How to test fuel sending unit to see if its bad?

[jesse977]

I dropped my tank and removed the sending unit. I noticed the ground wire was frayed so I fixed it. How can I check to see if the fuel sending unit works without installing it in the tank and putting the tank back on the truck? I have a74 gmc swb 350 engine. Can I hook up the sending unit to the truck to see if it works? Whats a good place to buy one online if its bad?

[jesse977]

Heres a pic of the frayed wire

[notyo_cheez]

Run a new ground, turn the key on and move the floater. If the needle on the gauge moves the sender is still okay. I'd just splurge for a new one, they aren't that expensive. About $60 from JCWhitney or your local big box parts retailer. They do tend to wear out...

[motornut]

watch some cheap ones the float/gauge will bounce all day for you...like mine....

[tucsonjwt]

x2 on the bouncing gauge. Spectra is the aftermarket brand I used on both tanks, and both cause the gauge to bounce when the vehicle is in motion. Spectra sending units cost about $40, Delco costs about $140-160. Spectra gauges do register correctly and steady when the vehicle is not in motion.

[old Rusty C10]

by me Advanced auto partsd has em in stock as does autozone

[SeanPaintsFlames]

As for the bouncy gauges- I wonder if bending the float towards the pivot area would make it a little tighter and less bouncy before you put it in.

[motornut]

I have bent them but for a different reason
up here we get frozen gas lines
doing so (up an inch or so)makes the needle move off the full quicker
but you end up with more left in the tank on empty
at 40 below on a tilted laneway ,can make the diff of go or nogo

as for changing or stopping the bounce, doubt it
I've read the cheaper ones don't have a part that keeps the needle from reacting so quick,hence can be made cheaper

[notyo_cheez]

Is that doohickey that keeps the float from bouncing an internal or external part? Just curious, if it's something that can be removed from the old sender and attached to the new one a fella could save himself around $100 off the cost of an ACDelco part?

[motornut]

Originally Posted by notyo_cheez

Is that doohickey that keeps the float from bouncing an internal or external part? Just curious, if it's something that can be removed from the old sender and attached to the new one a fella could save himself around $100 off the cost of an ACDelco part?

duno i havn't done it,It sounded like an electrical type part ,read here on this site ,if this is it then it explains the prob i have when i read spectra on the outside of the tank,not having opened it I am just assuming it's the same maker inside

[silvereagle07]

You can test the sender card with an ohm meter. Hook positive to terminal on top of sender housing and ground to your new ground lead. It should read between 0-95 ohms when moving the arm with no skips in numbers. You can get them at any local parts house. Ive had good luck with RockAuto.com . Here is a link to the parts. http://www.rockauto.com/catalog/raframecatalog.php

[hatzie]

The Corvette guys damp the gauge itself with a special silicone gel. There's a howto on the web.