Okay folks this one is getting really,really weird. I've been having trouble for a while with the truck stalling out like it ran out of fuel. I have to stop and crank and wait, crank and wait, etc. You all know the drill by now. It had a mechanical pump that was working just fine for the longest time. Then all of a sudden it started this crap.

I got P!$$ED tonight and install a Mr.Gasket Blue pump from Advance Auto Parts and figured okay problem solved.

Now here is where it gets really weird. I bled the filter out by pulling the valve out of the pressure check point and turning the key on till fuel came out. I then put the valve core back in and shut the truck off and took it for a ride to test it out.

Both tanks were completely full and have been kept that way to rule a broken sender out of the equation. I know both senders are broken off at about 1/4 tank level. So I never let the truck drop below about 1/3 tank. I was cruising along and it started surging and acting like it was going to stall and after doing this for a few seconds as soon as I pressed the clutch it died.

I coasted into a parking lot and popped the hood to check and make sure I still had fuel pressure. I figured maybe it popped a fuse and lost power but I could hear the pump running. I grabbed my valve core tool out of the glove box and pulled the core on the filter housing. All I got was air for a bit then after about a minute it started pumping fuel out of the fitting. I started it back up and drove it home and it stalled again. I checked it and again the filter was empty or close to it. I'm running out of ideas on this one. Any suggestions would be helpful.

 

My guess is that you have a rust hole in the fuel line somewhere before the electric pump. I have had this problem and its a pain in the but, you will not see a fuel leak because the hole is too small but it will suck air through it. If you can, try to run the truck from a five gallon can in the cab. Just get a piece of fuel hose and go from the can to the electric pump and drive it. If it runs fine you have narrowed down your search

 

How can it have a rust hole when my fuel lines are plastic? I'm fairly certain that the line from the tanks to the switching valve are plastic and the line from the switching valve to the racor filter are plastic switching to steel but that line is fine. I'll pull it inside and take a look again in a couple of minutes.

 

I have older fords and they have steel running under the motor cradle to the lift pump. If it has air at the schreader it is getting there before the pump, it almost has to because you have pressureized fuel after the pump. air leaks are the hardest thing to find, I would still try to run it off a seperate fuel sorce to eliminate the trucks fuel system and see if the problem stops

 

The only way to really check for an air leak is to cap off the line at the switching valve (if you have the problem on both tanks) and take the line off where it enters the filter and the pull a vacuum on the system and see if it holds

 

I know about the steel line under the engine cradle and I know for a fact that doesn't have a rust hole in it. I know this because it took me two days to make it out of stainless tubing. I'm pulling it into the garage in about 5 minutes to take another look and hopefully get it figured out. What a headache.

 

I had one that gave me so much trouble I drove around for a week with a fuel pressure gauge taped to the windshield wiper so I could see what was happening when it started to surge and quit. That one ended up being a blocked pickup tube (leaves in the fuel tank) you may have a blockage also but I doubt it

 

The fuel line that is built into the fuel pickup in the tank is steel and a short length of it is exposed on top of the fuel sending assembly. This exposed part of the fuel sender is notorious for rusting badly. Chances are that the steel line has a rust hole in it just before it connects to the plastic fuel line. If the top of the fuel sender is badly rusted enough, the fuel that leaks out will simply drain back into the tank, and you may not even have a visible leak under the truck. A blockage of the fuel pickup tube is also possible, especially if there is corrosion on the top of the tank.

If you already know that both senders have a problem, then it might be time to drop the tanks.

 

Looks like I'm going to be doing that here in the next week. I'll nurse it along for my trip today then on my way back I'll make sure to run the front tank down as low as I can get it. I'll probably pull the bed to do the work but that can change depending on my mood. I got a used rear sender of ebay for 27 bucks delivered so I guess now I'll have to find a sending unit for the front now too.

 

The o-rings on the couplers for th eplastic line may have failed as well, they are just like the ones on the motor, they can fail with the different fuel we now have. I have had that happen, and if you have disturbed the lines at all, that can also be an issue. The air is definitely coming in before the pump, and hopefully, you put the pump back near the selector valve, where it is best.

 

I'm about a foot or so away from the selector because the line coming from the selector is plastic then turns into metal about a foot away. I'm not happy about it but for now it is what I have to work with till I get another kit to make plastic fuel lines.

 

What if the tank vent was clogged? Have you tried running it with the fuel filler cap off?

 

Okay I just got back from my trip up to Melissa to pick up an axle for a guy on another diesel forum. I ran for about 5 miles on the front tank and got mad and switched over to the rear and ran the rest of the trip using the rear tank. The issue is definitely with the front tank part of my fuel system. I was running 75 MPH the whole way up 45 to Dallas getting 15 MPG. It never spit sputtered or acted up the entire trip after I switched tanks. Now I get the fun of going out and running a hose from the new electric pump to the rear tanks and using it the empty the front so I can find the issue. I'm tempted to pull the bed of to do the repair as I hate dropping tanks. I'l update after I figure out where the issue is.

 

You can get at the sender on the font tank without having to drop it, the main trick is either the exhaust or the driveshaft need moved out of the way so you can get up there.

 

I'll take a look at it after a bit. I'll figure out how to squeeze in and check it out.