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andy(at)suncoastjabiru.co
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 Posted: Tue Jan 17, 2006 2:16 pm Post subject: Cold weather starting and starter current |
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At last week=92s Sebring Sport Aviation Expo, we endured a couple of very
un-seasonably cold (for Florida!) mornings, and one or two of the many
Jabiru-powered aircraft there were reporting cold-starting issues. All were
eventually traced and fixed, but it=92s probably a good time to remind owners
of the need for good connections and a low-resistance path for the starter
current.
Unlike other aircraft engines where the impulse-magneto retards the ignition
for starting, the Jabiru has fixed-ignition so needs to be spun quickly to
energize the ignition units (coils) for a reliable spark. Colder conditions
will mean thicker oil (more engine friction), the fuel doesn=92t vaporize as
readily in the carburetor and the battery=92s ability to deliver the necessary
starter power is diminished. If the installation also has some
short-comings, it can (and does) mean the difference between a good start
and no-start at all. Here=92s some pointers, with apologies to those who
already know this stuff:
1. On the initial turn-of-the key or press-of-the-button the starter
will take almost 700 Amps from the battery. Once the engine is spinning on
the starter, (i.e. after about 1 rev of the crank) the current drops to
about 400 Amps. We recommend the Odyssey PC625 battery because it has a high
level of CCA (cold cranking amps=3D625). Not many other types of battery will
do this for the same size and weight. The thick orange cable attached to
the starter is the right gauge to carry this starter current; if your ground
/ return from the engine to the battery is less diameter than this orange
cable you will restrict the current when starting. For this reason, we carry
this cable by the foot in our store as well as the appropriate
swage-or-solder-on lugs. The connections of this starter and ground circuit
are equally important; if the engine won=92t start after spinning it over,
isolate the ignition and feel by hand the various connections at the battery
/ starter solenoid and the ground connection. If there is heat in a joint it
needs either tightening or re-making. In the later Denso (silver) starter,
any lack of tightness in the two retaining bolts means a poor ground-return.
I admit I hadn=92t spotted this until last weekend; the starter has rubber
seals between each of its major parts so it is clear that the bolts which
secure it to the engine=92s backplate are carrying a large proportion of the
starter current. Check tightness or even add an additional grounding strap
from the starter=92s free-end to the engine mount plate.
2. Other ignition-related cold-starting issues are pretty well-known:
check for spurious grounding of the ignition =91stop=92 leads (some call them P
leads); both Pete and I have experienced issues with faulty ACS ignition
switches. I remember stripping, cleaning and rebuilding one (watch for
flying springs and contacts!) and solved the problem but they are not
perfect. If you suspect the switch or leads to the coils, disconnect the
leads at the coils and try restarting. If it starts OK, you know where to
look but be prepared to stop the engine with the fuel shut-off! Spark plugs
rarely give problems if gapped (0.022=94 =96 0.024=94) if they are un-fouled with
lead and haven=92t previously been blasted-clean. Don=92t clean plugs, replace
them. NGK=92s iridium DR9EIX gives longer life and (I=92m told by Jabiru)
smoother running and response but I=92ve yet to try them. Coil gap with
flywheel (magnet pole-faces) should be 0.010 but rarely needs adjusting
unless disturbed. Condensation or carbon-dust from the central button inside
the distributor cap(s) will cause ignition issues but fairly rarely. Change
caps and rotors at 250 hours max. Spark plug leads last very well unless
exposed to the elements as per an un-cowled installation (pusher, etc) or
allowed to rub-thro=92 on the engine, so check them for cracking and/ or
rubbing every 50-hours.
3. Fuel supply: the =91enrichening=92 or choke circuit in the carby won=92t
work unless the throttle is closed fully. A high idle speed set by the
throttle-stop screw has been known to hold-off the choke. The enrichener
gets its fuel from the brass dip-tube which pulls fuel from a tiny jet at
the bottom of its tube in the float-bowl. This jet can get clogged by debris
or more likely the presence of water in the bowl which corrodes the aluminum
and bits clog the jet. When you have the float bowl off, try blowing down
the tube in the corner of the float bowl to check the jet. If you prefer a
primer (I can see why you might!) use the nipple on the bottom of the carby
next to the idle mixture adjusting screw; remove the blanking screw and
attach the primer line. The idle-mixture air screw should be about 1 turn
open. Richen the idle mixture by screwing it in, lean by opening. Adjust by
no more than =BC turn at a time. Old fuel in the tank has lost some of its
=91go=92 so try to ensure in cold weather you have a good fresh supply of gas.
Avgas at 100 octane will start better in the cold than the same-age car-gas
at 90-something. Give the engine a fighting chance by pulling the prop.
through a few blades with the throttle closed, choke on and fuel boost pump
on and switches OFF. This helps to reduce the friction in the engine and
induces some fuel/air into cylinders. Especially when you might be
frustrated and thinking hard about why your engine isn=92t starting BE SAFE
and respect the propeller as if it=92s live unless you know for sure it isn=92t.
Above all, don=92t keep spinning the engine on the starter hoping it will
eventually fire; with a Jabiru, if it=92s not going in a couple of revs, then
you=92re only adding to the problem by having a dead battery.
Hope this helps,
Andy
Suncoast Sportplanes, Inc.
39248 South Ave. Zephyrhills, FL 33542
Tel: 813 779 2324 Fax: 813 779 2246
www.suncoastjabiru.com
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mhcrowder
Joined: 10 Jan 2006
Posts: 42
Location: Cary, NC
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| Posted: Wed Jan 18, 2006 6:19 am Post subject: Re: Cold weather starting and starter current |
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Andy,
Some of the formatting didn't come through quite right in your message. Looks like apostrophes, quotation marks, and I am guessing greater than/less than didn't get translated. Since this is information I plan to put into my "saved" file, can you repost with these items cleaned up?
Thanks,
Michael Crowder
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lgingell
Joined: 10 Jan 2006
Posts: 50
Location: Lake California Airpark 68CA
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| Posted: Thu Jan 19, 2006 9:27 am Post subject: Re: Cold weather starting and starter current |
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The =92 and =91 are replacements for the " marks (quotes). I suspect Andy composed this in Microsoft Word, and pasted it in. Word (and many other applications) take the straight quotes " and turn them into 66's and 99's to make it "proper". There's a few other ones in there that I couldn't guess!
Cheers,
..lance
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Zodiac XL/Jab 3300
http://lancegingell.com |
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Andy Silvester
Joined: 10 Jan 2006
Posts: 18
Location: Marica, Rio de Janeiro, Brazil
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| Posted: Thu Jan 19, 2006 10:10 am Post subject: Re: Cold weather starting and starter current |
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Sorry about the spurious characters; I must make sure to compose the message here and not in Word in future! Here's (hopefully) the cleaned-up version (I can't get the line lengths consistent!):
At last week's Sebring Sport Aviation Expo, we endured a couple of very
un-seasonably cold (for Florida!) mornings, and one or two of the many
Jabiru-powered aircraft there were reporting cold-starting issues. All were
eventually traced and fixed, but its probably a good time to remind owners of the need for good connections and a low-resistance path for the starter current.
Unlike other aircraft engines where the impulse-magneto retards the ignition for starting, the Jabiru has fixed-ignition so needs to be spun quickly to energize the ignition units (coils) for a reliable spark. Colder conditions will mean thicker oil (more engine friction), the fuel doesn't vaporize as readily in the carburetor and the battery's ability to deliver the necessary starter power is diminished. If the installation also has some short-comings, it can (and does) mean the difference between a good start and no-start at all. Here's some pointers, with apologies to those who already know this stuff:
1. On the initial turn-of-the key or press-of-the-button the starter
will take almost 700 Amps from the battery. Once the engine is spinning on the starter, (i.e. after about 1 rev of the crank) the current drops to
about 400 Amps. We recommend the Odyssey PC625 battery because it has a high level of CCA (cold cranking amps=625). Not many other types of battery will do this for the same size and weight. The thick orange cable attached to the starter is the right gauge to carry this starter current; if your ground / return from the engine to the battery is less diameter than this orange cable you will restrict the current when starting. For this reason, we carry this cable by the foot in our store as well as the appropriate swage-or-solder-on lugs. The connections of this starter and ground circuit are equally important; if the engine won't start after spinning it over, isolate the ignition and feel by hand the various connections at the battery / starter solenoid and the ground connection. If there is heat in a joint it needs either tightening or re-making. In the later Denso (silver) starter, any lack of tightness in the two retaining bolts means a poor ground-return.
I admit I hadn't spotted this until last weekend; the starter has rubber
seals between each of its major parts so it is clear that the bolts which
secure it to the engine's backplate are carrying a large proportion of the
starter current. Check tightness or even add an additional grounding strap from the starter's free-end to the engine mount plate.
2. Other ignition-related cold-starting issues are pretty well-known:
check for spurious grounding of the ignition 'stop' leads (some call them P
leads); both Pete and I have experienced issues with faulty ACS ignition
switches. I remember stripping, cleaning and rebuilding one (watch for
flying springs and contacts!) and solved the problem but they are not
perfect. If you suspect the switch or leads to the coils, disconnect the
leads at the coils and try restarting. If it starts OK, you know where to
look but be prepared to stop the engine with the fuel shut-off! Spark plugs rarely give problems if gapped (0.022" - 0.024") if they are un-fouled with lead and haven't previously been blasted-clean. Don't clean plugs, replace them. NGK's iridium DR9EIX gives longer life and (I'm told by Jabiru) smoother running and response but I've yet to try them. Coil gap with flywheel (magnet pole-faces) should be 0.010 but rarely needs adjusting unless disturbed. Condensation or carbon-dust from the central button inside the distributor cap(s) will cause ignition issues but fairly rarely. Change caps and rotors at 250 hours max. Spark plug leads last very well unless exposed to the elements as per an un-cowled installation (pusher, etc) or allowed to rub-thro' on the engine, so check them for cracking and/ or rubbing every 50-hours.
3. Fuel supply: the 'enrichening' or choke circuit in the carby won't
work unless the throttle is closed fully. A high idle speed set by the
throttle-stop screw has been known to hold-off the choke. The enrichener
gets its fuel from the brass dip-tube which pulls fuel from a tiny jet at
the bottom of its tube in the float-bowl. This jet can get clogged by debris
or more likely the presence of water in the bowl which corrodes the aluminum and bits clog the jet. When you have the float bowl off, try blowing down the tube in the corner of the float bowl to check the jet. If you prefer a primer (I can see why you might!) use the nipple on the bottom of the carby next to the idle mixture adjusting screw; remove the blanking screw and attach the primer line. The idle-mixture air screw should be about 1 turn open. Richen the idle mixture by screwing it out, lean by closing. Adjust by no more than 1/4 turn at a time. Old fuel in the tank has lost some of its 'go' so try to ensure in cold weather you have a good fresh supply of gas. Avgas at 100 octane will start better in the cold than the same-age car-gas at 90-something. Give the engine a fighting chance by pulling the prop. through a few blades with the throttle closed, choke on and fuel boost pump on and switches OFF. This helps to reduce the friction in the engine and induces some fuel/air into cylinders. Especially when you might be frustrated and thinking hard about why your engine isn't starting BE SAFE and respect the propeller as if it's live unless you know for sure it isn't.
Above all, don't keep spinning the engine on the starter hoping it will
eventually fire; with a Jabiru, if its not going in a couple of revs, then
you're only adding to the problem by having a dead battery.
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
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Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
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| Posted: Thu Jan 19, 2006 11:30 am Post subject: Cold weather starting and starter current |
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Andy, when you originally sent this, on Jan 17, I got it perfectly. But
there was a second posting that came through with the goofy punctuation
marks (a neighbor who saw it said it was HTML encoded). Has this
anything to do with the Matronics vs. Yahoo thing?
Lynn
On Thursday, January 19, 2006, at 01:10 PM, Andy Silvester wrote:
| Quote: |
<info(at)suncoastjabiru.com>
Sorry about the spurious characters; I must make sure to compose the
message here and not in Word in future! Here's (hopefully) the
cleaned-up version (I can't get the line lengths consistent!):
(original deleted by Lynn to save space)
|
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
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