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Fuel level senders


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After tons of research I have discovered a few things abot the 97 XJ fuel sender along with a 97 TJ sender.

 

I was going to use the XJ tank in the truck but there is no way it is going to fit and not hit the driveshaft. Then I got to thinking about a TJ tank and sender. It is long and skinny like a MJ tank and could easily be fit in the stock location. I am not sure if the TJ sender will work the 97 XJ gauge correctly though.

 

The values for the XJ are,

20 ohm (full) and 270 ohm (empty)

 

The values for the TJ are,

20 ohm (full) and 220 (empty)

 

If I am thinking correctly, I will run out of gas before the needle hits the E mark!

 

The wiring is plug and play from the XJ harness to the TJ sender wich is a good thing.

 

But, will the 50 ohm difference throw my gauge all silly? I don't want to run out of gas and still have the gauge reading 1/4 tank. Is there a way to bring the TJ's value closer to the XJs when it gets down to empty?

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No way that I can think of. If you put a 50 ohm resistor in series with the sender output, it will just lower the gauge sensitivity, i.e. FULL will prolly indicate 3/4 tank. If you put resistance in parallel with the pot, it will just lower the overall pot resistance so that won't work either. You might be able to tinker with the value of the resistor across the fuel gauge meter movement, but I wouldn't, unless you had a decade resistance box and could set it up for a bench test w. the sender. So outside of changing out the pot itself, you'll probably have to live with it, unless you can fit the XJ sender to the TJ tank. :D

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It appears you are correct. If the gauge you have requires 270 ohms to register empty, and the sender you use only goes up to 220 ohms, the gauge can't ever indicate empty. It will stop at whatever point on the dial corresponds to 220 ohms.

 

Are you certain that the TJ sender is different? I have a 2000 XJ FSM and that confirms the 270 ohms. But I know a guy in NAXJA who put a 98 or 99 TJ cluster into a 97 XJ and he didn't encounter any problems (that he seemed to be aware of). I have always thought the 97+ XJ and TJ clusters were completely interchangeable, and that would seem to require that the sender values would also have to be the same. Of course, we used a TJ cluster with an XJ sender, so maybe his just registers empty before he runs out of gas, so he'd never notice.

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It is possible that he never did get the tank dry. I could deal with that fact that I always still had fuel in the tank and had to fill up more often. The idea of guessing when it was empty or counting miles does not go over well with me. I would hate for a sensor to go out and start eating gas and run out.

 

I called 2 different dealers and had them check the FSM and I read it on the web too. If a TJ cluster will go in with a little trimming than I will go with the TJ tank and cluster. Do you by chance know who did the cluster swap on NAXJA? I would like to read how hard it was to do.

 

Thanks for the tip Eagle.

 

EDIT: I found this on NAXJA

 

UPDATE:

 

well with all the conflicting info i decided to just go out and take out both my TJ and XJ's Cluster.

 

What do you know, there the EXACT same! so figured i would try it out i put my TJ one in my XJ Tada it works (everything). Then i put my XJ one in my TJ it works flawlessly too. My XJ is an AUTO and my TJ is a manual and both worked so i guess there you have it the XJ and TJ clusters are interchangeable after all! now both mine were 97's but i have been told that the 97 thur 99 are the same so if that holds true all 97-99 TJ and XJ clusters are interchangeable without any modifications!

 

Looks like I will be getting a TJ tank and cluster now!

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Do you by chance know who did the cluster swap on NAXJA? I would like to read how hard it was to do.

 

Thanks for the tip Eagle.

 

EDIT: I found this on NAXJA

 

UPDATE:

 

well with all the conflicting info i decided to just go out and take out both my TJ and XJ's Cluster.

 

What do you know, there the EXACT same! so figured i would try it out i put my TJ one in my XJ Tada it works (everything). Then i put my XJ one in my TJ it works flawlessly too. My XJ is an AUTO and my TJ is a manual and both worked so i guess there you have it the XJ and TJ clusters are interchangeable after all! now both mine were 97's but i have been told that the 97 thur 99 are the same so if that holds true all 97-99 TJ and XJ clusters are interchangeable without any modifications!

 

Looks like I will be getting a TJ tank and cluster now!

Yeah, they are directly interchangeable, which is why I'm so surprised the senders have different values. The idea was to have the cluster be cross-platform applicable. The guy I know who did it, several years ago, was Rich Pearson from PA.

 

I'd say you have two ways to go. I gather you're upgrading to the new XJ interior, since the sender values for the actual XJ/MJ are far different than either of the ranges you're discussing. You can use the XJ cluster and just find a TJ gas guage, or you can use a TJ cluster and, if you already have the speedo running for your MJ, swap the XJ speedo into the TJ cluster.

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