94 Xj40 Purge Valve test procedure
#1
05-29-2013, 10:19 PM
94 Xj40 Purge Valve test procedure
Hi - I've been trying to remedy the high gas consumption on my XJ40.
The car has displayed a fuel fail 23 code once or twice in the last 6 months - (o2 sensor reporting rich) and subsequently replaced the thermostat and temperature sensor. The engine management diagnostic also suggests other possible causes, a "lazy" oxygen sensor, fuel pressure too high, bad grounds, and a faulty purge valve.
I've read some threads regarding the purge valve, most regarding a purge valve stuck open which results in a gas smell etc. - I can't seem to find anything that refers to a purge valve that is stuck closed?
I'm not totally sure if that is the problem, but according to what other owners have said, this is what I've gathered:
1. You can test purge valve operation by listening for a loud click when the ignition switches on and another when the ignition is switched off.
2. Valve should hold a vacuum when ignition is switched on.
3. Valve should release vacuum when ignition is switched off.
The first test we did was to listen for the "click" as the ignition cycled on and off. One of us listened at driver's side wheel arch while I cycled the ignition and we heard nothing from that area.
Next we hooked up a vacuum gauge/pump to the purge valve hose at the intake manifold, turned on the ignition and pumped out a vacuum of about 20. The pressure held steady. When the ignition was switched off, the pressure gauge still showed the vacuum at the same reading. I waited for about a minute or so for the pressure to drop but it just held steady.
If I did these tests correctly, according to engine management diagnostics the valve is stuck closed and the valve should be replaced. (which I'm prepared to do, no problem.)
If that purge valve isn't opening to allow the "expected" flow of air to the manifold, the rich running (and high gas consumption) could be due to the reduced air in the air/fuel ratio caused by the valve not opening, right?
Before I go ahead and order a new valve, anybody else been down this road?
The car has displayed a fuel fail 23 code once or twice in the last 6 months - (o2 sensor reporting rich) and subsequently replaced the thermostat and temperature sensor. The engine management diagnostic also suggests other possible causes, a "lazy" oxygen sensor, fuel pressure too high, bad grounds, and a faulty purge valve.
I've read some threads regarding the purge valve, most regarding a purge valve stuck open which results in a gas smell etc. - I can't seem to find anything that refers to a purge valve that is stuck closed?
I'm not totally sure if that is the problem, but according to what other owners have said, this is what I've gathered:
1. You can test purge valve operation by listening for a loud click when the ignition switches on and another when the ignition is switched off.
2. Valve should hold a vacuum when ignition is switched on.
3. Valve should release vacuum when ignition is switched off.
The first test we did was to listen for the "click" as the ignition cycled on and off. One of us listened at driver's side wheel arch while I cycled the ignition and we heard nothing from that area.
Next we hooked up a vacuum gauge/pump to the purge valve hose at the intake manifold, turned on the ignition and pumped out a vacuum of about 20. The pressure held steady. When the ignition was switched off, the pressure gauge still showed the vacuum at the same reading. I waited for about a minute or so for the pressure to drop but it just held steady.
If I did these tests correctly, according to engine management diagnostics the valve is stuck closed and the valve should be replaced. (which I'm prepared to do, no problem.)
If that purge valve isn't opening to allow the "expected" flow of air to the manifold, the rich running (and high gas consumption) could be due to the reduced air in the air/fuel ratio caused by the valve not opening, right?
Before I go ahead and order a new valve, anybody else been down this road?
Last edited by Lawrence; 05-30-2013 at 03:08 AM. Reason: additional info
#2
05-30-2013, 12:50 PM
courtesy of jaglovers;
`
Purge Valve
`
Purge Valve
Fuel code 89, purge valve.
It's supposed to put a vacuum to the charcoal canister to suck out all those nasty gas fumes that build up in the tank and go into the canister instead of the air.
It's on the drivers side, above the charcoal canister behind the headlight.
The ECM looks at the O 2 sensor for a change when the purge valve is open, no change = check engine.
Purge drive circuit probably means connection or valve malfunction.
The valve can easily be checked by switching ignition on and off. It makes a very loud click. You can also check with 12V directly across terminals which is easier if you haven't got a friend. i.e. two wires to battery but be careful with dangling wires etc.
You can check valve operation by blowing down the tube off the manifold.`
one of your other suggestions, `bad grounds`, is something i`ve mentioned in another thread/post. before looking at replacing things, i would spend a day or so and go round EVERY ground / connection obn the car and make sure they are clean / good, especially in the engine bay!
It's supposed to put a vacuum to the charcoal canister to suck out all those nasty gas fumes that build up in the tank and go into the canister instead of the air.
It's on the drivers side, above the charcoal canister behind the headlight.
The ECM looks at the O 2 sensor for a change when the purge valve is open, no change = check engine.
Purge drive circuit probably means connection or valve malfunction.
The valve can easily be checked by switching ignition on and off. It makes a very loud click. You can also check with 12V directly across terminals which is easier if you haven't got a friend. i.e. two wires to battery but be careful with dangling wires etc.
You can check valve operation by blowing down the tube off the manifold.`
one of your other suggestions, `bad grounds`, is something i`ve mentioned in another thread/post. before looking at replacing things, i would spend a day or so and go round EVERY ground / connection obn the car and make sure they are clean / good, especially in the engine bay!
#3
05-30-2013, 07:10 PM
courtesy of jaglovers;
`
`
one of your other suggestions, `bad grounds`, is something i`ve mentioned in another thread/post. before looking at replacing things, i would spend a day or so and go round EVERY ground / connection obn the car and make sure they are clean / good, especially in the engine bay!
- but there again, something may be loose ...I'll be opening up the spoiler panel tomorrow and report back as to the condition of the canister and purge valve. Apparently, if the purge valve is clogged or blocked there is a possibility it can be cleaned and the canister cut open and refilled with fresh carbon granules for the cost of about $20 and a tube of epoxy. Will try that first.
#4
06-12-2013, 02:01 PM
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