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Diesel starting techneque

Old 05-21-2006, 03:16 PM
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Stuntguy13
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Default Diesel starting techneque

I have been away from diesel for a little bit and today I wanted to do a test run to get back up to speed on diesel operation before I got to the field. So, mounted my OS 40 FP with DD head in the test stand, fueled up, primed once in the venturi and started flipping. Well as I remembered this engine it was always very easy to start, would give me fits in the air but starting it was the best. NOT today, I flipped, closed in the compression 1/8 turn at a time, this went on for half and hour. Then I decided maybe I should use the starter. Well it didn't help. I then primed again in the venturi and still nothing, thinking there was nothing to lose I put a few drops in the exhaust muffler and then blew into it. Flip, flip - 1/8 turn in on compression (at this point I'm way in on compression) disconnect the fuel line, blow into the exhaust flip again then it fires and burns off the prime, flip again it burns off somemore prime, reconnect the fuel line - flip, flip nothing, prime venturi - flip ...... flip nothing. Small prime into exhaust, flip, fires, seem needle is to lean and misses and stops. After that I got nothing. Looking back it seems they like the "WET" exhaust prime and not much in the venturi, starter wasn't much use.

What did I miss?
Old 05-21-2006, 03:27 PM
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Motorboy
 
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Default RE: Diesel starting techneque

The wet engine make difficult to start the engine.

Remove all fuel from engine, back off the compression screw 1 turn up. Give the engine some drops of fuel in carburator and in the exhaust port. Close the main needle and open about 3-4 turn.

Flip the engine fast as possiple to get generate hot of compresion. While fliping the engine increase compresion 1/8-1/4 turn between 8-10 flips. it will ignite when the compresion are in right position. While engine are running, increase compression to max rpm, then lean out until the engine blurbing and screw back about 1/2-1 turn.

Overcompressed engine will loose rpm and sound hard work, back off and the engine will run fast.

Jens Eirik
Old 05-21-2006, 09:08 PM
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DerFly
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Default RE: Diesel starting techneque

If you really have to overcompress like this to get signs of life from your diesel, it is a safe bet to assume that the ether has evaporated from your fuel mix.
Old 05-21-2006, 11:39 PM
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Jim Thomerson
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Default RE: Diesel starting techneque

If it is not a fuel problem, there is probably something wrong which you have not detected. I'd be inclined to start taking things apart. If seems that nothing is wrong, you might take the muffler off so you can see what you are doing when you head prime. Put a squirt in the exhaust with the piston up. Turn the prop over once and then start flipping. Once it will run off the head prime reliably, hook up the fuel line and just crack the needle open. Keep head priming and flipping, opening the needle about a quarter turn each time until it keeps running.
Old 05-22-2006, 04:00 AM
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andrew b
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Default RE: Diesel starting techneque

I agree, wet engines are REALLY hard work, forget the venturi prime and just go on making the piston damp
Old 05-22-2006, 02:14 PM
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Motorboy
 
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Default RE: Diesel starting techneque

Wet engine make difficult because too much fuel will make air colder who are neccesary to make air hot under compression before fuel will ignite. With evapored fuel/air mix are easier to make hot and ignite under compression..

Jens Eirik
Old 05-23-2006, 07:16 AM
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Default RE: Diesel starting techneque

If the fuel is good and you have tried the above suggestions, lets go back to your original post.

Remove the fuel tubing and leave it off until you can easily run off primes. No need to complicate things.

From what you described (assuming good fuel) my guess is that you had it too wet. A wet prime will sometimes give you a false compression setting, that is, you need more compression.

Engines react to primes different ways. Some like intake prime, some like exhaust prime. I tend to avoid exhaust prime in favor of a couple of drops in the intake, whenever possible.

I prefer hand flipping, but many have gone to starters. I would suggest at least turning it over by hand before hitting it with a starter. Your choice.

Good luck with it.

George

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