Gas Tank Issues - Auxiliary is leaking and Main runs out of gas quick

72bullet · Sep 8, 2016

So I have 2 issues with the fuel system/tank in my recently purchased 72 Bronco

1) The auxiliary tank leaks when operating and after. I appears to leak around the sending unit. Here are pics prior to leak and post.

2) The main stock rear gas tank when filled shows full on gauge. I run it till it says empty but thats only 6-7 gallons. After on E I can run a gallon or two before it runs out. I read that this could be due to maybe a sending unit or something with fuel not getting out of the tank even though there is gas in it.

I am a newbie for sure. Hoping I can replace 2 sending units and Im all good. Seem like cheap and fairly easy fixes to attempt.

Bully Bob · Sep 8, 2016

Hi Bullet, welcome..!

The aux. tank is plastic. I would drain the tank (or use it up) , then remove the sender and inspect

the opening & surrounding area for cracks. A new sender wouldn't seal a crack.

There's an "O" ring seal the sender rests on. "O" ring may be cracked.

Clean-n-test the sender..., it may still be good. (hard to tell but that sender & lock-down ring look new)

Same on the main.., drain it down..., pull & inspect the sender & "O" ring.

Shine a light into the tank hole to see if anything looks unusual.

There's usually a screen on the pick-up tube end of the sender.

Sender may be out of adjustment, causing the wrong reading.

Tanks are pretty easy to remove if necessary.

BTW.., the "O" rings are actually square & the grove they sit in need to be clean.

Gasket type glue helps hold them in place on installation.

72bullet · Sep 10, 2016

Thank you Top Gun!

I took out the sending unit and here are the pictures

There is still gas in the tank, even though I ran it out of gas and stalled when I was using aux tank.

I can't see any cracks. I'm going to reinstall the unit with the O ring seal and see. Maybe there is something noticeable in these pictures. Perhaps the seal should be replaced? Not sure .

Bully Bob · Sep 10, 2016

Hard to tell.., with the pics. That gasket looks like it has a dent in it..?? May still work.?

The sending unit looks new.

The remaining metal mounting plate is sealed to the tank with a mating goo.., if i remember correctly.

Sometimes that seal can seep.

Anyhoooo., you see it isn't a tough job if you have to start over. (let's hope not... [-o< )

72bullet · Sep 10, 2016

Thank you. It was a fairly easy for me to get that unit off and back on somewhat.

Going to try that gasket glue. Rough going with the gasket. It stuck with a little oil but not sure 100%.

Glad I get to test all this out on the aux. before I do the main one.

Hopefully be able to put some gas in the aux tank by tomorrow and see. There is that dent in the gasket. Probably just get a couple to be safe. Thanks again.

72bullet · Sep 11, 2016

So I put back the sender with the seal and it still had a leak, maybe a bit less of a leak.

I drove it and then used the aux. tank that still reads at below empty. Before I used he tank there was no leaking.

After I used it, there was some leaking. The gas level was an inch below the sending unit when it was put back in. I did not put anyone fuel in it.

Perhaps the seal? I am going to order 2 anyway. The seal was tricky for me to put on. Seemed like it was a bit too small.

Bully Bob · Sep 11, 2016

Splashing around would have caused the leak to show up..., if I understand the statement.

Thowing powder like baking soda or flower all over the area sometimes helps spot the leak track.

Auto parts has that yellow sticky goo that works to hold gasket in place.

Works similar to contact cement. (Seems I used contact cement B/4)

Either way, the sticky only goes on the tank side., not the side that hits the sender plate.

Looked like there is some chunks broken off the plate on the tank hole. do they

meet up with the seal or are they further out on the edge..?

72bullet · Sep 12, 2016

Thanks Bully Bob.

I will try the baking soda technique. Used this stuff to keep gasket in place.

http://www.oreillyauto.com/site/c/detail/VER0/34000/N2362.oap?ck=Search_N2362_-1_-1&pt=N2362&ppt=C1984

This is what it looked like after the trip around.

I had a beer or two my last post so maybe my description was a bit off. Was having fun for sure.

Bully Bob · Sep 12, 2016

BEER is one of my favorite tools..!!!

I don't think that gasket sealent is strong enough...?

The rubber "O" ring type seal needs a real sticky simi-hardening glue., as it tries to pop out of it's grove.

Sticky like the adhesive on duct tape.

If the o-ring seals don't solve it.., may need the metal ring held on by those phillips screws or

the gasket under it.

Bully Bob · Nov 7, 2016

How did your sender project come out..? All dry I hope..!!

Any tips for others following your thread..?

Gas Tank Issues - Auxiliary is leaking and Main runs out of gas quick

72bullet

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