After many hours of work (and quite a bit of $) I have sort of figured out the problem, but not the solution. Here goes;

My fuel gauge never reads past roughly 1/4 full, no matter what. It seems to be accurate at and below that level.

I have replaced the original sending unit with a new one, it still does the same thing.

Here is the strange part; when I have the sender out of the tank, if I "manually" swing the float up and down, the dash gauge moves all the way up, down, in between, etc. So it looks like it should work perfectly.

AFTER I put the unit in the tank, is when the gauge will never go past 1/4 full even on a full tank.

I have removed and replaced the unit probably a dozen times, being very careful not to catch the float in the trough, etc. etc.

What is kind of odd, is that A) I have to put a little bit of pressure on the unit to get it to completely seal, not sure if that is from the float "floating" and putting some pressure on the unit, or if something inside is hitting something and B) the unit does not straght into the tank with no interference, I have to give it a fairly good push to get the unit all the way in past the 'bends' in the tubing.

I am pretty much out of ideas, now starting to wonder if it could be something nuts like a 'squashed' or incorrect fuel tank or some such thing. Any ideas? Thanks!!

 

I hope not, but the rubber tank inside the tank might be leaking.

So the gas gets "in between".

But that would mean that if you fill it up, you will only be able to get in just a few gallons, depending on how "high" the leak is.

How often do you have to fill it up?

 

doesn't seem like I have to fill it up more than I should; it's not my daily driver so I don't have a of history on the mileage etc. but I don't see any leaks outside the tank, and when I do fill it up it takes what seems to be a 'normal' amount, depending on the mileage since the last fill up (I pretty much go by the trip odo nowadays).

It almost seems to me like the float inside the tank is not able to go up all the way for some reason; why I don't know

thx

 

My 95 has been doing the same for about two months. The computer also says I have 200+ miles to empty, I ran pout of gas on the interstate when it said that. Like you, I fill up and reset the trip odo. More rescently I've been having fuel delivery problems (I think). I wonder if it is all related.

 

you may be right. Lately I'm starting to wonder if there is some kind of physical damage, or maybe even the wrong tank in the car.

The opening for the pump is not centered with the opening in the rear body panel for one.

But mainly, I removed the pump/float assembly from the tank, and outside of the tank the float/arm moved freely and the fuel tank registered properly all the way from empty to full, smoothly.

When reinstalling it, again I had to put moderate pressure on the unit to get it to seat all the way to the top of the tank, so I am now 99% sure that the float arm is hitting *something* in the tank, keeping it from registering as full and also from fully traveling properly. I have checked and rechecked to make sure the feed 'sock' lines up with the trough and nothing else binds.

Not sure what else I can do now, this one's got me puzzled.

 

Bladder in the tank blocking the arm?

 

Do you know anyone who has a 'bore scope' (flexible fiber-optic sighting tool with a light)?

Might require having a nearly empty tank to see though...

If so, they might be able to slip it in under the flange and see if/what obstruction it might be hitting.

 

as far as I can tell the bladder is not separated from the tank wall, but then again with the things I have found on this poor car you never know :-)

 

As you probably know the full tank resistive reading is approximately 110 -120 ohms, and the empty reading is approximately 10-20 ohms. Attach a ohm meter to the float sending unit connector making sure it is working correctly outside the tank. Then start installation of the float unit into the tank watching the meter. Depending on the level of fuel in the tank, for example if it was ¾ full, the expected meter reading might be (i.e.) 85-95 ohms. But if initial reading looks good at first, and then changes suddenly to 30 ohms at the time it is almost completely in the tank, then something is moving/restricting the float. I would like to use an analog ohm meter if possible as it might be better for this type of test. (If don't have one the digital would be fine.)

This procedure might not have a direct answer but might lead you to one or some additional thoughts.

 

is it possible that you are installing the sender 90 or 180 degrees off

 

That's what I was thinking.. On most VEH it matters, but I'm not sure about our vettes.

 

far as I can tell it only goes in one way. I've checked and rechecked pictures, posts and manuals and can't come up with much...thanks all

 

Just a thouight, Is it possible that the float is cracked & filling up with fuel? So instead of working like a float, It is like a sinker.. Just a thought...

Ant...

 

guess so, but the float assembly is new, part of the whole new sending unit that I bought as a complete assembly...tried the old one too just inc case, but the wiring on that float is all fouled up, still I don't think a new one would be bad though it's possible...thanks...

 

Any chance the float arm is faceing/mounted in the wrong direction? If I remember right, the float arm should point & pivot up and down toward the front side of the car.
Another thought: Perhaps check the resistance of the fuel sender at the pigtail connector just ouside the tank with the pump/assy still in the gas filled tank. Problem has the potential to be not only at/in the tank but the wires that lead back to the gauge cluster aswell.