I have a 91 350 Camaro. Lately after driving my car for a while when it has been hot. I am getting a strong gas smell. I have checked the canister, but it is the type with no replacement filter. My question is about the purge valve on it. While the engine is running i hooked up a volt meter and it showed a full 13+ volts there, but on the gas side of the valve there was no vacuum. I hope I am explaining this well enough. The top part of the purge valve is a vacuum line going into my intake and the bottum part has a strange valve setup on it coming from the gas tank. What I was wondering if there is supposed to be power at the valve at all times or if that valve is just not working anymore. Any help will be appreciated.

Thanks,
Steve

 

Like most other ECM loads, the +12VDC supply is present whenever the ignition is on, and the ECM provides the ground path for the device. Make sure that the positive and negative are both present across the solenoid, and not to a different ground reference.

As for the solenoid valve, you should be able to read a vacuum at the source line and at teh purge valve line when teh solenoid is energized. Make sure the purge valve is connected correctly and is getting the pilot vacuum signal from the solenoid.

 

I don't know if this will change it or not. But when i checked the voltage on the wire, all i did was hook up the pos lead to one end of the connector and the neg lead to the other end. Thats showed me the voltage. What i was thinking is that the solenoid should be active if there is power going to it, but there is no vacuum coming out of the bottom portion. Maybe i need a new canister, but i am just not sure.

 

It sounds like you were testing correctly, but you need to make sure there is vacuum on the inlet side of the solenoid. Usually, the EVAP purge line is from a timed vacuum port that only provides vacuum at part throttle (not at idle). It is often shared with the EGR vacuum source for the same reason Do you have a vacuum gauge that you can 'T' into the line?

 

I don't have a vacuum gage. From what i can tell by removing the line. I have a vacuum line that is constantly working and goes into the throttle body. When i have pulled off the hose to the line from the tank, there is no vacuum come from the valve that i can tell. That is whith full power going to the wire connection on it. what would happen if i hooked up the vacuum line directly to the line from the gas tank?

 

You really don't want to do that. You would risk collapsing the tank. The purge line only draws the accumulated vapors from the charcoal canister, which is vented to atmosphere on teh bottom. In that manner, the tank nver really gets any vacuum.

 

Thanks for all the help. I have also noticed what sounds like boiling water coming from my gas tank after driving for a while on a real hot day. I am thining that vent neer the tank that lets air in might be jammed or something.

 

The EVAP canister purge is obviously not clearing out vapors/liquid from the canister as it should, building pressure in the tank. If the solenoid is energized and not porting vacuum to the purge control valve, it may be time for a new solenoid valve. Trying to repair or unstick the existing one may be difficult.

 

"Boiling water" is a kinder, gentler way to describe it. I've heard it described more often as the aftermath of a late-night trip through the Taco Bell drive-through.

That would most likely be the tank pressure control valve. If the If it is relieving back at the tank, the EVAP canister may be plugged and not allowing vapors to escape through it.

 

I appreciate all the help. I will see if i can't replace that purge valve on the canister. What I don't understand is if there is supposed to be power going to that valve at all times. Even with just the key on there is power going to that valve on the canister. Is that valve supposed to be controlled by the computer or by something else?

Thanks
Steve

 

Well i pulled that valve off of the canister and with the engine running and 12+ volts going into the valve, there was no vacuum coming out of the other end. So I think the valve is shot. I am still not sure if that valve is supposed to have power to it at all times.

 

Does anyone know the answer to my above post?