Unimogdriver

Hello Guys,

I'm from Germany, and I do have a problem getting my PAW started, i got it from eBay because I'm really interested in such little engines, it is my first and only RC engine, maybe i get another if I manage to get it running. Here in Germany I can't get a ready to race Fuel so I mixed it myself. Sometimes when I try to start it, it fires 2-3 times then stopping again, and I can't get it any further than that. I tried for at least 3 days in the summer to get it started, then my arm nearly fell off and the holidays were already over, since then i didn't have time to try it again. The engine is equipped with a muffler and a carburetor. Maybe someone has a special tip for me, to get that little PAW running. The Engine will only be mounted on a nice wooden board and put on display, but it would be nice if I could start it, otherwise it looks a bit dumb when somebody asks if it works. At the moment it is cleaned and conserved mounted on a provisional test stand waiting to get started. The engine was originally packed and looks brand-new, and it has a very good compression as far as I can tell.

Greetings from Bavaria

Markus

qazimoto

My Feedback: (1)

The PAW 55 should run very well. So first a few questions. What size prop are you using? What fuel are you using? You do need about 30% Ether, a minimum of 20% oil and the rest kerosene. A third of each should work fine. ie 33.333% Ether 33.333% Castor oil 33.333% Kerosene

Unimogdriver

hello,

I use a 8x4 Prop, and yes i have mixed a third of each.

qazimoto

My Feedback: (1)

Ah! an 8x4" prop is far too big for a PAW 55, how about trying a 7x4".

Unimogdriver

Ah okay, i got it because I read it on the Paw website for running it the first few hours. I can get a 7x4, but do you think this is the reason for not starting?

qazimoto

My Feedback: (1)

The PAW website lists the 8x4 as the maximum load for the .55, .8 and the 1.0cc diesels. I'd guess that it's far too much load for a tight new .55cc engine. They do recommend a 7x4" prop for running in, which seems a much more reasonable load to me for the engine.

Will the engine suck fuel when you block the carby intake and turn it over by hand?

I don't use a muffler or a r/c carb I only use Free Flight or Control line engines. But the procedure is similar. On a new engine I just start with the fuel line disconnected, and back off the compression. Prime against the closed piston, flick hard and increase the comp about 1/2 a turn and repeat till it fires. When it does I turn up the comp just a little more, connect the fuel line, I wind out the needle valve about 3 -4 turns from closed, choke the engine sufficiently to draw fuel, and once again flick it hard. Continue till it runs steadily. Once it's running I increase the comp gently, let it warm up and lean in the needle. As it warms up it may be necessary to back off the comp a little.

There's quite a few good youtube clips about starting diesels like PAWs. They're worth watching.

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Unimogdriver

Okay, thanks i will get me a new prop, that shouldn't be a problem. Yes the engine sucks fuel and spits it out as mist through the exhaust. After a few flicks you can see it on the test stand. Okay i will try your method, do you think i can still use the fuel i mixed at the end of September after shaking it a little, it was stored in a metal pocket bottle?

Mr Cox

The fuel is very important, so try to find someone local that can help you with that. There should be events for CL flights, for instance, where diesels are used and they can help you to get some fuel. Even 0.5 liter will last a very long time on these small engines.

I would use a 7x4 prop to begin with (this is plenty of load and should give you around 7500rpm at full throttle) and don't use the muffler. Without the muffler you can simply prime the side of the piston when the port is closed and this should fire up each time, no need for a tank even. All engines are tested at the factory and the compression setting will be very close to ideal already. On the the latest .55 I bought directly from PAW it was actually set a little high and the engine would only rock back and forth rather than run (an easy adjustment to make though). The throttle can be set near idle for finding the correct compression setting, I've found that they start easier that way.

So first make sure that you have good fuel, then find a good compression setting by getting it to fire up consistently on each piston prime. Only after that do you need to connect a fuel tank and tune the needle. Flooding the engines with fuel is a bit dangerous as that can give you a "hydrolock" with resulting engine damage. The engines from PAW are great beginner engines, but you do need the correct fuel and some experience with the tuning of it.

Good luck and welcome to the wonderful world of model diesel engines.

qazimoto

My Feedback: (1)

Yes the fuel should be ok. Did you use pure Ether in the fuel or Auto starting Ether? Solvent grade Di-Ethyl Ether works well. It doesn't have to be Medical grade. If you're using starting ether it may be necessary to increase it's proportion in the fuel.

Unimogdriver

Thanks for the answers, I have the medical one from the pharmacy, this already was a struggle to get here and it was a lot of paperwork. That's Germany everything has its rules. I have been to lots of RC shops no one can get me some modeltechnics d1000. The only one in Germany who has it is 800km away and he can't ship it because of safety regulations. So i will get me a new prop and then test it again with your tips. But I think if I do it indoors i get a little sleepy with the ether, I hope the winter goes away soon, because I think the Engine won't start at all in -15°C snowy weather. Can somebody recommend a good 7x4 that's not to pricey?

Mr Cox

I quite like the JXF props, they are not as brittle and sharp as the APC ones. There is also the Graupner super nylon (grey) props, which might be easy for you to get, these are a little heavy but not bad for our low revving diesel engines. Their 7x3 is also worth trying for the .55 engine.

Unimogdriver

Thanks for the recommendation, i will try the graupner super nylon 7x3, because I could get it for half the price of the 7x4 because the shipping was free. Hope it will start up then.

fiery

My Feedback: (2)

"graupner super nylon 7x3"

Perfect prop for running in a PAW .55.

They are one of the highlights of the PAW range, a little jewel for reasonable cost. The speed it will turn a 6 x 4 propeller is surprising and if properly adjusted they do throttle most acceptably with the supplied R/C carburettor.

qazimoto

My Feedback: (1)

I thought that Graupner had got out of the small IC engine prop market. I've been after some of the Grey 6 x 6" ones for ages for my Oliver Tiger Cubs.

Mr Cox

They might have stopped making the 6x6 ones, and possibly the 6x5 ones too. I've stocked up a little I guess and haven't bought anything lately. The 6x3 and 6x4 still seem to still be available though. The 6x3 works really well on a converted PeeWee engine.

chevy43

It would be better if your fuel had an ignition improver in it.

Unimogdriver

Hello,

so today my graupner 7x3 has arrived, and of course i tried to start it. I got it started, it turns really nice, but after 10 sec, it always stops in top dead center, I can start it again afterwards but only for 10sec again. Then it doesn't start at all for a while and then it is the same as before. What does cause that in your opinion?
Yes, the ignition improver would be good, but the one mentioned at Paw website it is not available here in Germany.

qazimoto

My Feedback: (1)

Sounds like it's "running on a prime". Possibly the r/c carby isn't sucking fuel or that there's a blockage. Can you check it?

If it'll run for 10 seconds then there's nothing wrong with your fuel.

Unimogdriver

Hmm, the fuel-tank is connected to the RC carburetor and deeper than the intake so the engine has to suck the fuel, and the needle is 1,5 turns open, should i open it more, i didn't want to flood it?

Mr Cox

If it is running for 10 sec you should have enough time to tune the compression ratio and the needle. 10 sec sounds longer than a typical prime run, so most likely it is drawing some fuel. It is very easy though to open the needle a little and see what effect that has.

If it is a new engine you will need to run it in. For that it is important to run with a little lower compression setting and a richer fuel setting. If it miss-fires a little that usually means that you are on the correct side with the compression setting (i.e. slightly below optimum). The color of the exhaust residues is a fairly good indication of the running temperature, and in the beginning one should not let it become dark.

You usually need a higher compression setting to start a cold engine, but a lower compression setting to start a warm engine. These changes in compression ratio are typically about 1/4 of a turn around the ideal spot.

qazimoto

My Feedback: (1)

Yes, Mr Cox is right! Why not just open the needle a bit and add a tad more compression. It's very close to constant running :-)

Chris W

If the temperature is -15C and the engine is tight from being new then perhaps the old heat gun trick may work?

Unimogdriver

Hello guys,

thanks for the answers i will try it again in the next days with your tips, I don't need the heat gun necessarily because I tried it indoor in the basement but maybe I will warm it up a little. I know the exhaust gases and the ether is not that good indoor, but i opened the windows a few times. The finish line seems near

Unimogdriver

So it is me again and I got it started, it ran pretty smooth and constant, after around 3 minutes I stopped it with the fuel tap and mounted the muffler because of the mess it made in the basement, I turned it on again with the muffler and then I started experimenting a bit with the needle and the compression, but I set the mixture a little too rich and it stopped, I think I flooded it a little. Afterwards I drained the fuel and put in some Ballistol oil to conserve it. But the engine works just fine and I'm so happy. Now I have to wait for Summer to let it run in and build a nice wooden test stand for it, can't do that indoor, because of the emissions.

Thanks for all your Tips, it wouldn't have worked without you, when everything is ready and looking nice I will upload a Video and share it here. I think now I have to get another little Engine

chevy43

Glad to hear you are having success. If it stops at top dead center I would say that you need to reduce compression after it starts. The way I like to find the best run settings is to run it rich and under compressed and lean the needle and raise the compression a little at a time until you no longer gain RPM or it quits and then richen and loosen compression slightly from that setting.

Buy some diesel treatment at a truck supply or truck stop. Most brands have ignition improver. You need to use it more concentrated than the the directions say.