Fuel Gauge Intermittently Shows Tank as Empty - JeepForum.com
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post #1 of 10 Old 09-24-2021, 01:08 AM Thread Starter
CarolineW
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Wj Fuel Gauge Intermittently Shows Tank as Empty

Hi All,
Not long after replacing the Crankshaft Sensor which cured my problem of intermittent stalling when idling or going at low speed, the fuel gauge gave me a fright. The light came on and the needle was on empty. But there was close to half a tank full of gas.

Someone said that possibly the fuel level sensor inside the tank was failing. I was then told that there is no separate sensor to replace, one has to purchase a fuel pump system including sensor.

The issue is intermittent. Tends to rectify itself if the engine is shut down and re-started.

My worry is that the fuel pump could fail and I am stuck somewhere having to organize a tow truck.

Questions:
1. Is this issue something that a good quality scanner will identify so I know if the fuel pump absolutely has to be replaced? I have not had a scan done yet, don't own one myself.

2. Should I get someone to check the wiring from the fuel tank back to the dashboard if no code shows up a definitive problem with the fuel pump assembly?

I have done a search to read other posts about the issue but can't find exactly this one of intermittency. Thanks for any tips - I am sighing over the amount of repairs this car needs due to its age so any wisdom about diagnostic will be most welcome.

PS. The dashboard is not 100% The mileage light has been intermittent for a long time. Got a mind of its own...

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post #2 of 10 Old 09-24-2021, 05:34 AM
Delta0
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Have you checked grounds / earths yet?

Uniblurb posted the "Complete Guide to WJ Earths / Grounds" recently.
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post #3 of 10 Old 09-24-2021, 05:39 AM
Double E
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Common problem and both explanations you got are right.
A scanner is not going to pick up anything for this issue and it is not an issue external to the tank.

My story:
https://www.jeepforum.com/forum/f310...oblem-4198386/

Bad news is that the fuel pump will eventually need to be replaced. Start saving for that now as it can get expensive for a garage to do it. Find the part now and keep it close if/when it does fail on you entirely.
Good news is that it lasted 20+ years until it gave out and a replacement will probably go for another 20 years.
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post #4 of 10 Old 09-24-2021, 06:18 AM
jtec
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I agree with Double E removing a fuel pump assy on a 20year old vehicle - replace the unit don't rebuild just a portion.

Are there any other issues?
Have you checked codes with a scanner - there are fuel gauge codes. Key trick may not show them.
Add a can of techron fuel cleaner - MAYBE* deposits on fuel level sender .
I have seen wire yourself fuel pumps with bad wiring - twists, butt connectors etc.

* I remember A TSB addressed deposits on sender unit
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 10 Old 09-25-2021, 07:34 AM
cDee63
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Another thing to check is the connection under the vehicle. It is attached to the fuel tank skid with a rosebud clip,this is the connection the pump module plugs into. When my fuel pump failed it turned out to be that connection, the gauge worked fine. I bypassed the pump wiring and left the gauge wiring alone, have had no problem since.
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2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
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post #6 of 10 Old 09-25-2021, 05:49 PM Thread Starter
CarolineW
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Quote:
Originally Posted by jtec View Post
I agree with Double E removing a fuel pump assy on a 20year old vehicle - replace the unit don't rebuild just a portion.

Are there any other issues?
Have you checked codes with a scanner - there are fuel gauge codes. Key trick may not show them.
Add a can of techron fuel cleaner - MAYBE* deposits on fuel level sender .
I have seen wire yourself fuel pumps with bad wiring - twists, butt connectors etc.

* I remember A TSB addressed deposits on sender unit
Thanks Jtec. I have put in a bottle of Techron concentrate yesterday. Too soon to tell if it has done something for the fuel level float. But the gauge light did not come on today... Keeping fingers crossed.
What is a TSB please?
Otherwise all the grounds are going to be checked out next week and also connectors for everything. The fuel tank connector will be checked. Engine washed so that an oil leak can be found.
That's it for now!
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post #7 of 10 Old 09-25-2021, 05:53 PM Thread Starter
CarolineW
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Thank you cDee63. Have asked the mechanic to take a look at that connection on the gas tank. I did not understand your comment "I bypassed the pump wiring and left the gauge wiring alone, have had no problem since." But I am way out of my depth anyway.
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post #8 of 10 Old 09-25-2021, 06:15 PM
WJ60
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Quote:
Originally Posted by CarolineW View Post
What is a TSB please?

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post #9 of 10 Old 09-26-2021, 06:24 AM
cDee63
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Quote:
Originally Posted by CarolineW View Post
Thank you cDee63. Have asked the mechanic to take a look at that connection on the gas tank. I did not understand your comment "I bypassed the pump wiring and left the gauge wiring alone, have had no problem since." But I am way out of my depth anyway.
I meant I bypassed the wiring for the pump in the factory connection leaving the gauge wiring only. I then spliced into the pump wires under the back seat with new wires that run to the pump. I had to incorporate another connector doing this. The result is now I have 2 connectors vs just the one. The original only has the gauge wiring functional and the other is a connector for just the fuel pump. It was the quick lazy way to avoid replacing the entire original connector.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
High speed, low drag
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post #10 of 10 Old 10-10-2021, 10:32 AM
Wjinnc
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Yeah, mine did this about 5 years ago. Mine turned out to be the wiring harness where it wraps around the back of the engine. It had fallen on the motor and about 3 wires had bare spots in them.
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