Fuel gauge/sender issue.

[Pocket Chant]

Alright, so I googled around, but nothing seemed to fit my problem.

My car is empty when it says I have half a tank. I have an '87, so one pump/sender. The light comes on when I'm empty, at half a tank, and it appears to lower uniformly, meaning that 3/4ths is actually half a tank, etc. I bought a sender on Ebay, though it was accidentally a euro one that was too long, that did the same thing. Today I got another one, US Spec, same issue. I'm going to go pull my cluster and check the grounding screw, but I don't seem to have any of the issues relating to it. Also, when I fill it up it rests on F, and when I turn the car off, it goes all the way down, so it's not a problem with the needle position.

[nando]

my bet is you got a sensor for a late car, which actually has two senders instead of one, and 1/2 the resistance.

[ScHpAnKy]

my bet is you got a sensor for a late car, which actually has two senders instead of one, and 1/2 the resistance.

can you go into more detail about this?

[Pocket Chant]

my bet is you got a sensor for a late car, which actually has two senders instead of one, and 1/2 the resistance.

Only issue is, I just checked on RealOEM.com, on a 1/87 and a 5/91, the part (16141152266) is the same, so that doesn't make sense.

[nando]

on a late car each sender has about 1/2 the resistance of an early, single sender system. so if you use the wrong sender with the wrong car, your gauge will not read correctly.

the "reserve" light will always work as it's just a switch inside the sender.

[nando]

Only issue is, I just checked on RealOEM.com, on a 1/87 and a 5/91, the part (16141152266) is the same, so that doesn't make sense.

if yours has a 1 pump/sender then it's definitely not the same.

have you looked under the cover on the drivers side to see if there's a second sender? if there isn't then you definitely have the wrong part.

[ScHpAnKy]

on a late car each sender has about 1/2 the resistance of an early, single sender system. so if you use the wrong sender with the wrong car, your gauge will not read correctly.

the "reserve" light will always work as it's just a switch inside the sender.

so if that's the case, what's the cut-off date for early/late?

[Pocket Chant]

if yours has a 1 pump/sender then it's definitely not the same.

have you looked under the cover on the drivers side to see if there's a second sender? if there isn't then you definitely have the wrong part.

There is no cover on the drivers side, because I have an early model. And it's quite literally the same.


Early model, #9
Late model, #5

Both of them are part # 16141152266

EDIT: Also, since they're the same number, I have no clue how to get the right part. I'm also pretty sure I have the original sender, and it's doing the same thing.

[jlevie]

The right side level sensor is the same on early (55L) tanks which only have one sensor and late (63L) tanks that have two sensors. The two sensor tanks have the sensors wired in series so resistance range from empty to full is twice that of the early configuration. Thus the gauge in the cluster has to be different for those two variants. If you use a late model fuel gauge (or cluster) in an early car the gauge will do exactly as the OP describes. The fix is to replace the fuel gauge with the correct part for the car.

[Pocket Chant]

The right side level sensor is the same on early (55L) tanks which only have one sensor and late (63L) tanks that have two sensors. The two sensor tanks have the sensors wired in series so resistance range from empty to full is twice that of the early configuration. Thus the gauge in the cluster has to be different for those two variants. If you use a late model fuel gauge (or cluster) in an early car the gauge will do exactly as the OP describes. The fix is to replace the fuel gauge with the correct part for the car.

Once again, jlevie here to save the day.

Checking on RealOEM confirms that they are different, so that's most likely the issue. Luckily it's only $38 for the gauge. Thanks for the help.

[jlevie]

I don't know where you got that price. When I look up the part (62131374823) I see a list price of $88.26.

[Pocket Chant]

Pelican has it for *$39, not $38

[robrez]

Sounds like you got it figured out. I had the same thing happen when I installed an M3 cluster (small fuel tank) into my late model m20 (large fuel tank). The m3's cluster had a 55l fuel gauge which read as empty when there was still plenty of gas in the tank. I swapped out the m3 cluster's fuel gauge for the M20s 60l fuel gauge and it was fine.

[agent]

Yep, me too. I had a late cluster in my early car for a while and it read half full when it was empty.