How do I test a purge solenoid? / Diagnosing an EVAP problem

[Matt Brandsema]

My brothers 2000 Chevy Cavalier has a P0440 code. I am thinking it might be his purge solenoid stuck open because the engine seems to stumble a little bit during idle. My question is, where is it on a 2000 Cavalier? On my 98 Cavalier it is in the easiest spot to get to! (Right on the valve cover!) I peeked under his car real fast and noticed that his charcoal canister is back by his tank (Unlike my 98, which has its canister inside the right wheel well.)I am assuming the purge solenoid is also back there.

My REAL question is, how would I test this to see if it is bad? Also, if it IS good, what are some diagnostics I can do to pinpoint the problem in the EVAP system? Would I be able to rent a smoke machine to check for any leaks? Thanks!

Topic

[inxs]

I just googled chevy cavalier and P0440. I posted a link below about someone dealing with this issue:

http://www.j-body.org/forums/read.php?f … 7&t=144687

The post dealing with the wire harness looks like a good place to start. See if the wires going to the various valves are not broken. From the picture, it looks like those pictures are taken from under the car near the gas tank. The are you want to inspect is likely near one of the rear tires.

If you want to test a solenoid, a quick test would be to apply 12V and ground to each solenoid and listen for it to click. If one doesn’t click, then you likely have a problem and should do some further testing.

[EricTheCarGuy]

Normally you use smoke to aid in diagnosing evap issues. If it were me I would be tracking down a service manual or the service procedure for checking out that code, for every code they write a troubleshooting tree to follow to find and repair the cause, these are the best because the engineers wrote them and I’m usually pretty successful in finding the cause using this method. I’m wondering if someone on the forum has access to that information.

[novacheck]

Hey, I can get access to just about any service manual from 2006 and back. If you need any info from it, feel free to let me know. I can email you the P0440 diag flow chart for your vehicle. It is in PDF format.

[dreamer2355]

I also have access to Alldata for any make and any model of vehicle from 2011 to prior years through my Automotive Tech college if you need anything 🙂

[killman]

Had a P0455 (newer version of P0440) on my ’04 Grand AM with the Ecotec engine. For GM 4 cylinders (but not GM 6 cylinders) GM did not program in the DTC test where the PCM will test the circuit condition of the purge valve solenoid and vent valve solenoid so with the key on there will be +12 v on one wire. The other wire is PCM grounded so do not mess with it. If you have a shop scanner that can start the EVAP test and can feel the solenoids working. If the purge solenoid turns on and off with a pair of jumper clips then test then remove the purge solenoid from the car and use a 1 ft length of (IIRC) 1/4″ fuel line on the intake port of the purge valve and suck on it. There should be no vacuum leak and when jumpered it should be like sucking through an open hose. Do the same on the purge port side and you should have the same results. If not then the valve is bad. Test the vent solenold the same way as you did the purge solenoid by checking voltage, applying voltage and applying vacuum. Note that the only reason for the vent valve solenoid is basically to test the EVAP system but there is not test to test for it closing completely and not leaking enough vacuum tripping a P0440/P0455. From what I have seen online it is the most common component to fail and cause a P0440/P0455 on the GM car or truck. Stuck closed/dead purge solenoid will do the as well as a rubber hose that is bad and the fuel filler neck are quite bad for failing with a pin hole leak on FWD GM cars. Fuel caps that leak are quite common and can cause a P0440/P0455 but usually in combination with another leak. Check all visible plastic Evap lines in the system carefully, double check all rubber hoses, and triple check any rusty looking steel components in the system (including the fuel tank where possible).

FYI I changed out the fuel cap first (no luck), the purge valve solenoid (leaky when closed which would cause a P1441/P0496) and the vent valve solenoid (actually held vacuum off the car but very dusty inside with a spider nest ) using these testing techniques. Not the best way to do it for sure, but many mechanics are clueless on how to check these systems with smoke machines and at $55 from Rockauto.com for the parts much cheaper then taking it to a mechanic.

[sergio correa]

check for vacum leaks at the selonoid and you can test it whith a scanner it will aciviate

[Matt Brandsema]

Thanks everyone for the tips!

And Novacheck, that would be great if you could get me that information!

[CoolasIce2]

Quoted From sergio correa:

check for vacum leaks at the selonoid and you can test it whith a scanner it will aciviate

Test it with a scanner? That means you’ll need one that does bidirectional control. I don’t believe most scanners can do that. D:-)
On my Toyota I can hear it clicking when activated. It usually purges after 2 miles of driving as I’m sitting at a stop light. The idle becomes eradtic due to the air/fumes getting dumped into the intake.

[Author]

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