My '89 Jimmy (stock 350 TBI w/130,000 miles) cranks but won't start. Last night, my son had it sitting for about 3 hours with the ignition turned on to listen to the radio. Not sure if that's at the root of the problem, but tonight I pulled a plug wire at the distributor cap and didn't see any spark jumping across the gap while the engine was cranking. Any thoughts on what I should check first? Thanks!