Ngh 17 petrol

[Jamie sawyer]

hi everone. Long time since I posted. I've an NGH 17 petrol engine. I'm having serious issues getting it to go. It's never run since I bought it 18 months ago.

I've set it as per instruction manual no fire from it

Fuel is fine and new fuel

Using an electric starter and still not even a fire from it

The ignition system spark is working 100% fine

Can I try it on glow fuel with a glow plug in it ? Rather than petrol to see if it goes ?

I've tried every conceivable setting on the fuel mixture screws to adjust fuel supply and no luck what so ever on it going. When it was brand new it popped only once on flicking the prop but not since. Lost on this engine now. It's getting plenty fuel as it's coming from the exhaust port and soaking the bench

[cymaz]

I would strip the carb and see if there is muck in the fuel screen and around the diaphragm. As it has a walbro carb check the fuel needle height. Don't loose the spring....any doubt take the top off the carb in a large clear plastic bag in case something drops out....it shouldn't if you only take out the diaphragm. Is the pressure/ pulse tubing on securely? Make sure that there this is also no restriction for the air to flow freely.

Hope this helps somewhat.

[Jamie sawyer]

Hi Cymaz, I stripped carb this morning and no debri at all. I did wonder if it was choked also. I'm giving up for today. I think I might just send it to just engines to try. I've literally turned over every rock trying to start it. I even resulted in taking head off and warning it up inside with a blow torch to see if the hot engine would help with vaporisation of the fuel. Nothing has worked. It's my first petrol and think it could be my last lol

I've dealt with engines for 20+ years and never had an issue tuning or even starting like this. It's almost like there's a failure internally of the engine

[Jon H]

Petrol engines will not fire if they are flooded. I set up an evo15 a while back and the symptoms were exactly as you describe. I assume you are electric starting and this can make the issue worse.

I recommend you close the main needle completely, heavily prime the engine with a squeezy bottle and then crank it with the electric starter until it fires. It will likely then run for 10 or 15 seconds and stop. Open the main needle and then quickly try to start it. if it pops a few times then you get nothing then your slow run needle is too rich.

In this case, lean off the slow run 1/2 turn, close the main needle completely and crank it again until it fires up. Then you need to slowly open the throttle and open the needle just enough to keep it going and get the engine to full power. Once at full power and tuned for max rpm throttle back and if the engine stops, lean off the slow run some more and keep leaning it off until it will actually run at low rpm. Then you can tune the slow run as normal with the engine running.

[Jamie sawyer]

Hi Jon, the engine should at least fire with a few drops of fuel in it shouldn't it ? I've tried that also and nothing. I'll try it again as you've described. There is a low end needle and a high end. Should I shut both off completely? And keep choke on or off

[Jon H]

What I would do at this point is leave the choke off and disconnect the carb completely from the fuel supply. Then prime the engine with a bottle and try to start it. If it wont fire at all after 30 seconds of cranking with the starter then it is likely the fault is with the ignition and not the fuel supply.

A test for this would be to again prime the engine, flip a few times by hand, and then turn the prop slowly past compression to see if it fires. I recommend you use either a stick or hold the blade firmly with your whole hand when turning it so that it cant bite you. In the event that you feel it fire when turned slowly it is likely the ignition is too far retarded and needs to be advanced a bit. move the sensor a bit, then give it another go. if it fires up reconnect the carb to the tank and go from there

 

Edited By Jon Harper - Laser Engines on 15/07/2017 18:04:21

[Anthony Scott 2]

Perhaps the pump diaphragm has dried out & become too stiff to pump. It is an easy matter to take the diaphragm out & soak it in petrol for 10 minutes, you may see a remarkable improvement after refitting!

There is little scope for adjusting the timing, no more than 3-4mm on mine.

[Steve Hargreaves - Moderator]

Is fuel actually reaching the cylinder? What is the spark plug like after you've tried to start it? Any sign of any fuel?

An engine with ignition, compression & fuel should at least fire.....if one of these is missing it won't go...

[Jamie sawyer]

I took manifold apart today and the Diapghram is fine and soft. No blockages. I've ordered fuel tube as it's glow tube on it just now which is wrong. I've also ordered a proper mixing container for getting oil to fuel ratio 100% correct. 33-1 is the ratio which I'm unsure if I've mixed accurate enough not to cause issues. Compression wise today I'd say that there wasn't as much compression as I'd expect especially if I was flooding the engine at times. I'd have expected hydronic lock to a degree but the compression was the same all the way through

[Jamie sawyer]

Just to add fuel is definitely going through as the bench was saturated with fuel. When I put electric starter on prop it was spraying from exhaust port. I tried it as 1/2 open on needle and progressively opened doing 30 second bursts on electric starter opening idle screw up each time a 1/4 turn. It still didn't fire. Recommend screw setting is 2 full turns open

[Steve Hargreaves - Moderator]

That's the point though Jamie...are you flooding it? Is there evidence of petrol on the plug....if it's flooded the plug tip will be wet. If not then there is no petrol getting though & this is where the problem lies

[Jamie sawyer]

If the tank is emptying and spraying all over the bench surely it's coming through the piston port Steve ? I took the head off and the piston was coated in fuel. I couldn't actually see fuel on the head or plug though. I'd say I put 300 ml through it today trying to start it. I think you may be onto something on the compression thing though. I should be feeling more resistance I'd have thought!! I at one point poured a teaspoon of fuel into the plug hole direct and there was no additional resistance could the piston ring be goosed Steve ?

[Martin Harris - Moderator]

Have you tried Jon's suggestions yet? You may well be flooding the engine if you're seeing a lot of fuel coming through. Remove the fuel supply and clear the engine (I'd spin it with a starter with the throttle wide open, ignition disabled for 10 seconds) then enable the ignition and try a start (still no fuel) and assuming it doesn't fire, inject a small amount of fuel through the plug hole, replace the plug and try again. It should fire - if it does, try connecting the fuel supply again and see if it continues to fire or run.

If it doesn't fire during the test above, suspect the ignition (you say the spark is good - is it timed correctly?) or lack of compression. A simple finger over the plug hole while spinning the engine with a starter would give some indication although if you have access to a compression tester it would be better. Lack of compression may be due to the ring not having bedded in yet and may improve if you get the engine running.

Flooding could be due to carb problems on the pump side. Did you check the pump diaphragm and inlet needle valve? I assume you haven't been trying to start it on full choke - Walbro type carbs won't normally allow an engine to run on full choke - as soon as it fires once, open the choke and the engine should run on the next spin...

[Jon H]

petrol engines are quite in tolerant of incorrect fuel mixture. too rich or lean and they simply don't fire at all and it was something I encountered very early when developing my own engine.

Disconnect the carb from the tank and see if my suggestions above bear any fruit. The reason for doing is this was is you are taking one variable out of the equation as the needle settings or diaphragms etc are totally a non issue if the engine is only running on the crankcase fuel.

Petrol engines also have relatively low compression vs a glow so I wouldn't be worried about that just yet.

[Steve Hargreaves - Moderator]

Posted by Jamie sawyer on 15/07/2017 22:37:54:

If the tank is emptying and spraying all over the bench surely it's coming through the piston port Steve ? I took the head off and the piston was coated in fuel. I couldn't actually see fuel on the head or plug though. I'd say I put 300 ml through it today trying to start it. I think you may be onto something on the compression thing though. I should be feeling more resistance I'd have thought!! I at one point poured a teaspoon of fuel into the plug hole direct and there was no additional resistance could the piston ring be goosed Steve ?

I posted in response to your earlier comments Jamie...I think you must have written this as I was writing my comments.

I would certainly agree that fuel is reaching the cylinder in this case...& rather too much of it from what you describe.....do be careful with all this liquid petrol sloshing around too.....it wouldn't take much to end up with a nasty fire on your hands.

It does sound as if too much fuel is in there....as Jon has observed too much petrol will stop the engine firing as surely as too little. I think you need to dry the engine out & get rid of all the fuel in it if you can.....either by spinning it on the starter with the plug out or by tipping it up in various attitudes to empty the crankcase......I would also guess that the muffler is full of petrol too so make sure you empty that too. A lot of petrol here can stop it running too as the vapour can enter the cylinder & make the mixture too rich. Again be careful of the fire risk....

Are you sure you have a good spark? Is the battery fully charged etc. how are you testing it? It's not unknown for an ignition unit to spark happily at normal pressure but be unable to spark under compression.....a difficult thing to test for though I'd agree. Do you have another CDI you could use?

As for the ring not sealing again this is possible but remember petrol engines run much lower compression ratios that glow motors & also rings usually need a bit of pressure from above to expand & seal correctly....you usually don't get that just turning the engine over by hand. It should seal OK when spinning on the starter though.....how does it feel as you try to start it?

Personally I'd follow Jons advise....dry the engine right out, disconnect the fuel & try & start it with a few drops of fuel put down the carb. It should at least fire. If it does we know that compression/ignition are OK & the problem lies with the carb. If it doesn't then the compression/ignition side of things starts to look suspect...

Good luck...

[Jamie sawyer]

Thank you all for your advice. Very greatful of the knowledge you guys have on the subject. I will try drying it out and a small amount of fuel into the carb port. I'll keep choke off and have fuel tank disconnected. Just as reference how much fuel should I try first in port. Maybe a teaspoon full and see if I get a pop from the engine.

Thanks again 👍

[Jamie sawyer]

Ps. I'll use a 6v nihm battery this time also

[Rich too]

+1 on the ignition, I would try a known good unit.

[Jamie sawyer]

Ok I just tried it. 6v battery on ignition and plug out. I did get some fuel out of the exhaust port and shakes hell out of engine to make sure all fuel was out. Turned it over a few times to make sure it was dry. Put it back on mount and teaspoon roughly of fuel in plug port. Checked for spark and there was. Put plug back in and turned it over for 30 seconds with no take on the engine at all. I then put more fuel in carb port. Roughly a teaspoon worth again and 30 seconds on electric starter NOTHING NOT EVEN A POP

I suppose it's but a new ignition box then chaps

[Braddock, VC]

Without being facetious, something isn't quite right here.

I have an ngh 9 and it displayed the symptoms you describe, the prop driver was secured to the shaft with a double flat. It was a matter of turning the prop driver through 180 degrees and it was ok from there on.

You can check your ignition by turning the engine until the piston is near top dead centre, the magnet on the prop driver should be hidden by the sensor fastened to the front bearing housing, if it isn't then ascertain where it is and then suggestions can be made.

Also check the magnet is secure in the prop driver, after all, these engines are made in china.

[Jamie sawyer]

Magnet is there and also when it reaches TDC it's on the magnet 👍

[Martin McIntosh]

Yet more NGH problems then? (See NGH 38).

A teaspoon of petrol is an awful lot. One or two drops should be enough. You may have drowned the plug.

I have a RCG 30 which had zero compression from new but started and runs just fine.

I also have a RCG 50 which died on take off on the 7th flight. The motor would then fire once each time I flicked it but would not run. Faulty CDI unit.

[onetenor]

A spoonful is too much, A few drops only .It's vapour engines run on . not liquid

[onetenor]

Just thought if 4 stroke check valve seating and fit of inserts in head

[Jon H]

Posted by Jamie sawyer on 16/07/2017 16:46:59:

Magnet is there and also when it reaches TDC it's on the magnet 👍

Sounds like the ignition is too retarded to me as you want the spark to occur before tdc. The test I mentioned previously about turning the propeller slowly to see if you get a kick would show this but I don't know if you tried it.

I recommend you remove the plug and turn the engine over to make sure you can see a spark. Assuming you do you need to see when the spark takes place. If its around 30 degrees crank rotation before tdc then you are ok. Less than that might be a problem.