Backfiring problem.

[Shadrach]

Not to pick nits in this thread, but we are discussing is an "after-fire", not a "back-fire"...

[TonyPynes]

My M20F is one of those that pops occasionally on taxi. I had it in for some other work recently and my A&P says the number 3 exhaust flange is oozing oil...no other oil...compression is at 79, he cleaned it all up and looked for leaks or cracks with no luck.

I wonder if the oily flange and popping are related.

[TonyPynes]

My M20F is one of those that pops occasionally on taxi. I had it in for some other work recently and my A&P says the number 3 exhaust flange is oozing oil...no other oil...compression is at 79, he cleaned it all up and looked for leaks or cracks with no luck.

I wonder if the oily flange and popping are related.

UPDATE

Triad Aviation took a look at cylinders and valves and said all was well but found that the internal baffling was loose in my exhaust and there were very thin places. So we are installing new exhaust and believe this might have been the cause of my popping. They do not believe the oily flange to be indicative a problem....will see.

I will report back on results when I pick it up.

[Greg]

Has to be unburned fuel accumulating in the exhaust system, usually the muffler then a source of ignition like a red hot muffler baffle, red hot carbon deposit in the muffler, burning exhaust gases (so rich they don't all burn until get to more O2 like what's left over from another cylinder)  could be fuel flow is very uneven between cylinders at idle (spider worn out) clogged or dirty injectors or lines.

[butchgilbert]

IMHO it is very rare for any airplane to backfire in the flare, if that was normal then every airplane would backfire in the landing phase.

 

I think you have an exhaust problem/muffler issue resulting in the backfire on landing.  I have had this same problem, but mine was an easy fix due to a poor fit on the slip joints on the vertival exhaust stacks.

 

Do Mooney occasionally backfire on the ground after landing - Yes, even mine does (less so no that I had the idle mixture setting properly set after 13 years of ownership!)  It always smelled of unburned fuel on shutdown until I had this adjusted.  Experience is wonderful, but it's usually expensive.

 

Good luck.

 

Butch

[duke]

shadrack is 100% right. After fire and backfire are two completley different things. Backfire is usually caused by to lean a mixture and backfires out of carb or throttle body. Usually happens on startup on cold days with insufficient priming.

After fire happens in ex system from unburned fuel mixture igniting. Usually won't happen if ex system is tight leading to muffler. In my experience if any air can enter system between eng and muffler this can happen. this does not have to be a big leak and may not show any sign of ex leak. Negetive ares between ex pulses can draw in air through small leaks (overlapping slip joints) where ex won"t blow out. Same principal as varsol gun picks up fluid.