1999 Cav z24 - Fuel/Evap Lines

[pappyl]

Does anyone have a diagram for the fuel evap lines/valves?
I am troubleshooting a p00440 code - want to understand the location of the specific control selenoids,

Need to know purge valve location and the valve location under the car, etc ,etc,

Many thanks for anyone that can help...

[Tech II]

P0440 is a small evap leak......basically, all you can do is a visual inspection of the system....unless your see a bad line, bad connection, smell fuel, etc., there is not much you can do....

The PCM tests the system like this: it closes the vent valve, and then opens the purge, to pull a vac on the system, then it closes the purge valve and the PCM monitors the vac that should hold in a closed system(via the pressure sensor)....if the vac drops too fast in a specific period of time, then a leak is detected......

The first thing that should be done with a P0440, is inspect the gas cap.....does the contact surface of the fill pipe look rusted? Does the seal on the gas cap look cracked/degraded?

More often than not a P0440, is caused by a bad gas cap....so replace it and clear the codes...if it comes back, and a visual inspection of the whole system shows nothing obvious, then you are just wasting your time....the fasted way to diagnose the system is bring it to a garage....they have a bidirectional scan tool, and a smoke machine......basically, they seal the system, and pressurize it with smoke....then you look for smoke(with a car on a lift, this is fairly easy to do)......when you see smoke, you have found the leak......

[pappyl]

Appreciate your comments TechII,

I figure I can do a vacuum test on the lines and also check the purge valve to ensure it closes/seals properly.

I wanted to understand that mess under the car which is part of the purge canister and vent valve setup. That's why I requested the diagram.

I'll start with the easiest and most likely culprits and work from there.

I agree if I can't find it via the basic testing, smoke testing will probably be the only way to nail it.

Thanks

[pappyl]

After reset, not throwing code immediately, seems to take a few cycles to come up. Therefore suspect bad valves (below) & found both bad (small seal leaks).
As these are moving/activating parts, makes sense these are simply worn out.

Replaced
1) the purge canister vent valve under the car (right rear axle) (was not holding vacuum seal)
2) The purge selenoid Front lower left of engine (bracket off AC compressor) (also leaking)

Checked
- fuel cap/seal - ok
- the main line from purge selenoid to canister - ok.
- fuel tank steel neck - seems ok (but this would be candidate for rust/pinholes)
- vaccuum sensor on tank - did not check this as I'd have to drop the tank.

Now waiting to see if code is gone for good.
- If not will need to perform smoke test on tank.