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Hey all. My gas tank is leaking when I fill it up to full.

 

The previous owner said he did the following:

  1. Fuel pump
  2. Fuel filter
  3. Fuel line from tank to engine
  4. Fuel tank removed and washed out

My mechanic said the leak is coming from the sending unit, which he says appears to be welded to the tank, and recommends finding a new tank, sending unit, and fuel pump.

 

When I look for new tanks online, some mention "includes the lock ring and gasket for the sending unit".

 

What is the possibility the sending unit is welded to the tank? Is it more likely the gasket is leaking and/or not seated properly?

 

Thanks!

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22 minutes ago, Not said:

Hey all. My gas tank is leaking when I fill it up to full.

 

The previous owner said he did the following:

  1. Fuel pump
  2. Fuel filter
  3. Fuel line from tank to engine
  4. Fuel tank removed and washed out

My mechanic said the leak is coming from the sending unit, which he says appears to be welded to the tank, and recommends finding a new tank, sending unit, and fuel pump.

 

When I look for new tanks online, some mention "includes the lock ring and gasket for the sending unit".

 

What is the possibility the sending unit is welded to the tank? Is it more likely the gasket is leaking and/or not seated properly?

 

Thanks!

Lay underneath it and take a look yourself, look on the driveshaft side of the gas tank, if it's welded it will be obvious.  Idk why or how anyone would weld it on but I've seen dumber things.  Unless your mechanic has never seen this style of lock ring in which case, id find a new mechanic.  Take a picture of it and post it up so we can see what you are working with.

 

More than likely your tank is rusting and leaking somewhere.  Mine had a pin hole behind the fuel tank strap near the top and would only leak with more than 3/4 tank.  Others have had the fuel pump assembly rust out.  It's pretty common for these to occur.

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7 minutes ago, Dzimm said:

Lay underneath it and take a look yourself, look on the driveshaft side of the gas tank, if it's welded it will be obvious.  Idk why or how anyone would weld it on but I've seen dumber things.  Unless your mechanic has never seen this style of lock ring in which case, id find a new mechanic.  Take a picture of it and post it up so we can see what you are working with.

 

More than likely your tank is rusting and leaking somewhere.  Mine had a pin hole behind the fuel tank strap near the top and would only leak with more than 3/4 tank.  Others have had the fuel pump assembly rust out.  It's pretty common for these to occur.

Thanks for the reply. I'll get under it tonight and get some pictures.

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The outer retainer for the locking ring is welded to the tank but the sending unit is not welded to the tank. If it is welded to the tank then an utter moron did that. As @Dzimm mentioned, it’s more likely that your mechanic didn’t notice the actual locking ring. Another common area for gas leaks is around that locking ring and seal. Especially if it only leaks badly when full or over 1/2 tank.

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Here's two pics of the sending unit lock ring on the tank. In the picture taken from below, you can see that the paint is peeling off towards the bottom and that area smells like gas after I rubbed my finger on it. Is it best to replace the lock ring and gasket, or could some J-B Weld around the outside do it, or something else? I'm open to suggestions.

PXL_20210208_155216628.jpg

PXL_20210208_155243727.jpg

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If you can't actually see where the leak is coming from, replacing the o-ring seal for the sending unit is a relatively cheap and easy thing to try.  If it still leaks, at least you've ruled it out.  It could be leaking from the fuel lines (while under pressure with the truck running) from a loose clamp or a split in the line near the clamp, or from a failed weld (from rust) or a rust hole.

 

FYI- an emergency fix for a pinhole leak in the gas tank is rub the area with a bar of soap (regular bath bar type soap).  I've had a "temporary" fix last several years.

 

Also, this is just me, but I would replace that connector on the ground wire on the sending unit.  That open barrel crimp type connector is subject to corrosion.  I would cut it off, crimp on a new eye terminal (without the plastic barrel piece, just pull it off) in the proper gauge size for the wire, solder it, and then apply some adhesive lined heat shrink to the connection to protect it (slide the heat shrink on before making the crimp!).  This would be easier (and safer) to do with the sending unit removed and on the bench, like it would be if you replace the o-ring.

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The lock ring  and gasket usually aren't the problem. What often happens is that the steel tubes are (I think) soldered where they pass through the mounting flange, and the solder joint cracks. If you add enough gas to make it leak, you'll probably see it weeping around one or both of those two steel tubes. I think there used to be a member here who repaired that for other members, but J-B Weld has been reported to work well. You'll need to siphon out enough gas to stop the weeping, then clean both the tubes and the mounting flange VERY well, down to bare metal. Then mix up your J-B Weld and apply it.

 

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Glad you got it fixed.

 

I had the same problem and it was a struggle to find the seal and locking ring. autozone has it but for some reason there system doesn't have our jeeps in the list of applications.

part number (LO zero one).105911645_Screenshot_20190604-110913_SamsungInternet.jpg.28c7591c50df4a2a5fc66961d47e8dad.jpg

Looks like the price has gone up to $4 since then but thought putting this on here may help someone else in the future.

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Yeah as mentioned start with a new seal and lock ring.  If it still leaks then as suggested you can seal it up however I'd use a sealant specifically designed for fuel tanks rather than JB weld.  

 

Also, I'd be weary of having your mechanic doing anything else to the truck.  There is no additional welding or anything of the sort on that flange, it's factory.  If they haven't seen this style of lock ring, they likely have very little experience on anything but newer vehicles.

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My fuel lines that run through the flange were leaking.  Regular JB Weld worked for me for just under a year.  

 

For those with this type of leak, use the white-colored JB "WaterWeld next and it's the stuff to go with.  Don't waste your time on regular JB Weld.  It won't last.

 

Brazing is really the best, most permanent solution.  If/when my white WaterWeld fails, that's what I'll do next.    

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3 hours ago, ghetdjc320 said:

Mechanic never lines up the o ring properly. I used a touch of grease to hold the o ring in place and it sealed up great afterwards

It's way easier to do if you drop the tank. I was in and out of my tank several times when I got mine running, and I thought the effort to drop the tank was worthwhile. The replacement O-ring that came with my fuel pumps was too thick, I got one like the one above. Pretty sure I have the same thing going on with my son's Cherokee.

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I just got my 90 Comanche Eliminator. The first time I filled the tank It leaked profusely down the frame rail. I thought it was the fill hoses. It took several hours working through the fill door to get the hoses off. It wasn't the hoses, but the side of the tank had almost rusted through. Ordered a new tank and fill hoses from Rock Auto. Now I'm waiting for new hanger bolts since one of mine snapped. These bolts are made of unobtainium.

 

The holes in the first image are from me lightly pushing an ice pick against the tank side. The second shows where it had been leaking along the frame.

 

IMG_5410.JPG

IMG_5412.JPG

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