glow plug

i have a old cobra that i am working on and when i start it it runs fine untill i pull of the glow plug then it dies? i think it might be running to lean but any idea would help its a MAX O.S. 50FSR-H.

[darren_uk]

I'm not an expert on engines, but here's my bit of input until someone else advices further:

The electricity supply makes the glow-plug glow - once the engine is up and running the combustion continues to keep the glow-plug "primed" to continue to ignite the next intake of mixture.

I seem to recall the glow-plug element is coated with something that the fuel reacts with to cause the combustion?

Anyway: if I were having problems like you are, and I thought the mixture was correct, I'd try replacing the glow-plug incase it's the coating that has gone.

Damn, I'm sitting here trying to recall stuff I've read about in the past about glow-plugs - I seem to remember that if you look at the plug and the element is covered in an ash-coloured coating, then it's time to replace the plug (and I think it means the fuel might have been running too lean).

I'm really struggling here, which is just the way I would be if I had similar problems myself :-) I'm just thinking out aloud.

[Daz(DJLFlapper)]

Hi,
I had a simular problem with my engine. I would take the glo plug charger off and it would instantly kill the engine.
Mine turned out to be running too rich and the excess fuel was too much without the glo powered.
However I leaned it out to fined that it would then run for a while without the glo adapter on it.
Then I finaly made 3 changes,
1: I changed the glo plug for a new one.
2: I went from 10% Fuel to 15% fuel
3: I got the instructions for my engine just to make double sure that the needle settings were correct.

Having done this I started the engine and straight away I noticed that it sounded better. I took the glo adapter off and adjusted the main needle to let the rev come up slightly still with a good amount of smoke coming out of the exhaust. I have not had a repeat of the problem since.

As long as your engine is producing smoke whilst running it is getting oiled. I leaned it till it was running faultlessly I use an MDS38 and although it was not very good with 10% it has never let me down on 15%and the new plug.

Hope this helps, Remember if it's happening to you it has probably happend to others, Your not alone.

Regards,
Daz

[colin]

I sometimes get that problem when my engine been in storage for a while. What I do is to warm up the engine with the glow battery still plug in, and run the engine for about 2 mins on near hover speed.

Once the engine is sufficiently warmed up, the glow plug works on it's own normally.

my engine has been in storage and im running 20% fuel 'and to make i more of a problem i dont have the mannual for my 50fsr-h and O.S dosent have it on there site

[Daz(DJLFlapper)]

Hi,

The obviouse thing here is that you don't have the engine set up properly or it is an old engine that after its last bout of storage needs replacing.

The best way to go here is to take it to your local hobby store and allow them to set it up and give it a good check as to its condition.
I would remove it from the heli and put it on my engine test bench. Then I would make a note of the needle settings by turning them clockwise till fully closed. Make sure the carb is fully closed when you do this.
I would expect the main needle to be around 2-3 turns and the fine tune needle to be anywhere from 1-2'1/2 turns.

When you have done this set the needles to what they were and start it up. If it runs as it was with the glo plug adapter on then firstly lean the fuel some with a quarter turn of the main needle. The engine should gain in rpm slightly. If this does happen then take off the glo plug adapter and see if it will run this way. If it does not then turn the main needle a further 1/4 turn hopfully this should make the rpm rise.

If it does for a while and then stops adjust the main needle again but only by a 8th this time. Always check that you are getting smoke from the exhaust.
Make a note of needle sttings and what the engine runs like at that setting. Once you have the engine runing fairly well you can then make an adjustment to the mid or fine needle. only make small 8th adjustments and only when the engine is off.

I wish I was there to help you but that aint pos so if your not comfortable doing any of this then the shop is the best bet.

Something else just thought of what oil is in your fuel?
If it is castor and its been in storage then I have heard some of my mates talking about the way castor gummed there carbs and they had terrible running till they cleaned them thouroughly. Again check needle positions and see if these are gummed up. I also remember that one carb had an o ring gone due to his engine being run on 20%. He said these are often replaced now.

Good luck,
Hope this helps,
If you need more help let me Know
Daz,

We had someone that had this similar symptom a few weeks ago. There were lots of people trying to figure out what the problem was and it was something quite odd. If the other suggestions (they sound most likely the cause) don't work try this.

The problem was caused by air getting between the threads of the needle valve. To fix the problem the needle valve was removed, and a small piece of fuel tubing was installed over the threads. The needle does NOT screw onto the tubing. The tubing fills the gap between the needle and the carberator sealing the air leak.

if all the above fail be sure to check every screw on the thing including the glow plug for tightness
I had a similar prob and it was the head screws once and the carb mount screws another.