Gas Sending Unit Accuracy Fix
 

For anyone that has a GSL-SE, maybe other 1st gens too. I have had two of these with the identical problem in the gas sending unit that makes the fuel gauge inaccurate. Like it only reads up to 7/8 of the full, and moves non-linearly.
The factory install of the fuel gauge is incorrect because of being off by one set of mounting holes. There are 6 screws holding the unit into the tank, and it is installed 1/6 clockwise from vertical. It's basically making the gauge work at an angle instead of perfectly up and down.
If by chance you have this problem Take off your left rear tire, open the filler cap to releave any pressure, and hope the screws aren't rusted to hell. If the plug is pointed up and down I think it's right, I dont' remember which way its alligned with the float inside. It will most likely be askew, pointing at a 7-o'clock angle, which is incorrect.
Remove the screws, and pull the unit out, then install it so that the float moves vertically instead of at an angle.
I did this on my first GSL-SE and the fuel gauge on that car is PERFECT, 75 miles per quarter tank and a little left over for the low fuel mark.

Hope many people get helped by this, as fixing a minor inconvenience.

i have this problem after i put in a gsl-se fuel level sender unit in my gs

and my gas light stays on,

not too worried about it though,i plan to build a new rx7 soon enough:D

My fuel gauge hasn't worked since i bought the car 2 years ago. I just looked at the sending unit and the yellow wire with the blue stripe was disconnected. Had to soldier it on and now it works but olnly 7/8 like you said. Unfortunetly the nuts are a rusted bad so I probly can't turn it. Thanks for the tips to get at the sending unit though!

That's the other problem, that plastic shield doesn't do a good enough job keeping spray off that corner of the tank. I had 1/8 - 1/4" thick dirt packed all around there, and the contact and trace leading to the low fuel thing blew away when I hit it with compressed air. So much for finding a PA state car for less rust problems.

Wow, I'm having similar problems - when I get it filled, it goes up to half, then as I'm driving down the road, it goes down to 'E'. I'm going to try your method. The plug on mine is definetly pointing in the 7:00 position, so maybe if I reposition it, it will work. What's the difference between the 84-85 senders and the pre-84 senders?

As for the differences... no clue. I am guessing it's an assembly problem is all, and since i've only had two 84 GSL-SE's.... I don't know if it affects other 1st gens or not.

I'm suprised that this hasn't been covered by dealers or a TSB or anything listed here.

I took the sender out and got the gas light working, but the fuel gauge still doesn't work. Then I went to fill 'er up and it read 1/8 full and it went from 'E' to 1/8 VERY slowly. What do you think, bad gauge in the cluster?

If you take it out again... hook it all up and see if the gauge works when you move the float manually.

Next step.... may help to go through the measurement of the sending unit, and / or simulate that resistence on the wiring to see if your gauge is shot.

Well, I did move the float manually and it doesn't move the gauge at all. However, the light does come on when you move it to a certain point. I was checking resistance and everything checked out okay. It just doesn't make sense. When I get the tank filled, it moves the gauge a bit, but when I had the gauge out, no matter where I moved it, the stupid thing wouldn't register. How much is a new gauge?

check a junk yard.... only place i'd look for those 'hard to find' parts. guessing it's way more to get em through mazda.

Also check the wire harness, I know that there's a connector under the drivers side storage compartment that tracks water into it and may rust. so you may just have a bad connection there too.

That's probably it then. Which wires should I look for under the compartment? Thanks.

you'd have to get a diagram or ohmmeter to figure out which wire is which, but my guess is that's it.
if you take that compartment out, there's like a 30-40 pin connector there, I know mine had one wire broken off (rear overtemp deal I think). i'm sure that's a high source of problems. The RX7 has way too many connectors it seems, a source of many issues from what i've had to fix so far.
Good luck finging the right wire :)