Cold start procedure with PMAG

Since I have installed the second PMAG, my cold start procedure has not been on the mark as I like it to be and I was wondering what procedure other people use that has a better result.

The engine is an YIO-360-M1B and I used to hit the boost pump for about three seconds before cranking. I would have my idle cut off to the appropriate setting for the altitude (slightly out) and it always started OK. Since installing the second pmag, I get the feeling that three seconds of boost pump is flooding the engine too much. I have tried one second with not much good result and also I have tried 3 second of boost pump followed by the idle at cut off position (similar to the hot start) and that has yielded even worse result.

Just wondering what procedure others use with two PMAG?

Dual Pmags.

3-4 seconds of boost pump with Throttle and Mixture full rich.

Boost pump off and mixture cutoff.

Throttle is cutoff, them about 1/8 inch open.

Press start, 2 blade it fis and then full rich mixture!

Seems to work good.

Cold start with pMags

Throttle cracked open
Mixture at cut out
Boost bump on
Mixture to full rich for 3-5 seconds
Mixture to cut out
Boost pump off
Ignitions on (both)
Crank engine
Mixture to very lean idle after start.

For hot start same procedure except eliminate the "mixture to full rich for 3-5 seconds". Ease in mixture after you start cranking.

Carl

The mag you replaced when you added the second PMAG--------did it have an impulse coupler, or retard breaker/Slick Start setup?

Mike S said:

The mag you replaced when you added the second PMAG--------did it have an impulse coupler, or retard breaker/Slick Start setup?

Click to expand...

It did have an impulse coupler but I had also taken the tab off my key switch so both would be ungrounded unlike before when my right slick mag was grounded on the start.

Carl Froehlich said:

Throttle cracked open
Mixture at cut out
Boost bump on
Mixture to full rich for 3-5 seconds
Mixture to cut out
Boost pump off
Ignitions on (both)
Crank engine
Mixture to very lean idle after start.

Click to expand...

I think you forgot to say that mixture has to go to rich as soon as engine catches when cranking. Also, you should have full throttle as well as rich mixture when priming with the boost pump, then bring throttle back to idle and mixture to lean before cranking. The mixture goes to lean before cranking so that you don't flood it in the event of a non-start. I think AFP instructions actually tell you to have the purge valve at ICO for this step and then push it in when the engine catches, but the mixture knob seems to serve the same purpose just as well

Slightly different wording/procedure for me:

throttle open (in)
mixture full rich
boost pump on for 4 secs
mixture full lean (out)
crank engine
mixture immediately to full rich as soon as engine catches; you can lean later after started if you wish, although this isn't really necessary with a properly set up AFP system (per Don at AFP).

On colder days when the fuel isn't vaporizing quite as well as on a warm day, I have found that a 10 second wait after priming with the boost pump and before cranking improves my starting.

Erich

erich weaver said:

I think you forgot to say that mixture has to go to rich as soon as engine catches when cranking. Also, you should have full throttle as well as rich mixture when priming with the boost pump, then bring throttle back to idle and mixture to lean before cranking. The mixture goes to lean before cranking so that you don't flood it in the event of a non-start. I think AFP instructions actually tell you to have the purge valve at ICO for this step and then push it in when the engine catches, but the mixture knob seems to serve the same purpose just as well

Slightly different wording/procedure for me:

throttle open (in)
mixture full rich
boost pump on for 4 secs
mixture full lean (out)
crank engine
mixture immediately to full rich as soon as engine catches; you can lean later after started if you wish, although this isn't really necessary with a properly set up AFP system (per Don at AFP).

On colder days when the fuel isn't vaporizing quite as well as on a warm day, I have found that a 10 second wait after priming with the boost pump and before cranking improves my starting.

Erich

Click to expand...

Sorry - do not agree.

Carl

Fuel systems sometimes behave very differently WRT priming. Aside from the standard WOT/full rich during the prime, my -8 needs only a touch of boost pump. In fact it is only on long enough to hear it build pressure (slow down), and then off. Typically this is 1 second. Thats for the -8... My Rocket takes a longer run with the boost and my Hiperbipe took even longer.

And I start (crank) with the mixture full rich when cold.

Bavafa said:

Just wondering what procedure others use with two PMAG?

Click to expand...

I also have dual Pmags and have spent 4 years searching for the "starts like your auto" holy grail.
I think I've finally gotten close. I have an AFP with purge valve so ignore that if it doesn't apply
COLD START
Fuel selector left tank
Mags off
Throttle 1/2
Mix rich
Purge valve ICO
Boost pump run until max fuel pressure
Boost pump off
Purge valve in
Boost pump run for 2 sec max
Throttle slightly open ~ 1/4 in
Hit start and be ready to adjust throttle to keep engine running
HOT START
Fuel selector left tank
Mags off
Throttle 1/2
Mix rich
Purge valve ICO
Boost pump run 20-30 sec (purging hot fuel to right tank)
Boost pump off
Purge valve in
NO PRIME!
Throttle slightly open ~ 1/4 in
Mixture ICO
Hit start and move Mix lever slowly to max. As DanH reported earlier at some point the magic F/A mix point will be reached and it starts regularly. Also be ready to adjust throttle to keep it running.

Mike S said:

The mag you replaced when you added the second PMAG--------did it have an impulse coupler, or retard breaker/Slick Start setup?

Click to expand...

Bavafa said:

It did have an impulse coupler but I had also taken the tab off my key switch so both would be ungrounded unlike before when my right slick mag was grounded on the start.

Click to expand...

So, after removing the mag with the impulse coupler you now have starting issues.

Methinks it may be due to a timing issue more than fuel.

Doesnt make sense that removing a mag would cause you to need to change your fuel management protocol during start.

Mike S said:

So, after removing the mag with the impulse coupler you now have starting issues.

Methinks it may be due to a timing issue more than fuel.

Doesnt make sense that removing a mag would cause you to need to change your fuel management protocol during start.

Click to expand...

Mike,
Your logic is right on the mark but I don't have any other anomalies. I have verified the timing of the PMAG which is very simple and yes I have used TDC and not the 25 BDC mark and also now have the EIC which can verify that the timing in addition to the green light on the PMAG. Ironically, my hot start has been easier.
Perhaps out of fear of flooding it, I am starving it.

Thanks to all for their input and sharing their procedure.

Apparently I've been doing it wrong, but it seems to work for my injected, dual pmag setup on my airplane:

Cold start:
thottle idle, mixture rich, boost pump on, watch fuel flow and the instant fuel flow peaks and starts back down turn off the boost pump. The colder it is outside the more time I give it before hiting the starter...anywhere from immediately to 20 or 30 seconds, but it never gets that cold in the SF Bay Area.

I'm no expert but it seems to work for my engine. I used to cold start with mixture at idle cut off but had mixed results but I still use that technique for hot starts.

Bavafa said:

I have tried 3 second of boost pump followed by the idle at cut off position (similar to the hot start) and that has yielded even worse result.

Click to expand...

If you go to ICO after priming and you crank it for a while with no sign of a kick, it is highly probable you did not prime enough. When you over-prime and go to ICO, a few cranking cycles with no fuel and it will lean out the mixture in the cylinder enough to reach a combustible state and it fire's off (unless it's flooded). You add in mixture once it kicks (how fast you feed it in is a bit of art. Need to sense how over-rich it is). If you don't know the amount of prime required, it is easier to over-prime a bit and start in ICO. Not saying it is preferred, just easier, but be careful not to over-do it, as you can cause backfires. I will tend to under-prime a bit and if it doesn't fire in the first blade or two, I go full rich for a couple of blades, then boost pump on. If that still isn't working, stop and re-prime. If you over-do it and think you're flooded, go full throttle and ICO and crank until it kicks. It won't start (although it will sound like it's trying to), but gets you back to a known state where you can start over again. I discourage people from using 1/2 for full throttle to start an over-primed engine without a spring loaded throttle or good experience with the procedure. It's not the right way to do it, especially with no way to disconnect your engine from the propulsion mechanism. If you need anything more than 1200 RPM throttle setting to start, you're over-priming/flooding the engine and should be improving your start procedure through research and practice.

FYI, the amount of prime required is quite dependent upon ambient temp. You'll need about 3-4 times as much at 20* as you did at 70*

Larry

A starting routine with Dual PMAGS

I have had luck (150hrs or so) with the suggested procedure in the EMAG Installation and Operating Guide, LC114.27, page 20.

Fuel Injected Engines

A starting routine for fuel injected engines (suggested by E-MAG customers) is as follows:

a) Master ON
b) Open throttle ??
c) Mixture
d) Crank until first fire (typically 3 to 4 blades)
e) Feed in mixture gradually

The next issue I had was finding the "lean" position...
For my YIO-360-M1B:
"cold lean" - mixture knob 1/3-1/2 way out from full rich
"hot lean" - mixture knob 1/2-3/4 way out from full rich

But, as Mike said, you may have a non-fuel issue after replacing your previous mag.

Cheers!, Cam

Welcome to VAF!

Cam, welcome to VAF