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New engine help

cgeyman

cgeyman

Well Known Member
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Hi brain trust. My rv-9a has its AW certificate, but woe is me. My factory new Lycoming o-320 has had only three engine starts of 5 to ten minutes, but when I set out to fly today for the first time, my #4 cylinder was initially cold for the first few minutes. After throttling to 1200 rpm and leaning hard, it suddenly heated and gained temps in CHT and EGT to match the other three. Fouled plugs (carbon and oil I presume). Everything was good until runup, when switching to the Right mag suddenly was rough again with misfires, “pop popping” of ? Backfires. I aborted the first flight here at Missoula KMSO, elevation 3,200 feet and taxied back to my EAA hanger. I had confirmed equal 25 BTDC mag synch just two days ago. I pulled the plugs and they were less oily than a week ago, no lead, and just dark carbon soot film equally on all. Ughh. I am scared to fly knowing a spark plug is still likely not working. The champion rem38E plugs all checked on resistor testing 1700 to 1800 ohms. Should I just fly an orbit at 5,000 msl and let the engine “self correct” by setting the rings with power and rpm of 2600?

I have a call to our local mechanic for advice. I also have a set of Tempest plugs (same rem38E type) coming to see if this helps.

Any advice that is obvious to the break in experts? I don’t want to diddle around and varnish my cylinders by repeated ground runs as Paul Dye mentioned his hanger mates doing by accident. My setup is standard factory new Lycoming, fixed pitch Sensenich composite prop (ground adjustable with pin setting 4 for now). Two Slick mags and Avstar carburetor.
CalView attachment 78647
 
It sounds like a fouled plug that cleared then fouled again. I recommend you pull those plugs, inspect, clear the debris, and run it up again.

I had a similar issue during one of my Phase 1 flights (10 hours or so) that exhibited unexpectedly high cht/egt. An inflight mag check showed a problem on one of the plugs/leads. Initially, I could find no issue with the plugs but under bright light I finally discovered the tiniest piece of carbon bridging one of the electrodes. I had to hammer a piece of .032 safety wire flat in order to pick it out. Have had no problems since.

Hopefully, your issue is as easy a fix as that. Good luck!
 
On the engine, I assume you have some paperwork as to an engine run in Lycoming’s test cell? In other words THEY ran it successfully? Cold cylinder then not could be a new engine information system issue such as cht probe or ground to EIS. Does run up seem smooth until mag check? Id go through all things RIGHT MAG, verify timing AGAIN, pull cap check wires, switch all plugs from right mag to left mag. If issue moves to left, then a plug issue is most likely. Many A&P here on VAF, they will chime in soon. Might be how your key wiring/switch is wired.
 
When you said "cold" did you mean really not firing at all cold? If so that's not likely ignition (both plugs bad on the same cylinder at the same time..). If that cylinder isn't firing at all, can you do a compression test on it to see if a valve is sticking or some such?
 
On fouling the plugs - it would help if you start/warmup/taxi with the mixture leaned aggressively. Then go full rich for takeoff and all of the high-power break-in. If your mixture is not set correctly now, and "full-rich" for you on the adjustment knob is slobbering rich on the carb, then it would be easy to foul the plugs between the hangar and the runway.
 
When adjusting the idle mixture, go best idle speed, then a tad rich. Your idle cut off should bump a bit up in rpm then the drop off to zero quickly.
 
You’ve got some good troubleshooting tips to keep you busy already, and remember that regarding glazing a cylinder, ground runs are fine as long as you keep CHT’s below 300 degrees. Below that temp, you can do no harm, so keep the runs short. But by all means don’t go fly until you have sorted out that the engine is running well. As a DAR, I require an hour run time on the engine before I issue the Airworthiness Certificate…for just this sort of reason!
 
Thanks everyone for their wisdom. Agree, better to sort out now. Thanks Paul with the 300 degree CHT limit for ground runs should limit risk on glazing! Super helpful.
Cal
 
Ironflight said:
You’ve got some good troubleshooting tips to keep you busy already, and remember that regarding glazing a cylinder, ground runs are fine as long as you keep CHT’s below 300 degrees. Below that temp, you can do no harm, so keep the runs short. But by all means don’t go fly until you have sorted out that the engine is running well. As a DAR, I require an hour run time on the engine before I issue the Airworthiness Certificate…for just this sort of reason!
Click to expand...
Mahlon is OK with 350 on the ground run CHT's.
 
how much do the CHTs drop after the cylinder is broken in?? I am seeing 380 on 1 cylinder after only 2 hrs of flight time. Would you expect a broken in engine to run 30 degrees cooler??
 
In my experience O320's are prone to fouling the bottom plugs. If you put REM37BY plugs on the bottom fouling issues disappear. My first 320 would foul plugs in 15 or so hours even when leaning aggressively, which I always did. After switching to the 37BY's I could go 100 hrs between cleanings. Our flight school always ran the BY's on the bottom of their 320's for the same reason.
 
I switched top and bottom plugs and it is still the right mag misfiring, so it isn’t a plug issue. I remember having to take the right mag off to install the throttle and mixture control support bracket. I used the external timing pin when I re-attached the right mag, and I don’t think the accessory gear box gear moved, but I probably did something wrong. I am having my local A&P help me. We also have a magneto shop 30 miles away (Aircraft Magneto Service), if somehow I really screwed it up. 🫤
Cal
 
cgeyman said:
Hi brain trust. My rv-9a has its AW certificate, but woe is me. My factory new Lycoming o-320 has had only three engine starts of 5 to ten minutes, but when I set out to fly today for the first time, my #4 cylinder was initially cold for the first few minutes. After throttling to 1200 rpm and leaning hard, it suddenly heated and gained temps in CHT and EGT to match the other three. Fouled plugs (carbon and oil I presume). Everything was good until runup, when switching to the Right mag suddenly was rough again with misfires, “pop popping” of ? Backfires. I aborted the first flight here at Missoula KMSO, elevation 3,200 feet and taxied back to my EAA hanger. I had confirmed equal 25 BTDC mag synch just two days ago. I pulled the plugs and they were less oily than a week ago, no lead, and just dark carbon soot film equally on all. Ughh. I am scared to fly knowing a spark plug is still likely not working. The champion rem38E plugs all checked on resistor testing 1700 to 1800 ohms. Should I just fly an orbit at 5,000 msl and let the engine “self correct” by setting the rings with power and rpm of 2600?

I have a call to our local mechanic for advice. I also have a set of Tempest plugs (same rem38E type) coming to see if this helps.

Any advice that is obvious to the break in experts? I don’t want to diddle around and varnish my cylinders by repeated ground runs as Paul Dye mentioned his hanger mates doing by accident. My setup is standard factory new Lycoming, fixed pitch Sensenich composite prop (ground adjustable with pin setting 4 for now). Two Slick mags and Avstar carburetor.
CalView attachment 78647
Click to expand...
Certainly clean the plugs, your fouling should lessen with more break in time
 
mea culpa. Hard to know how boneheaded i can be. i swear I identified the tdc compression stroke with my thumb over #1 cylinder and my “thumb was blown off”, but my mag checked out great by aircraft magneto service testing. Steve, the slick mag guy, says they get sent in “bad magas” all the time that test perfect, and it is a case where the mechanic sets it to tdc on the exhaust stroke. misfiring guaranteed! Steve suggested taking tve valve covers off to ensure both valves are fully closed, as the best way to make sure you are on the compression stroke. ughh. anyway, works fine now,
Cal
 
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