Community Forums

johnjrod · 07-12-2016, 09:15 AM

Hello everyone.

Recently my RV (1984 Ford Econoline E350 - 7.5L 460 4bbl) failed the EVAP pressure test during a California Smog test. Lots of questions:

Q1 - Any suggestions on steps in which to troubleshoot and find the leak?

Q2 - Any suggestions on where to purchase the "hard to find" evap system parts, like charcoal canister, and purge control valves, for an old vehicle?

Q3 - Anyone use or know of other vehicle parts substitutes for the evap system?

Q4 - Any suggestions on how I can perform a pressure test myself to check for leaks after any repairs made?

I understand the evap system extends from the fuel tank to the carburetor but trying to find out what portion of the evap system is supposed to be pressure tested.

Thank you in advance for any help!

52motorscoot · 07-12-2016, 10:27 AM

I have a 1985 460 f350 that failed az test replaced gas cap and it passed

GBRG07 · 07-12-2016, 10:59 AM

Locking gas caps are often an issue.
If not cap have a good look at lines in eval system for cracking on rubber hoses.
Have seen filler neck hose clamps a little loose and leaking.

For a small leak you could try and isolate sections and pressurize with a few pounds air pressure and use soapy water to look for leaks.
Good Luck with it.

johnjrod · 07-12-2016, 11:23 AM

Quote:

Originally Posted by 52motorscoot

I have a 1985 460 f350 that failed az test replaced gas cap and it passed

I had initially thought of that, but in CA they remove your gas cap and install their evap pressure testing cap so they can pressurize the evap system from the fuel filler opening. Thanks for the feedback.

johnjrod · 07-12-2016, 11:35 AM

Quote:

Originally Posted by GBRG07

Locking gas caps are often an issue.
If not cap have a good look at lines in eval system for cracking on rubber hoses.
Have seen filler neck hose clamps a little loose and leaking.

For a small leak you could try and isolate sections and pressurize with a few pounds air pressure and use soapy water to look for leaks.
Good Luck with it.

I think you might be on the right track!

I went out and disconnected some lines -- before the charcoal canister -- at the back of the vehicle. I did a vacuum pressure test and it failed. so have to keep moving back til I find a leak.

I don't know if a vacuum test is a simple substitute for a pressure test so not sure if I was doing the right thing. But good suggestion on using air pressure and soapy water to find the leak.

Any suggestions welcome!

Thanks!!