Calgary Jeep Association

4x4 Related Groups => Tech Talk => Topic started by: unionjack on September 12, 2007, 11:26:32 AM

Title: vacuum lines
Post by: unionjack on September 12, 2007, 11:26:32 AM

hey folks i just wanted to know if anyone can help, a buddy has this 88yj with the 4.2l and we cannot get it to run!!!!!!!!!!!!!!! it starts and idles fine but when you stop at traffic light or something it stalls out, we have replaced spark plugs, cap,rotor, and now we are getting down to the vacuum lines and there is miles of it on an early yj, if anyone has any tips  or info that might help pls let me know as its coming close to getting rid of it!!!!!!!!!!!!!!!!!!!!!!!


thx
darren

Title: vacuum lines
Post by: Bnine on September 12, 2007, 11:40:27 AM

Pour water in the engine bay and listen for the idle to go to poop, or stall the motor. Thats vacum leaks.

Sounds more like a carb issue or possibly sticky vacum advance in the distributer.

Pull the advance line and listen for a change in idle to confirm advance is working properly.

Title: vacuum lines
Post by: unionjack on September 12, 2007, 11:47:23 AM

did the vacuum advance check and thats fine, never tried the water thing though, is it worth replacing all the vacuum lines its cheap enough,  and im gonna try the water thing tonight and see what happens, thx bill

Title: vacuum lines
Post by: 4PLAYZJ on September 12, 2007, 12:53:35 PM

another way to check for vacuum leak is with a can of air intake cleaner, spray the vacuum lines, throttle body gaskets and intake gasket.  Listen for the excessive engine RPM changes.

Title: vacuum lines
Post by: unionjack on September 12, 2007, 01:07:22 PM

well it looks like this jeep is gonna end up belonging to me, so now i have another project!!!!!!!!!!!!!!!!!!!!!! i think ill gut it and re-do the entire thing but thanks for your help much appreciated :lol:

Title: vacuum lines
Post by: Mudpig97 on September 13, 2007, 10:10:44 PM

Check for vacuum leaks under the intake.  Theres an intake heater bolted into the bottem and other stuff there can give lots of vacuum leaks.  Also check out this " nutter bypass".  Worked great on my 89 YJ and on my 85 CJ.  When I did this both times I completely removed the computer and all the vacuum operated systems.

http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/

Title: vacuum lines
Post by: calltrex on September 13, 2007, 10:33:22 PM

the stepper valve may get plugged up.

those carbs are junk

look for a motorcraft 2100 carb to replace it

Title: vacuum lines
Post by: Gearhead on September 13, 2007, 11:06:58 PM

Some reading / vacuum schematics n' stuff , carb fixes.

http://home.sprynet.com/~dale02/list.htm

Like Dava say's  , those Carter BBD  carbs are crap , a CJ pre 82 version is better but still a Carter BBD , this version does not use a stepper motor or microprocessor to control spark advance , fuel mixture or pulse air.

Attempts to pass emissions during the 80's varied , mostly by using unnecessary complexity and far too many vacuum controlled devices , it was a sad time for the American auto industry.


The "Nutter" bypass  

http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/



A write up on motorcraft 2100 swap

http://www.rocktaxi.com/motocraft/42carbswap.html

Title: vacuum lines
Post by: calltrex on September 13, 2007, 11:12:16 PM

I actually have a rebuilt mc 2100 carb

I guess i could sell it if your interested.  I dont need it..

let me know
cheers

Title: vacuum lines
Post by: unionjack on September 23, 2007, 07:03:12 PM

ok took care of the vacuum line prob now, and now the carb is pooched  i think, all is fine until im going forward and when i hit the brakes its like the carb gets starved of fuel and the jeeps stalls has anyone had this or heard of this happen??????, should i junk the carb and get a replacement or re-build it???? as im not too familiar with jeep engines some advice would be awesome