Canister Purge Solenoid

[1991vert]

How does the charcoal canister purge solenoid work? There are two wires going to it: Grey/Yellow and Red. I'd imagine one is positive and one is negative? Does this receive power while the key is on?

The reason I'm asking is because I do not have a stock ECU or main wiring harness so there is no connector, but I would still like to keep this.

Thanks!
Chris

 

[jrichker]

The red wire is postive with the key on. The gray/yellow is the computer switched ground. The computer provides the ground when the engine is in cruse mode. The solenoid valve opens and vents the gas tank via the line from the intake manifold.



Diagram courtesy of Tmoss & Stang&2birds

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[1991vert]

The red wire is postive with the key on. The gray/yellow is the computer switched ground.

so can i ground the GR/Y wire to the body?

 

[jrichker]

so can i ground the GR/Y wire to the body?

The computer provides the ground when the engine is in cruse mode. The solenoid valve opens and vents the gas tank via the line from the intake manifold.

This is a controlled process: open the valve at idle and you will probably have idle quality problems.

 

[1991vert]

This is a controlled process: open the valve at idle and you will probably have idle quality problems.

i have a secondary circuit on my computer for a second fuel pump that switches on when it see a certain TPS %. do you think if i used a 30amp relay and set the circuit to go hot when it sees the throttle blade open about 25% it would work?

 

[jrichker]

i have a secondary circuit on my computer for a second fuel pump that switches on when it see a certain TPS %. do you think if i used a 30amp relay and set the circuit to go hot when it sees the throttle blade open about 25% it would work?

That sounds good to me, give it a try.

 

[1991vert]

well after going out and looking at the wiring both wires are black...and i dont think it's dirt and grime. what now? how do i know which is which?

 

[HISSIN50]

If you're talking about your body harness wires at the CANP, turn the key on and put your meter on each wire. One will show constant accessory 12 V (this is VPWR). The other wire is the grounded control pathway.

You could use a SPST relay to switch a ground pulse to the factory control wire.

well after going out and looking at the wiring both wires are black...and i dont think it's dirt and grime. what now? how do i know which is which?

 

[1991vert]

i do not have a stock main harness...i do however need to hook up the solenoid. all i have is the solenoid itself with the harness coming off of that. both wires are black.

 

[Saleen0679]

Judging by the schematic it's not going to matter which wire is connected to the power source and which is connected to ground. The solenoid is like a relay in that when current flows through the coil an action happens. With a relay the contacts close and with the CANP the valve opens. The valve itself looks directional though.

 

[Red&black]

1991vert
Sorry to revive this old thread. I also have a non factory wiring harness for 351 cleveland with aftermarket EFI. I really want to use the emissions purge system. How did you wire the purge valve? THANK YOU

 

[jrichker]

The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?


The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:

The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:

 

[Red&black]

Big thanks to jrichker for the detailed response. I'm going to hook everything up like outlined. The only difference I see is that the purge valve will be open when the engine is running vs cruise only since I don't have 5.0 wiring or factory computer (351cleveland w/aftermarket EFI). I think this will be ok. I will hook it up and see. I'm not very skilled with electrical systems to know how to make it work for cruise only.