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Truck hesitates when starting

I have a '96 Chevy Silverado that twice (in about as many months) has had some trouble starting. When I turn the key the engine starts to crank, then there is a loud pop and the engine stops. When I crank it again the engine will start, although more slowly than usual. Ideas about what could be wrong?

Does it skip and run rough after starting?

Sounds like an air/fuel mixture problem. Vacuum device or intake manifold leakes would be the first place I’d look. Second would be a possible faulty fuel pressure regulator.

Is all the routine engine maintenance up to spec – from the owner’s manual? Are there any check engine codes showing or pending?

The truck runs fine after starting. It’s up to date on maintenance, and the check engine light didn’t come on.

You might want to check for a stretched timing chain.

Your engine has the wasted spark ignition system which means two spark plugs fire at the same time but only one cylinder has the proper air/fuel mixture. If the timing chain is stretched and this causes two intake valves to be open at the same time, and the plug fires in the wasted spark cylinder it can cause the fuel to ignite in the cylinder that should have fired. This then causes a backfire. The backfire then causes the engine to rotate in the opposite direction. Now the stretched timing chain has thrown the ignition and valve timing off in the opposite direction and the engine cranks slower.

Tester

That’s what I was getting at, Tester - stretched timing chain, or jumped time somehow. Common in high-mile 305/350s. Luckily if that happens, or the chain breaks, it just doesn’t run - no valve interference.

@Tester I don’t the poster’s truck is that sophisticated.

I’m almost 100% certain that it just has a regular ignition system (cap, rotor, plugs and wires)

Yep! You’re right. It has a distributor ignition system.

But I’d still check for a stretched timing chain.

Tester

@Tester yeah, a stretched timing chain will cause all sorts of problems

Ok so when I take it to the shop I’ll ask that they check/ replace the chain.

A Chevy v8 timing chain cannot be “checked”. U pay the shop 800 to replace it.

A loose chain on a small block Chevrolet engine usually gets noticeably loud at idle especially at cold start up long before causing any performance problems. Often worn chains are discovered when they scratch holes in the timing cover and leak a great deal of oil while the engine continues to run well. But removing the distributor cap and watching the rotor while moving the crank back and forth will indicate if there is excessive chain wear. As always it is difficult to diagnose problems from behind the curtain but whenever the circuit is cut to the ignition module it causes the coil to discharge and when in the process of cranking the engine, if primary voltage is interrupted it would likely cause a backfire through the intake or exhaust and the description leads me to wonder if there might be a problem with the starter momentarily drawing excess amperage or the battery is on its last legs.

To check for a stretched timing chain remove the distributor cap. While someone observes the rotor in the distributor, turn the engine over by hand at the crankshaft bolt and stop. Now turn the engine over in the opposite direction. If the engine can be turned more than 5 degrees before the rotor in the distributor begins to rotate the timing chain is stretched.

Tester

I guess you didn’t see the word “replace” in my post?

I guess you didn’t see first “check” in my post?

Tester

Tester I wasn’t talking to you but to stoveguy, although why I bothered I don’t know.

Thank you for your help everyone. I appreciate it!

Took the truck to a shop and was told that the chain indeed loose and could be replaced for $1100. Ouch. The shop has recently changed hands so I want to get a second opinion.

@Kristen that sounds like a very high estimate

You might want to shop around for a lower price. Your truck is not that sophisticated and many other shops should be able to handle this repair

Thanks db. I thought so too.