Primarily for general aviation discussion, but other aviation topics are also welcome.
Not a Robin 400 - but the much smaller engined Robin 2112.
Was told I would have to fit a primer or it would never start in winter.
You could crank it forever with no certainty of it starting - and with fear of fire!
Along comes my instructor.
Pulls through the prop.
Mixture to rich and prime with the throttle - usually 4 to 5 was enough .
With mags off, use the starter to turn the prop a couple of revolutions to get the fuel where you want it.
Mags smartly on and starts first time, every time.

I have started a visiting 2112 which was struggling in the same way - so it is not just specific to my aircraft and I have seen bigger Robins with key start have the prop pulled through by hand after throttle priming and start well. (But please, please check the mags are definitely off first.)
I can't believe how many subtle twists and incantations there are to coax individual engines into life. But I wish I could find one that worked on the particular O320 in my Pup. I have to allow at least half an hour to get her going in the winter. Cranking, letting the fuel drip out and the starter cool, cranking, dripping , cranking, go for a walk for 15 minutes, repeat. She goes in the end, but twice I've had the nosewheel on fire on the way there. And before anyone says I'm over-priming, I tried without ANY strokes last time, just to see what happened, and after two 10 second cranks there was still fuel dripping out of the carb.

The engineers (claim to) start her first time every time, but their described method doesn't work for me. Four pumps, throttle open a crack and both mags (in spite of the book saying one). Not even a hint of a cough when I try this. And of course you can't really practice because once she's started once there is no difficulty with subsequent restarts.

It's got to the point where I'm put off even trying in winter. So she sits in the hangar for three months. :( Grrr
I can't believe so many people are having so much difficulty . Have you noticed they are nearly ( all?) CofA ? and key start .
Every aircraft just by fluke on our field is PTF. None of them have key starts.
2 mag switches and a separate starter switch. Prime with mags off whilst sucking in on the starter for good suction into the cylinders 4 blades , turn on mags push starter switch works every time. No danger from hand swinging and flooding ..just keep battery well charged for a decent start. :D
Lockhaven, Ridders liked this
One reason could be a hardening of the leather washer in the accelerator pump in the cold weather. An engineer advised me that the composition of this washer can vary which could be why some engines start easier than others on a cold day. When the engine is hot the washer softens so it pumps the fuel better. I used to pump the throttle to try to soften the washer a little before even getting the aircraft out of the hangar leaving plenty of time for any fuel to drain before attempting to start, then giving three good pumps with time between each for the pump to fill. Seemed to work.
matthew_w100 wrote:I can't believe how many subtle twists and incantations there are to coax individual engines into life. But I wish I could find one that worked on the particular O320 in my Pup. I have to allow at least half an hour to get her going in the winter.....

Well, I flew a Pup Series 2 in a group for 8 years, and it always started very well, even in the cold. I can only suggest that you find a (new) Lycoming specialist and find out what is wrong - I certainly don't recall seeing fuel drip out of the carb so easily that often.
This morning -3 deg C, DR250.160, no primer.

Fuel pump on,
4 long slow pumps of throttle,
pull through 6 blades,
Key ignition start - gentle throttle pumping until it fires, no more than 10 seconds
Immediate return to idle position when it fires
Running on the second attempt.
sleepy weasel wrote:The best thing to do is have the carb checked - if the carb has muck in it which is blocking the accelerator pump then that could account for the poor starting - but also could cause the engine to miss a beat when you really need the accelerator pump to work - for example a go around.

My thoughts exactly on any fault with the accelerator pump, the priming function is just a secondary function.
Has anyone tried using Bradex Easy Start (or any other volatile aerosol) on an aeroplane engine?

In the classic car world (i.e. the same old engine tech our aeroplanes have) there is almost nothing that will not start following a good squirt of Easy Start. Anything that refuses this treatment has an actual electrical or mechanical problem.

Even if an engine can be (just) started without it in cold weather, using it saves a lot of wear on batteries and starter motors.
^^^^^^^ and can crack the piston-rings. Most commonly used to start reluctant diesels, many operators of which will tell" they become addicted to that stuff! will never start normally again." And similar IWT tosh.
It's primarily Ether and lubricant....volatile at low temperatures, highly inflammable. used in model IC Compression -ignition engines (mainly 2-strokes........many squirt too much into the inlet....hydraulic lock or large explosion, as opposed to the controlled burn of conventional fuel, shock on rings cracks or breaks them.....lowered compression, hard starting. just a waft whilst cranking is all that's needed!
Hadn't flown the share-o-plane robin this year, so paid attention to start process. About 9deg outside. Aircraft last flew 4 days ago, everything normal.

Both Mags (We're on Key Ignition so have to start on both)
Mix Rich
Pump Off
5 Pumps

Started after one blade.

Later on, engine lukewarm - two pumps and started after 3 - 4 blades. I'm certain you're over priming - if it takes more than 4-5 pumps your engine is shot.
sky_high30 wrote:Both Mags (We're on Key Ignition so have to start on both)

Almost all aircraft with "key ignition" start on the left mag only - the "start" position on the standard aircraft starter switch disables the right magneto. The only exception is the rare aircraft with dual impulse-mags.

The key point to remember is that an impulse mag at low RPM (<300rpm) fires around 30 degrees later than a standard mag. The standard mag will be timed to fire well before top-dead-centre (TDC), typically 20-30 degrees before TDC. During start-up, firing the spark this early places a huge load on the con-rod and crankshaft bearings, and can possibly start the engine spinning in the wrong direction damaging the starter motor, vacuum pump and other parts. By comparison, at low RPM, the impulse mag will fire roughly at TDC, thus is much less damaging to the engine and causes rotation in the correct direction. Once the engine has started and is running at 500+RPM, the time taken for the fuel-air mixture to burn means that the piston will have passed TDC before the explosion exerts any significant force on the piston and both mags can safely be used.