Ignition Problem Driving me Crazy

[MadMiracle]

1043949

I have a 90 YJ with 4.2 L carburated 6 cyl. engine. I've been having problems starting up my Wrangler when the engine is cold, especially in the cold. (50 degrees F and below). The engine rotates , but won't start. I have to hold the starter motor while revving the engine until it reaches near normal operating temps. Then the engine'll start, but then sometimes immediately stops. A couple tries after, it'll finally start and hold. This morning, with a cold engine, in about 40 degrees F, it started in just a couple tries and held. The hell's going on here? I don't get it

I've replaced the battery, ignition coil, spark plugs (haven't replaced the plug wires, distributor or rotor. They all seem to be in good dondition.) I've replaced and routed the vacuum hoses as properly as I could.

Fuel is reaching the carburator, (although, while accelerating, the engine'll hesitate slightly sometimes), the fuel pump seems to be working right, the choke is working fine, too. I'm not sure of the fuel pressure, though. Could the problem be with the ignition switch? Would a new ignition switch help start a cold engine in the cold? Also, I don't have a hot air tube that couples with the cold air snorkel in the air cleaning assembly? Would that help?[addsig]

 

[BobJ]

1043981

I doubt it's ignition related if it works if you hold the starter.



I'd check fuel delivery next.[addsig]

 

[MudderChuck]

1043987

The hot air tube to the air intake won´t help it start any better, but will help it run smoother while warming up. The only real starting problem I´ve had, is when the choke is a little to tight (most noticeable in cold weather). Try holding the choke open an eighth of an inch, pump the gas a couple of times and try starting (if it pops over it´s probably to much fuel, choke to tight). If it doesn´t pop over, could be poor spark or low fuel delivery. Also had trouble when the timing isn´t set to the specs. on the label under the hood (or in the book). Stalling a few times (smog carb.) seems to be the nature of the beast when cold.[addsig]

 

[MadMiracle]

1044002

Thanks for the advice everyone. A few days back, I tried holding the choke open, pumping then trying to turn the engine over, but that didn't work. But, at one point, when I finally got the engine to idle, I tried to see if the spark plug boots were in all the way. As I touched the top of the boot, I felt little shocks on my fingers. Nothing huge, just kinda heavy duty static charge shocks. I thought that was unusual and replaced the plug wires. I touched the new wire boots and didn't feel anything. I also replaced the fuel filter, hoses to metal fuel lines and clamps. I also took the idle pickup tubes and venturi cluster out of the carb and gave it a thorough cleaning. What sucks is that tomorrow, where I live it's supposed to be in the 60's and I usually don't have these problems when the temp is above 50 F, like today. I'll have to wait until it gets below 40-45 F to see if any of this has made a difference.



Again, thanks for the replies. Much appreciated.

[addsig]

 

[Jeeper89]

1044005

I have a 89 YJ witht he 4.2 Carb and mine does the same thing.It wount idle until it warms up.i have to sit there and keep revving it until it warms up.If you get sum starting fluid(make sure it has upper cylinder lube) and spray a lil down the carb it will fire right up and pump the gas as u turn it over.I just spray a lil down the carb and it fired right up.Dont use starting fluid all the time tho becuase it can be bad for it.[addsig]