Fuel problems 1989 F-250 460

[fatherdoug]

I've been having some issues with fuel delivery on the '89 with 460.

The mechanical switching valve and the frame rail high pressure pump were replaced a couple of years ago. Lately, the truck stumbles when accelerating, and it dies when I switch from the front to the rear tank. Since the fuel gauge does not read on the front tank, I ordered the whole setup for the front tank, sending unit and pump, which I will replace. After that I will order an in-tank pump for the rear tank.

The fuel filter on the frame rail and the relay for both the fuel pump and the EEC have just been replaced with no change.

Am I missing anything?

[dustybumpers]

do you have the fuel reserve canister in the lines?
It is the switch valve that keeps the fuel going back into the tank it came from.
Down by the high pressure pump,and filter is a can where all 4 lines come from the tanks, and go to 2 lines into the pump
They go bad, and don't let fuel come through, OR return to the pump

Some 460's had a "hot fuel" system, and didn't have this set up.

This is it
http://www.ebay.com/itm/1989-1997-Fo...5TvLEO&vxp=mtr

I have had 3 go bad on my 89 F350 in 500,000 miles

[fatherdoug]

I do have that valve, Charlie. I replaced it a couple years ago with an NOS Ford valve. The truck has about 1000 miles since the switching valve, frame rail fuel pump were replaced. Hopefully they haven't gone bad already.

[dustybumpers]

Fuel pressure guage in the rail will tell the story. Bad reserve tank will show low pressure with a known good high pressure pump

While hooked up, and running, pull the vacuum line off the fuel pressure regulator, if the pressure rises, it's good. If it stays the same, bad.

If it's bad, it will blow out the check valves in the reserve tank, and render it useless

You should also pull the vacuum line off the pressure regulator while the engine is off, to see if there is gas in it.
There should NOT be any gas in it.

[fatherdoug]

Thank you, Charlie. I appreciate the info. Can you point me in the direction of where the regulator is at? And I am assuming the pressure can be measured at the schrader valve on the rail?

Edit: I found the location of the regulator. Thanks again, Charlie.

[dustybumpers]

LOL. came back to help, and you had it covered.....

Yup, valve on rail. Harbor freight has a nice guage if you don't have one

Pressure should be about 10 lbs different with hose off.

[dustybumpers]

Another thing I had forgot, the lift pump in the tank COULD be faulty if it is not working when you switch tanks.
This system will work if the pump is not working, and there is over 1/4 tank of gas left.

Once it gets below 1/4, it will not work, as the level is below the high pressure pump.

Try unhooking the high pressure pump, then cycle the key to see if the lift pumps in the tanks are working

[fatherdoug]

Once again, Thank you! Good info. I have to replace the sending unit in the front tank, since it doesn't register on the gauge, so I ordered the whole works with the in-tank pump. I have to order a pressure tester. I don't want to drive 200 miles to get one.

Also, do the mounting bolts for the high pressure fuel pump provide the ground for the pump? I noticed yesterday that the mounting bolts for the pump are loose.

[dustybumpers]

I think....... ( old memory here)
The mounts are into rubber, to keep the pump from vibrating noise to the frame, the pump actually floats in there

There is a - and a + wire to the high pressure pump, no ground, but that from the computer, which is the wire hooked to your driver's side hood hinge

The other ground for the fuel inj sys for 85-89 is a wire on the inside of the core support, behind the headlight
You have to search for it, it's in the wire harness, but sticks out and fastens with a 5/16 pan head screw

[fatherdoug]

Thank you. I checked that ground out about a year ago when I lost the ground from the frame to the cab, as you so advised.

I did replace the fuel pressure regulator(what a pain!) today, but haven't driven the truck yet. The auto shop for the power plant had a NOS still sitting on their shelf. The mechanic gave it to me.