fuel gauge issue, please help!!

[1972BlueC20]

Replaced sending unit, still doesn't work heres what's happening :

This is what happens, when I fill up the needle stays where it was prior to filling up until I drive like 3 miles down the road. Sometimes it even takes till the next day. It then shoots just barely past full. From there it seems to work fairly accurately. It goes down a little everyday as I drive and put more miles on her. Since I'm not sure of the gauge, I always keep track of the miles driven so I don't run out of gas and get stranded on the side of the road. Once I have only about 1-2 estimated gallons left it only goes as far towards empty as a 1/4 of a tank. It may go further down towards empty if I drove somemore, but I'm too scared to run out of gas

When I remove the wire from the sending unit or remove it at the fuse panel there is no change on the fuel gauge.

Anyone have any idea what needs to be fixed or replaced??


Thanks!

[litew8]

I'm not sure. Is there a large float inside of the tank? Fill it up 3/4 of the way and shake the cab back and forth (give it hell) and see if anything changes. You can also search these threads with the Google box above. Just tick the 67-72 radio button before clicking search (Google). Quick search found this: http://67-72chevytrucks.com/vboard/s...d.php?t=456772

[michael bustamante]

Theres a black wire on the dash harness that should clip to the metal part of the dash. That might be off and that might have something to do with it

[1972BlueC20]

I just replaced the sending unit with a unit from LMC, it came with a float attatched.

[litew8]

If you've replace the sending unit/float, then yeah sounds like something down line

[Prescott]

Sounds like you have an intermittent electrical connection, or a bad wire.

[FRANKENSTEINC10]

When you remove the wire, the gauge should go well above full(key on of course).

[1972BlueC20]

yeah when I take the wire off, it does nothing at all....hmmm.....my next step is to check all the connections at the gauge and behind the cluster, then replace the gauge with a new one.....hopefully that fixes it!!

[TBONE1964]

Ok, here is how it works.

If you have lost the ground on the sending unit, the gauge will go past full (3:00)

If you loose power on the sending unit,(the wire that hooks to the stud) the gauge will do nothing and stay where it was last.

If you loose ground on the gauge itself, the gauge will go to empty.

If you loose power from the fuse box, the gauge will stay where it was last.

This is providing you do not have multiple problems. It sounds to me from your description of the problem that the gauge is just slow to react. My 72 pick up has a very slow reacting gauge. It works fine and does not have any electrical connection issues, it is just a slow gauge.

Hope this helps,
Tom

[1972BlueC20]

Thanks for the info Tom!

So if it's just a slow gauge, will replacing it with a new reproduction fix the problem?

[TBONE1964]

Originally Posted by 1972BlueC20

Thanks for the info Tom!

So if it's just a slow gauge, will replacing it with a new reproduction fix the problem?

I would think so. I don't have any experience with aftermarket gauges but they do use all new parts.

I test my gauges on a bench with a sending unit and I do get very slow factory gauges but also get some very fast ones. I do know the aftermarkets are reasonable at less than $40.00.

Let me know how it works or if you need more help.

Tom