Primarily for general aviation discussion, but other aviation topics are also welcome.
#1674416
We used to have similar problems with our Continental 0-200 and, some years ago, one member did have a fire. Since then we always follow the same procedure and it always starts instantly.

Blower fire for 30 minutes (Winter only)
Boost pump on until it stops clicking.
6 pumps of the throttle
Turn prop through 8 blades
3 pumps of the throttle
Throttle set and start.

This procedure worked on our clapped out engine as well as it does on our new one.
#1674453
We've experienced difficulties starting engines with carbs at our club on and off over the years. In the beginning, only some pilots have problems but over time more or less everyone is affected. Every time, investigations have shown problems with the magnetos. When replaced, problems disappear. You should have it checked out.

Following the POH rather than local lore should of course be the first course of action. But AIUI that's what the OP does. (We fly C172 and PA28 with both 160 and 180 hp Lycomings, and to my ears eight primings seem excessive. Two for cold starts in the summer up to three-four in the winter is what I'm used to. But whatever the Robin POH says should be right.)
#1674561
Here's an example of a POH that no one I knew followed as it was indeed a bit bonkers. I mean, would you pull through 4 blades with the throttle fully open, mixture full rich and no one inside, praying the mags really were off and there isnt a fault?

It resulted in a replacement of that section of the pups POH

Image

On my Pup, "rosie" which doesnt have a primer (or a key starter, Hatz :wink: ), I seem reliably to be able to start her every time on first/second press of the starter button, in all conditions*. I start on the left Mag.
Im pretty cautious of over priming, so I dont over prime on the throttle prior to start, two or three primes and I dont sit there with the fuel pump running for ages faffing about. I do pump the throttle on turning the engine.

I have some sympathy with Matthew as I have flown his aircraft "Bob" and had difficulty starting her when cold. Ive not seen the fuel running out but what I do is if she doesnt start after a few attempts, well I usually give it a break and have a cuppa and come back after 10/15 min and she starts.

Im pretty sure that its low temperatures that cause the fuel not to vaporise and thus make it more difficult to start a Lycoming in the winter.

*Mostly...!
edited to correct Him to Her :wink:
Last edited by Ridders on Sat Feb 16, 2019 9:40 am, edited 1 time in total.
#1674572
Ridders wrote:Here's an example of a POH that no one I knew followed as it was indeed a bit bonkers.

Image


It is errors like that which make me worry about the requirement (during PPL training*) to use the manufacturer's approved checklist. Every aircraft I fly (eight aircraft, seven types) has some sort of error in the "approved" POH. Most of the errors aren't as serious as the example above, for example only checking the vacuum gauge after closing the throttle, or switching off the avionics after shutting down the engine, but they should (IMO) still be corrected.

* Private flying, including self-fly hire, allows the use of customised (/corrected) checklists.
#1675495
Ridders wrote:Here's an example of a POH that no one I knew followed as it was indeed a bit bonkers. I mean, would you pull through 4 blades with the throttle fully open, mixture full rich and no one inside, praying the mags really were off and there isnt a fault?

It resulted in a replacement of that section of the pups POH

Image

On my Pup, "rosie" which doesnt have a primer (or a key starter, Hatz :wink: ), I seem reliably to be able to start her every time on first/second press of the starter button, in all conditions*. I start on the left Mag.
Im pretty cautious of over priming, so I dont over prime on the throttle prior to start, two or three primes and I dont sit there with the fuel pump running for ages faffing about. I do pump the throttle on turning the engine.

I have some sympathy with Matthew as I have flown his aircraft "Bob" and had difficulty starting him when cold. Ive not seen the fuel running out but what I do is if he doesnt start after a few attempts, well I usually give it a break and have a cuppa and come back after 10/15 min and he starts.

Im pretty sure that its low temperatures that cause the fuel not to vaporise and thus make it more difficult to start a Lycoming in the winter.

*Mostly...!


Even though it’s a “Bob” surely still a “she”?
#1675497
Johne wrote:Even though it’s a “Bob” surely still a “she”?
Oops your right, :oops: Sorry Bob!
Rosie started first press of starter button yesterday, after having sat for two weeks straining at the leash to be let out of the hangar.
#1675574
Bob didn't.

Let the sun warm the engine for a bit, cowling up.

One squirt on the throttle (apparently to get vapour out of the system?) then three more cranking the engine. Throttle just cracked open.

Mags to left (per this thread - normally I'd do both as instructed by my engineer), crank the engine for 10 seconds. Nothing. Wait 20 seconds, crank again. Nothing. Repeat. Couple of coughs. Repeat. Couple of coughs. Repeat with both mags, couple of coughs. Resisting temptation to shove throttle forward on the coughs, 'cos I know that floods her.

Stop. Get out and look (mags off first, obviously). Petrol drizzling onto the front tyre. Wait five minutes till stream abates. Try again. WooHooo! she fires. And off we go for a happy day's flying.

With a reluctant engine, what should I do when she *does* cough? As I said, shoving the throttle forward achieves nothing.
#1675592
I'm definitely not an expert.
But reading here, there is a pattern among some of the non-starters.......
Fuel dripping and "we leave it, have a cup of tea and away it goes"

I've only twice ever seen fuel drippng from an aircraft. Both times were my fault and the flooding resulted in a failed start.
I would definitely be experimenting from a directive of a much lower amount of priming.
Talking (in my experience of engines with priming done on the throttle),
all lycomings I've started needed only 2 or 3 throttle pumps regardless of how cold the day was.
While cranking, gently opening the throttle, but ready to catch the start to prevent the enging bursting into life and straight into roaring at 1600+ rpm.
Occasionaly if that wasn't rewarded with any life, (maybe 5 or 6 blades)
Then 1 or possibly two more pumps.

If experimenting results prove more is required, then perhaps the pump seals are shot and its only resulting in the same volume of fuel as a good one?

Obviously some guys on here have much more experience and knowledge than me but that's how I see it. :thumleft:
riverrock, flybymike liked this
#1675677
Matthew here is what I do, I have a few hours with her now and this seems to reliably work:

Mags to left
Mixture Rich
Fuel boost pump on
Prime twice with throttle
Starter master switch on
Push starter button & as engine turns pump throttle a little
Engine starts *
Mags both
Flick Starter master switch off
Observe oil pressure rising (kinda do this & last two all at same time)
Lean mixture back & Set 1100-1200 and warm engine

I have noticed that it’s very easy to over prime. I also don’t faff about between boost pump on and seeing the pressure rise on the PSI gauge, and the start.

If your poor starting continues, I wonder if it’s worth getting your maint org to check over the carb and look at the timing/mags. Couldn’t hurt.

*mostly first sometimes second press of starter.
matthew_w100 liked this