HIGH EGT & WON'T SHUT DOWN
in General Tech Discussion
13 years ago
Older 912UL (1997) with no air box and 138 hours total time on a Zenith CH701.
I knew the aircraft had carb problems when I purchased it so I overhauled both Bing 64 CV carbs. Needle jet is changed to 2.74 (it was running lean with a 2.76 even at position #4) and needle position at position #1. They appear to be functioning correctly (I synced mechanically and pneumatically) and I idle smoothly at 1800 RPM and it runs smoothly through the RPM range up to 5500. Idle air mixture screw is set at 1 1/4 turns (1 1/2 was too rich, I fly out of a 2100’ elevation strip). There is no dribbling from the carb overflow vent and the float levels are set level. I’ve got the prop (warp drive 68â€) set for 5500 on take off.
The #2 EGT (cyl. 3) runs high. It has run high since I purchased the aircraft. The probes are 68mm from the port (not 100 as the book says) and I checked to make sure the probes are grounded well (they are). I still get more than 100 degree split between right and left. The plugs look good (medium brown) with the #3 cylinder possibly a little whiter.
Usually the EGT is below the red line on takeoff and climb, but shortly after level off I can see temps over 1650 on the #2.
A differential compression check shows the weakest cylinder at 77 over 80 with the leakage around the rings (it was warmed up).
Any input on the EGT would be appreciated. Oh, and I did do an intake leak check by spraying starter fluid around the intake while it was running. No apparent leak.
Next issue. The last two times I have flow the aircraft the engine wouldn’t shut down completely. I could go to idle, shut one switch off a few seconds and then turn the key off (yes, it is a key switch) and it would kick over for 45 sec, to a minute. Once I even had to shut the fuel off to shut it down.
I check the ground at the switch, cleaned the grounding wires to the intake manifold and gapped the plugs at .26.
The second time is when I lowered the idle to 1800 from 2000 and it still does it. It does have a mag drop of approx. 400 on each side and when I do a mag switch grounding check taxiing out it appears to ground OK. Its the shutdown when it is hot.
Being an older engine it has both ignition modules on top of the engine (yes it has the ground wire service bulletin complied with and it is grounding well).
Sorry this post is so long. I’ve been dinking with this for 4 months now. I’ve picked up a lot of good information from this forum but I’m about at the end of my know how here. Any suggestion would be appreciated.
I knew the aircraft had carb problems when I purchased it so I overhauled both Bing 64 CV carbs. Needle jet is changed to 2.74 (it was running lean with a 2.76 even at position #4) and needle position at position #1. They appear to be functioning correctly (I synced mechanically and pneumatically) and I idle smoothly at 1800 RPM and it runs smoothly through the RPM range up to 5500. Idle air mixture screw is set at 1 1/4 turns (1 1/2 was too rich, I fly out of a 2100’ elevation strip). There is no dribbling from the carb overflow vent and the float levels are set level. I’ve got the prop (warp drive 68â€) set for 5500 on take off.
The #2 EGT (cyl. 3) runs high. It has run high since I purchased the aircraft. The probes are 68mm from the port (not 100 as the book says) and I checked to make sure the probes are grounded well (they are). I still get more than 100 degree split between right and left. The plugs look good (medium brown) with the #3 cylinder possibly a little whiter.
Usually the EGT is below the red line on takeoff and climb, but shortly after level off I can see temps over 1650 on the #2.
A differential compression check shows the weakest cylinder at 77 over 80 with the leakage around the rings (it was warmed up).
Any input on the EGT would be appreciated. Oh, and I did do an intake leak check by spraying starter fluid around the intake while it was running. No apparent leak.
Next issue. The last two times I have flow the aircraft the engine wouldn’t shut down completely. I could go to idle, shut one switch off a few seconds and then turn the key off (yes, it is a key switch) and it would kick over for 45 sec, to a minute. Once I even had to shut the fuel off to shut it down.
I check the ground at the switch, cleaned the grounding wires to the intake manifold and gapped the plugs at .26.
The second time is when I lowered the idle to 1800 from 2000 and it still does it. It does have a mag drop of approx. 400 on each side and when I do a mag switch grounding check taxiing out it appears to ground OK. Its the shutdown when it is hot.
Being an older engine it has both ignition modules on top of the engine (yes it has the ground wire service bulletin complied with and it is grounding well).
Sorry this post is so long. I’ve been dinking with this for 4 months now. I’ve picked up a lot of good information from this forum but I’m about at the end of my know how here. Any suggestion would be appreciated.
