Hey guys, need a little help. 1995 f350 4x4 crew cab.
From time to time while using rear fuel tank truck would die, but if I hurried up and switched to front tank it would pick back up and run fine. usually I could switch back to the rear tank and it would run but it might go 10 miles or 200 miles before it would die again. I suspected pickup tube might be getting clogged with something, so I decided to get rid of both tanks and install a new spectra 38 gallon. That I did. Finished project, put 15 gallons of fuel in truck and went for a spin. Five miles later it died again. I barely got it started and made it a mile from the house and again it died. Took out the fuel filter and the fuel bowl seemed too low. So with filter out and observing inside of fuel bowl while I turn over engine with key off, I see no fuel coming into bowl. Just some air. When I took out old rear tank
I only found the small round screen in the bottom of the tank. The rest of that assembly was extremely brittle and I couldn't find it. I just replaced fuel pump within 1000 miles. I disconnected the supply line from the tank and blew air though the line and the air comes out inside the fuel bowl at the top. I wonder if all those little pieces are in there somewhere.

 

Check your fuel pressure regulator screen, might be plugged up with crud.

 

FPR Screen very clean

 

I just looked again in my old rear tank and found the missing uptake screen parts. What is the best way to determine if the fuel pump is working?

 

Your fuel selector valve might not be switching full to your tank. Maybe by pass selector valve with some hoses and it's possible crud is stuck in pump preventing it to pump.

 

This is very possible if you did not take the fuel selector valve out of the fuel line loop. If you want the valve in the loop, disconnect the fuel lines from the selector valve, and blow air threw the valve from both the ports that run to the engine, then switch the valve to the other tank and blow air threw it again. This may clear the valve, as I have done this before.

 

I did remove the tank selector valving. I did blow air back into the tank and into the fuel pump and it went through on the supply line. I could hear it bubbling in the new tank. When I blew air to the front of engine it came out at the top of the fuel basin. I had the filter out. Doesn't the fuel go into the lift pump first?
Also, I have not checked the return line, if it was plugged would it prevent fuel from moving in the supply line?

 

I checked fuel pressure at Schrader valve and none whatsoever.

 

I would put a fuel line from the pump into a can of diesel and crank the engine to see if the new pump is working. If the pump fills the bowl and works with specified fuel pressure, then it must be a problem with the fuel pickup in the new tank or the supply line to the pump.

 

Good idea. I will try that this morning.

 

with empty lines its going to take a good minute or two of cranking to fill the bowl

I did this yesterday

 

I tried that so obviously pump not working or a line plugged up.
I just took out fuel pump. I blew air through that same line and it comes our of bottom of fuel bowl, so I guess not plugged.

 

so from pump inlet to tank line if free too? did you try to blow air that way as well?

I would do what airstreamer said, get about 10 feet of hose and put to pump inlet then other end into a jug of diesel

possible the fuel selector or a line is open and not allowing vacuum, to test you can get a vacumm pump hand held one with a gauge and see if it drops fast or make vacuum

 

When I installed the new tank I just bypassed the tank selector valve and spliced both the supply line and return line back together. If I break both those lines apart I can get air to go through them both ways. I have a new fuel pump coming so hopefully that will fix the problem.
One question: the supply line goes into the fuel bowl first as it comes from the tank, right?

 

Yes that is right. There wasn't a possibility you mixed up the supply and return is there? If you are trying to suck from the return the little end may be blocking it off