'01 Cold Start Problem

[Kahuna]

Hey all...I'm new here, but have a problem I'd like some advice on. My '01 4.0 is having some serious issues with starting in cold weather. It started last winter, but I managed to get through without much trouble. This year has been especially cold so far and now I'm having trouble just about every time I try to start it up. Here's what's up:

Any time the outside temp gets below 35 degrees or so, it cranks but doesn't start. I'm a bit of a do-it-yourself'er, so I bought a manual and started troubleshooting. I ran the prescribed tests on all the sensors that seemed to be related, and even replaced the IAC just in case. I also replaced the plenum o-rings that everyone seems to have trouble with. Everything seems to check out fine, but the problem remains. Any thoughts???

 

[ZO6_Vette]

Check ignition system (coils, plugs wires)
next fuel system pressure

 

[Kahuna]

Thanks for the suggestions Z06. The plugs and wires are fairly new. I replaced those first last year, hoping that the problem was that simple. I have not checked the fuel system pressure. Is there an easy way to do that?

In regard to fuel pressure: If the pressure was low, wouldn't I have trouble in all range of outside temps? Also, wouldn't I start to see lean codes from the ECM? As it stands now, the Check Engine light has never come on and there are no codes stored.

I read some other posts and am going to try cleaning the MAF, since it sounds like that can cause all sorts of problems. I'm pretty sure I have tested the MAF and got a normal reading though. In studying the repair manual I picked up, it mentions an air temp sensor in the intake tube. I cannot locate that sensor on my intake however. Could it be part of the MAF?

 

[John_Rock]

I have not checked the fuel system pressure. Is there an easy way to do that?

I've been meaning to buy myself a gauge so I can check the fuel pressure on my trucks. I bet, Autozone or Advance Auto Parts will have a gauge I can buy. There is a schrader valve(like the valves on your tires) on the fuel rail at the intake. That is where you hook the fuel pressure gauge to.

 

[ZO6_Vette]

Fuel pressure as check to see if the fuel pump comes on when the key is turned on.