johnson mile-master fuel tank

[tbone303]

Hi, is there a way i can check the mile master fuel tank to make sure that the seals are still good and hold the pressure good?

[1946Zephyr]

Yea. Just test it out with a motor, in a test tank. After a couple minutes running, shut it down and loosen the cap and see if it blows off the pressure. If your motor keeps running without dying, that is a good sign too. The main thing about these pressure tanks, make darned sure the inside is clean and no rust is present. Rust, over time will create pin holes and leak out.

[tbone303]

i haven't restored the motor to working condition yet but i'm asking in advance so when it does run i know how to use the tank, wouldn't gas be leaking out the top when motor is running if seals are bad? and to remove pressure form tank all you have to do is unscrew cap? thanks

[lindy46]

The gasket on top of the tank is usually the place where it leaks. You'll know if that's leaking as soon as you run the motor. You can test to see if the tank holds pressure by hooking up hoses to the tank - plug the "fuel" line and blow a little air into the "air" line. See if it holds about 5psi. Yes, loosen the cap to relieve the pressure.

[tbone303]

I tried blocking the fuel line and blowing in the air line but it didn't work i couldn't seem to get air into the tank. So i put a little gas in the tank and pumped a couple times and then open the cap and pressure came out, tried it a second time pumped and gas spit all over me, the gas cam out of the plunger hole. i kept trying and the same thing i would pump and gas would slowly leak from the plunger hole. Do i need a seal kit or just the gasket? did i do something wrong, or shouldn't have?

[F_R]

Gas coming out the plunger hole is a sure sign the diaphragm has a hole in it----Or the diaphragm support washers are bent or rusted----or the pump push rod is rotted at the bottom end---or the nut is loose on the bottom of the push rod----or---

Get the picture? You have to take it apart and see what's wrong and fix it properly. There is no other way.

[tbone303]

ok thanks i will look into it tomorrow and report back

[lindy46]

Pumping the primer button won't pressurize the tank - it just feeds gas to the carb to initially get the motor running. If you can't blow air into the tank air fitting, it is clogged up, and as mentioned, needs to be taken apart. Done that, seen that before.

[tbone303]

ok i tried it now with an air gun and got pressure into the tank three times and it held pressure each time. Now when i get the motor restored to working condition when i go to prime it when connected to the motor will it still leak at the primer button, or will i find out when the time comes if it works like it should? thanks for the help

[lindy46]

If it leaked before, it will continue to leak until you address the issue.

[tbone303]

i took it apart today every thing looked very good cleaned all the rust with metal wool and gas. No rust on any of the push botton components, diaphragm support washers were in mint condition weren't bent, no rust. The gasket was old looking and cracked when i was cleaning the tank. What are the parts that come with a tank reseal kit? .But the diaphragm had full of cracks around where the push button is here are some pics.

[tbone303]

By looking at the cracks would this be the cause of gas fizzing out the pressure push button hole?

[nwcove]

yep, that would be yer problem.

[tbone303]

bought the top gasket and diaphragm today off ebay for $18 shipped. The 2 o-rings in the adapter, screw gaskets, cap gasket, and diaphragm support plates i did not feel the need to replace because they were in very good condition.

[tbone303]

So i put my new gasket and diaphragm on the tank and it wouldn't hold pressure. I left it in for 4 hours and there was no pressure left in the tank. I put pressure in by blowing air in the air fitting. How long should the tank hold the pressure and what is the possible problems? thanks

[tbone303]

Also when i reopened the tank top the diaphragm was covered in gas, so gas leaked into the small compartment that the diaphragm and other small pieces are in.