I had a post the other day about my 97 breaking down for the first time and I had thought it was simply the fuel lift pump. After replacing that, I realized that my problem is a little deeper than thought, and has me stumped a bit.


First, the truck; 1997 F350 7.3, 4WD, Automatic (BD), Tymer air and exhaust, everything else is stock, original with 230K.


Truck has been running fine, but has seemed to 'bark' a little more than usual upon startup. Performance has been fine. The other morning, after a brief warmup, I made it about a quarter mile and realized it was starting to rattle, and wouldn't get over 45. I did a U-turn and it coasted to a silent stop roadside. Attempts to start resulted in the typical rattle and hideous sounds you would associate with air in the lines. Acted like it was starving for fuel, changed the filter, noticed the fuel bowl was empty. Checked for pressure on the lift pump outlet, there was minimal flow and zero pressure. Bad lift pump I thought. Installed a new OEM pump and attempted a re-prime. Nothing. Engine spun over with a sound of a consistent dead spot, almost like that hole was the only one trying to fire. After some major frustration, and filling the fuel bowl manually, it cleared the lines and fired. Cleared up quick, ran smooth, good oil pressure, sounded crisp, nice smooth acceleration on the pedal. After five minutes, I walk to the house for a minute, come back and the shop is silent. Fuel bowl empty again, attempts to re-prime fail, same problem at the lift pump. Switching tanks does not help. I blow the line from the pump inlet back to the tank, thinking blockage somewhere, line is clear. I attempt to pressurize the tank to re-prime the line and get no fuel to the motor. (yes there is fuel in the tank). I re-fill the fuel bowl manually as before, the engine will not start. The consistent 'dead spot' is gone, replaced by a consistent high pitched knock sound on the opposite side from the previous knock. I cant figure out why the lift pump is not producing.


My thoughts:
-Tank transfer switch bad, (although you can hear it working)
-Whatever pushes the plunger up and down on the lift pump isn't working, (not really sure what it looks like in there)
-I don't suspect a tank problem because either tank doesn't make a difference
-A good time for e fuel but I want to ensure my problem is captured with that install


Although not a regular here, Ive always appreciated the insight and humor of the folks here. Thank in advance.

 

blocked tank transfer valve could be it, enough trash in it and it can stick partially


more than 1/4 tank full?

 

Both tanks just under 1/4. Gauges have always been accurate.

 

go grab 5 gallons of diesel and put into one of the tanks and see if it works after




the shower heads are known to break off

 

The plunger is actuated by the camshaft so that is probably not the problem lol

Have you tried feeding the pump directly from a gas can? Get a new piece of fuel line, stick one end into the can, and the other on the intake of the pump? That would isolate your fuel supply system from the pump and let you figure out which one is the problem.

Did you have your FPR off when you pulled the fuel bowl?

Are you sure you plumbed the pump back correctly? I know it seems silly but it is easier to do than you would think.

 

clogged Fuel valve would be one thought


clogged shower heads in the tank would be my other...it is entirely possible both get clogged... especially if bad fuel aka water was introduced to the system at one point.

 

...............grr

 

I was able to pull the lift pump without removing anything else but the turbo piping. Nothing else was dis connected. The fuel plumbing is correct.

Water in the fuel is always possible but I by from the same place all the time, and there were no signs of water in the bowl.
Ill try that and if it works, start back at the transfer valve.
Getting a jerry can of fuel on the ground and running a length of hose up to the pump sounds like it would isolate the problem.

 

Oh yeah. Nothing seems silly at this point. I have a deer hunt in two weeks!

 

Truck primed fine with the jerry can. Pulled the transfer valve and blew all the lines out. Starts and runs good now. No problems during test drive.
My one complaint; Would it have killed Ford to run that valve 6" further forward so you dont have to drop the tank to remove it?
​​​​​​​Thanks again for the help!!

 

Drop the tank? Yeah, it's a little tight in there, but I had no trouble reaching mine with the tank in place.

Good to hear you nailed it, in any event.