[STEVE]

STEVE on February 5, 2023 at 11:14 pm #21821

Hi Vlad;
Thanks for getting back to me with your update.

The reason I asked if the P leads were correct is that many engines have an impulse coupling on the left magneto but not on the right magneto. An impulse coupling automatically does two things when starting, It retards the spark from 25 deg before top dead center (BTDC) the normal spark timing to about 5 deg BTDC; and it spins the magneto rapidly. This generates a hot spark. During start some magneto switches automatically disconnect the right magneto. If the P leads are not on the correct mag (there’s no way to know unless your mechanic disconnects one or the other P lead to determine is it’s “hot” or grounded when the key switch is on that mag. When the key is on the right mag position, the P lead on the left mag should be grounded-and vice versa..

Secondly, when a fuel servo comes back from a facility it must be adjusted for the correct idle mixture and speed for your engine. The settings the overhaul or checking facility will not automatically be correct for your engine.

Please check the P leads and set up the fuel system for the book parameters.

Please let me know how that goes.

Best,
Steve

[Vladimir Kostritsa]

Vladimir Kostritsa on February 3, 2023 at 9:58 am #21816

Hello Steve,

Thank you for a response.

The magneto was checked for magneto-to-engine timing first. Then mechanic send magneto to some shop (I do not remember the name right now but I can ask). In the shop the magneto was tested on the test bench. The shop returns the magneto back and say that “everything is within spec.”. It did not help. The servo (refurbished, installed with new (factory rebuild) engine) was send to Precision Airmotive LLC for testing. It also was returned with words “everything within the spec.”. After that I contact Lycoming product support (with my mechanic) and they say “check mag. first”… So, generally we are return to initial point. P leads is correct, of course. No significant rise of rpm when cut-off. Mechanic have checked it also. When started (it is really hard to start but it is possible some times), the engine works just great. Almost the same EGT/CHT for all cylinders, no rough engine, mags. looks good. Only one thing I have noted: by the instrument, Fuel Flow on the takeoff power is 26-27, but by engine manual is should be  24 max. 

Addendum: We send servo for test because:
– CFIs told when engine is not starting it looks like the engine become overflooding easily.
– Few times engine did not stop in mix. cut-off position. You need to push mix lever very hard all way down to stop the engine.

Vlad

[STEVE]

STEVE on February 2, 2023 at 10:55 pm #21815

Hi Vladimir;
When you say the magnetos were checked; do you mean they were checked for correct magneto-to-engine timing? Were they set to 25 deg before top dead center?
When you write the fuel servo was checked; please describe what you did. Thanks
Please check to see that the P leads are connected to the proper magneto. When the magneto switch is indicating R, the P lead to the left magneto should be grounded; and vice versa. If the P leads are not on the correct magneto, the engine will very hard to start.
I would start by making sure the idle speed and mixture is correct. The service manual describes what rpm to check the idle speed. When the engine is hot, at 1000 rpm, the rpm should rise approximately25 rpm when the mixture is pulled aft to shut down the engine.
It you don’t see or hear a rise, the mixture is too lean. If it rises more than 25 rpm, the mixture is too rich.
Keep adjusting the mixture and idle speed until they are correct. You will probably need to re set these adjustments when the weather gets hot again.
Check these items and let me know if any of these suggestions help.

Steve

[Vladimir Kostritsa]

Vladimir Kostritsa on January 30, 2023 at 5:19 pm #21804

Hello all,

My name is Vladimir Kostritsa, I am a maintenance officer for Santa Barbara Flying club.

We have problem with our Cherokee 6-300 N300DL. The problem is ‘engine hard start’.

Magnetos was checked, nothing wrong.
Fuel servo was checked, nothing wrong.

It looks like the engine get over flooded very easily. After few attempts dumping the gas from under the cowling. When engine is hot, the engine start more easily. If engine is cold, it is very hard to start the engine. One day it may not start at all, other day it may start after many attempts. Yet another day it may start after just couple of attempts. Looks like more warm air temperature, more easily it starts. 

The engine is about 150 hrs since factory overhaul. Battery is new, replaced with engine.

When started, engine is working just fine. The problem is the engine start intermittent.

I wonder if anybody experienced the similar problems. Or if anybody can recommend experienced mechanic (specialized for Cherokee 6 and Lycoming IO-540) in South California.

Thank you very much.