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Old 12-18-2012, 06:00 AM
Walt's Avatar
Walt Walt is online now
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,669

Originally Posted by Lars View Post
Instead of using the "rope trick" I used compressed air with a spark plug adapter, same as I've done a zillion times to replace valve springs on car engines, to get the valve spring off.
I agree, using air is easier, quicker and safer (I've heard of the rope getting knotted up and then you can't get it out).
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
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RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
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Old 12-18-2012, 07:05 AM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 6,557
Default Safer: to whom?

Be careful with that pressure! Cars don't have than big chopper up front when they decide to act on that pressure and rotate. That said, I would still do it, but i have had the engine rotate too. Exciting enough with a pull handle attached to crank nut . . . Just be careful to maintain TDC.

Back to RocketBob's comment on timing, is there any chance of incipient detonation? That can make an engine a tiny bit rough and it wont happen all the time, and could occur on multiple cylinders. A soft check, by retarding the timing a little, could address that question. Sometimes it is the quiet little voice that leads to success.

My $.01, (less valuable than $.02)
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Old 12-18-2012, 09:14 AM
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GeneL GeneL is offline
Join Date: Sep 2009
Location: Daytona Beach, Florida
Posts: 121
Default Miss

I feel your pain, I have had a similar miss in both a Tiger and my RV-7. To eliminate the "over advanced" situation at low manifold pressure settings remove the manifold pressure line, in P-Mags this will revert the timing to base mag timing. I think this will be a longshot.
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Old 12-22-2012, 04:15 AM
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Ant CB Ant CB is offline
Join Date: Feb 2011
Location: Sydney
Posts: 44

Certainly frustrating, I've been through something similar myself.

I'm with rocket bob, I'd be looking at the timing first.
Sydney, Australia
Fly for fun and for food
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Old 12-22-2012, 06:30 AM
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walkman walkman is offline
Join Date: Oct 2011
Location: Atlanta
Posts: 894
Default Don't get a standard valve spring compressor

Get a valve wizard from jolly time tools
RV-8 IO-360 (Bought)
RV-6 O-360 C/S (Sold)
Walkman aka Flame Out
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Old 09-08-2013, 08:46 PM
Speeddog7 Speeddog7 is offline
Join Date: Apr 2010
Location: Plano, Texas
Posts: 42
Default Followup to my engine problem (possible resolution)

I'm happy to report that I believe I may have finally found the source of the intermittent mis or stutter that my Superior IO-360 has had from day one in my Glasair. A week or so ago, I decided to (once again) test the fuel supply to the engine. I attached a clear hose to the output port of the gascolator. I turned on the boost pump and after getting a solid column of fuel exiting the gascolator, I began to notice air bubbles on a regular basis come down the clear line. In order to isolate the component causing the problem in order to rule out a fuel plumbing air leak or a faulty fuel valve, I connected clear tubing to the input and output ports of the fuel pump (Weldon brand) and ran them into their respective fuel cans. Turning on the pump, it quickly became clear that the Weldon pump was introducing air into the fuel system. I discussed the matter with Don Rivera at Airflow Performance and he agreed that it appeared the Weldon pump probably had a leaky shaft seal (I sent him a video of the air bubbles being pumped thru the clear line by the Weldon pump). Unfortunately, the Weldon pump cost about $700 bucks to overhaul, so I ordered up one of Don's new style pumps for quite a bit less. I got it installed this weekend and even verified that it was not producing any air like the previous Weldon Pump was. I flew the plane for about 45 minutes late this afternoon and I do believe (fingers crossed), that my problem has truly been resolved. The engine ran VERY smooth. Not one hiccup, burble or stutter like I've nearly become used to over the past 300 hrs. of operation.
So, IF my problem is truly resolved (time will tell), the lesson I need to take away from this experience is that air in the fuel system can most certainly produce an engine symptom that feels and sounds exactly like an ignition problem, a sticky valve, or possibly something similar to detonation.

By the way, about a year ago, I ran clear tubing between the fuel servo and the flow divider and then ran the engine. There were no visible bubbles in the line, so I declared that fuel supply was not my issue and went on to chase other potential ignition related possibilities. I have no idea why there were no bubbles in the line that day. Maybe the Weldon pump was having a good day,,, who knows.

I'll put some time on the engine and will report back whether my engine symptom STAYS fixed. I do appreciate everyone on the VAF that has helped me troubleshoot this issue.

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Old 09-08-2013, 09:17 PM
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tkatc tkatc is offline
Join Date: Nov 2007
Location: NJ
Posts: 1,747

The Weldon pump can introduce air into the system even when it's off? I figure while cruising you don't have the electric pump on...
My ATC opinion is NOT an official FAA recognized opinion, so any advice you get from me is ONLY my opinion.

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Building an -8! (Fuse)
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Old 09-08-2013, 10:16 PM
Speeddog7 Speeddog7 is offline
Join Date: Apr 2010
Location: Plano, Texas
Posts: 42

In looking at the troubleshooting guide published by the manufacturer of the fuel servo (Bendix / Precision), they indicate that boost pumps can leak air (without leaking fuel) whether they are on or off. This is probably why my problem didn't seem to change whether the pump was operating or not. That said, I did not test the pump by using another pump to suck fuel THROUGH the Weldon pump to see if it continued to produce air. I might give that a try though,,, just for fun.
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Old 09-08-2013, 10:29 PM
jimgreen jimgreen is offline
Join Date: Apr 2006
Location: Vancouver island, BC Canada
Posts: 403

There are a lot of us following this thread, feeling very relieved for you!
You have shown a lot of tenacity. Well done.
Jim Green
RV7 tip up
IO360 Whirlwind 200RV
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Old 09-09-2013, 12:53 PM
Speeddog7 Speeddog7 is offline
Join Date: Apr 2010
Location: Plano, Texas
Posts: 42
Default Thanks

Thank you Jim. It's been a long road troubleshooting this issue. I just hope I'm truly at the end. I've "thought" it was fixed in the past only to discover later that it was just foolin' me. We'll see.
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