Rough running/High EGT in Cylinder 2
Hello all
Any help/expertise/advice to assist with my problem would be greatly appreciated.
Rotax 912IS with Dynon Skyview: 300 hours.
No problems until recently when doing circuits and on climb-out Lane A solid warning light came on and Dynon Skyview annunciation "Land Aircraft" appeared. Didn't notice any roughness of engine operation at the time. Landed and shut down.
I have no access to a BUDS dongle.
Observations and investigations so far:
A. with both Lanes turned on and engine running: engine runs a little rough with cylinder 2 EGT rising immediately after starting, to reach approximately 170-200 F higher than the other three cylinders . Neither Lane A or Lane B warning lights come on and there is no Dynon Skyview annunciation of engine alerts/faults. If Lane A is turned off and Lane B remains on, the engine changes from running a little rough to normal/smooth operation and cylinder number 2 EGT reduces to the same as the other three cylinders within 15-30 seconds. If Lane B is turned off with Lane A remaining on, engine runs very roughly and cylinder# 2 EGT reduces quickly to zero.
B. With engine running, both Lanes turned on and cylinder # 2 rear fuel injector electrical connection disconnected: solid Lane A warning light on, smooth running and equal EGT of all cylinders. If Lane A is turned off there is no change of #2 cylinder EGT. If Lane A is turned back on and then Lane B turned off # 2 cylinder EGT reduces to zero and engine runs very rough.
D. fuel injector rail and injectors for cylinders 2 and 4 were removed and examined: resistance across terminals of all four injectors observed to be the same value using multi-meter and good spray pattern observed for each injector.
E. If the motor is cranked over with both Lanes turned on and fuel pumps off with both # 2 cylinder spark plugs removed and attached to high tension leads sparking is observed at the top spark plug but no sparking of the bottom spark plug. New spark plugs were then connected to high tension leads and the test repeated. Again no sparking of bottom spark plug was observed. When this test was repeated on #4 cylinder both spark plugs were observed to spark simultaneously.
F. Disconnecting high tension lead from top spark plug of #2 cylinder and engine cranked over: engine didn't fire.
G. Disconnecting high tension lead from bottom spark plug of # 2 cylinder: engine fires and runs as in A.
H. High tension lead exiting from top of Coil 1 ( labelled 'Coil 1T') connects to bottom spark plug of cylinder #2.
I. Spade terminals of the each positive and negative low tension wire into all coils were examined. They were all firm with no corrosion. Resistance was tested across positive and negative terminals of all the coils tested using a multimeter and observed to be the same for all coils.
J. Two new spark plugs were tried in # 2 cylinder simultaneously and made no difference.
My conclusion is there is an electrical problem resulting in no/poor spark at bottom spark plug of # 2 cylinder, but I have not isolated the cause. A new spark plug has been tried without benefit. The resistance between the positive and negative low tension terminals of Coil 1T is observed to be the same as the other Coils ( however I don't know if this is a valid test for testing the integrity of the coil).
Thanks
George
