Here it goes anyway...

2000 Chevy Silverado 1500 4WD, 130k miles.

Once in a while lately (more frequently the past few days) when starting the truck, it sounds like it is laboring to start kind of like how it would sound if the battery is not fully charged. It usually kicks right in and when it does, it starts knocking and pinging so loud, much like an engine that has over heated and is out of fluid or a really loud diesel engine. If I let it run for a minute or two, it goes away. If I stop the engine immediately and re-start it starts just fine without the noise.

Any idea where to start? Water pump maybe?

 

If you are getting knocking and pinging, it sounds like the lifters are dry. Might be problem with the oil pump.

 

That is what I was thinking...maybe the oil pump. I also figured I would change the water pump and serpetine belt too.

Another tech thought maybe the battery was draining somehow and drawing down low enough to effect the computer at start up.

I checked the voltage tonight and will check again in the morning to see if there is a drain but I am thinking oil pump.

The odd thing is I can immediately stop the car and restart it and it starts right back up fine. Maybe the oil pump shorting out or clogged or something?

 

Is it a 5.3L? I just read somewhere on this forum that they tend to sludge or coke out around the throttle body and the EGR valves...