2001 Jeep Cherokee Sport - 115K miles. The CEL light has been on for quite some time. Yesterday we tried out my new smoke test device. The only place we saw smoke was at the LDP filter.

Is that normal ? If the system is closed doesn't the air/smoke have to exhaust somewhere ?

The filter has part number 4612901 - it is possible to open the plastic casing and the filter inside looked in pretty bad shape. The cap which we opened had vents which would seem to allow air or something to escape. Does anyone know if the paper filter cartridge itself can be replaced rather than replacing the whole $50 USD part.

Looks like that part has now been replaced with Mopar part number 5085164AA and it doesn't look like that part can be opened.

Has anyone heard of this part being the cause of a 456 (small evap leak) being thrown ?

Any thoughts appreciated.

 

Merry Christmas !

Well we have purchased/replaced the LDP filter and that apparently is not the cause of our CEL.
At this point I have purchased a smoke machine, and replaced the fuel cap, LDP and the LDP filter as well as checking the lines.

The code thrown has always been 'small' evap leak. Is there anyway to isolate that down to a particular set of potential areas ?
My next thought was to add hose clamps...

Thanks

 

I had a small evap leak on my 2000 WJ that turned out to be the schrader valve in the test port, of all places! It's a special valve because it seals in vacuum, not pressure. The only way I could get one was to buy the whole vacuum harness from Chrysler. BS! I went to the junkyard and got 3 of the "T" fitting they are in for $3 and the first one I tried worked! Just replaced the whole fitting.

 

Your reply may be very relevant. When we removed the green screw on cap of the test port we found what you would see on any normal tire valve. A short stem valve which was removable.
The smoke unit I purchased on ebay could not accommodate that so we replaced the stem valve with basically a tee - like a sprinkler system.

So maybe we really didn't test anything at all. Just the space between the 'port' and the 'filter' ??

Thoughts appreciated.

 

You may want to check a couple of spots where plastic tubing is joined to metal tubing with rubber hose as the connector. In the engine bay along the driver's side fire wall, the plastic tubing runs vertical and connects to a metal tube with the rubber hose as the connector. Check the rubber hose for dry rot or cracks. That same metal tube is connected back to plastic tubing under the vehicle almost directly under the driver's seat. Check for dry rot, cracks and tight fit. Good luck.

Merry Christmas!

 

Thanks. I found a useful video on Youtube this morning and learned a few things. Apparently when performing the smoke test it is normal for smoke to come out the LDP filter. That part with shipping from the US cost me close to $100 USD. In the video the guy's smoke machine also could not attach properly to the test port and he pulled the two hoses from the LDP and tested both individually. The other point he made was that the "throttle plate must be open". I had never even heard of a throttle plate before watching his video and I know that is something we did not do when we ran our test. At this point I am considering buying a cheapo ($35 USD) air compressor which provides 130 psi and doing some of this testing at home rather than returning to the shop. The guys at the shop had already visually checked all the tubing from the rear of the Jeep to the front. At one point perhaps a year ago they did find an issue without a smoke test and the CEL was out for maybe as long as 6 months.

 

The evap system should not be pressurized at more the 1 psi! You can damage the purge valve and LDP if more is applied. Most smoke machines are internally regulated for this reason.

 

Yes - the smoke kit I have has a regulator that limits output at 1 psi.
Did you "open the throttle plate" when you looked for your leak ?

I'm also wondering if I should look for a UV flashlight...

Thanks.