Strange goings on with an FP40

[Doug Lawrence]

Hi guys, I am a newbie to the MF website/forum but not to modelling.I have an old Priory Models Silhouette (which will give a clue to my age!) powered by an OS FP40. Details are, inverted engine, centre of tank (brand new as is all plumbing) exactly in line with spray bar, Model Techs fuel 10%, 3 line fuel tank with vent connected to muffler, one supply line and one fill/empty blocked off on running. Engine will start and tick over for a short period then stop, no indication as to rich or lean, it just stops! However, if I hold the nose up the engine will tick over for ever and throttle up instantly BUT, if I drop the nose even slightly and slowly, instant stop! The only thing I have not tried is to take the vent off the muffler. Any ideas/suggestions will be most gratefully received! Cheers!

[Martin Harris - Moderator]

Iffy glow plug? What are you using? Does it run OK until the glow driver is removed?

It might also be worth lifting the head and checking the bore for flaking plating/pitting.

Edited By Martin Harris on 05/09/2017 23:38:54

[Philip Ogden]

If it will run with the vent off the muffler, the pressure nipple could be blocked.

[Doug Lawrence]

Thank you Martin and Phil. Plug is a brand new OS 8, I checked (and double checked!) all the plumbing including the exhaust nipple, quite clear. Engine runs perfectly with the nose slightly tilted but stops instantly when I lower the nose. I take your point about foreign objects in the bore and I will check this. I have been modelling for many years but I have to say this has got me very confused! Will report back when I've taken my head off (!)

[CARPERFECT]

There should be no flaking in the bore, its not plated , its not an abc engine, its just steel. i have a 30 year old 35 fp and it still runs fine.

[CARPERFECT]

the 35 and 40 fp come std with a idle bar glow plug, not sure if os still make them

[Denis Watkins]

It is very easy to fit a tank upside down on on its side if the tank is round, and the breather pipes finish up in the wrong position.

Or, where the internal clunk pipe is too long and stuck high or low in the tank, and when moving the model, the clunk feed comes out of the fuel.

Check these,

[Doug Lawrence]

Thank you CP, Yes, I do know it is an ABC engine but I guess no harm in checking for bits in the bore, As you can probably guess I am clutching at straws a bit. Appreciate your input!

[Peter Christy]

Doug, the earlier post by carperfect might hold a clue. I have a model with an old OS MAX 40 in it, and like yours, it is mounted inverted. I had no end of trouble getting a reliable tickover until I fitted an idle-bar plug. Now it will run all day at tickover.....!

--

Pete

[Doug Lawrence]

Peter, yes, I was on the point of replying to CP I didn't know that the FP came with an idle bar, I may have one knocking around somewhere so will give it a try. Thanks CP for the info. Thanks Denis, tank is oblong and clunk hangs as free as a bird!

[Martin Harris - Moderator]

My 40 FPs have always run reliably on Enya no. 3 plugs - not an idle bar in sight - and easily obtainable.

[Doug Lawrence]

Thanks Martin, I will add this to my list of things to try, one of them must be successful!

[Braddock, VC]

Fp has an air bleed carb iirc, look up thunder tiger 42 gp instruction manual, this tells you how to set the air bleed by tipping the nose of the model up or down.

Unless you have already cleaned the air bleed which are prone to picking up gunge it may be worth doing before disturbing the head.

If it has a two needle carb, sorry I spoke.

Edited By Braddock, VC on 06/09/2017 10:41:25

[Braddock, VC]

Just thought, the fuel isn't ancient, is it?

[kc]

I once had an FP40 that ran for years with no problem then then started playing up and eventually suddenly stopped. All the conventional cures failed. Eventually I removed the exhaust to find a big lump of carbonised fuel residue was moving around & able to block the exhaust completely. That's the first thing I would check on your engine as the problem goes away with tilting the plane upwards......

[Doug Lawrence]

Many thanks for all the input lads. Carb is air bleed, fuel is new and muffler is completely free of gunge. I actually stripped the carb as part of my efforts to find a cure, washed it out completely, no bits! I am going to try either a bar or 4st plug and I will certainly have a look at the Thunder Tiger instructions, I am reasonably confident that main and sr needles are set ok or at least very close but I will try all suggestions to try and make sense of it! Cheers!

[Bob Cotsford]

If it's not spluttering to a standstill I'd go with Denis' suggestion of checking the tank out. I've connected the pipes up wrong before now and spent many hap[py hours wondering why the engine would cut after a minute or two. If it is spluttering before it stops, check the tank height again and open the air bleed up a shade. The fact it will run nose up indicates either a rich engine or the feed out of the fuel with the model level. Will the engine run at full throttle with the model level or does it cut regardless of throttle setting?

[Doug Lawrence]

Hi Bob, no spluttering, no speeding up, just stops. I can't tell you how many times I have stripped the tank and plumbing down since this started. Tank is spot on level, no holes in feed or vent lines. I live in a slightly noise sensitive area so I try not to run motor at high revs for too long but I think it will continue to run on wot. Believe me however when I say I have tried all settings on slow needle to try and stop cut out when I drop the nose a bit. I didn't realise that, when new, the FP40 was supplied with a bar plug, there must have been a reason for this so I'm going to give it a go and if that doesn't work to try every other suggestion made by you nice guys above! Cheers!

[Nigel R]

"Enya no. 3"

MTs Firepower F6 or Maxflash M6 are also 'warm' rating and very good.

Did it used to run happily and this is a new thing, or is it a fresh install?

[Doug Lawrence]

Hi Nigel, thanks for your input. The model has been laid up for a few years but recently pulled out of the hangar and refurbished. You will see that all of the tank/plumbing/ carb areas have been renewed , cleaned etc. The aircraft flew perfectly previously (I am talking of a few years back) but memory prompts me that I did have to start it the right way up (engine is inverted in the model). Cleaning, resetting everything has resulted in being able to start the engine inverted but with the now problem of stopping when nose is tilted down (until model is level, not completely nose down). As said above, I have a raft of things to try so will get back to the forum if/when, I hope, there is a good result. Many thanks!

[Martin Harris - Moderator]

Have you tried starting it with the model inverted and does it run nose up/down and level while upside down?

Rich cuts usually waffle first and lean cuts normally rev up briefly...an instant cut suggests glow problems - does it do this with the glow connected?

[Engine Doctor]

hello doug . FP engines never came with idle bar plugs fitted , in fact they never came with a plug fitted at all . OS No8 , Enya No3 will run it nicely If you can find one a Taylor idle bar plug is a good option but hard to find these days and really not needed. Check the air bleed hole is clear as castor can block it and cause very rich idle . The Idle mixture screw should be screwed in until you can see it half way across the hole at the front of the carb. Running too rich can stop an engine dead . Have you tuned engine to peak revs then one click back(richer) before adjusting the air bleed for tick over ?

[Doug Lawrence]

Thank you guys, this is a wealth of info that I intend to try one step at a time. As stated the engine is inverted in the model and whereas the last time I used it, over three years ago, I had to start it with the model inverted and engine up the right way, I can at least now start it inverted. Everything connected with engine, tank and plumbing has been cleaned and/or renewed. Slow running has been adjusted (miniscule amounts at a time ) across rich to lean, same result! Plug is a brand new os8. I am going out in the garden tomorrow to create more noise and work through suggestions, if no luck (watch this space) I shall sit there eating worms. I love this hobby! Cheers guys!

[Doug Lawrence]

Well lads, I am sure you will be pleased to know that I have no idea what worms taste like!
I sort of had a feeling that it was the flame being put out (as stated the engine is inverted), but wasn't sure what to do about it until CP mentioned a bar plug.
I couldn't find my bar plug so I put in an OS F st plug and....bingo! A literal gnats whisker on the slow end (a bit leaner and I'm talking blowing on it) and she now runs up, down, sideways and whatever on tickover and full throttle. Also instant pickup on whacking the throttle open.
I do really appreciate all of your input lads (I assume there are no lassies out there, shame really!) The ability to throw your problems at other people and gain ideas and inspiration from replies makes the forum a Godsend. Thanks to you all!

[Phil 9]

FP40 is a nice little engine

Edited By Phil 9 on 07/09/2017 13:22:21