ignachuck

Dusting off an old thread with a new question:

I have a 56 Super 88 and recently replaced the sending unit. The gauge at the dash tested fine, by the way. So, with the tank full, the gauge stops just a tad under one half. Before taking the sending unit out, I wrote to the vendor to ask if he had tested it. He says that the unit should read zero ohms empty and 30 ohms full. I wrote back that everything I read says it should be 90 ohms full, and that's the problem.

Sanity check please.

Thanks,
Frank

oldcutlass

I moved your post to a new thread in stead of resurrecting an old one. If you remove the wire from the fuel sender the gauge should go to full or beyond. If you ground the wire it should go to empty. I believe your gauge may be a 0-30 ohm, 0-90 were 65 and newer.

Tedd Thompson

Double check your ground wire, they often corrode up and give bad readings. Remember they are grounded through the gas line with a Micky Mouse clamp and if the line has been altered, repaired (gas line spliced with rubber hose) they won't work correctly or at all....Tedd

Ozzie

My original equipment sender on my 1955 Olds reads 1.2 ohms in the empty position and 30.5 ohms in the full position. If the 1956 is similar and your gauge is correct, with a full tank, it should be seeing about 30 ohms where it is actually seeing about half of that. Perhaps you could try it with the sender out of the tank to see if the gauge is linear for its range of movement.

Clutch Cargo

Oldcutlass can you move my fuel gauge posts to new so I can get some help ?

Cutch

Clutch Cargo

Most FOMOCO fuel senders measure exactly as you describe 0 ohm and 90 ohms.
Some one made a mistake here.

Tedd Thompson

Don't think so, or at least 55's run on the 0 to 30 ohms. I don't know when they changed ,but early cars had the 0 to 30 as a standard.

Now my 55 will run out of gas with 1/8 showing on the gauge, I guess it always has but took me 20 years and a tow in Montana to find this out, I always run on the top half except that time...Tedd

Clutch Cargo

Thanks so much I fully intend to mock the entire assembly up out side of the car now that I have a new sender and a gauge from a 55

Vintage Chief

No one made a mistake - most pre-'65 GM cars read 0 ohms (empty), 30 ohms (full).

Vintage Chief

You can accomplish this on your own by (1) creating a new thread (of your own) with your own thread title, (2) copy/paste your piggyback (what you posted into other's) posts into your new thread; and, (3) delete your previous (piggyback) posts. Always best to create your own thread for better assistance. Good luck.

ignachuck

From the 30's into the 60's - 0 to 30 ohms.

Vintage Chief

Frank - Prior to the 30's they used a stick (I believe)?

Clutch Cargo

So what you read was the problem

Clutch Cargo

YESS!! I did as you suggest and success!!
I got a used 55 OLDS fuel gauge. and mocked up the system using a current limited 12VDC supply, jumper clips and a sending unit from a 58 Ford.
E reads at 1.2 Ohms and F reads at 29.7 Ohms.
AND with the tank lead disconnected it "pegs" exactly as described by others in this Thread
Thanks so much for all the expert help and advice

Clutch Cargo

Thanks Norm I am not that computer savvy

Vintage Chief

Understand...no worries.

Clutch Cargo

Thanks, Ozzie, for your most accurate information on this. I found that the meter operates as sort of a "Bridge" circuit with the unknown leg being 1 Ohm to 30 Ohms.
This makes the dual coil D'arsonval meter track in a nonlinear fashion. My test bed repeatedly measures one half full at 10 Ohms.

regards Clutch