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Discussion Starter · #1 ·
I'm just finishing up the newest version of my 05 Tj rubicon. Went ham on it this winter, 1 ton swap, dual 4links, full hydro, coilovers, 43" sx stickies ect. Im waiting until next year to do an ls swap so for this season I need to keep the 4.0. I've eliminated all the Evap stuff and am installing a motobilt fuel cell that uses the oem tj fuel pump.
Now for my question: There are two hard fuel lines running from the oem gas tank to the engine bay... one obviously goes to the fuel rail, the other one runs through a little valve looking thing and then into the side of the intake manifold. Can anyone tell me what this line is, I'm assuming some kind of vapor vent line and if I eliminated the rest of the evap system can I eliminate this too? Then I would only have a high pressure line to the rail and a vent/rollover valve on the fuel cell. (Im not concerned about check engine lights lol)
Thanks for the help
 

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You can eliminate everything, but, you might consider keeping the purge valve, and vent into the throttle body rather then venting into open air.
 

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Discussion Starter · #3 ·
You can eliminate everything, but, you might consider keeping the purge valve, and vent into the throttle body rather then venting into open air.
Thanks. So what would happen if I eliminated the purge valve and what does the purge valve do? Sorry I'm not an engine guy lol
 

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Discussion Starter · #4 ·
Edit... Double reply
 

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Excess fuel vapor needs to be released. Old cars used venting fuel caps or otherwise vented to air (through a filter). Modern cars trap fuel vapor in the charcoal canister, then the pcm opens the purge valve when the engine is warmed up, venting it into the throttle body, to be burned. This allows less fuel to be lost due to evaporation, and no fuel smell in your garage.
 

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Discussion Starter · #6 ·
So im still wondering....
The line and little valve looking thing that I described in my original post... is that the purge valve? All my evap stuff has been gone for years,because it was in the rear wheel well and in my way and everything works fine. The only thing left is two factory hard lines from the gas tank to the engine, one goes to the rail and one that goes into a some kind of little valve and then straight into the intake manifold. Is that the purge valve or something different? If so what is it and do I need it?
 

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Yes, thats the purge valve, controlled by the pcm. If you remove it, and just vent straight into the intake, you will likely smell fuel vapors escaping through your air intake.
 

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One line is the fuel supply line to the fuel rail, like you noted. The other is a vacuum line that drives the leak detection pump behind the passenger rear tire wheel well. It pressurizes the tank, then the ECU monitors the pressure for a fixed amount of time. If it doesn't hold the pressure like expected it throws a code and a CEL. It's #6 in this schematic:
3115849
 
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Discussion Starter · #11 ·
One line is the fuel supply line to the fuel rail, like you noted. The other is a vacuum line that drives the leak detection pump behind the passenger rear tire wheel well. It pressurizes the tank, then the ECU monitors the pressure for a fixed amount of time. If it doesn't hold the pressure like expected it throws a code and a CEL. It's #6 in this schematic:
View attachment 3115849
Excellent thank you for the explanation that really clears things up even more. So the big question now is since the rest of the entire evsp system is already gone is there any reason to keep that vacuum line or should I just cap it at the manifold and remove it. If its pointless to keep it and won't effect performance I'd rather just eliminate it. LS swap is coming after this season anyway.
Btw Legality isn't an issue either as the jeep is just a buggy now used exclusively on private land.
 

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Excellent thank you for the explanation that really clears things up even more. So the big question now is since the rest of the entire evsp system is already gone is there any reason to keep that vacuum line or should I just cap it at the manifold and remove it. If its pointless to keep it and won't effect performance I'd rather just eliminate it. LS swap is coming after this season anyway.
Btw Legality isn't an issue either as the jeep is just a buggy now used exclusively on private land.
If all of that module is gone, I don't see a reason to keep it (the line). Just another chance for a vacuum leak if you keep it, so I'd cap it IMHO.
 

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Discussion Starter · #13 ·
If all of that module is gone, I don't see a reason to keep it (the line). Just another chance for a vacuum leak if you keep it, so I'd cap it IMHO.
Well that's good news thank you!
I was just concerned that unplugging and capping it could cause it to run bad or cause other issues
 
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