Hey guys prolly dumb question, but first diesel. Getting ready to drop tank cause it clogs up and won't let truck run. What do I need to look at as far as in the tank? How do I clean it. What's beyond repair. And do them tanks have sending units if the tank is bad and I have to replace
1984. 7.3 idi

 

Sending units aren't readily available. Luckily for you the '84 didn't have the infamous Cone of Failure in the fuel tanks so just drop 'em, clean them, put them back together.

Some of us prefer to pull the bed then dropping the tanks when working on the sending units since it's easier, but if you're having to flush the tanks they're coming out anyways.

 

From the FAQ:

Fuel tank sending units, pickup tubes, and bed removal:

Fuel Tank Sending Units

 

I pull the bed, that freaking rear tank is a pain!

Many do it without doing so, I have several times, never again!

In fact my 94 currently has the bed off to fix the sending unit and rebuild the rear end (when I find a housing).

-Enjoy
fh : )_~

 

Just pulled both tanks on my `86 two days ago. Front tank is simple enough. Rear tank just takes a little patience. Remove hose clamps where fill tube connects outside of frame. Drop the two straps, pull tank down. Reach up, remove both fuel lines and sending unit connector. then let tank fall to ground. Takes about 10 minutes, if you are the least bit mechanically inclined.

 

So you can't get a pump anymore?

 

You can get fuel pumps all day long.

It's the sending units in the fuel tanks that are hard to find for various years. See that thread I linked to.

Just clean and reuse yours.

 

That's cause you're young!
I do highly recommend staying that way ...

Us old farts don't bend and twist like you youngins do ...

-Enjoy
fh : )_~

 

Eating dirt and rust is no fun either. I won't do the hard way again, wisdom sometimes follows age.

 

All depends on your circumstances. I'm about to turn 56, and I can slide under the truck WAAAAY easier than I can handle a bed removal. We also have just a single-width gravel/dirt drivewy with three trucks, a trailer and a station wagon all in-line, so there'd be no place to put the bed once we got it off. The only thing I didn't do right the first time, dropping the tank, was using ratchet straps to ease the skid plate down, then again to ease the tank down. And use them to get the tank / skid plate back in place.

To your original questions, all fuel tanks have sending units; you wouldn't get a fuel gauge reading otherwise. If you're chasing a clog, first thing you need to do is determine which tank is doing it, and whether it's the selector itself that's got the clog. I'd eliminate everything downstream of the tanks before dropping either one.

 

I just repaired both sending units in my `86. Also picked up new shower heads.

I replaced the tiny little circuit boards in both of them. Just one little spot to solder back. Very straight forward and simple.

The wiper was worn out on rear tank. Had to swap the arm and housing from a donor 460 truck. Arm required some creative bending to clear everything, but not too bad. Some of the sending units will come apart easily, others no so much.

After all that both gauges now work.

 

A point of clarification: the fuel pumps in these trucks are not electrical pumps in the fuel tanks like modern vehicles. They are a traditional lift pump bolted to the side of the engine block.
Behind and below the alternator if you are trying to locate it.