lhpdiver

We have had a 'small evap leak' in our 2001 Cherokee for a long time now. The last thing we tried was to replace the evap leak detector. We bought a new mopac gas cap. The mechanic eyeballed the tubing etc...

So now I have bought a $75 (plus $50 shipping to Mexico) smoke tester on ebay (over 2000 happy customers). The documentation is a little skimpy. Where would I attach the hose which will emit the smoke ? the evap leak detector ?

Thanks

fb97xj1

You can disconnect the hose for the brake booster at the intake, and use that. Some vehicles have a test port for this sort of thing, but im not sure if the XJ ever had one.

dave1123

I know for a fact my 2000 Cherokee does. It's a T fitting with a green cap on the vacuum supply to the purge solenoid valve. It contains a special schreader valve that opens at 1/2 lb. of pressure. It looks like a normal tire valve, but isn't.

dave1123

I have to correct what I said about that schraeder valve. It seals on vacuum. It opens when you screw on the smoke tester. Sometimes all the leak is is a cracked rubber elbow. I've fixed them with a loop of rubber fuel line. On my 2000 WJ, the schraeder valve wouldn't seal so I went to a dealer to get one. They had no listings for the valve, but I could order the whole tubing system. BS! I went to the junkyard and grabbed 3 of the T fittings for $3. The first one I tried worked.

BTW, right next to that T fitting with the valve in it is a T fitting with a rubber cap on it. If you've got one of those, that'll work as a smoke injection site. To test just the fuel tank area, pull the rubber line off the carbon canister and inject the smoke there. Look for pinholes in the fuel filler pipe. Rust is common there. And the cap, of course.

lhpdiver

Thanks ! I found the valve you refer to. It has a green cap and a tag on it which reads "Evap Test Port" :-)

I'll print off your comments and bring them with my smoker to the mechanic (he has the air supply).

Thanks again.

country2

What you also can do remove to 2 lines at the evap pump hook leaktester line to the line with the green cap and plug the other line. Make sure he has his air pressure turned way down. I have seen some vids where they used cigar smoke and blow into it. Now my 2000 was throwing a small leak code and a large leak code the large leak was the vent line at gas tank and believe it or not the small leak went away whan I realize someone had the evap pump mounted upside down!

dave1123

OH MY GOD, YES! keep the air pressure low. The smoke tester should only be putting out less than 1 (one) pound of pressure. Most of them you just plug in your shop air line and the pressure is controlled inside the tester. I think that is stated on the tag on the valve, do not exceed 1 pound of pressure. The whole evap system is powered by vacuum and you could blow the diaphragms in the pump and purge valve.

Cummins93

You can isolate the issue by putting a short length of tubing off the leak detection pump and capping it. If the small leak code is still thrown it is a problem with the LDP count. This method can also be used to get through an emissions test temporarily.

lhpdiver

So today we finally got to take the smoke machine for a spin. It was pretty easy to use. The hardest part was attaching it to the test port. We ended up removing the test port and attaching a similar one which had the stem valve removed.

The only place we found smoke being emitted was at the "AIR FILTER. EVAPORATIVE EMISSIONS SYSTEM LEAK DETECTION PUMP FILTER. FILTER. VAPOR CANISTER FILTER. " Mopar part number 05085164AA. To be honest there was a lot of smoke coming from that filter. We removed it and opened it. We didn't see how that piece could ever be airtight. The cardboard filter was in pretty bad shape and I'm sure it has never been replaced in nearly 20 years.

Could that really be the cause of the small evap leak or are we missing something ? There was SO much smoke coming from that filter that I would have called it a large evap leak.

Thanks