does the RJM harness have charcoal canister evap hookup?

[bcmbcmbcm]

Hey folks,

I am trying to hookup a proper charcoal canister system with the purge solenoid on my 1974 with EFI. I didn't see any connections on my RJM harness for the purge solenoid. Am I missing something? I found instructions for a universal harness online but not the EB harness. These instructions did not indicate instructions for the hookup for the CC purge solenoid.

If I don't have them, should I run new wires straight from the computer?

Thanks in advance,

Brett

 

[Viperwolf1]

The standard RJM harness and now the Ron Francis harness do not have the wires or even computer pins for the can/p solenoid. It can be added if you have a pin. Can/p needs to go to pin 31 and a connection to VPWR.

 

[xcntrk]

FYI: that solenoid is a PITA.

I learned the hard way and ran all the wires including adding the new pin to my EFI harness. Got it all hooked up and plumbed into the upper intake. Mounted the solenoid on the firewall. The EEC commands the solenoid to open only when above a certain rpm and when there is no throttle. When those conditions are satisfied, the solenoid open, but it's not simple open/close. Instead it pulses at a rapid rate. Well that pulsing and constant psst sound is very audible! I thought it was an exhaust leak (closest thing it sounded like) and the sound would resonate right into my interior being mounted on the firewall.

Long story short, the solenoid is noisy and all that effort to wire & plumb it is unnecessary. The easier and simplified approach is to plumb canister purge into your intake PRE-maf (I plumbed mine into my intake filter). You don't have mess with the solenoid, won't introduce a vacuum leak going before the MAF, and the vacuum is low enough to not cause issue but still draw vapor.

Lastly regardless of which approach you choose, I would suggest a roll-over valve on the vent line between the tank and canister.. just in case

 

[brianstrange]

I have a smog package (Engine side only) I have listed. When I strip the harness, I can throw in all the wires from the pins to the connectors. PM if interested.

 

[bcmbcmbcm]

I read that too.

FYI: that solenoid is a PITA.

I learned the hard way and ran all the wires including adding the new pin to my EFI harness. Got it all hooked up and plumbed into the upper intake. Mounted the solenoid on the firewall. The EEC commands the solenoid to open only when above a certain rpm and when there is no throttle. When those conditions are satisfied, the solenoid open, but it's not simple open/close. Instead it pulses at a rapid rate. Well that pulsing and constant psst sound is very audible! I thought it was an exhaust leak (closest thing it sounded like) and the sound would resonate right into my interior being mounted on the firewall.

Long story short, the solenoid is noisy and all that effort to wire & plumb it is unnecessary. The easier and simplified approach is to plumb canister purge into your intake PRE-maf (I plumbed mine into my intake filter). You don't have mess with the solenoid, won't introduce a vacuum leak going before the MAF, and the vacuum is low enough to not cause issue but still draw vapor.

Lastly regardless of which approach you choose, I would suggest a roll-over valve on the vent line between the tank and canister.. just in case

I was thinking of doing that. I have a BC arctic air box though. I haven't looked to see how to plumb it. It would be neat if I could put the new CC below the air box out of sight and just run some hose straight up.

 

[mtxride]

FYI: that solenoid is a PITA.

I learned the hard way and ran all the wires including adding the new pin to my EFI harness. Got it all hooked up and plumbed into the upper intake. Mounted the solenoid on the firewall. The EEC commands the solenoid to open only when above a certain rpm and when there is no throttle. When those conditions are satisfied, the solenoid open, but it's not simple open/close. Instead it pulses at a rapid rate. Well that pulsing and constant psst sound is very audible! I thought it was an exhaust leak (closest thing it sounded like) and the sound would resonate right into my interior being mounted on the firewall.

Long story short, the solenoid is noisy and all that effort to wire & plumb it is unnecessary. The easier and simplified approach is to plumb canister purge into your intake PRE-maf (I plumbed mine into my intake filter). You don't have mess with the solenoid, won't introduce a vacuum leak going before the MAF, and the vacuum is low enough to not cause issue but still draw vapor.

Lastly regardless of which approach you choose, I would suggest a roll-over valve on the vent line between the tank and canister.. just in case

xcntrk, have you had any issues with this? I've also been running this set up for a few years but there's been a few times where I've had issues with fuel filling the canister and puking into the intake. It happened once when off road on steep declines (I've since got a roll over value to hopefully solve this) and again the last time I filled the tank. It was a warm day and the fuel expanded out through the vent line into the canister. I'm not yet sure what to do about this. I can move the canister up another 8-10 inches in the engine compartment or maybe I should just not top off on warm days :-[

 

[Viperwolf1]

xcntrk, have you had any issues with this? I've also been running this set up for a few years but there's been a few times where I've had issues with fuel filling the canister and puking into the intake. It happened once when off road on steep declines (I've since got a roll over value to hopefully solve this) and again the last time I filled the tank. It was a warm day and the fuel expanded out through the vent line into the canister. I'm not yet sure what to do about this. I can move the canister up another 8-10 inches in the engine compartment or maybe I should just not top off on warm days :-[

Move the canister up.

 

[mtxride]

Thanks viper, I'll give that a try.

 

[xcntrk]

xcntrk, have you had any issues with this? I've also been running this set up for a few years but there's been a few times where I've had issues with fuel filling the canister and puking into the intake. It happened once when off road on steep declines (I've since got a roll over value to hopefully solve this) and again the last time I filled the tank. It was a warm day and the fuel expanded out through the vent line into the canister. I'm not yet sure what to do about this. I can move the canister up another 8-10 inches in the engine compartment or maybe I should just not top off on warm days :-[

Yeah that's a tough one. Moving the canister higher (as Vipr suggested) would certainly help. Also reducing the amount of vacuum used to draw vapor by ensuring your purge line is far down the intake may help too. I literally added an elbow to the bottom section of my cone filter where the purge line interfaces.

What type of canister are you using and do you have the proper vent caps on the top? They're supposed to prevent vacuum from drawing down the tank vent line. I'm using a Mustang canister and it has 2 vent caps. I also noticed the some late model stock EB (carb) canisters only have 1 cap. Lastly the roll-over switch may help. It doesn't have to be upside down to operate, I think a moderate incline would shut it down as well.

Here's a thread that has some more info about plumbing and roll-over valve.
http://classicbroncos.com/forums/showthread.php?t=261451

 

[mtxride]

Yeah that's a tough one. Moving the canister higher (as Vipr suggested) would certainly help. Also reducing the amount of vacuum used to draw vapor by ensuring your purge line is far down the intake may help too. I literally added an elbow to the bottom section of my cone filter where the purge line interfaces.

What type of canister are you using and do you have the proper vent caps on the top? They're supposed to prevent vacuum from drawing down the tank vent line. I'm using a Mustang canister and it has 2 vent caps. I also noticed the some late model stock EB (carb) canisters only have 1 cap. Lastly the roll-over switch may help. It doesn't have to be upside down to operate, I think a moderate incline would shut it down as well.

Here's a thread that has some more info about plumbing and roll-over valve.
http://classicbroncos.com/forums/showthread.php?t=261451

I'm using the same Mustang canister, but I do not have any caps on the vents. I usually see that most people have a mushroom cap on one vent. Should I do the same? And what are these mushroom caps exactly? Do they completely seal off the vent, or do they have some other function?

My purge line enters the end of the air filter through a grommet then continues until it is near the MAF, I'll also try moving it further away to see if that helps. I like the elbow idea, I'll probably do that as well.

I guess I have this vent system all messed up!

 

[xcntrk]

The CAPS allow fresh air to draw into the canister as the vacuum sucks the fuel vapor. Without fresh air coming in, you risk the vacuum siphoning fuel out of the tank. However without the CAPS in place, I would assume those ports are just an open vent which would sort of defeat the whole system of recirculating vapor. Can you literally see down into the charcoal canister through those 2 vent ports where the caps are supposed to go?

 

[mtxride]

Yep, it's just two open vent ports, I can see into the canister. So are you saying the caps are like a one way valve and only let fresh air in but not out? If so, you're right, that would definitely defeat the purpose of my setup. Any idea where to get the caps?

Update: Found the caps here - http://www.foxresto.com/1979-93-Mustang-5-0-Charcoal-Canister-Cap-p/4879006.htm

 

[bcmbcmbcm]

Ok so if I were to play Devil's advocate here, why wouldn't the factory plumb the CC directly to the intake upstream of the MAF?

Why is the solenoid so noisy? I have a 1987 5.0 mustang and I never noticed it...maybe that is because it is close to the front of the car away from the firewall?

What about wiring the solenoid to a momentary toggle switch and giving it a few seconds to breath out to the running car after I fill up for gas or every morning? How much vapor actually accumulates in the CC after all?