1959 Coupe Deville Fuel Gauge Problem

[indetrucks]

So my 59 runs out of gas when the gauge reads between 1/4 tank and empty (1/8th remaining).  I know.. it's already low so why not just fill up at 1\4 tank remaining?  Well, that's what I do, but I would like the car to run out of gas when the gauge is on empty, not when it's still showing 1/8th of a tank remaining.

Is this a float issue?  I have heard of floats developing pin holes, thus causing them to sink a bit... but this would cause the gauge to read lower than it actually is.  In my instance, my gauge is reading higher than it is.  I'm obviously not the original owner, so I cannot determine if this has always been like this or not.

Any recommendations short of dropping the tank to investigate the float?

[Eric DeVirgilis CLC# 8621]

I'd say there's a 99% probability the problem lies in the tank.

Have the problem in reverse on my '62: Gauge registers less than full when full; ample fuel remains long after passing E. Issue began when gas tank was replaced.

I'd advise against fiddling with it as it could be opening a can of worms - best to let sleeping dogs lie and leave it for another day such as if/when the tank needs to come out for another reason.

[bcroe]

So my 59 runs out of gas when the gauge reads between 1/4 tank and empty (1/8th remaining).  I know.. it's already low so why not just fill up at 1\4 tank remaining?  Well, that's what I do, but I would like the car to run out of gas when the gauge is on empty, not when it's still showing 1/8th of a tank remaining.

Is this a float issue?  I have heard of floats developing pin holes, thus causing them to sink a bit... but this would cause the gauge to read lower than it actually is.  In my instance, my gauge is reading higher than it is.  I'm obviously not the original owner, so I cannot determine if this has always been like this or not.

Any recommendations short of dropping the tank to investigate the float?   

First thing to check is the wiring to the tank.  Make sure the ground wire to the tank
unit is well grounded to the frame.  Grounding the gauge wire to the frame there
should send the gauge to E, opening it should go past F.  If ll those tests pass, you
are looking at pulling the tank and the tank pickup unit.  No big deal (if its near
empty).  Tanks need to be checked anyway.  Bruce Roe

[indetrucks]

Yep, I'll go ahead and check the ground just to be sure.
Dropping the tank right now doesn't sound like a whole lotta fun.  It wasn't exactly a party when I had to drop it in my 67 GTO, so I don't think this will be much different.

[Matt Innocenzi]

I agree with Bruce and to add one more, it could be the float arm.  The arm affects the resistance on the sending unit which affects the display on your gage.  If it is reading fuller than it really is, you will have to bend the arm down.  Also make sure it is not bottoming out on the bottom side of the tank.

[curly]

My 59 always read empty when I first got it. Pulled the tank, freed up the float arm (it somehow got stuck behind the fuel line). It did the same thing then, running out of fuel at 1/8 tank.  I recently replaced the sending unit with a new reproduction and it now reads 3/4 full when it is full. I did pull the tank and tweak the float arm, no luck with that. As suggested, I am just going to live with the problem.

T Lewis

[indetrucks]

I agree with Bruce and to add one more, it could be the float arm.  The arm affects the resistance on the sending unit which affects the display on your gage.  If it is reading fuller than it really is, you will have to bend the arm down.  Also make sure it is not bottoming out on the bottom side of the tank.

This is what I was thinking as well (providing there is nothing hindering it).  But it turns in to a guessing game as to how much downward bend to put in it.
If I decide to drop the tank, I will post up my findings

[Dan LeBlanc]

I've got a similar problem with my 61.  When the gauge reads empty, there is still 5-7 gallons left in the tank.  I've just learned to live with it.  I can't justify dropping the tank to bend the float arm.  It's had a new sender installed before I bought it so best leave it alone.

If I find an NOS sending unit for a 61, then I'll drop the tank and install that.

[Coupe Deville]

I had the same problem on my dads 59'. I replaced the sending unit and made a new ground strap from the tank to the frame and all of the problems went away. A lot of fuel gauge problems I see are almost always the ground or a sending unit issue.

-Gavin