Gas gauge twitching - JeepForum.com
 
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post #1 of 15 Old 09-15-2016, 04:59 AM Thread Starter
CornflakesYJ
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Gas gauge twitching

Good morning. I took the Jeep on a 125 mile trip and noticed once I hit half a tank of gas, the gauge needle started twitching and jumping from half tank to a full tank. It seems to be predominant when I hit a bump or take a turn. Is the needle needing to be greased or do I need a new fuel sender assembly in the tank? I appreciate the help.

-Tyler

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post #2 of 15 Old 09-15-2016, 07:16 AM
Que89YJ
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You really need to fill out your profile. The electrical is very different from year to year and its impossible to recommend anything without it.

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post #3 of 15 Old 09-15-2016, 09:07 AM
fishadventure
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Once I hit a half a tank of gas I'm either about to immediately run out - or I've got about 7 gallons left.

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CrankingIS turning over
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post #4 of 15 Old 09-15-2016, 10:30 AM Thread Starter
CornflakesYJ
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This is a 1988 YJ 4.2L/5 speed. To my knowledge, the fuel sender is original, along with the guage itself. I'll fill out the profile when I can get to a computer. From what I've read, it mostly seems like guage that is the problem for not reading accurately or consistently.
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post #5 of 15 Old 09-15-2016, 11:29 AM
Que89YJ
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No, its not usually the gauge. There are several test you can do to eliminate the rest of the system. Do you have a manual for it? Do you have a meter and know the basics?
Try this first:
http://www.jeepforum.com/forum/f12/r...er-how-991307/

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post #6 of 15 Old 09-15-2016, 04:23 PM Thread Starter
CornflakesYJ
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Wow that's a great link. I'll read up on that and learn a thing or two
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post #7 of 15 Old 09-15-2016, 05:15 PM
Chrisnvegas
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I'm going to guess your Jeep is fuel injected.
If so, there is a "cup" your fuel pump sits in at the bottom of the tank.
It's plastic and becomes warped over time which interferes with the movement of the sending unit.
This usually happens when the fuel level reaches about half.

It happens when you take turns or hit bumps.
It can also become "stuck" until you hit another bump.

There are two cures, both involve dropping the tank.

One is remove the cup altogether.
The cup is there to capture fuel so when fuel is low in the tank, the pump doesn't starve when you hang a corner
making the fuel wash to one side or the other.
So cup removal can have a consequence.

Or another is to trim the top edge of the cup that has become warped with a sharp razor, this is preferred.

I learned this from forum member @Drednot , so credit to him for the cure.

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post #8 of 15 Old 09-15-2016, 06:07 PM
Que89YJ
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Quote:
Originally Posted by Chrisnvegas View Post
I'm going to guess your Jeep is fuel injected.
If so, there is a "cup" your fuel pump sits in at the bottom of the tank.
It's plastic and becomes warped over time which interferes with the movement of the sending unit.
This usually happens when the fuel level reaches about half.

It happens when you take turns or hit bumps.
It can also become "stuck" until you hit another bump.

There are two cures, both involve dropping the tank.

One is remove the cup altogether.
The cup is there to capture fuel so when fuel is low in the tank, the pump doesn't starve when you hang a corner
making the fuel wash to one side or the other.
So cup removal can have a consequence.

Or another is to trim the top edge of the cup that has become warped with a sharp razor, this is preferred.

I learned this from forum member @Drednot , so credit to him for the cure.
I'm betting it's the sender that is corroded and bad. I have a spare steel tank and sender for the TBI.

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post #9 of 15 Old 09-15-2016, 06:12 PM
Chrisnvegas
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Quote:
Originally Posted by Que89YJ View Post
I'm betting it's the sender that is corroded and bad. I have a spare steel tank and sender for the TBI.
Yeah, I reread his symptoms.
If the cup is warped it probably wouldn't jump to full.

You may be right

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post #10 of 15 Old 09-15-2016, 11:53 PM
baritone_mike
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My 88 with a 2.5L does the same thing, it is the gas sloshing around in the tank. I don't know if it is supposed to do it, but my gauge is perfectly accurate there is just no damping. Unless it is on F or E it bounces around when you hit bumps or take turns, my gauge has never became stuck. And the only time I have managed to starve the pump of fuel was taking a left turn with less than a gallon in the tank.

˙ɹǝʌo ɹǝʇndɯoɔ ɹnoʎ dılɟ sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
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post #11 of 15 Old 09-16-2016, 06:38 AM
Que89YJ
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If the gauge works until it hits 1/2 tank then the wiring is good. The question is whether its the gauge or sender. It is almost always the sender in the tank. The older Jeeps are not designed to deal with the alcohol in the gas and the senders corrode because of it. Cornflake I think you can bet on replacing the sender in the tank.

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post #12 of 15 Old 09-17-2016, 09:18 AM Thread Starter
CornflakesYJ
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Thank you everyone for the responses. I'll look into replacing the fuel sender to fix the issue. I know it's not normal, and after reading some writeups with similar problems, I am fairly sure it's a corroded sending unit.

Que, I'll PM you and see how much you want for yours. Thanks again everyone!
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post #13 of 15 Old 09-18-2016, 02:01 AM
Drednot
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Just an FYI about rapid bouncing fuel needle....There is an electronic dampening circuit in the gauge itself that disregards the rapid signal from the sloshing fuel and just moves the needle slowly. That can go bad from glitchy signals from a corroded sender sweep

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post #14 of 15 Old 09-19-2016, 12:58 PM Thread Starter
CornflakesYJ
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Could that prevent my tank from showing my gas level when below a half tank? Once my tank level hits a half tank, the twitching starts, and an accurate gas level is impossible to read.
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post #15 of 15 Old 09-19-2016, 01:05 PM
Que89YJ
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Quote:
Originally Posted by CornflakesYJ View Post
Could that prevent my tank from showing my gas level when below a half tank? Once my tank level hits a half tank, the twitching starts, and an accurate gas level is impossible to read.
No it's a sending unit issue. Google mts yj fuel system. They have it. Make sure you get the right year.

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