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Old Mar 26, 2019 | 03:06 PM
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Badbrewer's Avatar
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Fuel gauge problem

Hey guys. I have to post this here. I can't post in series one troubleshooting for some reason. I have a 08 40th anniversary edition 8. 82700 miles. I got her out last week after the winter hibernation. Still running strong. I filled the tank up and the fuel gauge only went to 3/4 full and the rapidly dropped to half tank. Yesterday the low fuel light came on. Started her this morning and it read 1/4 tank. I just filled it back up with just over 8 gallons and the same thing happened. Any thoughts? I do premix with idemistu. Thanks

Last edited by Badbrewer; Mar 27, 2019 at 06:03 PM.
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Old Mar 28, 2019 | 05:43 PM
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From: Belton, TX
You driving hard?

I mean if your sitting above 4K rpm all the time it’s probably just it’s gas’s guzling self. But that sounds a bit more severe than normal. I go through fuel fast but that sounds bad. When is the last time you had plugs/wires/coils done?

oh also I have my 40th badge in my glovebox (previous owner said ppl steal them all the time so he took it off) I’m gonna chance it and put it back on. Is yours in the original spot?
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Old Mar 29, 2019 | 12:55 PM
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Yes badge is where it belongs. Even when I fill the tank the gauge won't register above 3/4 tank. I don't think my mpg has change. Plugs and wires have about 3000 on them

Last edited by Badbrewer; Mar 29, 2019 at 12:59 PM.
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Old Mar 29, 2019 | 01:17 PM
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Originally Posted by Badbrewer
Yes badge is where it belongs. Even when I fill the tank the gauge won't register above 3/4 tank. I don't think my mpg has change. Plugs and wires have about 3000 on them
Have you installed a new fuel pump?
Mine's been squirrelly since I did.
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Old Mar 29, 2019 | 01:22 PM
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From: 2017 Miata RF Launch Edition
Sounds like a problem with the right side fuel sensor.

IIRC, the fuel pump is on the left side but it constantly pulls fuel from the right saddle, refilling the left. So, for the first half of the tank, the ECU is mostly looking at the right side sensor. Once that empties, it starts paying attention to the left side.
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Old Mar 29, 2019 | 03:42 PM
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I haven't messed with the fuel pump. It was changed under recall by the previous owner.
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Old Apr 22, 2019 | 03:41 PM
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Well I think I found the problem. Driver side sending unit float doesn't seem to like fuel anymore. It floats in water but if you push it down in gas it will stay down. Weird. Anyone know where I can get a sending unit on the cheap cheap?
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Old Apr 22, 2019 | 07:22 PM
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From: Belton, TX
Originally Posted by Badbrewer
Well I think I found the problem. Driver side sending unit float doesn't seem to like fuel anymore. It floats in water but if you push it down in gas it will stay down. Weird. Anyone know where I can get a sending unit on the cheap cheap?
Thanks for the update man I appreciate it. That is definitely odd. Water is more dense than fuel though so that could be the reason.
i would try LKQ pick your part, though rx8s are getting harder and harder to find. Just keep on the look out at your local salvage yards.
best of luck man.
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