Canister purge valve delete

[fokkerj]

Hello all I am wanting to do away with the canister purge valve and it looks like a 60 ohm 2.4 watt or higher resistor will do the trick for the circuitry, but is there any kind of vacuum test that the computer will do that I need to fool to prevent a CEL? Also I am noticing a lack of EGR on my car so is EGR a California only thing for A 91 SHO?

Thanks all.

 

[rubydist]

egr was CA only on the mtx models. I did some rewiring on my red 94 to keep the canister venting all the time - I think there was a writeup on shotimes about it. No CEL resulted from the changes I did.

 

[chevrolet]

Is the purge valve an important part of the fuel tank vapor system? Including pollution/emission control?

 

[rubydist]

Yes, the canister can get fuel-logged if the tank is overfilled, etc. and the purge valve lets those fumes vent into the intake to avoid polluting the air. If the canister gets filled w/ fuel, you will have a sometimes faint, sometimes strong fuel smell around the car when you first get in it. As I said, my red 94 has the canister venting all the time, which took care of the fuel smell and has not resulted in any pollution-related problems - it still passes the emissions tests w/ flying colors.

 

[Devin]

That is really interesting. My 87 smelled like gas everytime I filled it up. Now I know why.

 

[NJSHO]

There is an orifice in the T that joins the canister purge solenoid to the gas tank and the vapor canister. This can become clogged with a yellow waxy substance. In my car this caused over pressurization of the gas tank (vapor couldn’t make it to canister or intake) and caused gas to spray from the fuel filler cap when on the track. I got black flagged a couple of times for that.

The purge valve is designed only to open when at a cruising speed, when the fuel vapor can be mixed in the intake with little impact on emissions (paraphrased from the ford CD.) Allowing it to open all the time may hurt emissions if they test your car at idle, this is an educated guess (otherwise why would ford have gone through the trouble of only having the valve open at speed.)

I removed my purge solenoid when I was diagnosing the problem and had no CE light.

 

[fokkerj]

The reason I brought it up is I am building a mid-engine car and I am doing away with the ford fuel system and using a fuel cell instead. Any of the EPA stuff is just garbage or extra weight. I also plan on using the cel so I think I am going to use a resistor to fake out the code.

 

[NJSHO]

As stated there is no need for the resistor since it throws no code.

 

[fokkerj]

Ah hah sorry missed it. That is good news. Thanks for your input guys that means there are two more wires to eliminate and no worries of a stupid EGR system. Also delays the need for a tweecer for a little longer.

 

[rubydist]

The canister system is separate from the egr, and if you eliminate the egr you will trip the CEL - the pcm will report that it does not detect the egr valve opening.

The line that goes from the exhaust manifold to the egr valve has two pressure taps. Between these taps is an orifice, and the sensor looks for a pressure difference across that orifice to detect the egr opening and the egr flow. If it doesn't see enough flow, the CEL will come on. This will occur within 2 minutes of startup when the engine is warm, or after the engine gets warm if started cold.

 

[fokkerj]

No it looks like my engine never had an EGR system at all. There are bosses for it, but they have never been machined.

 

[rubydist]

49 state mtx cars had no egr, all others did (89-95).