Take a screwdriver with an insulated handle. Insert it into the plug boot and hold it 1/4 from the frame/engine. You must have a blue spark, anything else orange/yellow ect. is an ignition problem.

 

do you mean it starts but doesnt run? because if you have fuel and spark, but it wont stay running when you release the key, this drives me along another way of thinking.

 

engine turns but will not start. turn the key and the engine cranks fine, but wont actually catch. the only theory we have to go on at this point is bad gas. we replaced the fuel filter, and the gas smelled stale, so this is our best theory right now. beyond this the only possibility is timing. seeing as how the engine has <10,000 miles on a chain driven timing system i cannot see how this would be possible, but it beats my sisters theory of gremlins in the engine.

 

assuming the starter is not slow, and you have spare time. have you inspected the timing chain?

 

Probably late to the party, but I'll give my 2 cents. It only takes three things for an engine to run. Fuel in the right proportion, spark at the right time, and compression.

Instead of throwing parts at it, start from the beginning. Are you getting spark at the right time? Use a timing light to verify. Next, are you getting fuel in the right proportion? You can use the timing light to watch fuel being injected into the throttle body. Too much and you'll smell raw gas at the exhaust. Too little and you'll get no "fire". If you think there is not enough, squirt a little starting fluid or gas from a squirt bottle into the throttle body. If it tries to fire at all, you likely have a fuel problem. Try holding the throttle fully open and see if it tries to fire. If so, you're getting too much fuel. Pull the spark plugs and see if they're wet. Of so, you have too much fuel or no spark. Pull a plug and touch the outer electrode to ground, then have someone crank the engine. Do you get a good blue spark? If not, check plug wires, distributor cap, etc.

I guess what I'm getting at is, narrow down the problem by eliminating all of the things that are working right until you find the one that isn't.

 

Thanks for all of your help guys. Truck is running perfectly now. Turned out to be a perfect combonation of old gas and improperly gapped plugs (autozone sold us the wrong pre-gapped plugs.) like i said before, timing was fine, fuel pressure was fine, and we were getting spark... Just getting weak spark. Shes tip-top now. Got the emissions done and it not only passed, but the emissions were nearly non- existant. Cleanest ive ever seen.