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Fuel Gauge Not Functioning

22K views 15 replies 9 participants last post by  carusoswi 
#1 ·
Hey everyone,

This is probably more noob than I want to believe, but I bought my 90 GSX a while back now, and the fuel gauge has never worked. The needle just sits on empty. The fuel light still works, so I know when I'm getting low, so that's good.

Everything else on the cluster works perfectly, so I'm guessing it's not connection related. I guess the motor for the needle itself could be dead, but how can I test that? Buy a new cluster and see if that works?

Maybe it's the sender, which I assume is on the fuel pump assembly, or close by? How do I go about testing the sender? Can I test it? I would assume that since I still get my low level light, the sender is ok...

I searched around but couldn't find anything on this...all I found were tach issues. I looked at the pin outs seeing if there was anything there, but didn't expect much and found nothing.

Basically, since I've not dug into this spectrum before...what is the list of logical steps towards diagnosing the cause of this? Preferably starting with the cheapest/easiest step and working up from there.

I could assume since I still get a level light, the sender is ok, and since the rest of the cluster works, the connection is ok...so am I left with a dead needle?

Thanks,
Adam
 
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#2 ·
Hrm. Do you have a spare cluster sitting around?

With all the hassle it will take to repair the cluster if it is a burned out motor, you will probably just bite the bullet and throw one in there. The gas light runs on the same signal as the needle does, it comes on when I *believe* there is 0.2v or less in the circuit, and the easiest way to test for that is with the fuel pump out, to pull up the little floater thing, and check the voltage with a multimeter, and watch the multimeter's voltage change as you slowly let the float drop down the mount shaft.

I say that's the easiest way, simply because you'd have to pull the gauge cluster out to check anything else, but, maybe you're lucky and the shaft is turning inside the needle, but the needle just needs to be glued back on!

If you really DID want to keep the original cluster, it would be as simple as de-soldering all the links that hold on the motor, and soldering on a new (hopefully tested) needle assembly, but like I stated earlier, unless you're REALLY good with a soldering iron, you can easily munk up the whole cluster.
 
#3 ·
Unfortunately I do not have a spare cluster, so I would have to buy a known working one first, then hope that is the issue. But, that's probably going to be the best bet...I'm sure the needle is still attached because it hasn't swung straight down, and doesn't bounce at all. It's just frozen on E. I'm guessing the motors have physical stops in them so the needle doesn't go below E or above F...because there aren't physical stops that I can see on the front that would be holding the needle on E.

It would be nice if there was a way in the pockletlogger or other OBD software that could send voltage to each gauge through the dataport to move the needles to check for functionality. I mean...that doesn't seem like a far stretch, does it?
 
#4 ·
Well, you can do that! the sending unit on the in tank fuel pump has wires coming out of it for that specific reason. With the standard 3 wire setup (I haven't taken mine apart in a while, so this is pretty general) One is a positive, one's a ground, and one's a sending wire. The easy way to check the gauge is to touch the sending wire across the ground wire, removing the resistance from the actual unit, and see if the needle moves.
 
#5 ·
The wires are easily accessible from just under the back seat, right? They come out of the top of the fuel pump mounting unit right? I'll dig for some more info on those wires and maybe try that out.

Thanks :cool:
 
#6 ·
Does it still have the stock pump? If it has been upgraded the person that did the swap may have bent the float arm or gotten it snagged so the gauge doesn't register. The reverse happen to me in one of my cars. The float arm got bent and wouldn't register past 1/2 empty.
 
#11 ·
This sounds like my problem (and I'm searching now for an answer). I recently experienced a fuel pump failure - left me sitting and I had to have the car towed. Dealer put in a new fuel pump and I had to wait an extra day because some part of the fuel line was broken, so they had to order a replacement part. Long story short, the tank was full when the pump failed. I happen to notice that the low fuel light came on when the needle registered 1/4. Kept an eye on the needle and it never moved over some 45 miles. Stopped for gas and the fill-up was slightly over 15 gallons (means I didn't have much fuel left in the tank, for sure).

I asked the dealer to look at this and the reply was that I need a new sending unit. $80 for the part (no problem I think), and $300 to install (I balked at that figure, thinking they should have caught this when the tank was down for the pump replacement).

I'm going to live with this situation until I exhaust other avenues of fixing it without having to layout so much money.

Wish I knew what more of what to look for, but figuring if I keep searching/asking here, I'll eventually find the answer.

Like your car, my light comes on at the proper time - when it stays on steady, I figure I'm safe for 50 miles if necessary.

Additional advice would be appreciated.

Caruso
 
#7 ·
Yep, the car is still 100% stock. I guess damage is a possibility if he tried to change the pump, then bailed on the project. But, if the float operates both the gauge and the light, and it was the float that is causing the "E" reading all the time, shouldn't the light be on all the time?
 
#8 ·
Not necessarily. If the float is as old as the car, they will develop leaks and fill with gas. Depending on where the leak is, there could still be some air in the float.

If this is the case, when you put gas in the tank, the float will rise just enough to kick the light off (while still being submerged) and will fall back down when you are running empty.

Sam
 
#13 ·
There are in fact two sensors on the AWD cars, since the tank is split into two main sections by the driveline tunnel. Each outputs half the total voltage for the reading.

I'm guessing that one of my floats is cracked, because my gas gauge accuracy varies each time I drive the car.
 
#15 ·
Which is the signal line, and what should the reading be? I'm guessing it should be very small, and if it's large, then that's the problem?
 
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