I recently got an 04 Limited 44,000 miles and have noticed a deep humming / vibrating noise coming from the rear when the vehicle is parked. It only lasts for about 1.5 seconds and then is quiet for 10 - 15 minutes and it does it again. I've laid under the back end and was thinking it was a fuel pump, but when I had the key turned on the fuel pump sound is a faster, higher pitched sound. The noise is coming from somewhere around the fuel tank.

I'm new here and have a few questions, but will post them one at a time. If anyone knows what this is and how to fix it, your help would be appreciated.

This has been posted before but no answers yet,I hear the same thing from mine,Maybe it's the fuel pump?I first noticed mine when tent camping next to the KJ - it woke me up every 1/2 hour or so,Anyway Semper Fi my brother..

_________________
2004 sport 3.7
OME coil lift.
Clevis lift.
Mopar skids.
5-speed manual.
235 70 17 Firestone destination AT'S on stock rims.
Gen 4.5 a-arms

Most likely the evap purging the built up gas vapors from the evap canister.It's located next to the fuel filter on top of the gas tank.

I had a hiss while engine was running and a for little bit once engine was turned off...it was a loose hose off of the evap canister above the fuel tank as mentioned by tjkj

_________________
Brian, Blue KJ in PA
LOST#99, Mid-Atlantic LOST
Blue 2003 KJ Sport

RL Super Skinks

Ok, so I've either got a gremlin or an active Evap system? I guess I'll find out this winter. Are there any concerns about draining the battery? I assume since no one seems to know what it is, it's ok to just ignore it?

It's my daughters ride and I don't want her to be stranded.

This will do it at random intervals when the Jeep hasn't been running for several hours. It will even do it when it has not been driven the entire day. If it's a loose hose how hard is it to get to?

First off.....Welcome....Glad you could get L.O.S.T. with us.You came to the right place,but we're not concieded,just convinced.
Sounds like TJKJ2002 has the right idea,in that it's probably the purge valve,and there may be a problem with a relay or something activating it more than necessary. You might try and see if you can pull up a trouble code to help determine where the problem is.Keep us posted as we all enjoy solving problems.

Ron

_________________
Ron
03 Red Libberty Sport
3.7 V6 Auto 4x4
Lifted
Cooper Discover ATRs 265/75/16
American Racing 16x8 Polished Baja Wheels
Moog Lower Ball Joints
Member#051397 L.O.S.T. Midwest

Thanks for the welcome. Would this be a simple code that a local Autozone could pull, or are you talking paying money for a good code read?

I think you could do a key cycle retreival,and get in the ballpark.Starting with the key in the off or locked position,turn the key to on(not crank)and back off,three times within 5 seconds,leaving it on,on the third cycle.The light will flash....once and pause breifly,and then flash twice.That is a code 12 wich only means your start of the test.then it will begin flashing hard fault codes if you have any.Such as 2 flashes,short pause,4 flashes,would be a code 24,and so on.
The test should end with the seperator code of 55,or 5 flashes,pause,5 more flashes,and 55 only means the end of test.
So both 12 and 55 are only begininmg,and ending points,and have no bearing on hard fault codes.DC's self test are kinda slow compared to others,so be patient,and read flashes carefully.If you miss something,you can turn the key back to off for a few seconds and repeat the cycle.Hope tis helps,and if I screwed something up here then someone bail me out,as I work on sooooo many different brands that it's hard to keep up.

Ron

_________________
Ron
03 Red Libberty Sport
3.7 V6 Auto 4x4
Lifted
Cooper Discover ATRs 265/75/16
American Racing 16x8 Polished Baja Wheels
Moog Lower Ball Joints
Member#051397 L.O.S.T. Midwest