Fuel gauge not working

[powerpiston986]

97 jeep tj wrangler gas gauge not working reading = Empty I installed new fuel pump and still gauge reading = Empty
I did some troubleshooting and notices that if I disconnect the Pump the gauge works ok
any body have an idea what can I check I also did the self diagnostic on the cluster gauges and all the gauges worked ok including the fuel gauge
right know I'm out of ideas has any one seen this problem before I sure could use some Ideas.

 

[Chris]

That makes no sense. If you disconnect the fuel pump, there is no power to the fuel level sending unit, so there's no way the fuel gauge would be working (and if it is, it would just be the gauge cluster moving it with no actual measure of the fuel in the tank).

If your fuel gauge isn't working or sometimes works and sometimes doesn't, it's the fuel level sending unit going bad in the tank. To replace it, you need to drop the tank and remove the fuel pump.

 

[KCsTJ]

@powerpiston986 before u do anything else, take your vin # and call a Jeep dealer to see if the factory recall for the fuel pump has been "completed".
There is a recall for 97 TJ fuel pumps. You may know all this.
It's worth checking into unless you already have.

 

[powerpiston986]

97 jeep tj wrangler gas gauge not working reading = Empty I installed new fuel pump and still gauge reading = Empty
I did some troubleshooting and notices that if I disconnect the Pump the gauge works ok
any body have an idea what can I check I also did the self diagnostic on the cluster gauges and all the gauges worked ok including the fuel gauge
right know I'm out of ideas has any one seen this problem before I sure could use some Ideas.

That makes no sense. If you disconnect the fuel pump, there is no power to the fuel level sending unit, so there's no way the fuel gauge would be working (and if it is, it would just be the gauge cluster moving it with no actual measure of the fuel in the tank).

If your fuel gauge isn't working or sometimes works and sometimes doesn't, it's the fuel level sending unit going bad in the tank. To replace it, you need to drop the tank and remove the fuel pump.

Yes it dose make sense let me explain how I did the test I disconnected the plug to the pump then I connected another fuel sensor unit with out the pump from another year 97 jeep that I had laying around I turn on the ignition switch
and the the gauge work perfect I moved the flout up and down and the gauge read the hole sweep
but once I connect the plug back to the pump in the gas tank, the gauge stays on empty
I put two new complete pump and its doing the same
(ones you turn on the ignition switch it sends the signal to the fuel level sensor and the other side of the sensor is connected to ground. some how I'm suspecting I have and issue with the harness wires underneath the jeep
that is shorting out the signal wire to the gas pump circuit. what do you think

 

[powerpiston986]

@powerpiston986 before u do anything else, take your vin # and call a Jeep dealer to see if the factory recall for the fuel pump has been "completed".
There is a recall for 97 TJ fuel pumps. You may know all this.
It's worth checking into unless you already have.

Hi thanks for the info I dint know a recall would be still active for a 22 year old jeep
I replace the fuel pump twice with brand new pump one but the problem still their
I done some troubleshooting and I believe I have a wire problem shorting out the flout signal

 

[KCsTJ]

Hi thanks for the info I dint know a recall would be still active for a 22 year old jeep
I replace the fuel pump twice with brand new pump one but the problem still their
I done some troubleshooting and I believe I have a wire problem shorting out the flout signal

The recalls NEVER expire, so you might check, who knows.
One guy I told takes his 97 jeep to the dealer and boom, new fuel pump absolutely free.

 

[Chris]

Okay, well now it makes a lot more sense that you explain it in detail

I had the same problem with mine, literally. The weird thing is that I was able to resolve mine by pulling the pump and just messing with the float. I put it back in and magically it worked again.

You could have a short in the wiring, but it’s also possible thst the float is potentially jammed against something inside the tank or just needs to be pushed up and down by hand a few times. This did the trick for me at least.

 

[Kelly F.]

I'm also having issues with my fuel gauge, I have since I first bought the Jeep. After testing the wiring Ive found only 1 wire (green on Jeep side) is getting power. The green connects to the red on the fuel sending unit.
If I disconnect the battery the gauge works but gives a false reading until I cut the Jeep off.
not sure how to chase this power issue , unless there is a wiring schematic to go by. Possible ground problem within the harness?
Also, fuel pump is new just changed this past weekend as I thought that may have been the issue.

 

[LONGJP2]

not sure how to chase this power issue , unless there is a wiring schematic to go by. Possible ground problem within the harness?

What are your issues?
IIRC, there is a fuel level sender test procedure in the FSM.
https://wranglertjforum.com/attachments/1999-tj-service-manual-pdf.14034/

 

[Kelly F.]

What are your issues?
IIRC, there is a fuel level sender test procedure in the FSM.
https://wranglertjforum.com/attachments/1999-tj-service-manual-pdf.14034/



View attachment 409920

In short there is no power on the receiving plug, my gauge will give a false reading of full if I unhook the battery for any period of time

 

[LONGJP2]

In short there is no power on the receiving plug, my gauge will give a false reading of full if I unhook the battery for any period of time

IIRC, only the pump uses power.
The gauge is controlled by the PCM.

FUEL GAUGE SENDING UNIT The fuel gauge sending unit contains a variable resistor (track). As the float moves up or down, electrical resistance will change. Refer to Group 8E, Instrument Panel and Gauges for Fuel Gauge testing. To test the gauge sending unit only, it must be removed from vehicle. The unit is part of the fuel pump module. Refer to Fuel Pump Module Removal/ Installation for procedures. Measure the resistance across the sending unit terminals. With float in up position, resistance should be 20 ohms. With float in down position, resistance should be 270 ohms.

 

[Skywarrior]

My 2006 gauge works at start.then after a few minutes the check engine light comes on you watch needle drop until low level lite comes on. P0462 is the code. Restart and gauge reads for a few minute and process repeats. Anybody seeing that code?

 

[Jerry Bransford]

My 2006 gauge works at start.then after a few minutes the check engine light comes on you watch needle drop until low level lite comes on. P0462 is the code. Restart and gauge reads for a few minute and process repeats. Anybody seeing that code?

Sounds like the fuel gauge sender has gone bad, it is spot welded onto the fuel pump assembly inside the gas tank. But it could just be a bad connection for the fuel pump at its main connector located at the outside top front driver's side corner of the gas tank. I'd unplug the connector and reseat it to see if that helps.

 

[Skywarrior]

My 2006 gauge works at start.then after a few minutes the check engine light comes on you watch needle drop until low level lite comes on. P0462 is the code. Restart and gauge reads for a few minute and process repeats. Anybody seeing that code?

Any recommendations on a replacement pump? Prices vary quite a bit

 

[Skywarrior]

OK, I finally dropped the tank and replaced the pump . I inspected the connector, which is dead center top of the tank, no discrepancies noted. I rolled tank under jeep, hooked up connector and powered up. Fuel gauge went to full then slowly fell to empty (tank is empty) illuminating lo fuel light. Code 0462 still present. Cleared code and repeated process. Code 0462 popped again. Any suggestions?

 

[macleanflood]

Pull the pump, actuate the float arm in it's full sweep and have someone observe the dash...or cheat like I do with a GoPro on live to my smart phone.

Might also need to ohm out and continuity check the wires all the way to the PCM connectors.

-Mac

 

[Skywarrior]

Pull the pump, actuate the float arm in it's full sweep and have someone observe the dash...or cheat like I do with a GoPro on live to my smart phone.

Might also need to ohm out and continuity check the wires all the way to the PCM connectors.

-Mac

I ohmed out to PCM and all check good. Do you know where I would find the ground points?

Resistance good on new pump sender.

 

[macleanflood]

There is a complete list of ground locations in the FSM. Let me know if you want me to dig it out.

At least in the 97 version there is...

-Mac

 

[Skywarrior]

put tank with new pump back up. I checked the pins 2 and 3 at pump. Had 10 volts on 2 and a good ground on 3. Put five gallons in tank. Cleared codes, started engine. About 1/4 tank indicated for 90 seconds then CEL light on and needle heads to empty illuminating low fuel light on the way. Drove to gas station and filled tank. Cleared codes. Tank read full for about 90 seconds, then CEL and needle goes to empty. Code P0462 every time.I repeated the process several times and get same result, time elapse varies a bit. Instrument cluster test is good. Has anyone had to change a PCM to fix fuel level indication?

 

[Skywarrior]

Finally fixed! Removed PCM and used scotchbrite around mount holes and did same around screw holes on firewall. Cleaned and re tightened ground G105 on engine block. Tie wrapped bundle to keep it off starter flange. Op check good! Happy Thanksgiving