Popping/after fire/backfire

[Jstov]

I have noticed that if I lean it all the way out while taxing it tends to not be as loud, but it still pops. I lean it to the point that if I have to go up a slight rise while taxing I need to richen it up to have the power to go up it. If it was overly rich wouldn't it go away when I lean it out?

[Chkaharyer99]

I have a Titan IO-360. Mine pops as well when its hot. Mostly after landing and taxing. It's more pronounced after re-fueling, hot start and taxing. Leaning helps quite a bit and switching the fuel pump on temporarily also seems to help when it's popping off.

Download: "Troubleshooting Techniques for the Precision Airmotive RSA Fuel Metering System"

Look at page 8: "Off Idle Stumble".

http://www.precisionairmotive.com/Pu...s/15-810_b.pdf

Mine was running excessively rich and using the above I was able to bring it into specs.

[Jstov]

I talked to our local A&P yesterday and we are going to look at everything on Monday. I will post our results afterwards.

[Jstov]

Well so far no smoking gun. We pulled fuel injectors checked for even flow and all as good. Checked valves cold and all seemed good. Did a check on the vacuum system with carb cleaner with engine running and did not see a change in RPM. Next check will be go fly and check valves warm. We ran out of time or we would of done it today. I will post results when we get to it.

[mannanj]

Originally Posted by MikeyDale

I believe you may be going thru exactly what I went thru with my new RV7 with a IO360. I test ran the engine and after it got hot, it would pop and backfire some at low RPM's and Idle. This drove me crazy! I thought my plugs were fouling and wound up buying fine wire plugs ! Still didn't cure it! Then I started noticing, it never happened when the engine was cold, only when it was hot and especially when taxing after landing. I have come to realize that it is fuel boiling in the injector lines. At Idle, fuel flow is very small and it has time to get hot in those tiny injector lines sitting right on top of those HOT cylinders, especially in that tight cowl on a hot day after landing. Having straight pipes with no muffler amplifies the popping! I was having lunch recently at 52F sitting outside and saw two RV's taxi by after landing and guess what, they were popping just like mine!

Most likely the cause, Justin.

[Jstov]

I agree Mannon but we are just going through the motions. I am just trying to eliminate all the possibilities before I resign to that being the cause. Do you think blast cooling the fuel pump might help?

[edsong]

Are you using 100 LL ?

[mannanj]

Originally Posted by Jstov

I agree Mannon but we are just going through the motions. I am just trying to eliminate all the possibilities before I resign to that being the cause. Do you think blast cooling the fuel pump might help?

It's possible. Probably at the speed it's happening, I don' think so. If you've the time, rig one off an old Cherokee.

[Jstov]

Yes I am using 100LL. I will look if I can easily blast cool the pump and see if it helps. On another note if it ever gets cold this year here in Florida maybe I will just try flying one cold day to see if that makes a difference.

[jrs14855]

Lees likely to be the fuel pump. This is usually caused by the injector spider and hard lines to cylinders getting hot and causing erratic fuel flow. Standard on the Pitts with fuel injection.
A solution is search of a problem but if you want to throw money at it, enjoy.