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Fuel tank...vents?

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I dropped my tank yesterday to prime and paint it and replace the filler hoses before I put the new steel skid on it. On the top of the tank there are 2 little "porcelain" type fittings. One has a hose attached, the other is broken off at the nipple with no hose.


The tank is in good shape (for an 88) with only minor surface rust.


My question is, do those "nipples" need to have a hose attached AND where do the hoses go??

Would this be cause for a failed smog (CA) when I finally take it down to re-register.


Also, if I have a space between the tank and the skid would there be any advantage at all to insulating the tank with that foil/bubble wrap stuff or...?

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Just wondering. I've dropped 4 MJ gas tanks so far. All four of them the above mentioned vent hose had been caught between the tank and frame and was effectively 'cut off'. Am I the only one?

As for the grommets, if stealship doesn;t have them try a industrial supply like Graingers.They're rubber. They can be trimmed.

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"little "porcelain" type fittings" are roll over check valves. they stop fuel from leaking out of the fuel vent system when you turn you MJ upside down. they are mostly standerd shape and size on all fuel tanks. so you can find a bunch of them at the junk yard.


I do not think missing one will give you a fail becouse they both meet up at a T fitting befor the charcoal cannister The Idea of the system is to let the fuel vent off on warm days. the fuel vapers are stored in the charcoal cannister and sucked out when you start the motor. when you look at the charcoal cannister you should see the one small line coming from your tank and a bigger line going from the charcoal cannister to the air cleaner. every time I have seen them do the emissions test, all they did was check to make sure the charcoal cannister was there and the hoses going to it did not have any cracks.


the space between the tank and the skid is there to give the skid some room to absorbe bumps, so stuffing some thing in it would not help any

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  • 2 weeks later...

How can you tell if the tank vents are actually working? On my old '87 I rarely had any type of hissing when I opened the gas cap. The '90 has so much pressure that it hisses as soon as I put the key in the gas cap (haven't even turned it yet). It hasn't been above 55 degrees yet which makes me wonder what will happen when it gets warm. The tank is new but the check valves are OE.

I checked the system yesterday. I can apply 15" vacuum and it will hold and not leak down at all. Also if I open the gas cap with 15" vacuum on the evap line it doesn't change.

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