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redjoe79 12-12-2009 09:59 AM

Loud Fuel Tank Noise
02' TJ, 4.0L, 5spd, 41,000mi.
After daily 15mi commute with engine off getting loud knocking noise from what seem inside the fuel tank. Can feel the viprations through rear tires. Started happening about a week ago and usually lasts about 5-10min then goes away. No CLue except have had an ASD code for about a year which my mechanic and dealer can not track down.

stevens243 12-12-2009 10:17 AM


Next time it happens, pop the gas cap to see if the tank is being pressurized (over or under). May be a bad vent. Usually, that wouldn't let the jeep run but maybe it's pulling just enough air to continue to pump gas...

redjoe79 12-12-2009 02:21 PM

Remeber unscrewing gas cap and hearing preasure being released and that has never happened before. What do you suggest?

stevens243 12-12-2009 06:07 PM

Was the pressure leaving the tank or (more likely) trying to get in?

If it's trying to get in (as it should be) I think you have a pinched or clogged vent tube.

In the rear fender where the fuel line runs from the fill cap to the tank, there is a vent also. Check the vent and ensure it's not bent.

After that, it's time to download the field service manual and do some reading up on it. I don't have a full version of acrobat to cut the diagrams out and I have the 05 FSM anyway.

You can find the full FSM on a link in the general jeep discussion. I'll post the link shortly.

redjoe79 12-13-2009 08:11 PM

Ok thanks I'll look into that.

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