1999 gmc jimmy cranks and has spark but only does it when cold out?

will be this heater mixer valve its vacuum operated

could be a vacuum leak or faulty valve

What brand of distributor cap did you use? When you say it won't crank, do you mean it won't even turn over? Or just turn over and not start up?

sounds like a bad cam/crank sensor?

Yes, the crank shaft position sensor tells the engine when to send fuel and spark to the cylinders in conjunction with the camshaft position sensor. If the crank sensor isn't working properly, the engine doesn't know when do do anything. Depending on what the other codes where, I'd highly suspect the CPS. It's not terribly hard to get at nor expensive of a part, but you will need a diagnostic scanner capable of doing a Crankshaft Learn procedure.

0.045 for the 4.3l

Check the Distributor Cap and Rotor Button (If it Has One) they might be worn. I have to replace mine on my 99 Jimmy 4X4 once a year (give or take)

try the oil pressure switch, that was a common problem on Gm trucks when I used to work on them, the oils switch was bad and woulden't allow it to start and the ones I worked on were on the back of the distributor.

If there is no spark and no fuel I'd look at the crank angle sensor. This detects the motor position and the ecu fires the plugs and injectors respectivly. Is there fuel pressure at the injector rail or no fuel at all?

not a lot of help in what you have put was their any noise of it loss of power or anything if it turns over and dosent fire up could possibly be a fuel problem or its not getting a spark to start it

disconnect the negative cable but leave the positive cable on
if this does not work then it will have to be scanned