SonexBuilders.net

My plane is very sensitive about its starting procedure. On a cold engine, first start of the day, you got maybe 20-30 seconds worth of cranking before the battery is too weak to turn the engine over fast enough to ever start. ( Jabiru 3300 )

I probably should have a larger battery in it, it currently has a Odyssey 625 in it, brand new matter of fact, But a bigger battery would require a new box, and would add more weight so I would like to keep the smallish 625.

Too many times since I bought this plane I have had to use jumper cables to the car to get it going. I could live with that if I could easily access the battery, but pulling the cowl is a PITA.

Wondering if anyone has figured out a practical easy way to jump start one without pulling the cowl.

One idea a buddy gave me was to buy something like this, and extend the leads long enough to pass through the firewall into the cockpit, install the ends of the leads with eyelet type connectors to the battery, then if needed, can just access the other end of the cord in the cockpit, plug in the booster box and jump it off and then disconnect once running and stow it in the luggage area or leave in the hangar. Your thoughts?

https://www.amazon.com/dp/B07MJBDD5K/re ... HJ1ZQ&th=1

I always carry one of those jump packs with me in my plane and check it every month to make sure it is holding a full charge. You can run wires through the firewall, which is the most convenient way to actually use the jumper if you need to, or you can fix a jumper wire to a place that you can reach it under the cowl, maybe near the gear leg, and just attach the jump pack or charger to it when needed.

I have done it both ways.

I mounted an Anderson plug to the gear leg bracket its flush with the bottom of the cowl. Its mainly used as a charging port but I have used it as a jump starter on a couple of occasions. Sorry its not a great photo of the bracket itself, the bracket is made from left over 6061 angle

Steve
Sonex 892

This is what I did to plug in a trickle charger. I have a matching wire/plug that has alligator clips on the other end to attached to an external battery. With the connector inside the cowl, when I take the cowl off the connector easily disconnects itself. When I put the cowl back on I just reach down and plug the two ends together.

http://www.mykitlog.com/users/display_l ... 107&row=61
http://www.mykitlog.com/users/display_l ... 069&row=57
http://www.mykitlog.com/users/display_l ... 070&row=56

But honestly, having to jump the plane regularly really is an issue that you need to solve, even if it involves some short term pain. I have an AeroVee, so not a Jabiru, but it starts within 1 - 2 turns of the prop, even in the winter (I preheat). Not sure what's the norm for a Jabiru, but 20 seconds sounds way out of line.

gyroron wrote:My plane is very sensitive about its starting procedure. On a cold engine, first start of the day, you got maybe 20-30 seconds worth of cranking before the battery is too weak to turn the engine over fast enough to ever start. ( Jabiru 3300 )

I probably should have a larger battery in it, it currently has a Odyssey 625 in it, brand new matter of fact, But a bigger battery would require a new box, and would add more weight so I would like to keep the smallish 625.

Too many times since I bought this plane I have had to use jumper cables to the car to get it going. I could live with that if I could easily access the battery, but pulling the cowl is a PITA.

Wondering if anyone has figured out a practical easy way to jump start one without pulling the cowl.

One idea a buddy gave me was to buy something like this, and extend the leads long enough to pass through the firewall into the cockpit, install the ends of the leads with eyelet type connectors to the battery, then if needed, can just access the other end of the cord in the cockpit, plug in the booster box and jump it off and then disconnect once running and stow it in the luggage area or leave in the hangar. Your thoughts?

https://www.amazon.com/dp/B07MJBDD5K/re ... HJ1ZQ&th=1

I am NOT a Rotec fan, but I will say they have a very effective cold starting electronic ignition system that replaces one of your mags. Makes cold starting easy. https://store.rotecaerosport.com/e-ignition-kit

Jabiru also sell a cold start kit which temporarily retards the spark on one ignition, only whilst the starter is activated. Once the starter is off it returns to the normal 23 deg BTDC. I have a home spun version of this on my plane and it certainly allows the engine to fire even with a tired old battery at very low RPMs. With a few wiring mods it should be able to be hand propped.

Info on the jabiru system
https://jabiru.net.au/wp-content/upload ... pickup.pdf

sometimes its a almost instant start.... sometimes its not.

I don't know if I am not letting enough fuel flow into the manifold before hitting the starter, or if I am letting too much into it.

I was told that I am supposed to turn fuel on, mixture full lean, throttle lever bumped forward somewhat ( high idle position ) ,hit starter button, and once prop is moving push mixture into full rich.

I have also been told to do all of that the same except to push mixture in to full rich, wait 4-5 seconds, then push in starter.

The issue I think is the battery is undersized for the engine and you will only get 3 to maybe 4, 10 second tries, before the battery is drained down to the point of noticably lower cranking speed.

Could be a issue with the starter, or the wires getting hot, or any of a number of things, but I suspect its simply the battery is not designed for the high draw of turning over this large of a engine.

On the website, odyssey recommends this particular battery for two stroke jet ski applications. They don't recommend it for four stroke jet skis. Most four-stroke jet skis have 900-1500cc modern fuel injected engines based somewhat on modern motorcycle engines. And they don't recommend this battery for them! And hear I am trying to start a cold 3300cc engine that is turning a heavy prop, with no choke or primer and a crude way of fuel mixture supply.

Battery does seem small, Have no starting issues with my 3300 and a PC680. Iridium plugs are a big help in starting, the sharper points tend to fire at a lower RPM. Pre-heat also helps and not just for starting, but to insure oil is warm enough to circulate at enough volume to lubricate everything.I am using a Bing carb so if yours is an Aero-Carb, cannot help with that.

David A.

Here are a couple of photos of the jump start post on a Sonex. The post is insulated from the airframe and extends through a hole in the cowling. The cable goes directly to the battery + terminal. I have one to mount on my plane but the brass post diameter has been reduced.

Now I can’t get the photos to attach. Suggestions?

Msing48 wrote:Here are a couple of photos of the jump start post on a Sonex. The post is insulated from the airframe and extends through a hole in the cowling. The cable goes directly to the battery + terminal. I have one to mount on my plane but the brass post diameter has been reduced.

Now I can’t get the photos to attach. Suggestions?

Email it to me if you could. my email is sawad13@msn.com