Hope I have fixed it

[Harthy]

One thing with starting my Jab that I do now without thinking. I don't just pull the choke out, I hold it right out. I noticed that if you pull it out and let it go, it will creep back in a little. This would be enough to not get full choke and would cause hard starting.

 

Just a thought and might be worth investigating.

 

Harthy

 

 

[Guest The Bushman]

cold starting Jab

 

Hi Jab Phil

 

Will be coming down to Loxton later this year and will bring the gear to resolve your hard starting Jab

 

My Jab and and several other had this problem now all start after scraping the ice from the wings simple takes 1/2 hr

 

The Bushman:score 010:

 

 

[Tomo]

As Harthy says - we must fly the same machine!

 

 

[Jabiru Phil]

Hi Jab PhilWill be coming down to Loxton later this year and will bring the gear to resolve your hard starting Jab

My Jab and and several other had this problem now all start after scraping the ice from the wings simple takes 1/2 hr

 

The Bushman:score 010:

Hi bushman

 

many thanks for your offer

 

I promised you a carton for the secret previously which still stands :thumb_up:

 

just call 0418806466 and I will be there

 

one point I have to mention is that we have no issue with the 4 cyl Jabs at all here re cold starting

 

looking forward to your visit. I would gladly visit you if and when convenient if OK

 

Thanks for the contact

 

Phil

 

 

[ianboag]

Start Ya Bastard

 

That's the brand on the ether can from Super Cheap. Always worked for me .....

 

 

[pudestcon]

That's the brand on the ether can from Super Cheap. Always worked for me .....

Slarti's new handle maybe:cool:

 

Pud

 

 

[jetjr]

Make sure the earth wire is on the same end as power wire, and theres a wire from rear to front of starter has been installed.

 

Without it they have poor earth return through starter bolts. Starter body has Orings which isolate the end

 

 

[Tomo]

That's the brand on the ether can from Super Cheap. Always worked for me .....

If you can help it... it's HIGHLY unreccomended to use ether on aircraft engines.

 

 

[ianboag]

Hi Tomo

 

Can you quote me an authoritative source for that opinion?

 

The Jab is a pretty simple not-very-high compression four stroke. If you give it a pre-start puff, the ether is all through in a couple of engine revs. How much harm can that do?

 

I'm not trying to yank any chains here - I just want to understand.

 

IB

 

 

[Harthy]

I'll go with Tomo on that about the ether. I have been in in the machanical game for many years and taught it for 11 years. My advise is to keep ether away from any engine that is in good condition.

 

If your engine doesn't start you have other problems that need looking at. Ether's main use is for engines that require compression for ignition (Diesel engines). Worn engines or cold ones will lack the heat generated on the compression stroke for ignition(Diesel engines).This when it can be used. So unless you jab engine is way down on compression( In that case it shouldn't be flying), I would keep ether away from it.

 

If used incorrectly, ether will cause excessive knocking and can burn away the top of your pistions

 

Harthy

 

 

[Tomo]

Hi Tomo Can you quote me an authoritative source for that opinion?

Well, I don't have any 'quotable' literature for you, but I'm a Mechanic, and have been playing with engines for about 15 yrs - and my Dad who is also a mechanic for about 28 yrs. And if you talk to most mechanic's, you'll get similar responses.

 

The Jab is a pretty simple not-very-high compression four stroke. If you give it a pre-start puff, the ether is all through in a couple of engine revs. How much harm can that do?

As Harthy above has stated. I tell people Ether is like a panadol, it will keep you going, but you have a problem and it's not going to fix it. If a petrol engine has compression, fuel, spark... it will start and run. If you decrease the compression, it may still run, but will have trouble starting - ether will make it start, but you are now operating on an engine with a known problem somewhere. On the ground - well the worst that can happen is it stops, no big deal.

 

How do you know if you are squirting to much? If you flood an engine with fuel... it won't fire exactly. If you flood an engine with ether, you now have a gas filled bomb, you can blow something, melt the pistons... all sorts of disturbing stories.

 

Low compression? Yes petrol's haven't as much compression as a diesel... another reason they can get more damage done, because they can't handle the excess pressure exerted if its over done.

 

Don't get me wrong, ether is great stuff ( ;) ), but don't use it on new engines, and if your aircraft engine needs it, I wouldn't be flying it. It is great stuff for diagnoses, if an engine runs on ether, you know you have a fuel problem. If it refuses to fire on ether, you have a spark or compression issue.

 

Hope that helps.

 

 

[Vev]

Tomo,

 

 

Re Ether and problems with using it in aero engines.

 

 

These commercial available sprays are usually made up of 60% Mogas, 30% Diethyl Ether and 10% Ethanol … give or take a few %.

 

 

Basically these are designed to increase the cetane number in diesel application, which is gabout helping start a cold engine where the fuel quality is low and in very cold climates.. In Oz we have high quality diesel and it doesn’t really get that cold, therefore it’s a little more difficult to make an argument to use these products.

 

 

When you use this stuff in an aero engine it has the same effect of reducing the octane and it speeds up the flame burn and can cause detonation .. Not a good thing for any engine any time.

 

 

The chemistry can also impact on seals and other components and can cause plasticisation (make thngs go soft) of seals, o rings etc.

 

 

Hope this helps.

 

 

Cheers

 

Jack

 

 

[ianboag]

I completely take the point that diesels with a bottle of ether attached - and a button to keep squirting it - can have a problem. That's not what I am talking about.

 

When I use ether on a cold day, I put a puff of the stuff into the intake, then get into the plane and crank it ... Generally it's puff puff vroom vroom.

 

Used this way there is enough ether vapour in the system to provide one stroke's worth of volatile high flammability fuel that gets to the cylinder and eats a spark. Used this way it's hard to "flood" it or use "too much". The ether is a vapour - if I do "too long a puff" the ether vapour just overflows back out the intake.

 

A 3300 engine sucks 3.3 litres of air/rev. The induction box is maybe 5 litres .... so all the air in the box is sucked through in 1-1.5 revs.

 

The "engine problem" faced here is a reluctance to start from cold when the oil is thick, the battery is not at its best and fuel doesn't seem to get to the cylinders as vapour. Reduce the effect of any of these and the beast will go. Once it has started and run for a little while the problem goes away.

 

Cheers IB

 

 

[Tomo]

The ether bottle with a button set up - is generally only on engines that haven't got "Glow plugs". I've fitted them to Caterpillar engines that used to use "Pilot" engines to start them. The beauty about the pilot engine was the exhaust from it warmed the main engine up. Take away the pilot engine and fit the starter motor adaption, and it will refuse to start without a bit of ether.

 

Glow plugs fixed a lot of cold starting issues.

 

Anyway, that's another story.

 

Your engine sounds like it needs to spin faster - could it be the start solenoid? The factory fitted ones seem to leak, and people change them to a high quality ones with great results.

 

Btw, 3.3ltrs per rev sounds a bit generous.

 

 

[Harthy]

If you feel ether is not a problem, no one can stop you from using it. The point is, you have other issues to sort out, whether it is thick oil or a bad battery, or what ever.

 

Ether is convenient, easy to use, and it works. But don't!

 

Harthy

 

 

[Tomo]

A 3300 engine sucks 3.3 litres of air/rev. The induction box is maybe 5 litres .... so all the air in the box is sucked through in 1-1.5 revs.

Bit irrelevant I guess, but just for your interest sake -

 

One revolution on the 3300 engine would inhale about 1.665ltrs of air, now that is an off the shelf figure (for want of a better word). As there are a lot of factors relating to that, but lets go with this figure for the time being.

 

On the first revolution of the 3300 engine - pistons 1 4 5 do their bit, then on the second revolution 2 3 6 do theirs - either sucking, blowing, or firing - respectively. So basically the engine has to do 2 revolutions to suck in 3.3ltrs of air - {in a perfect world}

 

 

[facthunter]

Sure.

 

Another way of lookijg at is that with a perfect fill ie 100% (volumetric efficiency) each cylinder fills once every second revolution, so it is 3.3 litres every two turns, as you say tomo. nev

 

 

[ianboag]

True. My error. It takes 2-3 revs to suck out the airbox, not 1-1.5 ...

 

IB

 

 

[Jabiru Phil]

I visited Jabiru factory yesterday and was talking to Don from the engine department about my cold starting problems. He will drill out the CHOKE jet for me which he says should fix.

 

A couple of weeks 'till I get back to the cold mornings for the test. I will report back.

 

Phil.

 

 

[facthunter]

Detonation and Starting.

 

Enrichening the choke is the way to go. Ether is a cetane improver used in model aeroplane engines to make the fuel self ignite under compression. This is the opposite effect of octane. It RESISTS igniting UNTIL the spark plug sets it on fire. (which is what you want to happen). Under the effect of ether the occurrence of ignition is unpredictable. It can be quite early and this will cause detonation. This is much the same as taking to your engine with a sledgehammer. DON'T DO IT, unless its a worn out diesel tractor and the indians are coming over the hill and your life is at stake unless you escape. Nev

 

 

[Powerin]

Another way of lookijg at is that with a perfect fill ie 100% (volumetric efficiency) each cylinder fills once every second revolution, so it is 3.3 litres every two turns, as you say tomo. nev

And that theoretical 100% would only be at full open throttle wouldn't it? You are sucking in a lot less air at half or closed throttle aren't you? (unless it is a diesel of course)

 

 

[Tomo]

And that theoretical 100% would only be at full open throttle wouldn't it? You are sucking in a lot less air at half or closed throttle aren't you? (unless it is a diesel of course)

Yes indeed Powewin. One of the reasons you always do a compression test with the butterfly on full throttle.

 

Btw some diesels do have a butterfly - Some of the older Perkins for one.

 

 

[ianboag]

Orright guys orright. I have written "I will never squirt SYB into my engine again" 500 times. You lot are like someone who sees me having a glass of wine with dinner and launches into a story about liver failure :-)

 

Jab forums (this one, Yahoo and the UK one) do have a lot of annual posts about cold starting problems though. I have heard of

 

- jumper cables

 

- hot water on carb

 

- 20 minutes of electric heater into the bottom cowl hole

 

- various things about earth wires on starters

 

- ether

 

The drill-out-the-choke-jet one was one I hadn't heard.

 

In the end when mine had constant cold starting issues I just modified it to have two batteries, because jump starting it on the external wire I had under the cockpit always worked. No further problems after that. It may of course have introduced a new hazard that I didn't think of.

 

IB

 

 

[Guest Wigg]

Could be like the bloke who was running late on cold morning, plane refused to start so ran his car up to front of plaane & jump started the plane that way. Lost both car & plane.

 

 

[Jabiru Phil]

GOOD NEWS, :big_grin:

 

The 230 now starts first try, infact ony a revolution or two and push in choke.

 

The temp has been cold but not freezing as yet. I am confident that the mods (mainly the choke jet drill out) has solved the problem. The larger battery, new solenoid, earth starter mod have also had an effect.

 

The difference is amazing, just pull out choke and hit the button and push in choke, where before, the choke had to be left on for a minute or so and the gradually pushed in over 20 seconds or so or the motor would stop.

 

Many thanks to the guys for their suggestions.

 

To Bushman...Was the choke jet the mod you had in mind?

 

Regards,

 

Phil.