if im posting this wrong, I apologize. I have a 96 GMC Jimmy 4.3 4wd. my problem first started when the key was getting hard to turn, so we switched out the ignition lock cylinder (where i put my key into to turn) ... after that, no start. getting fuel and spark. cranks just won't turn over. brand new battery, starter, and spark plugs. after about a month, decided 'what the heck'... tried it again and it randomly started up! since finally starting, it starts up fine! now where I'm having my issue is that after a day or so without being started, it does it again (cranks wont turn over) ... about a month or so later, takes a few tries, but starts! as long as I remember to start it up every day its fine but when it goes a day or two without starting, it does this to me every time! any advice or help please?! thank you : )

 

You say its getting fuel but is it getting the correct volume of fuel? you need to do all the fuel system checks to see if the pump pressure is good and the regulated pressure is also within spec. test pressure at the gauge port at the manifold and test max pump pressure at the fuel filter outlet and let us know what you've found.

 

we already used the fuel pressure gauge to check all of that, everything was perfect (boyfriends buddys works at a shop and helped us out) but noone ive asked can understand why it does this? #stumped I thought maybe the computer/brain or something had to be reset, maybe?

 

Is the SECURITY light on or flashing when you try to start it? Replacing the lock cylinder & key will cause the Passlock system to disable the injectors if it doesn't recognize the key, which if it's a new key, it won't.

 

That's what I figured ... tried turning the key on for 15 minutes, 3 times, then try to start (to reset the computer?) Didnt really seem to work. do you know what would fix that problem?

 

If the security light is on, here's the deal. If it's not on, the security system is not the problem.


From the factory, the security system is programmed to recognize two keys. There is a procedure, (usually outlined in the owners manual) to add more keys. One of the original keys must be used to turn the ignition to the RUN position to initiate the learning process. This will require reinstalling the original lock cylinder. If neither of the two original keys will turn to the RUN position, the security system will need to be reprogrammed using a Tech2 scanner with the appropriate software, (GM dealer).

 

I definitely thought that was the cause since I didnt have this problem until the switch... but i dont see a security light flashing.

 

The vehicle has some sort of security system from the factory. 1996 might be called PasskeyII, I can't keep all of them straight, (PasskeyI, PasskeyII, Passlock, etc) If there is a security light in the instrument cluster, (provided it works) it should illuminate with the bulb check when you initially turn the ignition to the RUN position, before you start the engine.

 

hard to see, but using my flash, you can barely see where is says 'security' above the antilock light on the cluster board.
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but when turning the key to the RUN position, this is what illuminates - security doesnt illuminate at all. also doesnt blink or anything afterwards.

[IMG][/IMG]

 

In the 2nd image, the bulb should light up like the others. Now we know the bulb is out, but it still doesn't tell us if the security system is definitely the problem or not. Might be an LED or a bulb, and the cluster has to come out to repair it either way. Or it could be a problem with the security indicating system not working. If it's a bulb it's easy, but if it's an LED it needs to be desoldered from the circuit board and a new one soldered in. You can do one of two things: Replace the bulb/LED, (figure out why the light doesn't come on) or continue looking for a problem that might not exist.