alwan16

My fuel gauge is broken now and just sits at empty. I want to test the sensor. Anybody have any information on this? A page in the shop manual or a webpage? TIA.

Flybye

I have the shop manual. When I get home, I'll let you know how to test it.

poss

iTrader: (5)

anyone ever figure this out? my low fuel light came on last night, I stopped and got gas, the light turned off, but the gauge is still on empty

any ideas for what i should check first?
TIA

RonKMiller

It's fairly easy to test however replacing it is the way to go and really easy to do. (since you need to take it out of the tank anyway to test it....)

$62.70 from Malloy Mazda shipped to your door. List $112.34.

alwan16

the low fuel light has a different sensor than the actual gauge. to test the needle sensor you just use an ohmeter after you have pulled out the sensor that is mounted with the fuel pump. the low fuel light sensor can be tested similarly. hook up and ohmeter and dip in and out of gasoline/other liquid.

RonKMiller

Unless I am seriously confused (which has happened more than a few times...) replacing the entire sending unit will fix the problem without getting into testing individual components and is relatively inexpensive for the average guy - like me.

There is no question you are correct in your analysis, but chasing down individual components can drive anyone crazy - like me!

duboisr

Stop do not remove the tank to get to the unit. Pull up the carpet and remove the unit from the top of the tank. the repair may be as easy as bending the scraper to the resister coil.

poss

iTrader: (5)

cool, thanks guys. I want to troubleshoot this problem and not just start replacing parts (i've said it before and i'll say it again, i'm a broke college student with nothing but time ...evidentally not enough time for a job ). what resistance should the rheostat read ( I'm assuming it works off of a rheostat concept).
as far as I know, it could be something in my dash giving me ****, so i want to find out what it is for sure.
anyway, thanks again guys.

RonKMiller

Um, yeah, that would make sense since that's where it is mounted and takes all of 5 minutes to remove......did anyone say you needed to remove the tank???

Boy howdy - do I understand trying to save money and fix it without new parts. Unfortunately I don't think it can be done in this case - but I sure admire him for giving it the old college try!

I'll look up the resistance later today.

poss

iTrader: (5)

so I go out for a little drive today and it's worked it's way up to 3/4 tank (when it's actually full), so it is all screwy. i'll pull it out of the tank next weekend and see if I can figure out what is happening in there.
thanks guys

RonKMiller

OK, now I KNOW you will have to replace the sending unit. Don't even bother wasting your time testing - the rheostat portion is simply worn out.
Sorry.

But....if you insist - the testing procedure is in the Electrical Shop Manual and by clicking the Mazdaformance ad at the top of the page you should be able to download a copy - I think.

alwan16

it is possible that your resistor part of the sensor is okay and maybe just the float came loose and is sitting in some funky position. mine came off completely. all i had to do was clip it back to the metal rod it was supposed to be attached to. that and replace the entire tank because the baffling had come loose

TEDDER1

iTrader: (1)

****? i'm having my tank replaced this week too because of the baffles...?! and they knocked the floater off the level.

SleepR1

Ok, my gauge is reading at 1/4 level, eventhough I topped off the tank. WTF? What do I replace here? The tank? The floater? The fuel pick-up? I'm confused!?

poss

iTrader: (5)

mine just kind of started working again and I haven't had a problem since. I figure i'll take a closer look when I install a new fuel pump.

SleepR1

How many tank-fulls before your gauge started to work again? Ahh, the FD Rx7...it's always sumpthin...

poss

iTrader: (5)

I have a theory about why mine stopped working. It was about 80F here for a couple of days, then it went down to 20-30F OVERNIGHT!! my guess is that water condensed somewhere that it interfered with the the level sensor. once it got warm again, it worked. Kinda strange.

SleepR1

Mine mysteriously fixed itself today. The needle just jumped back to the level I think it should be 3/4 full (after 1 and a half days of driving off of full tank). W I E R D, huh?!

poss

iTrader: (5)

good to hear

karken29

If you want to determine if your gauge is working, ground out the wire that goes to the fuel tank sensor. Your gauge should read full.

Open the circut and you should read empty... Typically, the connection becomes corroded and you either get a false reading or no reading.... The tank sensor can go bad if there's been water in the tank... in which case it should be replaced

poss

iTrader: (5)

update:

My gauge started acting weird again so I pulled the pump/level assembly out of the tank. I cleaned the rheostat area with some fine emery cloth.....VOILA!! (sp?) It works correctly again. It just had a back varnish built up on it.

So for anyone with an irregular gauge, try cleaning it before spending $60+ dollars on it like someone suggested.