laytonl Posted December 27, 2017 Report Share Posted December 27, 2017 I had an engine hiccup today and welcome thoughts on the cause. I departured this morning on a trip in my ‘92 J. Run up, takeoff, and departure were normal, however just before reaching cruise altitude I left a slight vibration or engine stumble and glanced at the EDM 900. I noticed the #3 EGT was significantly higher than the others and the CHT was normal or maybe a little low. I leveled off and the problem persisted. I attempted to lean the mixture and the engine ran very rough. I turned back to the airport and when close to the airport I did a mag check which didn’t show anything unusual. On landing, with the power at idle, the EGTs were all normal but a quick run up caused #3 EGT to rise again. I took the plane to my mechanic. We first checked, tested, and cleaned the plugs. On run up the #2 cylinder was cold (CHT 80F, EGT 200F), all other cylinders were fine but I couldn’t run it up to full power due to the stumbling engine. Next we pulled the prop through and felt strong compression on all cylinders. We didn’t do a compression check though. We cleaned the injectors and did several run ups. All readings were normal. EGTs were all within 20 degrees of each other. We re-cowled and did one more run up before flying. All was still normal so I took off for a test flight. Takeoff and climb out were normal but after about 5 minutes the engine stumbled and #4 EGT went low as did #4 CHT. I retarded the throttle to land and the #4 values came back up. A full power run up on landing yielded the same low readings on #4. At this point it was dark and we were tired so we went home. Any ideas what is wrong? Lee Quote Link to comment Share on other sites More sharing options...
Marauder Posted December 27, 2017 Report Share Posted December 27, 2017 15 minutes ago, laytonl said: I had an engine hiccup today and welcome thoughts on the cause. I departured this morning on a trip in my ‘92 J. Run up, takeoff, and departure were normal, however just before reaching cruise altitude I left a slight vibration or engine stumble and glanced at the EDM 900. I noticed the #3 EGT was significantly higher than the others and the CHT was normal or maybe a little low. I leveled off and the problem persisted. I attempted to lean the mixture and the engine ran very rough. I turned back to the airport and when close to the airport I did a mag check which didn’t show anything unusual. On landing, with the power at idle, the EGTs were all normal but a quick run up caused #3 EGT to rise again. I took the plane to my mechanic. We first checked, tested, and cleaned the plugs. On run up the #2 cylinder was cold (CHT 80F, EGT 200F), all other cylinders were fine but I couldn’t run it up to full power due to the stumbling engine. Next we pulled the prop through and felt strong compression on all cylinders. We didn’t do a compression check though. We cleaned the injectors and did several run ups. All readings were normal. EGTs were all within 20 degrees of each other. We re-cowled and did one more run up before flying. All was still normal so I took off for a test flight. Takeoff and climb out were normal but after about 5 minutes the engine stumbled and #4 EGT went low as did #4 CHT. I retarded the throttle to land and the #4 values came back up. A full power run up on landing yielded the same low readings on #4. At this point it was dark and we were tired so we went home. Any ideas what is wrong? Lee Lee - December must be the month of "engine hiccups". I had one earlier this month as well. What plugs are you using? I had a similar issue with Champion massives that would intermittently fail. When you said your mechanic tested them, did he check to see what the resistance was for the plug? Paul from Savvy had me check this with the problem I had and it was showing a number of the plugs showing high resistance. One cylinder had both plugs that would intermittently fire causing a stumbling issue. Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 27, 2017 Report Share Posted December 27, 2017 Did you rotate any plugs? Do a baby jar test for fuel flow. Fuel pressure OK? Does boost pump fix it? Do you have the dual mag? 1 Quote Link to comment Share on other sites More sharing options...
kmyfm20s Posted December 27, 2017 Report Share Posted December 27, 2017 Funny I had the exact same thing. Run ups on the ground showed no real mag problems until I did several full power run ups with the mag. Replaced the mag and ran great. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 27, 2017 Report Share Posted December 27, 2017 1) Sounds to me, a fuel injector may be the challenge.... The baby food jar test showing the FF of each injector is going to possibly show something stuck in one of them. a partial blockage in one may cause excess flow showing up in the next. See if a run-up on the ground will show one EGT peaking before the rest.... If nothing shows, Lean some and repeat. Then lean a lot and repeat. Wait... Since you have cleaned the injectors already.... skip to number 2) If you have any screen shots of your JPI graphs from the last flights... this would be a good place to post them... 2) the intermittent nature of it also sounds like a mag, plug, wire issue... 3) Briefly... Cylinder #4 was running well until in Cruise. The flame went out, until the throttle was brought back and the flame came back on... MP of the good and bad events... RPM of the good and bad events... FF of the good and bad events... Hours on the mags? Time to post the JPI graphs if you have them, Lee. PP thoughts only, not a mechanic. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted December 27, 2017 Report Share Posted December 27, 2017 Check the point gap and internal timing. Quote Link to comment Share on other sites More sharing options...
cliffy Posted December 27, 2017 Report Share Posted December 27, 2017 When you cleaned the injectors did you mark them and put them back in the same cylinder they came out of? Same problem moved to another cylinder. Did you check fuel screens to see if "stuff" was coming down the fuel lines? Coke bottle test on the injectors? Just thinin' 1 Quote Link to comment Share on other sites More sharing options...
Sean S Posted December 27, 2017 Report Share Posted December 27, 2017 I see a problem with #3, then #2, then #4. This is a serious moving target. 1. Did the plugs get returned to their original position? 2. Did the injectors get returned to their original position? Try to make only one change at time to the systems for trouble shooting. With the problem moving around, it has to be something common to all the cylinders. Magnetos appear to be isolated, so my next step would be to check the fuel flow divider to make sure fuel is coming out of all the ports equally. 2 Quote Link to comment Share on other sites More sharing options...
neilpilot Posted December 27, 2017 Report Share Posted December 27, 2017 4 hours ago, Bayern Speed said: I see a problem with #3, then #2, then #4. This is a serious moving target. 1. Did the plugs get returned to their original position? 2. Did the injectors get returned to their original position? Try to make only one change at time to the systems for trouble shooting. With the problem moving around, it has to be something common to all the cylinders. Magnetos appear to be isolated, so my next step would be to check the fuel flow divider to make sure fuel is coming out of all the ports equally. Agree. I fought a similar, very intermittent problem for a couple years and it finally brought me down. Read last paragraph of NTSB N1310W. https://www.ntsb.gov/about/employment/_layouts/ntsb.aviation/brief2.aspx?ev_id=20120721X23053&ntsbno=CEN12FA463&akey=1 2 1 Quote Link to comment Share on other sites More sharing options...
cbarry Posted December 27, 2017 Report Share Posted December 27, 2017 Could it possibly be a fuel contamination issue? Are you getting any particulates (fuel tank sealer breaking down...) when you sump the tanks? When you cleaned the injectors, were any of them partially clogged? 1 Quote Link to comment Share on other sites More sharing options...
INA201 Posted December 27, 2017 Report Share Posted December 27, 2017 I had a similar problem. Take a look at this thread. It ended up being the fuel spider on top of the engine. While moving through the diagnosing of the problem we found Champion plugs with extremely high OHM resistance and replaced all with Tempest plugs, replaced all injector nozzles, and retimed the engine. There was also another thread that was similar ending up with it being the spider(also called flowdivider). Be careful in diagnosing before just flying around to test fly. After it was all said and done my engine has run great since. Neilpilot also had a scary issue. Quote Link to comment Share on other sites More sharing options...
FloridaMan Posted December 27, 2017 Report Share Posted December 27, 2017 There was an M20j crash as well that was caused by corrosion inside the fuel spider at the top of the engine. The high EGT makes me think it’s an ignition issue and could be related to altitude. If you fly it again, see how high you can go and if it returns. I know my old mags would start to misfire around 17,000ft. 1 Quote Link to comment Share on other sites More sharing options...
mike_elliott Posted December 27, 2017 Report Share Posted December 27, 2017 Just now, Antares said: I know my old mags would start to misfire around 17,000ft. non pressurized mags tend to do this Quote Link to comment Share on other sites More sharing options...
gsxrpilot Posted December 27, 2017 Report Share Posted December 27, 2017 I'm curious about the mag check you did in flight? Did you "normalize" the display on the EDM 900 first? Also were you running full rich or were you leaned out at all? I know you said that leaning seemed to make the problem worse. A "normalized" display and a mag check done while leaned, will quickly isolate the problem cylinder. Quote Link to comment Share on other sites More sharing options...
kmyfm20s Posted December 27, 2017 Report Share Posted December 27, 2017 1 hour ago, mike_elliott said: non pressurized mags tend to do this More so when they are bad. Quote Link to comment Share on other sites More sharing options...
laytonl Posted December 27, 2017 Author Report Share Posted December 27, 2017 Guys, thanks for the comments and suggestions. I’ll answer your questions as best I can in this post. 1. Plugs are all tempest and one year old. We cleaned and checked resistance on all. The plugs went back to their respective cylinders. We did a test run at this point and had the same problem but s different cylinder. 2. We did test the fuel flow (being from the South we use Dixie cups instead of baby jars!) and #2 and #4 had noticeably less fuel in the cups. 3. When removing the injectors we put them in individual baggies to keep separate and put them back in their respective cylinders. All test runs after this were perfect and was confident we had found the problem so I elected to make a test flight. After 5 minutes the problem returned but on a still different cylinder. 4. When I did the in flight mag checks it was full rich because the engine stumbled with any leaning. Neither the original or test flight were above 4,500 ft. It’s a 3000 dual mag and was overhauled 2 years ago. 5. The mechanic is out of town today so we will start back on the problem tomorrow. We both feel that it’s a fuel contamination issue of some sort and it is randomly clogging injectors. I called the mechinac who did the Annual (this past November) and he said the fuel screen was clean when they checked. Our plan is to open the fuel spider and also check the fuel screens for trash. 6. I tried the Electric boost pump on and off and didn’t see any difference. 7. I forgot to download the JPI data. I will do that tomorrow. 8. The engine was overhauled in 2009 - before I bought the plane in 2012 - and now has 800 SMOH. It has always been hangared and is very clean with no rust or corrosion visible. i appreciate everyone’s comments. Lee Quote Link to comment Share on other sites More sharing options...
DonMuncy Posted December 27, 2017 Report Share Posted December 27, 2017 It would seem unlikely to me that a bit or bits of foreign matter would migrate to different cylinder locations like that. I would be more inclined to think magneto. This from someone with no knowledge trying to apply logic. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted December 27, 2017 Report Share Posted December 27, 2017 It would seem unlikely to me that a bit or bits of foreign matter would migrate to different cylinder locations like that. I would be more inclined to think magneto. This from someone with no knowledge trying to apply logic. His original problem was high EGT #3, this is usually indicative of an ignition problem (spark plug not firing) and a low EGT is a plugged injector, so I’m with you, if moving around its the mag.But I have no expertise either (just reading JPI manual). Quote Link to comment Share on other sites More sharing options...
mooniac15u Posted December 27, 2017 Report Share Posted December 27, 2017 44 minutes ago, teejayevans said: His original problem was high EGT #3, this is usually indicative of an ignition problem (spark plug not firing) and a low EGT is a plugged injector, so I’m with you, if moving around its the mag. But I have no expertise either (just reading JPI manual). A partially clogged injector will usually give a high EGT because the cylinder is running lean. 1 Quote Link to comment Share on other sites More sharing options...
FloridaMan Posted December 27, 2017 Report Share Posted December 27, 2017 1 hour ago, mooniac15u said: A partially clogged injector will usually give a high EGT because the cylinder is running lean. I found my clogged injector a couple years back by leaning. If leaning while the problem is occurring causes the EGT to go up and then way down on the cylinder, it's fuel. I'd ground the airplane at least until inspecting the fuel spider if it were me. I'd ask an A&P, but I think that fuel spider is something that you can open and disassemble yourself, but I think it might be ok for the A&P to put it back together. Don't tear the diaphragm. Quote Link to comment Share on other sites More sharing options...
laytonl Posted December 27, 2017 Author Report Share Posted December 27, 2017 My first thought was a mag problem too. I did a mag check and couldn’t detect any change in the conditions. It was just a normal slight rise in all EGTs and a slight RPM drop. I could not do a lean mag check because the engine stumbled so badly when lean. As long as I ran full rich the only indication of a problem was a slight stumble and a high #3 EGT. I am interested in seeing the JPI data to see if it correlates with my recollection. Lee Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 27, 2017 Report Share Posted December 27, 2017 When doing the Dixie cup test... were you able to measure or weigh the difference? Or just visible? I am leaning more and more to something blocking the fuel upstream from the cleaned injectors themselves... 1) The problem is occurring at all times, but shows up during Leaning.... dissapears again after enrichening. The underlying problem remains... 2) doesn't seem to be a problem while being full rich... 3) Dixie cup test indicates two cylinders are leaner than the others... how much leaner...? 4) JPI data will show what is not working properly. 5) If it is a spark plug, EGT increases with one dead plug. It takes two dead plugs In a cylinder to really cool a cylinder... 6) if it were the airflow... The MP gauge would be showing funky data. Airflow interruptions to individual cylinder intakes is near impossible to make occur. Even more challenging to have show up on different cylinders... 7) Check to see if you have any rubber lined fuel hoses on the way to the injector system. These have been known to flake off sending rubber bits downstream to the spider... 8) Neal's description of a rubber bit in the spider is extremely interesting. 9) another thing that would/may cause air flow to a cylinder issue... sticking valves. A very JPI findable issue... and dental camera in the spark plug hole.... stuck valves don't move cylinder to cylinder... 10) ? PP thoughts that come to mind... not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted December 28, 2017 Report Share Posted December 28, 2017 A partially clogged injector will usually give a high EGT because the cylinder is running lean. But then it should be a small rise, ie stays below normal peak EGT, if already LOP it should drop, a spark plug problem will rise 75° or more, should be easily distinguishable. 1 Quote Link to comment Share on other sites More sharing options...
mooniac15u Posted December 28, 2017 Report Share Posted December 28, 2017 27 minutes ago, teejayevans said: But then it should be a small rise, ie stays below normal peak EGT, if already LOP it should drop, a spark plug problem will rise 75° or more, should be easily distinguishable. With a clogged injector it is usually impossible to run anywhere near lean of peak. You typically see elevated EGT on the affected cylinder when running full rich and that cylinder peaks very quickly when leaning. I have had two partially clogged injectors and both showed EGTs higher than normal. I don't recall exact numbers but I do remember it was obvious from the graph on the engine monitor. Quote Link to comment Share on other sites More sharing options...
takair Posted December 28, 2017 Report Share Posted December 28, 2017 Did you do the Dixie cup test again after cleaning injectors? You can also try the test without the injectors to see if it is upstream, just do it fast. When slumping your tanks, do you ever see particles? Degrading sealant can migrate. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.