1988 Ford F250 won't hold but 13 gal in front tank and 16 gal in rear. I ran out of fuel just to see if I was using all of the fuel in both tanks. Has anybody else had this problem? The tanks don't seem to be bent or pushed in. When I have the selector on the rear tank, the gauge goes way past full when it is actually full. When it reaches approximately 1/4 tank it goes back to full. Once I got in thinking the rear tank was full and ran out of fuel.

 

sounds like you have the infamous busted off pickup lines

bad news is to fix it you're gonna have to drop the tanks and attach a peice of feul hose to whats left of the pickup line so it reaches the bottom of the tank

someone should be along who knows how to troubleshoot the gauges in a little bit

 

Thanks for the info. Ares the fuel hose that you mention in the tanks?

 

He is talking about the pickup tubes inside the fuel tanks ... They are plastic and notorious for breaking off, Most just add a piece of rubber hose to extend the pickup tube back to the bottom of the tank and cutting a V in the end prevents it from sucking to the bottom of the tank and blocking flow, It also sounds like your sending units are bad, someone will be along that can explain a testing procedure for testing the sending units.

Unfortunately you'll need to either lift the bed or drop the tanks, neither are an easy task and either can turn into a total nightmare, especially if the vehicle is rusty.

-Enjoy
fh : )_~

 

lift the bed, its so much easier to remove 6 bed bolts instead of dropping 2 tanks, having to deal with the hoses and plugs above your head. you can get the replacement screens from ford, they dont have the one that it calls for, i can not for the life of me remember the ones i used, but it was for a psd.

 

I had this same problem sort of, I did the same thing though,3/8" fuel line to the sending unit and cut a V so it wont suck on the bottom, and its been working good for a month so far, I plan on it being a permanent fix

 

This is saying that I need to open up the tank and take out the sending unit?

 

What is the testing procedure for the sending units?

 

I apologize for asking so many questions. What wires, hoses, and any other connections do I disconnect when I remove the bed. I don't want to miss any.

 

I have two diesels. The one with the fuel tank problems is 1988 F250 Lariat. The 1984 has a problem getting fuel up to the fuel filter. I was told to check the lift pump. I thought that the fuel pump. was in the tank. Now I am told it is at the front of the engine on the passenger side. I am not at home now. If the lift pump is the problem, is this the same as the fuel pump on a gas engine?

 

On gassers of late 80's (with EFI) they had a pump in the tank. On our diesels they have a lift pump (similar too, but different than) on the front passenger side of the engine.

If you are pulling the bed, you need to unhook the wiring for the tail lights, and disconnect the fuel filler neck hoses. Also any extra wires etc you may have for trailers/campers that sort of thing.

To test the sending units themselves, use an ohm meter and measure the resistance from empty to full, seems to me (off top of my head) it should range from about 50-200 ohms, but just a wild a$$ guess!! Most common problems are pinched/shorted wires, grounding it out, or sometimes issues with the float on the unit. Of course when you are in there, may as well check on the pickup tube, and do the hose with a v cut trick to resolve that if they are broken off.