Confused about Distributor Vacuum Vent lines

[RADDOX]

HELP !!!
Couple of weeks ago I am messing around the enigine and push the rear vent line on the distributor out of the way. The truck immediatly starts missing. Now the truck has a miss and accelearates like a one lunger tractor ! When I move this line around it causes it to go from missing to not running at all. How is a vent line causing this and what do I need to do ? It is not kinked and all I do it push it around to effect the engine. It is the original metal line as is the engine and all the plumbing.

Thanks !

[ZGjethro]

Are both of the lines connected at the carb and the distributor? I am not sure if you are having and air leak or if you are affecting the timing by wiggling the distributor

[RADDOX]

That's what I can't figure! Both lines are tight as is
The distributor. All I do is push the rear line towards the
Front if the truck and she dies. Pull it back and it runs. Kinda

[DJ]

Possibly a cracked line that opens up when you push on it.

[ZGjethro]

any chance the distributor housing is cracked and is flexing as you move the tubing?

[RADDOX]

I've checked the everything that's visable and it's all rock solid and tight.
Maybe it's time to start checking the invisible !

[w30bob]

Raddox,

Let me make sure I got this straight......the distributor vent lines are solidly connected on both ends.....to the distributor and to the carb intake.....right? Then when you push on the vent line somewhere between the connections the engine runs like crap. Is that right?

thanks,
bob

[RADDOX]

Thats what's happening !

[w30bob]

Raddox,

I have to admit..........this is one of the most interesting posts I've read on here in a long time!

Tough to troubleshoot without being there, but just thinking it through it sounds like one of two things. Either that vent line is carrying current (and grounding when you move it) or it's allowing air to enter the elbow under the carb when you move it. I would think if it was the latter it would be more subtle than you describe. But if it's electrical it would act as you describe.

I know....it sounds crazy.....but just for shits and grins I'd disconnect the vent pipe at the distributor and put a voltmeter between the distributor and the pipe with the ignition turned on. Then I'd put it back together and check for continuity between the vent pipe and the engine block (ground).

You definitely have a weird one on your hands......but keep us informed......I'm dying to know the answer.

later,
bob

[RADDOX]

I will give anything a try. It's driving me nuts how a
Vent line us doing what it does. Besides it's inhibiting
My driving !!! Don't like to chug along

[Cal_Gary]

Could be a cracked fitting where the vent line attaches-I once had to make a 100 mile service run to fix a Freightliner because the driver stepped on the fitting that comes out of the air compressor and cracked it... Lard-ass....
Gary

[Sal]

By any chance, are either of the vent lines attached to the engine manifold or the vacuum part of the fuel pump and not the air horn ? (before the carb and after the air filter) Also does the truck run any better if the choke is pulled out partly ? If it does then that's a good indication your dealing with a vacuum leak.....


Sal

[MSeriesRebuild]

Based on what we have seen with crazy symptoms and vent lines, Sal has hit on the most likely scenario. These lines on jeep engines are plumbed into the vacuum system. The first thing I'd think of with these symptoms is someone who didn't have a clue has tried to route them via vacuum plumbing. Check out the plumbing, it is highly likely you have a vacuum leak because the vent lines are plumbed incorrectly.

[DJ]

G

[MSeriesRebuild]

Was it running good before the moving of the lines made it misfire? If so I'd check for a cracked line at the fitting. If you didn't replumb it I it wouldn't be mixes up lines.

If vacuum plumbing is in the mix, as long as there is no leak in said plumbing, no skip will occur. However once a leak becomes active within the vacuum circuit, (such as what could occur when the line is moved by hand) engine cylinders that are closest to the leak will cease to draw the gasoline/air mixture, thus the affected cylinders will begin to skip as a result of no fuel being drawn in. In the case of the 230 engine's design, when a vacuum leak occurs, generally 2 cylinders will be affected.