mikeamondo

Hi guys... I'll be dropping the tank on my '67 98 Town Sedan in a week or two. Gauge sits pegged at 3 oClock.... way passed full.... constantly, until I unplugged it at the connector in the tank and grounded it, at which time it went to empty. Rehooked and it went back to 3 oclock.


I removed, cleaned and replaced the grounding screw at the tank to no avail... although I'm still a little dubious of it, so prior to tank droppage, I plan on grounding that with an alligator clip to the frame to be certain.


So... to the question... I very, very rarely use a multimeter, but would like to test the old canister type and see if I can make it work before I swap it for a non-canister type from Rock Auto.... which will work, but will likely float all over the place.


Can someone walk me through the tests I should do once I drop the tank, to see if mine can be repaired? Basically... what I should expect to see, what I should set my multimeter to and what I should connect it to, etc. Sorry that I need the handholding here, but it's been a while.... and of course, electrical stuff is pure voodoo.

oldcutlass

It should ohm out from 0-90 ohms. To test you can hook up the sender to the wire that runs to the gauge and provide a good ground and move the float up and down with the key in the on position.

MDchanic

Okay, here's your fuel gauge circuit:

+12V (Instrument Power) ------> Fuel gauge (Driver's side + terminal) -----> Fuel gauge windings -----> Fuel gauge (Passenger side - terminal) -----> Tan wire -----> Tank sender -----> Rheostat (0-90Ω) -----> Ground.

The sender should read 0 - 0.6Ω at E, 44.9-45.1Ω at ½, and 88 - 90Ω at F.

- Eric

mikeamondo

I received my new sending unit (1972 Lesabre) from Rock Auto for my '67 98. I think I have a solid grasp on the steps for the job and testing the old unit before replacement.


Now... is there a need for a special tool to remove the sending unit from the tank... to loosen the locking ring? If something else can be made to work, what is it? Thanks!
Mike

MDchanic

Just use a hammer and a drift against the recesses of the retaining ring, one at a time, counterclockwise, until the fingers are released.

- Eric

Oldsmaniac

You may want to soak the area with wd40 or the like as the locking ring gets crusty and rusty and can get stuck.

mikeamondo

Not to be stupid... but a hammer and 'drift'? Do you mean just tap against the ring in the right direction until it starts to loosen? Maybe I'm visualizing this thing incorrectly.

wls559

Yep, tap until the little ears that stick up are in the opposite position of where you started. Getting it back is the part that gets a little frustrating.

Bill

oldspackrat

Make sure to clean that area of the lock ring really well before removing it. Compressed air works well. I'm also nervous about working with gas & tanks & always use a hammer on a brass punch so as not to create any sparks on top of the tank. If no brass, maybe spray it down with water from a mister or something? Maybe too cautious but rather be that way than not cautious enough.

mikeamondo

hmmm... good thoughts... I don't have a brass punch, but I bet I can find something plastic or rubber that will do the trick. Thanks for the advice... I plan on dropping the tank this weekend if I have her back from the mechanics following her rear end rebuild... if not it will be a couple weeks down the road...