Sending unit / fuel guage question.

[ajrn]

Hey--

I've got an '82 Diesel..

The guage won't read full-- no matter how much diesel is in the tank..

The most it will read is about 5/8's... It will go lower, as the fuel is burned out of it..

Does anyone know how to diagnose one?? That is-- does the sending unit use variable resistance (a rheostat/float arrangement).. OR is it something ugly and harder to 'decipher??'

I'm in no rush to drop the tank-- A ) it's running, B ) it's WINTER!!

I'm just thinking, when I replace the fuel lines to run B100 (biodiesel) it wouldn't be a bad idea to look into this.. :thumbs_up

Is there a chance 'vegitation' is keeping a 'float' from 'floating??' (ewwwww!)

[GypsyR]

Most likely you have a pinhole in your float. The float looks very much like a ping-pong ball. Mine was completely full of diesel when I got around to pulling it off. It's been sitting on a shelf for 3-4 months now and still full of diesel. Funny diesel can get into the float but not leak back out. A new replacement float is the only solution.

[asav8tor]

Not too hard to drop the tank. Only two nuts opposite side of the filler. You might be able to drop it leaving the lines connected, in which case the tank would not need to be 100% empty. ( the less fuel the better though ). The sender has a quick disconnect wire and simply twists to remove.

While you are at it, bend a small hook on a coat hanger, reach down the sender opening and pull out the fuel screen. Throw it in the garbage. Do not replace it.

mike

[ajrn]

Sort of figured the float "wasn't..."

Like I said, I'll have to drop the tank in the spring-- but in the meantime, I'll keep rolling, as is.. Can't run serious biodiesel in January-- you never know from day to day where the temp will go..

Are replacement 'floats' available-- or do you have to replace the whole sending unit?? I wonder if you couldn't drill the old one, drain it, and close the hole by using fiberglass resin or something 'fuel resistant.'

[GypsyR]

Yes, you can swap the float. It just fits into a wire loop at the end of the "arm". I considered drilling, etc, but still can't think of an adhesive that I would rely on to stick to the float.
I happened to have a spare brass float for my '89 Ford Bronco and discovered it fit handily. I suspect it's a tad too heavy though, my gauge doesn't quite register to the full mark when the tank is filled. At some point I will look into obtaining a correct float but I can now at least put it off for a quite a while.

[toddshog]

Hey Mike, is this strainer also used as a weight for the fuel pickup tube? I am going to pull my tank soon and flush it as well as clean the screen but I was planning on leaving the strainer on as I thought it may also be weighted. If it is not needed I will yank it and rely on the primary filter.

[asav8tor]

No, the strainer is not used for weight.

At the bottom of the tank sits a plastic cup. It is held in place by tabs bent from sheet metal braces spot welded to the bottom of the tank. The strainer fits in the cup and can be pulled out of the sender opening with a piece of wire (coat hanger wire works good). Just bend a little hook on the end to grab the ring and pull.

If you cut the tank open you will find the bottom of the plastic cup is made of rubber. As the strainer becomes plugged the rubber bottom will suck up to the fuel inlet and block the fuel. This will cause the engine to quit. After the engine quits the suction is lost and the engine can be restarted. The process will repeat until the rubber will tear and block the inlet preventing the engine from running. At this time you must cut the tank open to get rid of the rubber bottom. Much easier to just pull the strainer, leave it out, and rely on the engine compartment filter before all of this happens.

Mike

[toddshog]

What I wanted to know. I need to pull the sending unit (guage doesn't work) anyway so I will pull it off then. Thanks Mike.

[asav8tor]

My fuel gauge was inop as well. I discovered the ground was the problem. I ran a new ground wire connected via sheet metal screw on top of sender to frame.

mike