greenmtboy

Ok guys, I think I might by onto something...

Does anyone know if the EVAP system leak detection pump makes a faintly audible, steady "beeping" sound? I may be going nuts, but I swear a heard such a sound the other night just before my CEL came on. The code thrown was P0455, Gross EVAP leak. Does the LDP run all the time, or only for a short time after start-up? Oh, and where is said pump located?

Thanks!

Muaddib420

I had a p0455 turned out it was a bad gas cap. Might wanna try replacing that first.

greenmtboy

OK, here's a brief update...

I just went out and started the vehicle up, and popped the hood to listen around. About a minute after start up, I did in fact hear the beeping sound, and now I have located the LDP, which against the firewall on the passengers side corner. It appears to have a diaphragm, which is what I imagine does the pumping, and indeed, it was beeping. It sorta sounds like a bird chirping, and now I'm wondering if this is normal, or if the pump is bad.

BTW, I don't smell gas anywhere, and I really don't think the cap is bad. There could definitely be some issues with the charcoal canister though, as the steel lines going to it are really rusted.... but let's start with this LDP.

Any insight is appreciated!

greenmtboy

Here is a good article explaining the function of the LDP and related EVAP system: http://autorepair.about.com/library/a/1h/bl010h.htm

I think this is at the core of my problem. The beeping sound is the pump trying (unsuccessfully) to maintain pressure on the EVAP system. You wouldn't normally hear it because it wouldn't cycle over and over if the system was leak tight.