is an open wire or shorted to some other wire. 10 to 20 ohms is OK for the energize portion of a relay because of the windings to make the magnetic field in order to pull the contacts together.....but a wire from point A to B......nope...must be less then 1 ohm. Also...the inertia switch....a simple cut-off switch..should have much better continuity then that....less then a half ohm. For the inline pump to run constant....a wire must have been jumpered or a wire melted to another within that circuit. Be aware that most in-tank pumps of the low pressure kind don't make enough noise to notice...if you still have the OEM pumps.....replacement pumps are a hold 'nother story. You need to correct the constant running of the inline pump first...major safety issue ! Then .....verify voltage to the in-tank pumps.....which is also on for a moment then constant while cranking/running. Also check for ground of the harness to the tank. The only way to verify the in tank pump is actually puttin' out once you verified voltage/ground, is to unhook the respective line at the fuel reservoir and observe the fuel output when you cycle the key on. One of our members...subford.....has links to all the photos you need......just need to apply the troubleshooting.
Phillip