umm, didn't know a muffler could do this

[JackstandJohnny]

so went to trevs friday night, put a new muffler on the 93 ZJ 4L  didn't get a click from his garage before jeep died..... at 11 at night of course too. so.  cut the old exhaust out, bolt in new muffler. also cut the Cat out and straight piped it. done it before on these; because it only has one 02 sensor (upstream, before the cat) 

so, jeep dies not a click from trevors.  stutters, then hear a loud bang and ZJ dies.  i tried to crank it over and nothing.  got it towed back, and pulled the muffler. still no start.  i have spark, fuel and air........... nothing.  as far as i can see, i think it won't start because its super flooded.  i pulled the sparkplugs and its sitting  (attempting to dry it out)

anyway, what would cause a muffler to explode like that?  also, it smells like fuel when  you take a wiff..............  any ideas?

[FiEND]

the cat burns unburned fuel.  maybe you are running super rich or have a bad cylinder that is leaking fuel into the exhaust.  a little buildup and blam.

[cLAY]

Did you do any welding on the exhaust?

[JackstandJohnny]

no welding on the exhaust. its all on by clamps at the moment.;

Al, there is no code from the O2 sensor, or any in general, so i assume its running normal; but it does smell like fuel, so you may be right? 

i was also pretty curious why it would stop the jeep in general too..........

[Vinman]

I've seen an old Ford pickup backfire and open up a brand new muffler, it looked like a bird spreading it's wings.

Vince

[esi]

With a bad cylinder or injector putting fuel into the new muffler. The brand new insulation might have soaked it all up until the muffler got hot enough to ignite, and then pow. Did all the plugs look the same when you pulled them. 
 Or you might have just got a friday muffler that wasn't assembled properly. 
  By the pictures it looks like it blew your door right off as well.
Take it back to point of purchase and raise a stink.

[JackstandJohnny]

took a whiff of both mufflers, the stock one and the 'new one' and the new one does smell like fuel. guess it did explode   but the why is what irks me now.  the old muffler doens't smell like fuel at all; 

all plugs looked the same; they were brand new.  and wet with fuel (from crankin it ofer so much)

if i can get it running tomorrow i'll probably get a new muffler and a cat. it ran before with a cat/muffler, so it should rn again
if it starts

[esi]

If you already have plugs out, a compression test might not hurt. Maybe take your fuel pump fuse out first though.
I can't see a cat thats really old burn that much fuel. I would think it would just clog itself. Hope the bang didn't do any engine damage.

[JackstandJohnny]

ya. and the bang was fairly loud.  there are a tonne of vehicles running around without cats; i'm thinking the muffler was just junk.......... it IS an Autovalue special........

engine damage, i don't know of yet..... compression test isn't a bad idea either..............

[JackstandJohnny]

cleaned spark plugs and put it back together.   still no start. 

so i have spark at all plugs, plugs look brand new and are in good condition; no pre ignition wear, or oil residue or anything like that;)  theres fuel in the rail;  pressure is good; fuel pump whirs on startup. ...

and nothing.  i''ve not done a compression test; i guess thats next.............


any ideas what the heck i did to get such a situation?

[CatSplat]

That's pretty bizarre. Somehow the fuel vapour got to the muffler then ignited, that's not exactly a common situation. Stuck injector or a bad fuel pressure regulator, maybe?

[morerpmfred]

In my youth , driving with a standard in a small town in northern Alberta on a friday night would turn the ignition of at speed wait about five seconds and turn key back on  thennn  BANG  . You got unburned fuel in the muffler then BANG .  Did you check everything on the ignition side including all the plug wires ? was one of the plugs excessively wet ? carbon tracking in the cap ? cap vent plugged ? loose power supply wires on the coil ? ground ?

[JackstandJohnny]

yea i'm pretty sure the muffler exploded due to fuel in there.  just trying to figure out whats causing the excess fuel

tomorrow new coil will go in and i'll hit pnp and pick up a bunch of new sensors to see if thats the culprit......

and when i pulled the plugs they were soaked in fuel.

[SwampSinger]

Monsieur Jean... what are you doing man?  A guy your size should have a bigger beer fridge.

Geezzz... 

[JackstandJohnny]

Monsieur Jean... what are you doing man?  A guy your size should have a bigger beer fridge.

Geezzz...  

doesn't matter how big it is if its empty



trev, from research i guess if it gets a bunch of fuel in there it can actually ignite;  so its time to figure out how fuels getting in there. bad timing, misfire, or something. 

will change coil and map tonight as i have a couple kicking around; anyone have a good CPS i could swap in? they aren't cheap.......  probably do an O2 sensor too...