Cold Start Troubles

I have a 91 XJ with a 4.0 that runs like a top with one exception. Every time it sits long enough to get cold it's hard to start. It will turn over and die right away. I have had success with cranking and giving it gas to hold it at 2000 rpms until it warms up but if you let it drop the Rpms it will stall. Any help with this issue would be appreciated.

Extended crank times when cold are "generally" due to loss of adequate fuel pressure. That can mean anything from the pump all the way to the injectors. Some comprehensive fuel pressure testing using a gauge and the factory service manual might be helpful in isolating the cause.

To help confirm loss of pressure, a quick and dirty test is to try the poor mans prime after engine sat overnight.

1. Turn key to on position (don't crank engine)
2. Fuel pump will energize and run for 2 seconds
3. Turn key to off position
4. Repeat steps 1-3 twice more
5. NOW crank the engine.

If it starts quickly, then loss of fuel pressure is almost assuredly the problem because all you did was to manually prime and build up pressure in the fuel rail.

However, when you mention the word "stalling", that could be indicative of a different problem. Marginal battery voltage can create a stalling symptom. Load testing your battery would be a good idea just to eliminate that from the suspect list.

Your temperature sensors (intake air, and coolant) might not be telling the computer to richen up the mixture, like putting the choke "on" with a carbureted system. Check those for proper resistance (ohmeter).

To add the battery is new, fuel pump and filter is new, NSS is new, both temp sensor in the water neck and the one on the rear of the block is new. Haven't tried the poor man's fuel pressure check yet but I will and I will report back on that ASAP.

"temp sensor in the water neck" is the efan switch; "the one on the rear of the block" I'm going to a**ume you mean the driver's side rear of the head, and that is the temperature gauge/idiot light sender. I may be wrong, but I believe that the Coolant Temperature Sensor, CTS, that provides input to the PCM is still under the manifolds in the block on the 91--but I may wrong.

Hey let me know if this does anything for you...I am starting to have a similar problem...

On cold start I can have mild to a horrible long crank time...then when it fires the idle is kinda low and sputtering...at times it won't even fire w/out giving it gas, I can sit there and crank all day and nothing will happen until I started playing w/ the throttle. I'm going to do some minor tests today to figure it out....

Also this use to happen w/ the jeep, but well over a year ago...in the fall of last year, it has since stopped until about 2 weeks ago. Mines a '92, however the motor is a '98 ZJ HO

p.s. also, it smells rich as hell coming out of the tail pipe w/ a puff of raw fuel when it does finally start when I have those long crank times...so maybe its not a "lack" of fuel...

Idle Air Control valve. This is the mechanism that the computer uses to control the amount of additional air that the engine gets during a cold start condition. It sits right on the side of the throttle body. They do fail and will cause hard to start and horrible idle during warm up.