Truck stalled the other day for no apparent reason. Got it too start once after, but it idled like the timing was way off. Now it won't start at all. I've replaced the plugs, and checked for spark. Seems ok. No apparent water in the oil, but the radiator was very low on coolant for some reason; never seemed to heat up, and I've not ever seen a leak. Plugs were wet with fuel when I replaced them so I'm guessing it's getting gas. I also checked the timing belt, and it is intact and seems fine. Stumped. Any help would be appreciated.