INA201 Posted January 1, 2016 Report Posted January 1, 2016 After an hour flight doing touch and goes, and flying around the Blue Ridge Mountains on a beautiful severe clear day the story begins. I was on my way south descending into my home airport pattern when the EGT and CHT on cylinder #1 slowly progressed downward to zero, followed by a rough engine, and an intensified "close in final", and ironically the best of the six landings for the day. Taxiing in, the #1 remained cold until shutdown. Oh well, exhaust valve? Mag? Induction? A friend and I pulled the plugs on #1 to inspect, put them back in, and ran the engine. Doing a mag check as well, everything appears appropriate and normal initially. Now #2's EGTs begin rising while the other cylinders #s appear normal and then the #2 goes cold, engine begins running rough, a little backfiring etc., so we shut her down. My friend is thinking I'm crazy and that it was cylinder #2 that went cold in the first place. I begin thinking, hmmm this is quite possible because after all I was under duress. We find a mechanic and do a hot compression test with 78, 76, 74, 80 as the result. We pull the valve cover on #2 and all looks well and good rotating through a few strokes. Pull the injector on #2 and it is clean. Put good plugs on #2 and its time to try again. Same result, the engine starts up, runs smooth for a bit, mags work separately, EGT on #2 rises and then goes to zero. There's some backfiring with noticeable flames coming out of the tailpipe(it's dark by now). I'm done for the day! A couple days later we inspect for induction leaks, install new Tempests all the way around(recommended as a possibility) and go for another run up. Wow, quick start up, numbers coming up evenly, mag checks looking good, leaning raises EGTs appropriately, and then........#4 goes cold. Roll the plane in for a bit and try again later. Now #4 doesn't even fire off. Also cold to the touch. At this point I'm back to confirming that #1 was down in the first place. Done again for the day! Has anyone heard of such? "Random cold cylinder disorder?" I've looked at troubleshooting and can't find anything that resembles this situation. Fuel pressure is good btw. We have not checked timing, leads, or the fuel injection system other than the nozzles yet. It acts like a mag, which this one on the 78'J is the dual. The mag issue is that the whole cylinder goes down. Different cylinders go cold with both left and right mag settings continuing to run the "Hot" cylinders. My mechanic wants to check the fuel system on Monday. I will update this thread when we know more. Happy New Year! Quote
Andy95W Posted January 1, 2016 Report Posted January 1, 2016 I'll throw out a guess at the fuel distribution unit on top of the engine ("spider"). Quote
carusoam Posted January 1, 2016 Report Posted January 1, 2016 Things that come to mind.... 1) fuel 2) air 3) spark (and timing or loose/worn mag) 4) compression Seems like you have identified a few things already. Is something somehow blocking the fuel or air trying to get to the engine? Is something keeping the plugs from firing? (Ground straps not connected) how much time since OH on what kind of mag do you have? For each screen or filter you change, open it up and collect anything that falls out for later identification... These are questions of a PP, not a mechanic. Best regards, -a- Quote
gsengle Posted January 1, 2016 Report Posted January 1, 2016 I've had that symptom twice once lyc once cont. one was spalled cam causing intake lifter to not open enough -> overhaul time... The other time was a blocked injector. Have you cleaned your injectors? Sent from my iPhone using Tapatalk Quote
carusoam Posted January 1, 2016 Report Posted January 1, 2016 1) Checking fuel flow and distribution is somewhat easy. Requires 4 identical glass jars and a timer... Their is a typical gun solvent that is often used Hopps(?) 2) checking the lift on the intake valve may be easy for a mechanic. How many hours since MOH. 3) Checking valve health for wobble and carbon build-up. Think stuck exhaust valve when going this way. Really thinking a stuck valve (partially open or partially closed) can cause problems upstream that may show up in the next cylinder in line. My stuck exhaust valve experience in an O360 came with terrible vibration and horrible lack of power. The valve contacted the piston... Best regards, -a- Quote
Yetti Posted January 1, 2016 Report Posted January 1, 2016 I vote mags. Possibly spark harness. What does the fuel pressure leak down check show? 1 Quote
mike_elliott Posted January 1, 2016 Report Posted January 1, 2016 Have your A$P do a valve wobble test on #2 if you don't find anything with the spark or fuel to #2. With it going cold, it very well could be a valve sticking open once up at temp. This happens when CHT's get too hot and cokes the oil on an exhaust valve stem in a Lyc. 360. IF you have an engine monitor, download the data and it should tell you what the heck is happening. Quote
rbridges Posted January 1, 2016 Report Posted January 1, 2016 I'm interested to see what the culprit is. With it changing cylinders, I'm kinda stumped. Quote
Browncbr1 Posted January 1, 2016 Report Posted January 1, 2016 Take all the injectors off and put the end of the lines so they pour into solo cups. Turn on electric fuel pump. Have someone outside and tell you when to turn off so that the cups are about halfway full. Verify each cup is evenly full and without contamination / debris. Do this a few times. Quote
INA201 Posted January 1, 2016 Author Report Posted January 1, 2016 (edited) Thank you guys for your input on this. The other three cylinders operate in what appears to be a normal fashion while only one is cold during each individual run up. Each mag R and L will continue to operate engine even when one cylinder goes cold. Engine time is 800+- on a 2003 rebuild. Mag has 955 total hours (2002)and 270 since 500 hour(2010). Fuel servo rebuilt in 1985. Haven't done an OHM check on wiring harness, yet, but will regardless of other findings. One of the Champions had 54,000 ohms(cylinder 3), others tested fine. New Tempests now though. Engine ran very well prior to this, great power, smooth, etc. No visual airflow or intake restrictions. Hopefully doing leak down check, flow test, clean injectors, and inspect spider Monday. The thing that makes me predict ignition is that it will start and run normally then one of the cylinders goes down once the engine warms up. Could the mag be rigged up some weird way? It is definitely a strange issue. Edited January 1, 2016 by INA201 Quote
Yetti Posted January 2, 2016 Report Posted January 2, 2016 Exhaust valves coked. Ream all Exhaust valves with .494 Ream. Rope trick, http://www.caa.si/fileadmin/user_upload/pageuploads/AD-NOTE/AD-2006/093_sb_SB388C.pdf 1 Quote
INA201 Posted January 2, 2016 Author Report Posted January 2, 2016 Yetti, certainly could be valves. I looked through the SB and my logs and no mention of the tests being performed. Looks like a test that should be done regardless of my current situation. I have had no morning sickness or signs of sticking valves to this point which leaves me still open to ignition and fuel as well. Quote
Shadrach Posted January 2, 2016 Report Posted January 2, 2016 31 years is a long time for a servo to go unopened. I'd send that out for OH just on GP. It's inexpensive in terms of aviation. 1 Quote
carusoam Posted January 2, 2016 Report Posted January 2, 2016 My stuck valve occurred on on take off. About 500' agl with my flight instructor on board. First 10 hours dual after purchase... No other signs were indicated. Without the physical damage, there would be no signs. I got to purchase a new cylinder assembly after that. Spend a few bucks now, you are authorized... It is good to have a JPI, or other. Best regards, -a- Quote
FloridaMan Posted January 2, 2016 Report Posted January 2, 2016 I'd look at the spider. There was a J totaled with injuries where there was corrosion inside the spider that caused a failure on takeoff. Your symptoms sound like a clogged injector, except it's changing cylinders. Do you have the dual magneto? Have you tried switching mags when this is happening? Quote
Browncbr1 Posted January 2, 2016 Report Posted January 2, 2016 (edited) 10 hours ago, Shadrach said: 31 years is a long time for a servo to go unopened. I'd send that out for OH just on GP. It's inexpensive in terms of aviation. +1. Should be about $200. Shortly after I bought my plane, I experienced a partially plugged injector shortly after takeoff. So, I had my entire fuel delivery system rebuilt after we found debris kept coming through the lines. The cost to overhaul the servo, pump, and spider was $1200. I consider this as cheap life insurance and a bargain for peace of mind, knowing what you have under the cowl. If you have any debris in the fuel, I recommend doing this and overhaul the gascolator. Some will argue to overhaul the fuel selector also. Oh yea, I forgot. When you are pumping fuel into the solo cups like I posted earlier, toggle the fuel selector valve back and forth continuously, as it will help break up any debris that may be collected in the valve. Edited January 2, 2016 by Browncbr1 Quote
Yetti Posted January 2, 2016 Report Posted January 2, 2016 If you pull the engine through by hand when cold do any of the cylinders feel "soft" Quote
mooniac15u Posted January 2, 2016 Report Posted January 2, 2016 The backfiring suggests that fuel is getting to the cold cylinder but not igniting. Quote
INA201 Posted January 2, 2016 Author Report Posted January 2, 2016 Yetti, I will pull the prop through this afternoon and see. Brown and Antares, I've had the fuel selector rebuilt, and replaced the engine driven fuel pump recently. Should I have the gascolator, servo, and spider rebuilt if all of the testing leads to ignition issues? Is the fuel distribution an on condition or go ahead and do it regardless situation? $1200 seems pretty reasonable. I was thinking it would be 3AMUs all in. Was that recent from a local shop or did you send it off? Dual mags BTW. Carusoam, I've got a JPI700. The JPI and touching the cylinder has really helped confirm the weird cold cylinder situation. Mooniac15u, It does appear that fuel is getting to the cylinders based on the backfiring and visible flame when it's dark. I'll post my cold prop pull through later on today. Certainly hope to have more facts on Monday. Quote
rbridges Posted January 2, 2016 Report Posted January 2, 2016 If it were an older car, I'd say it's a bad distributor. It's almost like a cylinder loses the spark. I'm assuming gas and air are getting to the cylinder based on the backfire. I'm just not sure how both plugs would go cold since they come from opposite magnetos. Quote
carusoam Posted January 2, 2016 Report Posted January 2, 2016 Send JPI files over to... Savvy analysis.... See current thread regarding... Savvy http://mooneyspace.com/topic/17356-my-engine-is-talking-to-me-and-im-finally-listening/#comment-250495 How does that sound? -a- Quote
DonMuncy Posted January 2, 2016 Report Posted January 2, 2016 I would discount the probability of valve or cylinder problems. Highly unlikely to have one of these problems switch cylinders affected. That leaves fuel or spark. Although it is possible for something to be going on intermittently in a mag, I think it is a little unlikely to move from one cylinder to another. I think debris in the spider which could float free between start-ups and lodge in another orifice is the highest probability. That is where I would look first. But remember, when you hear hoof beats, sometimes it is a zebra. Quote
Shadrach Posted January 2, 2016 Report Posted January 2, 2016 It does seem like an ignition issue. Do you have the "Dual Mag"? 1 Quote
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