fuel sender unit

[ozbowhunter]

almost scared to ask this
is there an easy way to get to the fuel sender in the gas tank on an 82 gmc step side it looks to me like i have to lift the cab is this the only way
the reason im asking is the fuel guage keeps going to full and i know its not full on the new dash i am fitting or can there be any other reason for this ?

[bohmankid]

drop the tank. But I would rule out grounds and electrical connections before doing this. invest in a multimeter.
on my 3/4 ton i can access the sender unit by sliding the bed back about a foot. I don't know how it is with the SWB.

[88Jimmy4x4]

Drop the tank it's real easy
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[pontgta]

http://forum.73-87chevytrucks.com/sm...ic,9294.0.html


These are the instructions for a fleetside, but should be the same for the stepside.

Check for grounds.. for an 82 should only be 1 wire at the sending unit.. and then a ground.

[motornut]

full? or over full?
overfull or 3 o'clock , i'd check the sender wire

[sqzbox]

Before you drop thetank, buy new tank straps. chances are the old ones are rusted and unable to be used again.

[hatzie]

The senders are right behind the cab. If you look between the cab and bed you can see the fuel lines and sender connection.
I've cut off the bed bolts, removed the filler neck hoses, and lifted the tail of the bed to slide 2x6 lumber between the bed rails and the frame. You can lift the rear far enough to clear the bumper and slide the bed back a foot or so on top of the lumber.

With 3 or 4 buddies you can pull the bed off the frame completely but you don't need to.

[ozbowhunter]

ok update
i have dropped the tank and removed the sender unit then reconnected it and moved the float and got response on the guage but when put back in the tank and reconnect to wires the guage moves to just over full again and will not return to empty when turned off also if i disconnect the sender wire it gauge moves to 3 oclock it looks as if the tank is 3/4 full if i look in it
any ideas out there?

[hatzie]

Did you re-attach the ground wire from the sender to the frame?

[ozbowhunter]

yes tried another ground and got the same response it seems it might be the wrong sender as it shows full untill it drops to around half the tank?? is it supposed to return to E when ignition is off ?

[hatzie]

Since you have the tank out...
Pull the sender and put an meter on the the sender from the ground connection to the sender stud.
Set the float close to parallel to the flange. It should read 90ohms.
Drop the float all the way down. It should read close to 0 ohms.

If it ohms out OK your problem is upstream. Wiring resistance or gauge. If the gauge just goes to F then the wiring is probably OK.

Short the sender wire to a frame ground with the ignition on. The gauge should go to E.

[ozbowhunter]

ok have done as suggested and heres what i get the ohms read from 0 to 110 ohms at the top (full) of the sender if i ground out the sender wire the guage goes to e if i touch the sender wire to the ground wire the guage goes to e

but when i set the sender back into the tank it reads just over half which is correct but when i turn off ign ition it stays there
im thinking a new sender unit is needed thoughts guys?

[hatzie]

110 ohms is a little high for full... 110 ohms will place the needle above the full mark. The float arm may not reach the top of the resistor coil when it's installed... Can you lift the float past the point where it would contact the top of the tank when installed?

If you plug the sender in and clip the sender ground wire to the frame, where you tested the sender wire, does the gauge move as expected when you move the float from bottom to top?

[ozbowhunter]

ok now im so confused i only get power to the dash when the i pull the lights on ??? when i turn the left turn signal on the right comes on everything has gone haywire what have i done??? also the brake light will not turn off?? this is so weird

[hatzie]

Loose grounds will do funny things. Not funny ha ha either.

[ozbowhunter]

have checked all grounds (at least what i can find) will keep looking

[ozbowhunter]

ok i have traced all ground wires back from the instrument cluster used a continuity tester and ever ran a direct wire from the battery negative terminal to the soldered junction of all grounds behind the cluster and still have the problems
could it be a bad light switch?
if i turn it while the ignition is on it effects all the lights and different things happen?
but if i disconect it i still have problems if the system runs throught his switch could this be it ?
i checked the hazard switch and all the dash lights come on with it
just dont know where to look next all grounds in the engine bay are ok as well
i even tried a spare cluster i had still cant sort it

[ozbowhunter]

Good news everything is working but...... I put in a new fuel sender unit and attached the earth to the frame and the gauge still will not return to e I tried 2 different gauges and same thing
I did put the old earth and the new earth to the same point should I remove the old earth??
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