Why wont it start?

I have been having an intermitent problem with my XJ not starting on the first try when the temperatures are below 30 degrees. It has been slowly getting worse. The problem is that when I try to start it, it will crank over like normal and attempt to start like normal, but it doesn't start. It acts like it is going to start. The best way that I can describe it is that the motor runs for about 2 seconds and then dies. But it never reaches a full idle. If I try to start it a second time, it will fire right up and run like normal. To me it seems like something is on its way out and I really don't want to get stranded somewhere.

The Jeep 1993 XJ 4.0 AW4
134,000 miles

What I have done to try and make it better, I have also changed a lot of this stuff to help out my sub par gas mileage
New
Fuel filter
Air filter
O2 Sensor
Map Sensor
Coolant Temp Sensor
Air Temp Sensor
Cap, Rotor, Wires (Accel)
Plugs (Champion Truck)

I have also run a fair share of Sea Foam, Lucas Fuel Injector Cleaner, and even a can of BG44K. I have also had my battery and alternator checked out and both are good. Any new advice would be great, thanks.

Have you tried replacing the crankshaft position sensor? I know too much heat can trigger it to fail, not sure about cold. It would explain an intermittent stall/no start problem though.

what about TPS sensor also

Are you waiting for the fuel pump to stop priming before you start?Go for a ride around the block park it and turn the engine off.In a few hours pop the hood and find your fuel rail,there is a little pressure relief valve....unscrew the cap and depress the valve.There should be some fuel pressure still built up in the system....that's is there to aid in the next start up.If not then you need to find why its not holding pressure.

hth.

Thanks for the replies. I am sorry that I haven't responded sooner. I have been helping my dad to get his rebuilt motor put in his toyota pickup. I havn't checked the CPS. I guess that it could be the problem. I kind of figured that if it was bad, it would cause maybe an extended crank before attempting to start. I have also been trying to remember if I replaced my TPS. I will have to get out my volt/ohm meter and check it out. I really like the idea about checking my fuel pressure. I am going to scope it out tomorrow. If it isn't holding pressure, what should I check? Would replacing the fuel pump be good preventative measure? I am not really sure how long they are supposed to last. After 13 years and 134,000 miles, that is a lot of fuel that it has moved.

When I bought mine 4 years ago the fuel pump was one of the first things I replaced as a preventative measure since it had 169,ooo miles on it.Now I'm not saying that you should replace the fuel pump...thats up to you.See if its putting out the correct pressure first.

Try unplugging and plugging back in the cps sensor....sometimes the connector gets coroded.Some people go as far as to cut the connector out and solder the cps wires.

I am not really sure how long the fuel rail should have pressure after it has been sitting, but after my 8 hour shift at work the other day, I had nothing. Not even a little dribble come out when I opened the valve. Where do you suggest that I purchase a new fuel pump from? Would some place like autozone have a decent one, or is that something I should get from the dealer?

Next time you go to start your xj turn the key untill you hear the fuel pump start then turn the key back off.....do this two times then try to start it.What this does is fully pressurize the fuel rail.

Don't take offence but you're not touching the gas at all upon start up are you?Ask me how I know.....when I was a teenager my first few vehicles were carbed so I was used to pumping/hitting the gas upon start up.The first fuel injected vehicle I owned was an xj and needless to say it didn't respond well to what I was doing.