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pcv valve vacuum line?


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yeah i have the skinny one in the back. but on the front i believe all thats on mine is a pvc valve stuck in the front hole with a piece of hose going nowhere. can't get to it to look right now. had to move it out of the garage for the hurricane. i'll get it back in there tomorrow and see if i can figure it out.

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yeah i have the skinny one in the back. but on the front i believe all thats on mine is a pvc valve stuck in the front hole with a piece of hose going nowhere. can't get to it to look right now. had to move it out of the garage for the hurricane. i'll get it back in there tomorrow and see if i can figure it out.

Well, that's backwards. The larger front tube should connect to the intake tube between the air box and the throttle body. The front tube is the INLET, and it's supposed to be sucking filtered air from the air box INTO the engine.

 

The skinny line at the rear connects to the intake manifold, and that;s the one that sucks the fumes out of the crankcase and into the intake air stream so it can get burned in the engine. _IF_ you wanted to use a conventional PCV valve (and I have considered trying one for maybe an AMC 258 engine, which is about the same displacement), it should go in the rear grommet and be connected to the intake manifold.

 

Putting a PCV valve in the front grommet will absolutely guarantee that NO air can get into your crankcase. If the rear tube is sucking at all, it'll create a huge vacuum and air will have to be pulled in from somewhere it wasn't designed to be pulled from.

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it might not have been a pcv valve. i'm just going off of memory so it might have just been a 90. also the jeep doesn't have the stock airbox lid. somebody before me put an aftermarket cone filter on the intake tube. there is also a small filter on a small tube next to the air filter.

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yeah i have the skinny one in the back. but on the front i believe all thats on mine is a pvc valve stuck in the front hole with a piece of hose going nowhere. can't get to it to look right now. had to move it out of the garage for the hurricane. i'll get it back in there tomorrow and see if i can figure it out.
It should not have a PCV valve as our trucks do not use them in a 4.0L. If it has a PCV valve it is something someone has rigged up. My previous links show what is needed. The picture below is not great, but it shows what the set up should look like. You should need #1 and possibly #2...

 

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Well Ok then It does work and that is the right part right???

 

That is the tube that fits on the rear of the VC and runs right with the fuel rail and bends off to a nipple in the intake manifold between the throttle body and first intake tube runner. It'll be what pulls the crankcase fumes/blow-by out of the top of the engine. The front line (bigger OD) is where fresh air will be brought into the VC if needed; at the same time that front hose runs from the VC to a connector that snaps together with like 6 more plastic vacuum lines and then goes to the air box lid/cover. When that small OD line on the rear of the VC gets plugged, or the bushing swells up and chokes any negitive pressure the blow-by/fumes will then be sent to the air box, because of what is called Venturi effect. The Venturi effect is simply suction from air being pulled from the atmosphere into the engine also pulling the fumes out the front tube and with those fumes oil gets pulled along to mainly because of a reed valve type of baffle thats not present in a hidden front tower under the VC. So when the the fumes and oil go through the front the oil will drip down into the air box and then start to leak out from the inner fender. At least thats my theory on what goes wrong when it doesnt work as it suppose to. whew...

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