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Excessive pressure in fuel tank?

R

Rainman

NAXJA Forum User
Location
Sydney, Australia
Hello,
Was driving yesterday got a strong smell of petrol in the cabin,
I determined it was not coming was not coming through the cabin fan intake.
A/c was on windows were up and it was 40*C outside
Petrol tank was over 3/4 full.
When i looked at the Petrol (gas) cap could hear & see gas vapour escaping. when i undid the cap the pressure released.
I'm pretty sure that that sort of pressure in the petrol tank is not normal.
So two questions:
1) what would cause the excessive tank pressure.
2) how is the petrol vapour getting into the cabin.
Any input appreciated
Thanks and regards.

95 xj sport.
 
Ive never owned a jeep of that vintage, so i cant say for sure, but theres something clogged somewhere. There should also be a roll over vent somewhere?!? Check those lines, replace if needed. It could be the lines up to the fuel vapor cannister, typically if its the fuel cannister, it will smell NASTY. Allmost vomit inducing, imho.
 
Rainman said:
you mean vent as in the evap system that goes to the charcoal canister?
Click to expand...

There'll also be a purge valve that might be stuck closed.
It should be located at the top of the charcoal canister
and have an electrical connector and evap hose connected.
 
There are two rollover valves on the top of the fuel tank. they attach to two rubber vac hoses. The nipples on the valves are made of plastic and after 20 years or so of age, fuel, heat etc the plastic gets hard and brittle and can break off.

I found this on my 88 MJ. Bot nipples had broken off and I had a strong fuel smell both outside and inside the truck. A little fuel had also sloshed out of the top of the tank.

The two hoses then meet in a T, and travel towards the charcoal cannister, eventually going into a metal line that bends up and along the firwewall...then back into a rubber line that plugs into the cannister.

If there is no vacuum sucking the fumes out of the tank (via the cannister and hoses and valves) you'll get a strong fuel smell, especailly if the weather is hot. You should be able to reach up and feel the valves on the top of the tank and see if they are broken or detached. If they are connected, just follow the vent/vac lines forward to the cannister. One or both of the lines could be broken and just not doing it's job.

The valves cost about $20-$25 each at the dealer. Bulk vacuum line should be availble for cheap. No specail fittings past the two valves.
 
ParadiseXJ said:
There are two rollover valves on the top of the fuel tank. they attach to two rubber vac hoses. The nipples on the valves are made of plastic and after 20 years or so of age, fuel, heat etc the plastic gets hard and brittle and can break off.

I found this on my 88 MJ. Bot nipples had broken off and I had a strong fuel smell both outside and inside the truck. A little fuel had also sloshed out of the top of the tank.

The two hoses then meet in a T, and travel towards the charcoal cannister, eventually going into a metal line that bends up and along the firwewall...then back into a rubber line that plugs into the cannister.

If there is no vacuum sucking the fumes out of the tank (via the cannister and hoses and valves) you'll get a strong fuel smell, especailly if the weather is hot. You should be able to reach up and feel the valves on the top of the tank and see if they are broken or detached. If they are connected, just follow the vent/vac lines forward to the cannister. One or both of the lines could be broken and just not doing it's job.

The valves cost about $20-$25 each at the dealer. Bulk vacuum line should be availble for cheap. No specail fittings past the two valves.
Click to expand...

.............thanks and regards.
 
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