Fuel sender signal wire options

[WSS]

I have a fuel gauge "problem" with my dash swap. The gauge I bought is a "240 Ohm Empty - 30 Ohms Full", the sender is supposed to be 220 empty and 20 full. Close enough. Problem is thje needle sits at 15/16 full when the tank is just topped off and drops to 0/0 in about 15 miles of driving.

I picked up the sender wire from a harness in the engine compartment (C-103) in the black connector hareness.

Any help would be appreciated. I assumed it was a bad gauge and I bought another and it is doing the same, So I rule out bad gauge.

Thanks for any input.

 

[Wildman]

What about going back at the tank with your spare gauge and hook into the wires there to just test it to see if you get the same results? Tap into either the wires or plug near the tank?

 

[WSS]

Good idea. I can reach the harness from the left rear behind the wheel. I can tap it right there. If it works, just run it to the gauge along the frame. There may be a issue with "ground", I may have to pull the ground from the sender along with the signal to the gauge.

 

[motomick76]

How about checking with an ohm meter? Check it at your dash and back at plug near tank. Near tank should be 4 prong flat plug. Outside are power/ground for pump and center is tank level. 220 ohms is full, 20 is empty. Check it again just before your converter, after converter, and at where gages are. Somewhere there is a discrepancy.

 

[WSS]

I have checked ohms at dash. 30ohms is what it is showing now and There is about 15-16 gallons in the tank. I was hoping to see 190-200

the original cluster was fine. Gauge worked good. Good to know the centers are the sender units. I was told by a few sources that the ground may need to be direct from the sender to be accurate. So I will test between those two pin outs. Thanks for the info.

 

[Wildman]

Is where you picked up the signal at the plug on the firewall before of after the PCM?

 

[motomick76]

I have checked ohms at dash. 30ohms is what it is showing now and There is about 15-16 gallons in the tank. I was hoping to see 190-200

the original cluster was fine. Gauge worked good. Good to know the centers are the sender units. I was told by a few sources that the ground may need to be direct from the sender to be accurate. So I will test between those two pin outs. Thanks for the info.

Start doing backwards from the dash and find every connection. Check until you get your 190 to 200 ohms. It is gonna get tedious, take your time.

 

[CharlesHS]

As others have posted... run test wires direct from the gauge to the fuel level sensor and see if you get the correct readings; if you do... then you have a lot of resistance in the factory wire run and harness connections. Clean all the harness connector pins along the way from the sensor to the gauge.
Might just be easier to run dedicated wires between the gauge and the sensor; the problem with the factory harness may return at a later time.

 

[someguysjeep]

i'm gonna be dealin with sender issues too possibly.

check post 10 & 11 maybe it'll help.

 

[WSS]

Is where you picked up the signal at the plug on the firewall before of after the PCM?

I am not sure. I think it was a direct wire from the sender. If it was after the PCM, my problems would make sense. I think a fresh run to the gauge from the sender is going to be the ultimate solution. Bypass any possible issues with the PCM too.

 

[WSS]

As others have posted... run test wires direct from the gauge to the fuel level sensor and see if you get the correct readings; if you do... then you have a lot of resistance in the factory wire run and harness connections. Clean all the harness connector pins along the way from the sensor to the gauge.
Might just be easier to run dedicated wires between the gauge and the sensor; the problem with the factory harness may return at a later time.

I think your last sentence may be the way to go. I did the same with the oil and temp sensor, ran all new wires. Those gauges are flawless, work great. I "T'ed" the temp sensor so I could still see the temp on my scangauge (OBDI port). Since the T, the temp code has not been thrown.

 

[WSS]

i'm gonna be dealin with sender issues too possibly.

check post 10 & 11 maybe it'll help.

Where are post 10 & 11 located? Are those on the tank connector?

 

[Wildman]

Where are post 10 & 11 located? Are those on the tank connector?

I was wondering the same. I think he meant to post a link to a thread and forgot?

 

[someguysjeep]

LMAO , ya the link might help,,,,,,duhhhh on me.

https://www.pirate4x4.com/threads/97-tj-fuel-sender-ohms.359526/

 

[Wildman]

LMAO , ya the link might help,,,,,,duhhhh on me.

https://www.pirate4x4.com/threads/97-tj-fuel-sender-ohms.359526/

It happens to all of us..

 

[WSS]

I am back at it this weekend. I unplugged the connector above the tank and checked the ohs on the middle pins and had 122ohms I estimated I had 1/2 tank. 1/2 tank would be 110ohs. So close enough. I replugged and noted the colors of the pin out wires, brown/yellow stripe and blue. Found a good spot to tie into the harness st rear of skid plate/trans mount. Tested the wires agoin to double check, same 122ohms. pulled the wire(s) through the firewall and put some heat shield around the vulnerable areas. Tested again inside the cab, same 122ohms. Getting closer, should have it sealed up today!

Here is the pin connector on the tank:

test inside cab:'

'

 

[motomick76]

Awesome! Glad to see this getting solved!

 

[Wildman]

Now get this all figured out so you can do mine next....

 

[WSS]

I managed to get the gauge working at a high cost though. I know have 2 codes 505 and 118. And the Jeep runs crappy, low idle, lopey, stalls on start up, etc.

The end result was A) using a common ground and B) cutting, not tapping into the sensor wire but re directing it to the sensor post on the new gauge. I am (at this point) having trouble erasing the codes.

 

[Wildman]

Yep you most likely need to not use the common ground and not cut that wire. These things are really picky about how stuff is wired up.