The GMC CCKW

Hi all.

I'll have to change my fuel sender that seems to be defective.

I would like to know if I can remove it with the fuel tank in place or if I'll have to take the tank off? I have a cargo 353 truck with a few inches space between the tank and the bed.

If your tank is on the right side [passenger side ] under the bed you will need to remove the tank ,i could not get mine out!!

Ok thanks.

And how can I remove the tank without getting flooded with the gas that is still in the line to the pump? I mean, when disassembling the pipe line on top of the tank.

The manual lever on my fuel pump is broken. How can I do to prime the pump when reassembled?

I have always felt that getting some gasoline on you is like getting the grease and oil on you. it is just part of processes of owning old military vehicles. I don't think you can remove the fuel line without spilling some gasoline, but the tank will have to come off to remove the sending unit. You might want to drain as much gasoline out of the tank with the drain plug in the bottom into clean cans as this can be a lot of weight when removing the tank from the supports.

You could raise the cargo bed too.

Thats an idea. I Never thought of that. Thanks Doc.

Not a problem 777.

I done mine not so long back. just undo the bolts holding the tank straps on and unscrew the sender wire and the fuel pipe and slip the tank out but please bear in that the tank is an horrible shape and can be hard to handle....especialy when you have 4 gallons left in it

I emptied mine by sucking out the fuel with a pipe and it was also a great excuse to clean the tank as it was full of rust....I used my wifes vacume hoover

Thanks Jack!

And what about priming the pump when reassembled?

No worries.

I just turned her over and up it went, thankfully it isn't like a diesel engine

In fact, I don't know what is the problem with the sender. I don't know if it really the sender that is defective. I intalled the votage reducer (12 to 6 Volts) from Jim Carter Classic Truck Parts. Then, as it was not functionning, I did some tests like explained in the manual furnished with the reducer. that's how I came with the idea it's the sender that's defective. I hope it won't be given away. I'll have to buy a new sender before.

AAA, tank senders have a habit of rusting up here in Europe, as condensation builds up in the tank, from warm days and cold nights.

The float mechanism simply stops working. Free it up and you might be OK. A simple test with a meter will tell you if the "electrical" part is functioning OK.

I usually understand well how things do work when I can part them. I'm curious to see how it looks like.

Hi 777, The tank unit looks like this; the float rises and falls with the level in the tank, and as it does it turns a vertical shaft through a gear mechanism.

The unit is shown here on its side, the round fitting flange should of course be at the top!

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The turning shaft moves an electrical contact over a resistance winding mounted in the top circular housing. Altering the resistance, adjusts the voltage to the Fuel Gauge, which in turn controls the amount of needle movement.

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Hope that helps you.

If you accidently short the + lead to the fuel gauge to the sender lead, the sender is ALL done!

Be careful!

If you are doing 12v, you need a regulator, not a resistor. The regulator produces 6v from 0 load up to the current limit of the regulator. Last time I bought one it was ~$18 from JC Whitney. It has an additional lead that has to be connected to ground.

dr deuce wrote:If you are doing 12v, you need a regulator, not a resistor. The regulator produces 6v from 0 load up to the current limit of the regulator. Last time I bought one it was ~$18 from JC Taylor. It has an additional lead that has to be connected to ground.

That's what I bought. Took your advice.

Make sure that the tank, or at least the sender is grounded. I usually connect a wire with a lug and star washer on it to one of the sender mounting screws and connect the other end to a convient place on the frame.

No ground, no work....

Disconnect the wire from the sender terminal and see if the resistance changes when it moves up and down.

dr deuce wrote:Disconnect the wire from the sender terminal and see if the resistance changes when it moves up and down.

The only one test I haven't done yet.

Today, I have checked the resistor of the plunger. There is not continuity at all throught the sender. Nothing moves when moving the plunger.

It seems I'll need a new sender. I'll let you know in a few days.

Yup!