cus

Hello,
I'm having some trouble with the fuel gauge & sender. Way back when I started the restoration on my 1973 Delta 88, I purchased a new sender for the tank, have had it hooked up to the gauge for some time now, & just putting about $10 of fuel in the tank at a time, all seemed to be working OK.
I've finally got the car on the road now, so drove to the gas station & put in about $30 of fuel, the gauge went from about 1/4 to nearly empty? so
not sure what's going on there. When I disconnect the brown wire & turn
on the ignition the needle goes over F as it's meant to, connect it back up,
& back to just off empty, I'm thinking it should be reading 1/2 full.
Any help appreciated,

regards, Cus

oldcutlass

What happens when you ground the wire?

cus

Ok, grounded the brown wire at the rear from the guage, came back from 3 o'clock position to F with ignition on.

oldcutlass

Well it should have gone to E. Now you need to get on the brown wire at the gauge and ground it and see if you have the same result.

cus

Sorry, came back to "F" from gauge being grounded, no change from sender

Junkman

Sounds like you have switched the wires on the sending unit. I once bought a Mustang 2+2 that had been repro'd. I thought that I had a full tank of gas, and ran out of gas on a hill, with a jersey barrier in the middle. That was a nightmare to back it down the hill once the police stopped the traffic at the bottom. Rolled it into the gas station at the bottom of the hill, and filled the tank. The needle went to empty. Got underneath, and found that the previous owner had cut and switched the wires. Don't know if it was deliberate, or due to a "repair". Switched them around, and no more problems.

oldcutlass

If you grounded the brown wire at the gauge and it only went to F, you have a gauge issue. Is there a full 12v at the other side of the gauge.

cus

Hello Eric, looks like just under 9 volts all the way through, does the power feed into the circuit on the rear trunk harness next to the fuse box?

oldcutlass

No, the power is direct to the gauge. The wire that runs back to the sender is the ground side that runs through a rheostat (float assy). Was the 9 volts measured at the gauge?

cus

No, I haven't measured at the gauge, very hard to get to the terminals with the meter.
I'm presuming it should be 12v intead of 9v though ? Must be a bad connection somewhere.

cus

Ok, so have removed the cluster & hooked back up, there is 12 volts at one side of the gauge & 2.5 volts at the other, & 9 volts down at the connection to the fuse box. In the meantime I filled the tank & the guage started working for a day, then dropped off to empty again, very frustrating!!

oldcutlass

Read this:
http://www.modsandrods.tv/2012/03/29...uel-gas-gauge/

cus

Certainly looks like it's at the gauge end, considering it doesn't go to empty when
the broken circuit is grounded, but it is intermittent?

oldcutlass

Intermittent usually means bad connection somewhere.

cus

Still haven't found the short. Ran a remote wire from the fuse box to the connection behind the rear bar, no difference. Starting to think about fitting a remote guage
under dash, I've seen a couple of round face Oldsmobile fuel guages for 1973 models,
would they work, or what would you suggest,

regards, Cus

tru-blue 442

http://www.rockauto.com/en/catalog/o...ding+unit,4436

Sounds like it's time to R&R the sending unit.

oldcutlass

Its got a problem in the wiring or the gauge based on his troubleshooting.

cus

Can I retro fit a 90 ohm gauge under dash,

oldcutlass

Yes

cus

I'll give that a go with some new wiring, will see what happens

cus

OK, with the new guage, was able to test all the wiring.
Got back to the sender unit, used a separate power source & new guage, still on empty,
using new wiring from the sender pin. So looks like the sender is the culprit, really ticked off, was new when I flushed & re-painted the tank, always had about 1/4 full & guage
worked fine, as soon as I got the car on the road & filled up, went to empty, popped back
up for a day & has since stayed on empty, I haven't let the tank go below 1/2 as yet.
Will see what happens in a few weeks. At one stage I put a fuel stabilising additive in the tank, but wasn't much, only for a 1/4 tank, not sure if that has had anything to do with it. Getting a new sender is a bit of a pain in Australia, with freight, not much change out of $200 AUD, & 3 weeks, regards, Cus

oldcutlass

Lets perform the test again. What happens at the gauge when the wire is removed from the sender with the key on? What happens at the gauge when you ground the sender wire. When you performed these tests above to the original gauge it went to F when you grounded the wire, it should have went to E. With the wire removed it should go past F.

cus

With the new & in dash guage, if the sender wire is disconnected, needle goes over full,
on the new guage if the sender wire is grounded, goes to empty but on the old guage ,
just pulls back to around full.

cus

Did some surgery n the old original sender & got it bench testing ok with the new guage, the rubber had perished a bit around the brass sender pin, so must have been arcing on the top plate, anyway got it working, but wouldn't use in the tank. So connected to the sender wire at the connector at the rear bar & trunk, the dash guage worked, but not completely accurate, was at about 3/4 when I pushed the float to high, & sat a bit off empty when pushed the float to the bottom, but now know there is definitely a problem with my new sender, probably something very simple, but I don't want to go thru this again in a hurry, so might just replace it. If the guage is also a bit of a problem, I could disconnect it & wire up the new one, but would like to keep it original if I could, as long as I get some indication of the fuel statis I'll be happy with that.

oldcutlass

Based on the above, the new gauge works correctly, old gauge does not.

cus

The sender seems to be the main problem

oldcutlass

If your sender is the swing arm type you can bend the arm so it reads correctly.