I need some help as I think I have a leak in my fuel tank evap system. I get a SES light and OBDII Po442. I ran a smoke test today and here is how I did it. I took loose the line from the rear to the tank vent valve and connected the smoke line on the line at the tank vent valve to the rear. I got smoke at the RR wheel housing. The filter that is connected to the leak detection pump leaked smoke. I feel that I'm doing something wrong. Can anyone help. I have a 2003 MC not an "S".
Thnaks, Ron

 

There is a good chance that the o rings that seal the electrical connections going to both the vac pump in the rear unit and the vent valve attached to the engine are leaking. I fought this problem for months, and the smoke test the dealer offered showed nothing. After I disassembled the pump unit -fairly easy- and the vent valve -difficult, requiring a dremel tool- I lubed the seals around the connections with dielectric grease, and the problem went away.
Here's a breakdown of what I did:
https://www.northamericanmotoring.co...ighlight=p0442

 

Ancient Mariner ... I have already replaced the tank vent valve, gas cap, leak detection pump on tank in the RR wheel well. I applied a smoke test and got smoke coming out of the RR wheel, smoke came out of the filter on the LDP.
Do you have any suggestions? Ron

 

Whoa! Throwing money at it is the hard way to cure a problem. Like I said in my earlier post, the problem I had wasn't so much the vent valve or pump, but rather the connection where the power wires go into the units. You might try gooping some dielectric grease into those connections to see if it makes a temporary fix.
The problem with the smoke test on the LDP is that you're pressurizing the system (slightly) rather than applying vaccum. It's not exactly the same thing. What will fail under vaccum might work under pressure and vice versa.
I admit to being a little stymied here: That whole system is pretty straightforward and simple and the chances of a leak coming from one of the various hoses is pretty slim. They're buried in the body and pretty well protected. Try the grease thing. It's quick and simple and if nothing else, you'll eliminate at least one area.

 

Thanks for getting back .... I'll try your suggestion on the electrical connections @ the pump & tank vent valve. Ron