97 Pontic Bonneville won't start

#1

My wife’s 1997 Pontiac Bonneville will not start. The starter is turning the engine just fine, and every once in a while it sounds like a cylinder or two are firing, but mostly I just hear the starter cranking the engine. I’ve checked all the coil packs, and all are generating sparks. I’ve replaced the spark plugs, cam position sensor, crank position sensor, and MAP sensor. I am getting fuel to the cylinders. I’ve also checked the timing chain, and all appears well there. Any ideas?

#2

You may want to go back and be sure the valve timing and ignition timing are correct. My info says this has a chain, however on a vehicle that old the sprockets may have worn out and the chain stretched and slippage may have occurred.

#3

To be sure you are getting fuel to the cylinders, use Starter Spray (or, similar) into the intake tube.
In case the engine is flooded, as you crank, hold the gas pedal to the floor. Then, as (if) the engine starts, ease up on the gas pedal.

#4

The timing chain looks just fine, as do the sprockets, neither show any significant signs of wear. The chain is tight.

#5

I found the problem. This engine uses a two piece intake manifold. The lower portion is metal, the upper is plastic. Lo and behold, over time the upper piece cracks, leaking coolant into the intake. Replaced the upper manifold, and cranked the engine with the plugs out to dry them out.