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Faulty fuel level readings; Fuel gauge is erratic
Topic Started: Mar 5 2015, 10:04 PM (704 Views)
Mendoza117
Fresh Fish
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Every time I put gas. My fuel level gauge goes past full even though I only put 5 gallons. Then after a while of driving it goes down to almost 3/4 tank. At start up fuel level could be really low or really high (almost full) then after driving a while it goes back to halfway. I could be getting to my destination and fuel level be at empty. After I turn it on 30 min later when leaving my destination fuel level is back at halfway at start up again. Could this be a faulty fuel level sensor? Or is this how geo metros fuel gauges work? Also when I go around large corners fuel level goes to empty.
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dayle1960
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Fastest Hampster EVER

It has to do with the wiring from the fuel sending unit to the gauge. It is 20 years old and through the years it has deteriorated. 99.999% of metro owners have this problem and just try to live with it. Don't worry, just learn how to read your fuel gauge. Also keep track of your mileage between fill ups and once you get to a set mileage then fill up.
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Metromightymouse
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Powdercoat Wizard

It sounds like your sensor has dead spots and is likely worn out. You can remove it from the tank and try to clean it, but if you are going to the trouble to pull it out you probably would only want to do it once. As far as I know there are no new sources, so you have to get one used somewhere.
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myredvert
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myredvert

Quote:
 
Or is this how geo metros fuel gauges work?
They do, but not when they are working normally. ;)
Quote:
 
It sounds like your sensor has dead spots and is likely worn out.
Quote:
 
It has to do with the wiring from the fuel sending unit to the gauge.
Both possibilities are quite possible.

Moving components constantly exposed to alternating periods of being submerged in liquid that can contain water have been known to wear, corrode, and not work normally after nearly 20 years, especially if it has ever sat unused for any extended period of time anywhere with "non-desert" humidity levels. And old wiring and connectors in cheap cars has been known to break down, become damaged and/or corroded over time as well.

There is a diagnostic procedure in the Factory Service manual that was thoughtfully designed to systematically isolate the problem to the chassis (wiring, connectors, gauge, etc) or the sending unit before you remove the tank and tear into it and start throwing parts money at it. It's not a bad idea to remove and clean your tank, but that's not the funnest of jobs, and typically not something you want to do until you know for sure you have to or have eliminated all other possible causes. One of those "if it ain't broke, don't break it and get yourself soaked in gas while doing it" kind of things.

(link>>) 1994 FSM Section 8A-31, Electrical Diagnosis, Instrument Cluster with Gauges. Chart #6

I don't know if the procedure in the 1994 FSM in the forum library is identical or not, it's very possible that even if the connectors and such are the same, the wring colors referenced may have changed. I would try to see if someone has a 97 FSM that they would be willing to copy that section from it.

Better yet, get a 1997 FSM and be done with that important item. It could possibly save you enough time and parts-darts money that it would pay for itself with just this one issue.
:cheers
And if you do end up dropping the tank and pulling the sender, clean the tank well and replace your filter and any lines that may be showing any signs of their age at the same time. If you feel adventurous and want the experience, there is an excellent thread somewhere by Bad Bent (IIRC?) that discusses cleaning the sender and seeing if that fixes your problem. If it doesn't work you can simply do it all over again, knowing it will take considerably less time the second time around. :D
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Hanuman
"The Almighty Grounds Cleaner"

pull your back seat cushion and you will find the wiring to the fuel pump and sender unit. sometimes the "but shuffle on the back seat over the years will unplug/partially unplug the wiring clips or damage the insulation on the wiring causing shorts to ground.

inspect the wiring ad harness connectors for damage and fit.
if good, you can drop the tank 4 bolts, use a jack and lower the passenger side down while using blocks to support the drivers side., disconnect the 2 fuel and 1 vapor line and lower tank.......remove pump and further inspect wiring.
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45MPGWHAT
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Does anyone know of where you can get a new sending unit...? Does anyone even make one? I haven't seen any on Rock Auto.
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dayle1960
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Fastest Hampster EVER

45MPGWHAT
Mar 7 2015, 03:21 AM
Does anyone know of where you can get a new sending unit...? Does anyone even make one? I haven't seen any on Rock Auto.
Unobtanium. Just try to find a low mileage metro in the JY and maybe it would work. I personally doubt it though. Just saying.
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myredvert
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myredvert

Just my .02, but you may want to consider following the actual diagnostic procedure provided in the FSM for troubleshooting a fuel indication problem. It only requires a voltmeter to check resistance of the wiring on either side of the previously mentioned connector before you drop the tank.

(link>>) 1994 FSM, Section 8A-81 Electrical Diagnosis, Instrument Cluster with Gauges
The "Symptom Table" on page -7 includes "Fuel Gage inaccurate" which refers you to Chart 6 on page 13 of that Section.

If you want to drop the tank based on the probabilities, go for it. It's a reasonable gamble based on collective Metro experience. If you prefer to first confirm which direction from the connector the problem is, while you already have access to the connector and a voltmeter, those checks are pretty simple and straight forward.

Sometimes guessing based on experience, usually when the options, possibilities, and consequences of an incorrect guess are minor, e.g, checking/cleaning a connector, is a normally expected process described in detail by the FSM itself in its' "Diagnosis Troubleshooting Procedures," with simple items to check when applicable listed in sections entitled "Preliminary Checks" and "Diagnostic Aids." But when the consequences of a wrong guess, however educated they may be can be more notable (such as unnecessarily dropping the tank), assuming where the problem will be found while ignoring the procedure that was carefully designed to prevent those consequences, in the words of the late, great, wise Dr. Spock...

...and can and often does lead to wasted time, effort, and money.
Edited by myredvert, Mar 8 2015, 08:26 AM.
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Mendoza117
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I want to thank you all for the very useful information!!! Once I get a chance to trouble shoot ill let you guys know what I find!
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Car Nut
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Like Dayle says, just track your mileage for now. Too cold to be screwing with a fuel tank right now. Unless you're blessed with a heated garage, or live in AZ. Order a FSM, start reading & wait for better weather.
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Hanuman
"The Almighty Grounds Cleaner"

:ermm: too cold to work on a metro?
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