W-27

I replaced the gas tank, sending unit & wire, both gas lines but the gas gauge needle drops to 1/4 full when there is actually 1/2 tank left. Is the situation coming from the actual gauge or the new sending unit?

joe_padavano

So this is the old gauge and a new sender. Did the gauge do this before? If not, what's changed? Sounds like the sender.

W-27

I was doing it even prior to replacing all those parts just not as badly as it drop now. Are they any electronic components in the actual gauge that could have gone bad?

Koda

Is the float floating?

W-27

I cant see it but since the gauge needle goes up and down one would think so but I do not know how to check.

Koda

Sorry, I meant like fully floating in terms of not being waterlogged. I think the only way to tell is to pull the tank on that. Maybe check other solutions first. If I recall correctly, unplugging the sender should make the gauge go one way, and grounding the lead should make it go the other way, though you should get better advice than mine.

jpc647

The previous owner of my car told me the new sending unit he bought for the car did something similar.

I've never taken my take out, but he told me he removed the float from the new and put it on his old sender, and it worked. Again, that's what I was told. My gas gauge does bounce around a little bit under 1/2 in corners and stuff sometimes, and it seems like 1/2-e is left than F- 1/2. But the car is 40 years old, I'm sure the gauges weren't spot on from the factory.

oldcutlass

These old Abody fuel gauges were never that accurate in the first place. Just a mechanical float with a rheostat attached. It depends on the contours of the tank as the fuel level drops. Some can ride up at full or near full forever and move really slow to 1/2. Once they hit the 1/2 mark it seems they go to 1/4 quickly and then the needle will fluctuate from E to 1/4 and then finally stop moving. When it stops moving its time to really worry about running out of fuel. Others models can operate the opposite, drop like a rock from full to 1/2 and then take forever to get to E.

I personally try to fill up when it reaches 1/2.

hookem horns

I find it to be directly correlated to use of the pedal on the right.

Eric pretty much nailed it and maybe learn to live within the variances you see rather than try to fix something that may not be fixable. I find the needle stays on full for a long time, moves fast from 3/4 to 1/4, and then moves slow again below 1/4. Seems like I recall having cars that did that back in the day too so does not seem odd to me.

W-27

Well I checked for a short in the electrical system but didn't find one than I checked the ground wire and its grounding fine. I don't know if a new sending unit would do it but next time I am in there I will replace it in the meantime I will do it by mileage (10 miles per gallon as its a 455 forced air induction). Thanks for every ones help.

lemoldsnut

Back in the day I used to fill up and then go hey watch how fast it goes away. If I floored it the gauge would drop like a rock and then return. I find that still today like that on my 67 cars.

Kind of funny actually