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PRINTABLE
VERSION
IMPORTANT NOTES: THIS
DIAGRAM REPRESENTS ONLY ONE POSSIBLE STARTER WIRING
SCENARIO. THERE ARE OTHERS.
DO
NOT USE THIS DIAGRAM AS GUIDANCE FOR INSTALLING YOUR
STARTER!
Installation information is ALWAYS included with each starter
and can also be found on the product specific pages of
this website (listed in blue blocks above left).
Also,
DO NOT REMOVE THE STARTER FROM THE AIRCRAFT TO PERFORM TESTING! For accuracy and relevance, starter testing should be conducted in the aircraft while the starter is in its failure
mode (start switch/button "on" but starter
performance is not pleasing you).
Do NOT use jumper cables,
a friend's battery, or auto store battery testers to test
aircraft starter systems. It never provides
valuable/constructive troubleshooting information.
Use an analog voltmeter if at all possible. An ohmmeter will not provide useful information - keep it simple & follow these easy steps:
Pretest Considerations: If possible, visually inspect the starter and/or interview pilot/operators for starting history. Indications of long cranking periods, burning odor or smoke from the starter, kickback(s), a cracked starter mount, a fast spinning starter w/no prop movement
(for Sky-Tec NL model starters replace shear pin), oil in starter, grinding noise or a damaged ring gear are generally indications that the starter is in need of repair and the following tests will not be helpful. Remove the starter for repair or overhaul (the NL model starter shear pin is FIELD REPLACEABLE - do not return to Sky-Tec for shear pin repair).
Testing Relevance: The following testing procedure is most relevant to Lycoming starters and some Continental starters that are low performing including slow cranking and/or failure to crank the engine over a compression stroke. If a starter is damaged by overcranking or a stuck firewall solenoid, voltage in step one may read below acceptable levels thus incorrectly indicating a potential battery problem. Therefore, in such cases some consideration must be to the pretest conditions noted above (if it smells burned...). If the only effect of energizing the starter results only in an audible “click” with no prop movement, confirm step 2 to isolate problem to starter or starter contactor.
For Sky-Tec CvST3 (Continental) model starters: Sky-Tec CvST3 starters feature an inspection port. If starter rotates but prop does not, remove inspection plug and note clutch drum rotatation. If rotation is observed, starter is OK - suspect starter adaptor.
Start Here:
|
TEST |
RECORD |
RESULT |
ANALYSIS |
|
Record voltage at the battery while cranking
the starter in its failure mode. |
______
VOLTS |
Below
11V / 22V? |
Yes
- Voltage at battery drops below 11V / 22V?
Questionable battery. See Testing Relevance above as a
shorted (cooked) starter will pull voltage down
appreciably. However, if starter rotates at all, this is
generally not a shorted starter condition.
Address battery issue - no need to proceed with
remainder of troubleshooting.
No - Voltage at battery
remains above 11V / 22V?
Proceed to Step 2
|
|
Record voltage at the starter while cranking
the starter in its failure mode. |
______
VOLTS
|
Below
10V / 20V? |
Yes
- Voltage at starter drops below 10V / 20V?
Not a starter problem. The starter needs 10V
/ 20V to do its thing. Below that, all bets are
off. Suspect Cables, terminals and/or
solenoids. Or maybe that airframe just isn't up to
the task.
If the difference between Step 1 and
Step 2 is more than 2 volts, Proceed to Steps 3
& 4 to find airframe voltage losses.
No - Voltage at starter
remains above 10V / 20V? And the starter's performance
is not pleasing you?
Click here to return
the starter to Sky-Tec for analysis/repair. There
is nothing more you can do.
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OPTIONAL
AIRFRAME VOLTAGE TROUBLESHOOTING
(Perform only if battery remains above 11V / 22V in Step
1 and starter receives less than 9V / 18V in Step
2) |
|
|
|
|
Record
voltages between each and every cable
terminal and across solenoids while
cranking the
starter in its failure mode.
|
Assuming
the voltage difference noted in Step 2 exceeded 2V / 4V,
flush out any appreciable loss in voltage in any cable
or solenoid by placing the meter along each link in the
diagram. A tight electrical system will lose no more
than 0.5 volts between the battery and starter. Be sure
to conduct these tests while cranking the starter in its
failure mode (when it's powered but not pleasing you). |
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|
|
|
Record
voltages between battery & ground
and starter & ground while
cranking the starter
in its failure mode.
|
If no appreciable loss of voltage is noted in Step 3, flush out the integrity of all electrical system grounds. Pay close attention to battery and engine grounds. Clean up or repair any questionable ground connections and re-test. |
Returning a Starter
to Sky-Tec
After you've completed the troubleshooting process and
determined the starter needs servicing, click
here to obtain a Return Authorization number
online.
Common
Complaints and Credible Culprits
|
Complaint |
Question |
Culprit |
The
Bump & Run |
When
starter engages, the prop moves (some distance), and
then stalls on the first compression stroke. After
repeated attempts, starting is successful (usually). |
Does
it happen any more (or less) when the engine is hot? |
Voltage.
Rarely a starter issue. Sky-Tec starters do not have
a "weak" state. Provided sufficient
voltage, they either work great
or don't work at all. Typically, this slowing of the
cranking is a sign of a loss of voltage. If it
happens when hot, suspect bad cables or solenoids.
If it happens when cold (or always), suspect a bad
battery. But the Troubleshooting
Test (above) can help isolate the voltage loss. |
The
Bump & Grind |
When
starter engages, it makes a terrible
"grinding" noise. |
Has
the engine ever had a kickback
when cranking? |
A
spark before Top-Dead-Center while cranking will break
starters (and other accessories as well). In the
case of old, heavyweight starters, kickbacks broke teeth
off the ring gear. Sky-Tec LS/PM & HT starters
(excl. HTI starters) are designed to break when an
engine fires before top-dead-center during
cranking. In some cases, they bend instead of
breaking giving the illusion that they're up to the task
but the grinding noise is an indicator not everything is
well. Fix the ignition problem then send
that starter in for a repair. |
Clicks
& Crickets |
When
we attempt to engage the starter, we hear a
"click" but NOTHING happens |
Run
the Toubleshooting Test
(above)
What
is the voltage while cranking at the starter? |
If
the starter is not getting voltage, suspect the
aircraft's firewall solenoid or switch.
If the starter is receives >10V / 20V, suspect the starter's on board
solenoid has failed (if so equipped). Send
that starter in for a new solenoid. |
Clicks
& Crickets with the smell of burned metal |
When
we attempt to engage the starter, we hear a
"click" but NOTHING happens. |
Smell
your starter (hey, dogs do far worse). Does it
smell burned?
Does the battery
pull down excessively when you energize the starter?
|
Well,
a fried starter is caused by one of three things:
1) The switch
failed and held closed even when released (kept the
starter solenoid/starter engaged for a period of time
that exceeded the published operating
limitations).
2) The firewall
solenoid stuck/welded for a period of time that exceeded
the published operating
limitations,
or
3) The yoke actuator (pilot/operator) held the starter
switch on in excess of the published operating
limitations,
You best send
that starter in for a repair.
|
Don't
Let Go |
After
start button is released, the starter stays engaged for
nearly a second before releasing. |
Does
it stay engaged only for 1/2 to 2 seconds? |
This
is normal operation for a permanent magnet starter
(Sky-Tec LS, PM, & ST2, ST3 and ST5, models).
Although power is removed by releasing the key/start
button, a permanent magnet motor will actually provide
power to itself as it winds-down and will keep the
starter drive engaged for about a half-second until it
loses sufficient RPM to fully disengage. Normal! |
Hang
'em High |
It
appeared as though the starter drive gear stayed engaged
for some length of time after the start button/key was
released |
Did
you see smoke? Does the starter smelled like burnt
metal? |
A
stuck firewall solenoid (starter contactor) can ruin
your day AND your starter. Many older Cessna
and Piper aircraft starter contactors are notorious
for "welding shut" after years of use (often
accelerated by the use of a high-current draw
starter). Some of those older contactors (or
relays as the case is) just cannot handle the increased
starting current loads over a length of time. In
some cases, the manufacturer even specified the wrong
kind of starter solenoid in the application in the first
place (see Cessna
Firewall Solenoids). You may have few options besides
overhauling or replacing your starter after
replacing the culprit firewall solenoid. |
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Rd Granbury, Texas 76048
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