Engine won't start! Any tips?

[OBK!]

Over the passed few weeks, with the decreased mean temperature :mad: I have have come across a few flat batteries due to engine start problems!

I was just wondering what tricks all you people have up your sleaves for getting them going? I was happily turning the engnie over at Wycombe a few days ago but nothing, nothing even a spit! ....flat battery so I called upon an engineer who brought out a ground power unit, attatched it and I gave it another try, still nothing!

"Do you want me to have a go?"....."YES PLEASE!" to my delight :D about 3 turns and he had it going, but I noticed he used this odd procedure, Mixture OFF, Full throttle and cranked her up, as soon as she spluttered mixture full, and half throttle then stabilised her at 1200rpm..

Just wondered what other ways there are of getting the donkey going?!

[poetpilot]

Just for starters, you could try fuel ON/pump ON, prime a bit as required, then all switches OFF, brakes ON and (check those switches are indeed OFF):eek: hand swing through 8 or so revolutions... saves the battery, gets a leedle oil circulating and hopefully primes the cylinders each with a shot of go-juice.

[2Donkeys]

he used this odd procedure, Mixture OFF, Full throttle and cranked her up, as soon as she spluttered mixture full, and half throttle then stabilised her at 1200rpm..

That "odd" procedure is the standard way of dealing with a flooded engine. If it worked, as you say, then the implication is that you had previously flooded the engine, either by over-priming or over-pumping the throttle before your start attempts.

[FlyingForFun]

OBK,

Never had this happen on an aircraft, but seen similar on cars several times.

Could you describe the symptoms a bit further? You said you were turning the engine over, but "nothing, not even a spit". Does this mean the engine was turning? Because if it was, it isn't a flat battery. As 2D says, the mixture-off procedure is for a flooded engine, and probably means you've over-primed the engine, or possibly left the throttle too high.

If your battery is genuinely going flat in the cold weather, you'll need a new battery. But I think, if you are actually having battery problems, it's more likely to be caused by the fact that you're turning the engine over for a lot longer than usual, because your priming procedure isn't getting the engine started.

FFF
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[OBK!]

I think maybe that time the battery was half flat, because compared to the ground power unit, the prop was hardly rotating. When the ground power unit it was spinning faster on ignition.

FFF,

Primed 6 times, cranked it up, nothing happened. The prop spun but no life in the engine. The enginner told me it was the weather...

[Flyin'Dutch']

OBK

Sounds like you are heading for a new battery!

Get one now; it is pretty inevitable that you need one and it saves you a lot off hassle and irritation.

FWIW

I always pull the prop through for as many blades as there are cylinders.

Of course make sure mags off; throttle closed and brakes on.

Serves 2 purposes:

1. You check the compressions and ensure they are all similar.
2. Breakes the oil film and is said to reduce the resistance when starting

Make sure you are priming adequately (which can be quite a bit more if it gets cold)

Dunno where you are based but here in middle England it has not been really cold yet so if the same applies to you I would expect not too many starting problems just yet.

So if you do think about a new battery and if that does not sort the problem (although I suspect that it will be fine then if you can handswing it and get it to go on the third attempt) get an engineer to have a closer look.

Starting probs in an engine which was fine until recently may well indicate more problems on the way! :eek:

MHO of course

FD

[bluskis]

Read again what two donks said.

What the mechanic did was indeed the normal procedure for starting a flooded engine.

Engines are particularly easily flooded when trying to start hot.

Best thing is to try without priming, and if this is a non starter, prime and try again, but just a little prime.

If this fails , prime to make sure you are over rich, then do what the mechanic did, mixture to cut off, throttle open, ond on firing advance the mixture and adjust the throttle to the point the engine keeps running.

If this fails, take a half hour break and start all over.

This is for an injected engine, I have forgotten if it is the same for a carb engine.

[Saab Dastard]

OBK!,

I remember reading in my Trevor Thom that you shouldn't fly with a flat battery, even if you can start the engine with a ground APU.

The reason is that the alternator will not work (and hence charge the battery during flight) if the battery is completely flat as the alternator needs to draw some current to work.

2p

SD

[OBK!]

No it wasn't completely flat, radios worked fine for me to call tower and tell em' to delay my ETD for abouty 15mins unless otherwise told...just wasn't throwin the prop fast enough i guess.

[big pistons forever]

I find that if any piston engine is being truculant the best bet is to deliberately flood it. This way you know where you stand and If you crank with the mixture at idle cut off and the throttle wide open the engine will ALWAYS start. This works for every engine I have ever met ( C65 to P&W R2800 ). If the OAT is around 0 deg C or colder, however you have to be carefull about induction or stack fires. If it is really cold it is much better for the engine to preheat before starting. One trick I have used on flat carburated engines when it is cold out is to set up for a normal cold start but leave the primer out while starting. As the engine fires slowly push the primer in. The extra gush of fuel will allow the engine to pick up enough to stay running. Another trick is if an otherwise normal small piston engine suddenly will not start, it might be the MAG impulse coupling is hung up. With the MAGS off rotate the prop slowly. there should be a definite click as the impulse spring is released. If you do not hear it take a piece of wood and give the left MAG a good bash. This procedure once saved me from having to spend a night at a deserted wilderness airstrip.

[Skylark4]

Big Pistons
It`s not always the left mag. I heard of one fairly recently where the inpulse coupling was on the right mag. May have been the Chipmunk.

Mike W

[basil fawlty]

1. please invest in a new battery. any battery over 2-3 years old will be suffering from "sulphated" plates, which will short out some of the cells which will result in a much decreased amp hour rating.
2. you don't specify aircraft type but it seems it is not a fuel injected engine....so i suggest prime once, throttle slightly open, turn over, if no start then prime again and it should go on the second attempt. if it attempts to start open the throttle and keep the starter turning it may well fire up!

[BEagle]

Probably a weak impulse mag and a tired battery! Low temperature, poor fuel atomisation and a 'fatter' spark is needed to light the fire. Also the low temperature will reduce the battery capacity.

But the temperatures haven't been particularly low yet this year at Booker........

[LowNSlow]

The speed the engine is cranked over doesn't make much difference.The spark generation of the impulse mag is dependent of the strength of the springs in the mag rather than the speed it is turned. As an example, watch a big radial engine starting, they don't very quickly initially.

On a hand start engine, one cure for a warm engine that refuses to start is to deliberately flood it as big pistons said, then with the mags off, throttle open wind the engine backwards through twice as many rotations as there are cylinders leaving one of the blades just on a compression. Reset the throttle, turn on the impulse mag (right hand mag on a Cirrus engine) and give it a swing. 9 times out of 10 it'll fire up first swing. One warning though, if you turn an engine with a vacuum pump fitted (if the aeroplane doesn't have venturis dangling on the outside it's got a vac pump :D) it'll probable wreck the blades inside as they are designed to run in one direction only. As an aside, the vac pump can also be damaged by an engine backfiring and turning backwards for a few blades.

[david viewing]

Beware of fire!!

This talk of deliberately flooding, etc., has a danger. If excess fuel runs back down the carburettor bore into the hot air changeover valve, it can ignite if the engine spits back without starting.

This seems to be a real threat if the throttle is pumped because many engines have an accelerator pump just like a car. Priming is different because the primer injects into the inlet manifold away from the carb, where on some engines at least it collects without running back.

We discovered that opening the trottle 5 times on our PA-28 was enough to have liquid fuel running out of the (leaky) hot air changeover box.

Of course the golden rule in the event of carb fire is to continue cranking and preferably start the engine before shutting down to investigate the damage. But the engine not starting is how you get into this mess in the first place...

I don't know what a 'safe' number of primes is - some CFI's use 8 which seems a lot to me. Any comments?