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  #1  
Old 12-06-2017, 07:05 PM
drone_pilot drone_pilot is offline
 
Join Date: Jan 2014
Location: Hobbs, NM
Posts: 195
Default IO360-A1A Needs Help

Hello All,

Iím sorry that this post is so long but trying to provide plenty of detail...

Airport Elevation is 3600 feet.

I installed a used IO360-A1A engine on my 7A after having it rebuilt. It has always been hard to get the mixture lean enough at idle. Likewise, after flying and getting the engine hot it idled horribly after landing. Iíve read a lot of articles that made me feel this is normal but a few weeks ago the engine quit on final after pulling it back to idle and I landed about 100 feet short of the runway threshold. The only damage was a totaled threshold light, scuffed paint on the side of my nose wheel fairing, and my ego.

I immediately pulled the entire injection system off of the airplane and sent it to Airflow Performance. They overhauled the whole thing.....servo, flow divider, reduced the size of the restrictors, new injector lines. After installing it wasnít as tough to get the idle leaned although I have a hard time getting a definite 50 rpm rise pulling lean to shutoff. I have a very light 3 blade Catto Prop if that makes a difference. I know the inertia is not as great with a metal prop.

I flew touch and goís to stay in the vicinity of the airport and test the system at all power settings. The first two touch and gos went great. The the third touch and go, I got engine roughness after pulling the throttle to about the 1200 rpm range. I increased the the throttle up a tad to smoothness and forced the plane down. Once I had the runway made, I pulled throttle back to idle. As I was flaring, I could see the prop getting too slow. I slightly increased the throttle and saved the engine from dying. I taxied to the ramp and noticed the hot idle was much better than it had ever been. Some local pilots also commented on how much better it was running.

I taxied to the ramp discouraged by the roughness that I feel would have killed the engine at low rpm. I set the mixture to full rich. I slowly increased the throttle until about 1/2 inch before full throttle where the engine would completely lose power. Just like it was flooding out entirely. This repeated over and over again. Before takeoff, I always have leaned the engine so I didnít know this was an issue. The lean was usually pulled out 1-1/2Ē before takeoff. Engine runs all the way up to full throttle with that setting although the static rpm is only about 2000 rpm on the Catto 3 bladed prop.

When the engine was rebuilt, the mechanic timed the engine. I purchased the piston stop, timing indicator, and mag timing light so I could verify the timing. My engine has a placard calling for 25 degrees before top dead center but I have read where Lycoming moved the spec to 20 degrees. When I checked the actual timing, I am seeing about 18.5 degrees before top dead center.

Would this timing cause the engine to drop out at full power? I am seeing 360-390 degree CHTs. Peak lean shows about 1425 degrees on the EGT.

Please help me to troubleshoot.
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  #2  
Old 12-07-2017, 08:24 AM
mahlon_r mahlon_r is offline
 
Join Date: Jan 2005
Posts: 946
Default

your timing shouldn't be an issue. What is the fuel pressure while all this is happening?. Merry Christmas, Mahlon
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  #3  
Old 12-07-2017, 08:36 AM
BobRv4 BobRv4 is offline
 
Join Date: Nov 2012
Location: Gilbert, AZ
Posts: 77
Default check plugs

I would pull all the plugs and try and get a reading on whats going on.
Maybe post the pics to see if anyone can help.
Will probably tell you if you are over lean or too rich.
Next I'd check for induction leaks, intake tubes seated correctly against the clys
rubber boots no holes. I would set timing correctly to 25.
If you an impulse mags, make sure the mag has "snapped" or impulse has fired before timing.
Let us know what you find.

Last edited by BobRv4 : 12-07-2017 at 08:41 AM. Reason: more info
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  #4  
Old 12-07-2017, 09:18 AM
n816kc n816kc is offline
 
Join Date: Jan 2005
Location: Winter Haven, FL
Posts: 199
Default AFP idle

I've got the same engine and AFP system on my -6. Went thru the same scenario in setting my idle mixture - my first flight landing was dead stick when the engine died on short final. Make sure you're adjusting the idle setting when the engine is hot, a cold idle setting may not be ideal.
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  #5  
Old 12-07-2017, 09:33 AM
TS Flightlines TS Flightlines is offline
 
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Location: Ridgeland, SC
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Default Shameless plug

for Don's Injection 101 course. Makes troubleshooting much easier!
Tom
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  #6  
Old 12-07-2017, 10:37 AM
jliltd jliltd is offline
 
Join Date: Sep 2013
Location: Rancho San Lorenzo
Posts: 259
Default

I am at 4,000 elevation (same as you for all purposes). I had heck trying to get the idle mixture to give me any rise at all when pulling idle cutt-off with my parallel valve engine. It sounded like a radial at idle but ran good at higher rpm. Taxiing in hot it would fart and backfire and I had to go full rich to help. Unlike yours mine has a stock Bendix RSA-5AD1 fuel servo. That didn't matter in my case. We tried to adjust idle mixture to no end and the number of turns on the idle mixture link was way out of spec. We even went as far as replacing the fuel servo with an exchange. Replacement didn't make any difference.

Shout out to BobRV4 for his post above. Amongst his checklist is one item we found. The one-piece induction tubes on the parallel valve engines use a large o-ring seal where they stab into the intake sump during assembly. Apparently the fellow who installed the induction tube for cylinder #2 "rolled" the seal when pressing in the tube or subsequently fitting it and didn't notice it. Thus I had a big honkin' induction leak there. Removal of the induction tube and rolling the seal straight and applying DC-4 prior to re-assembly made things fine and the engine ran normal. I encourage that to the o-ring type seals used at the sump end of the induction tubes be lubed prior to assembly and a subsequent inspection prior to first start as the seals can shift when aligning the flanges on the cylinder head end.

Jim
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  #7  
Old 12-07-2017, 04:01 PM
drone_pilot drone_pilot is offline
 
Join Date: Jan 2014
Location: Hobbs, NM
Posts: 195
Default

Thanks for all of the great advice! I'll begin troubleshooting and let you all know what I find out.

Mahlon - Fuel pressure runs pretty steady at 28 with the boost pump on and drops to 26-27 with boost pump off.

I also ran across a post early this morning (search XP-400 Still Coughing) where the timing between the cam and crank was off by one tooth and created almost an identical problem at full rich and high power as what I have. I also read that I can set the #1 cylinder to top dead center, pull the rocker cover to the #2 cylinder and check for both valves to be closed. Moving the prop left or right a little should open either the exhaust or intake valve depending on direction. At top dead center both should be closed. If one valve is open, then there is misalignment in timing between the cam and crank. While there tonight, I'll try this since it's not too big of a job to accomplish and may save a lot of tail chasing in the grand scheme of things if there is a timing error assembled in. I had a local mechanic rebuild the engine who is pretty good but after getting to know him better, I have seen him make mistakes. I feel it could be possible that he missed the timing on the gear teeth. I hope not but I'm going to check just to make sure.
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Last edited by drone_pilot : 12-07-2017 at 04:12 PM.
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  #8  
Old 12-07-2017, 05:18 PM
Jrskygod Jrskygod is offline
 
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Location: Edinburg, TX
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Default

As I was reading the original post I was thinking the symptoms were exactly what I experienced in the past with a recently overhauled engine. The internal timing was off by one tooth. After going through the previously enumerated procedure as provided to me by a lycoming technical representative it was determined that the engine was mistimed. Upon further examination it was determined that the idler gear was mismarked. Once we reset the idler correctly the engine performed as it should. That was one expensive lesson as we chased a fuel problem for a long time without a cure.

The timing is pretty easy to check and I would do so since the engine was recently overhauled and the timing could have been set wrong. You might save a bunch of work and money.
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  #9  
Old 12-08-2017, 11:54 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 2,417
Default

Quote:
Originally Posted by drone_pilot View Post
I also read that I can set the #1 cylinder to top dead center, pull the rocker cover to the #2 cylinder and check for both valves to be closed. Moving the prop left or right a little should open either the exhaust or intake valve depending on direction. At top dead center both should be closed. If one valve is open, then there is misalignment in timing between the cam and crank.
Both valves are slightly open at TDC during the EX/IN stroke transition, though they may appear closed. You are not looking to verify that both are closed, only that a turn in one direction will equally close one and open the other. The behavior will be opposite in the other direction. If only one valve is moving, that is a clue that cam timing could be off.

Larry
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  #10  
Old 12-08-2017, 02:13 PM
mahlon_r mahlon_r is offline
 
Join Date: Jan 2005
Posts: 946
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Since the fuel pressure is good( I am am assuming that your instrumentation is accurate) I would vote for the valve timing as well. Valve overlap on number two should be happening when number one is at TDC. Valve overlap is as one is closing and the other is just opening. The procedure is listed on page 11 or 12 of the Lycoming troubleshooting guide.
https://www.lycoming.com/sites/defau...es/SSP-475.pdf

If the valve timing is off the overlap will occur several teeth of the flywheel away from TDC not just one or two. If it is occurring within one or two teeth of tdc on the flywheel then it is OK and your feel of the valve movement is a little off.
Merry Christmas,
Mahlon
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