Webster Engine fails to start

[serhat]

Hello,

I have finished my webster engine and planning to run on glow plug for a while.
O.S. .12cc glow plug engine carburetor,A3 glow plug and %10nitro/%18 oil aircraft fuel are used as suggested by Joe.
I am sure about the compression and timing,however it does not work.
Do you have any idea about the type of glow plug to be used on this engine?
Thanks for any other suggestions/comments.

Brgds

 

[Ed T]

Glow ignition engines are glow assisted diesel engines. That is, they rely, to a significant extent, on the heat generated by compression to fire off the mixture. They also have the glow plug to provide a bit of heat especially for starting. ASSUMING that the valve timing and all are correct the most likely cause of failing to run is that the compression is too low. I don't know what the nominal design compression of the Webster is, but I'd bet it's a bit on the "relaxed " side to make a pleasant running ignition engine. This low compression may be inadequate for the glow ignition. The relatively low RPM and 4 cycle operation may mean that you will have to keep the glow plug powered all the time, rather than just at starting, since there will not be a lot of "fire" to keep it hot, There are also plugs made specifically for four cycle glow engines which help with these issues. That said, there may be along and illustrious history of these engines running perfectly on glow plugs. I don't know. I'd still be inclined to look to the compression first. Could be bad valve sealing, just not enough in any case, poor piston seal, dimensional error on any of several parts (it wouldn't take much), bad glow-plug battery, old fuel ( this can really keep you guessing).
If there's compression, fuel, air, and fire (from something) it should at least fire once. Getting it to do it several time in a row is an added challenge. Good luck!!

 

[bearcar1]

All of the above things could be causing you problems but two things spring to my feeble mind that may possibly be exacerbating the starting/running issues. The first that I wondered about is the size of carburetor being used, if the venturi throat is too large there may not be sufficient fuel 'draw' to initiate a good charge to the cylinder. The second thing is coupled with that statement and regards the distance the charge has to travel ei: how far away from the cylinder the carb is. Again if the distance is too great, the valves may not be open long enough to effectively pull the charge into the combustion chamber. It is difficult to tell but all of these factors can and do come into play. Begin by eliminating the obvious potential problems first such as being certain the plug is in fact being lit by the battery and that the battery is in fact capable of performing that function. It may be that you will have to supply constant voltage to the plug in order to maintain good running. Let us know what you have/have not done as far as eliminating some of these basic factors, I'm sure that the combined knowledge on the forum can get this thing to start and remain running, hopefully without a great deal of rework. A very handsome engine BTW, I do like the polished copper fuel vessel.

BC1
Jim

 

[crankshafter]

Serhat.
Nice engine.
When I look at your Webster the first that comes to mind is that the intake valve- spring seems to be a little bit stiff. Try with a real week spring, you only need a spring that is just closing the valve. Do you have blow-back in the fuel-line? If so make a small fuel controll- valve and place it in the fuel-line just below the fuel inlet of the carb. How do I know oh: :noidea:
Just my 2cent.

brgds
Crankshafter

 

[serhat]

Thank you Ed and Jim,

Let me tell you what I have done so far to fix the problem.
First of all,to be sure about the compression,I have replaced the bronze piston rings with o rings (qty 2) so the compression is perfect now.I am also sure about the valves as I have tried them several times and they close and open perfectly.
Jim,
you mentioned about the distance between the carb venturi and the cylinder,its really an interesting point.I have never taken this point into consideration.It is around one and a half inch.
My battery is 1800ma and 1.2 volt.Do you think that it is not sufficient for a good glow?
By the way,the fuel I am using isfresh,purchased last week.

Waiting your comments
Thanks

 

[serhat]

Hi Crankshafter,

Thank you.
I have changed that spring several times.It is just closing the valve and opens easily with the compression but of course not more than 1-2 mm.
What do you mean by fuel regulator? The carb has an inlet adjustment needle.Is it something different?

 

[crankshafter]

Serhat.
Here is my starting procedure: Open the throttle to 1/4( aprox.) Ignition on. One finger to open the intakevalve, thumb to close the intake on the carb, flip the engine couple of times to draw fuel in to the cyl., fingers away from valve and intake and flip- flip, of it goes.This works for me, BTW: I use points/coil, and 95 octane ;D.
Here you can see the small contoll-valve right at my thumb, it has a small bearing- ball inside to prevent the fuel from being blown back in to the fuelline/tank.

One more thing do you have a went.-hole in the fillercap :
PS: if you like I will dismantle the controll-valve and take a pic. of it.
CS.

 

[serhat]

Hi CS,

I do the same to fill the cylinder with some fuel prior to first attempt but it didnot work.Ignition system has a powerful spark and totally different from the glow plug.
I would like to see the detals of your control valve.

Thanks again.

 

[crankshafter]

Hi again.
I will dismantel the controllvalve and take some pics. hopefully tomorrow
CS

 

[Ed T]

The compression seal and the valve seals may all be perfect and you can still have too little compression to initiate ignition. The 1800 mah battery should be fine for this purpose if it's charged up. I presume you've looked at the glow plug when hooked up to the battery just to check out that sub-system. It should glow bright orange/yellow. While you have the plug out, you might inject a few drops of fuel into the cylinder and see if you can get it to fire off of a prime. If so, it would point you in the direction of the fuel supply as discussed above. Failure to fire on the prime would point in the direction of the compression or the glow plug. If you have transparent/lucent fuel lines you should be able to see the fuel move toward the carb if you choke the carb with your finger and turn the engine over. Just like choking any other engine, this should draw fuel into the intake system. Is the glow-plug an idle bar plug? If not, that might help keep the filament hot.

 

[serhat]

Hi Ed,

No it is not an idle-bar plug.
I will purchase an F type glow plug for 4 cycle engines and if available with an idle bar,tomorrow.
If it does not work with the new plug and maybe with a new 1,5V baterry,I will directlt switch to ignition system.

 

[crankshafter]

Hi serhat
I have a couple of pic. of the controll-valve. Here we go:

In/ outlet 2.4mm drill, 5mm thread in the valve-cage, on the other half a small o-ring for sealing. in the outlet bore ,a thin wire to prevent the ball to be sucked up and restrict the outlet. Hope you understand. ;D
Ah so you comes from Turkey. I been there several times. Side,Marmaris,Alanya, and so on. Nice contry/peoples
CS

 

[serhat]

Hi CS,

It is a very nice check valve.I'll try to do it.
The F type glow plug will come tomorrow.Lets see if it will add some value or not.

I live in Istanbul but travel to south of Turkey every summer.I would like to welcome you in Istanbul on your next visit to Turkey.

You can see my other engines and model boats I have built on below blog

serhatece.blogspot.com

Brgds

 

[serhat]

Hello,

The new glow plug F type also did not work.I have injected some fuel before replacing the new glow plug(as suggested by Ed).
Engine started for a 3 or 4 turns and stopped again.
So the reason of failure is unsufficient fuel/air supply.
What I have done?

1- replaced the o rings on the piston and once again became sure about the compression.
2- Replaced the intake spring with a more softer one.It works fine on the tests.

Result:

Nothing changed.

As it has been advised by bearcar1 ,the intake system on this engine has a long way to cylinder and even a good compression is not sufficient for a proper operation.
Another important point is still the glow plug which is not providing enough heat as a spark generated by a standart ignition system.

 

[Ed T]

That' some progress. It has now run infinitely more than it had before. I have to ask because I don't know your level of experience with these things so don't be insulted. Did you open the needle valve on the carb? When the NV is open some and you choke the engine and turn it over you should suck a ton of fuel into the carb/intake. This should be pretty obvious. Fuel dripping out of the carb etc. If this doesn't happen, something is amiss. So, try that and we'll go from there. Good luck!!

 

[serhat]

Hello Ed,

Yes.I have tried several needle openings,1 turn,2 turns and even 3 turns.Normally it should work with one and a half turn.
The carburetor I am using does not have a venturi or a very light one.Do you think that can effect the flow of fuel to the cylinder?
I have added some pictures of it.

 

[metalmad]

Hi serhat
very nice looking Webster,mine would not run until I made gaskits for the valve block
Im not much of a machinest im afraid lol
and I agree with crankshafter about the intake spring, it does look to my old eyes a little heavy.
Cheers Pete

 

[Ed T]

AHA!! a clue.If the carb you are using does not have a venturi ,to speak of, it is not going to draw fuel very well if at all. This is especially the case since the engine you have is moving far less air than the two cycle engine the carb was intended for. Many two cycle engines , especially in car applications, are intended to run at full throttle most of the time and utilize a pressurized fuel system to maximize performance. This greatly reduces the need for the vacuum created by the venturi for fuel delivery (eliminates it in some cases) and increases performance. I have played with an off road r/c car and it won't run without the tank pressurized. So, the lack of a venturi certainly is not working in your favor.
A QUICK look at your nice model did not reveal a vent on the fuel tank. Maybe I just didn't see it. This too will prevent the engine from running well if at all and the weak fuel draw will only make the effect worse. Of course, if you decide to pressurize the system, you won't want a vent, but pressurizing with the engine you have would not be pretty. The fuel feed issues are independent of the ignition system, so you're going to have to figure it out to get it to work.

 

[cobra428]

serhat,
Most model engines use muffler pressure into the fuel tank then out to the carb (sealed system). So you may have to open the needle valve more. If you choke it (finger over venturi) do you get a pop out of it? Make sure your glow plug ligthts a very bright red.

Tony

 

[serhat]

Hello,

Metalmad,

I have already changed the intake spring.The one you see on the picture is the old one.The new one is softer.I added a picture of it.I used gaskets between the layers of the intake system.

Ed,

Yes you are right.There is no went hole on the tank but I completely opened it during my tests.

Cobra428,

Yes I get a small pop when I choke it.
As for the glow plug light,it is bright red at the begining but not after several attempts.

Thanks