Any idea why my friend's exhaust exploded?
 

Prior to this incident, my friend's 1996 Chevrolet 1500 pickup with a 5.7 liter engine, would be difficult to start. The other day when he tried to start it up, there was a huge explosion which tore open his muffler and spit out chunks of the catalytic converter the size of your fist onto the street below. The muffler burst open at the seam on the driver's side and looked like an open clam shell.

I am no expert but does anyone feel that either the fuel pressure diaphragm could have leaked fuel into the cylinders or possibly one of the poppet valves from the spider stuck open to cause such a powerful after fire?

Thanks for any help.

Re: Any idea why my friend's exhaust exploded?
 

Yes, its from running rich. Check engine light has probably been on for awhile, I would bet.

Might want to check a few other things also
 

The very first time I experienced slow/no starting, my "friend" came over and assumed I didn't know how to fire up an engine.

Not knowing what I know now, he jumps in and cranks it over and it backfires. Nothing like your friend experienced. It still didn't start.

After I looked at the plugs, I realized 3 on the right bank were black from having run rich. I immediately knew it was the cap. So I changed the plugs cap and rotor. It fired right up but the starter made a bad noise.

Well when it back fired, it blew the nose cone off the starter. So thanks to my smart friend, I had to buy a starter. So I got a Denso style with no nose cone. Incidentally, they are much easier to shim then nose cone starters.

After that incident, I experience a long cranking or no start condition every couple of years. All due to a cap and rotor that go bad about every 2 years or so.

Once on x-mas eve I parked it and it ran fine. Day after x-mas day try to drive to family and it won't fire up. I knew it was the cap and rotor and replaced it and fired right up.

While your example could be injector issues, the more likely problem is weak spark.

Remind your friend that it is recommended every 50-60K miles to tune up including plugs, cap, rotor, ignition coil, front O2's. Yes the last 2 items are tune up parts.

Re: Any idea why my friend's exhaust exploded?
 

I've never seen the ignition coil listed as a tune up part on anything. And that's crazy how quickly your caps go bad. Lots of moisture and corrosion where your at?

Re: Any idea why my friend's exhaust exploded?
 

Thanks for the information. His truck was skipping a while back so I replaced the rotor, the cap still looked good so I just shined it up a little with some fine sandpaper and the skipping went away.

Not sure if this is true but someone told me the gap will grow over time between the rotor and the cap, thus causing a skip. The tip of the rotor wears enough to creating a larger gap for the spark to jump across. Seems to make some sense.

Re: Any idea why my friend's exhaust exploded?
 

Think about a damp coastal environment. That makes a difference. I usually do a tune-up on my truck with plugs and cap every two years because of Calif. smog testing. My coil has survived going on thirty years and four engine blocks.

Re: Any idea why my friend's exhaust exploded?
 

One other problem with those caps is they can have an internal crossfire from one line to the other. They have internal traces to get the contacts to the sides. They can, for lack of a better term, side fire. I have a brand new Delco cap doing it.