Sending unit

[terryt]

my sending unit has developed a leak where it meets the tank 1990 mj 4.0 long bed

any thoughts what I have to do 

[ghetdjc320]

A new lock ring and gasket are probably in order. Pretty simple swap, just make sure to keep the area clean so dirt doesn’t get in the tank when you remove the old gasket. MTS carries the parts you need among others. Part numbers GMLR-1 for the locking ring and GMOR-1 for the gasket

[terryt]

Do I need to frail the tank somehow 

[ghetdjc320]

43 minutes ago, terryt said:

Do I need to frail the tank somehow 

Just get it below the sending unit which should be anything less than about 2/3 tank 

[terryt]

Last question what is MTS

[terryt]

it does look like it is the lock ring 

[ghetdjc320]

MTS is a company that makes sending units and related parts. https://www.mtscompany.com/lockrings.htm

[coolwind57]

I had to braze my sending unit.  it was leaking where the tubes meet the disc mount.  If your gasket doesn't work for you, you may have to braze. 

 

I did Marine JB Weld which worked for nearly a year.  Regular JB Weld will not last but a few days.  This is your temporary fix.

 

I hope you get dealt the easy hand and have only to replace the gasket.  Good luck.

[terryt]

Do you think I should just replace the whole sending unit? My concern is my luck my fuel gauge will not read correctly when done 

[ghetdjc320]

1 hour ago, terryt said:

Do you think I should just replace the whole sending unit? My concern is my luck my fuel gauge will not read correctly when done 

MTS can send you the correct gauge sweep sending unit. There are only two gauge sender sweeps, 90- & 91+

[terryt]

What is a gauge sweep

[ghetdjc320]

1 hour ago, terryt said:

What is a gauge sweep

It’s the resistance reading that the fuel level sender sends to the gauge. Renix era jeeps from 90- read about 85-100 ohms when full and 0 when empty. HO era from 91+ read 0 ohms as full and 100 ohms as empty. Basically the opposite sweep between the two sending units. 

[Pete M]

I just did a pump swap on a clean southern truck this past year.  ended up replacing literally all of it: tank, pump, hoses, J-hooks, etc.  If I ever have to drop another old tank for any reason, I'm just going all-in the first time.   

 

but I guess for a simple gasket change, I might try just the gasket?  it's not fun working under there.  I don't want to do it twice.   

[eaglescout526]

I think doing the XJ is a lot less fun and forgiving than the MJ. With the MJ at least you can get the sending unit out without some fancy finagling and you can actually sit up while doing all the work. Vs the XJ having a whole axle in your way. 

[TurboedMJ]

27 minutes ago, eaglescout526 said:

I think doing the XJ is a lot less fun and forgiving than the MJ. With the MJ at least you can get the sending unit out without some fancy finagling and you can actually sit up while doing all the work. Vs the XJ having a whole axle in your way. 

Agreed. Dropping the tank on an MJ vs an XJ, I could do 3 Comanches in the time it took me to do one XJ. Can't remember why tho. Mostly the rear axle being in the way, and having to use a pipe to break loose some of the skid plate bolts on my XJ. The breaker bar was bending... I found it made everything easier to either remove the driveshaft or zip tie it off to the side, so it's out of the way.