Cold Start Help

[mccdeuce]

I have read almost every starting thread on here so please go easy.

78 M20J with IO-360 A3B6 with split mags and 250 hrs since factory reman.

Previous owner taught me starting procedures he used. 

Cold: Mixture rich, prop fwd, throttle fwd, boost on for 2 seconds, throttle 1/4", and crank. 

Hot: flood the engine and do flooded Start procedure. 

I changed the hot start procedure to what I had read here - do less! Leave everything as is and crank.  Works flawlessly. Have zero issues. 

Saturday in Melbourne FL (OAT 60s) could not start cold.  Ended up walking away for 30min. Eventually got it with several movements of mixture and throttle I couldn't tell you what I did. 

Sunday in Tampa FL (OAT 50s) no issues whatsoever starting cold.

this morning in Chapel Hill, NC (OAT 34 w/some frost out there) I cannot start at all. External power included. maybe one cylinder would catch on a few of the attempts.  

 

I was under the impression that Cylinder heaters were not needed until below 20. I'm thinking it's more of a mag issue, or ignition switch issue. Engine also running hot I think. Going to download EDM700 data tomorrow. 

Edited November 28, 2016 by mccdeuce

[Bob - S50]

Which model do you have?  Techniques will vary depending on whether you have a carburetor, Lycoming, or Continental.

[mccdeuce]

Sorry yup. Should have listed that. 

78 M20J with IO-360 A3B6 with split mags and 250 hrs since factory reman.

[Bob_Belville]

It might not be your present issue but I would suggest tweaking your cold start procedure:

• Throttle, mixture, prop all forward.
• Boost pump 5 sec - watch fuel pressure to be sure it peaks (in really hot weather I might go 4 secs, in cold 6 sec)
• pull mixture to cut off position, throttle to ~ 1/4" open ( don't be in a big rush at this point, 30 sec or more)
• Crank. When it fires advance mixture slowly. If it doesn't fire after ~10-15 seconds it might help to give it a little fuel by cycling the mixture quickly. 

A weak starter, fouled plugs, or a low/weak battery will be aggravated by colder weather. 

[yvesg]

I preheat my C model as soon as it is 32 F or less. I had some situations here and there where it would not start without pre-heat around that temperature. For around 20 F is would be worse.

Yves

[Bob - S50]

I agree with Bob's suggestions.  We also have a '78 J but ours is the A3B6D.

Cold:

• Throttle 1/4" to 1/2" forward.
• Mixture full rich.
• Boost pump on for 5 seconds, watch to ensure you get fuel pressure.
• Mixture idle/cutoff.
• Crank
• As it catches, smoothly advance mixture  to about half way toward full rich and be ready to catch the throttle to keep the RPM from going much above 1000.  I find that if I go all the way to full rich, sometimes it chokes the engine and kills it, especially if I advance the mixture too quickly.  About half way forward seems to be pretty close to the idle mixture.  Once it's started, I lean until it starts to stumble, then enrichen just enough to run smoothly.

Hot:

• Same as above except skip the mixture rich and boost pump steps.

Warm:

• Try a hot start.
• If that doesn't work, modify the cold start.  Instead of 5 seconds of boost pump, hit it just long enough to get a fuel pressure, probably a second or less.

Another Bob (am I Bob2 or Bob3 or...?)

[Oldguy]

I will chime in with the "Bobs" with the addition of making sure when I shut down, the throttle is set for a 1000 RPM idle unless I know I will be doing a restart within the next few hours. Then the throttle is set at 1200 RPM. Usually takes less than 4 blades to get it running either way.

[ArtVandelay]

I've been told in cold weather you can't be too rich, so for 32 I do 10 secs, 40s, 8 secs, 5 sec is normal.

you may want to have magnetos serviced (new points), and clean and gap spark plugs.

[mccdeuce]

Appreciate the thoughts. Still no luck. Took cowling off to let ambient air warm up there. Seemed to want to catch but still won't turn over. 

Took a pic of the left mag. I had never heard term lag before. This is different than timing correct? 

[mccdeuce]

Finally started. Time to head home to tools and mechanics. 

[Cyril Gibb]

I found that the electric pump initial output varies quite a bit when cold and/or the plane has been sitting for a while.  To make my starts completely reliable and consistent when cold, I keep the mixture in cutoff until the fuel pressure is in the green before opening the mixture for X seconds (where X works best for your particular plane after experimenting) and then going back to cutoff before cranking.  For me, I also prefer to be very slightly too rich so I always know which side of the "too lean or too rich" mixture I'm on.  After a blade or two, the mixture will lean to the correct firing ratio.

As usual YMMV

 

[gsxrpilot]

My solution for cold starting is living in Texas. It's still in the high 70's today. Of course if you need tips on Hot starting, we can talk.

[Bolter]

2 hours ago, Oldguy said:

I will chime in with the "Bobs" with the addition of making sure when I shut down, the throttle is set for a 1000 RPM idle unless I know I will be doing a restart within the next few hours. Then the throttle is set at 1200 RPM. Usually takes less than 4 blades to get it running either way.

Maybe it is unique to my J, but the switch on the throttle for the gear warning is perfectly located at throttle start position.  I prime as the Bobs described, then pull throttle to closed, then open to just past the "click".  This seems ideal to start in most cold conditions.  

-dan

[Bartman]

When less than say 40f I have found this to work without fail on my 1977 J with IO-360 A3B6D

1. Balls to the wall
2. Boost pump for at least 5 seconds, up to 8 sec when really cold.
3. Mixture cut off and throttle at about 1000 RPM
4. WAIT FOR AT LEAST 10 SECONDS to allow fuel to vaporize, longer if really cold
5. Crank and start normally
6. If she does not start right away, stop cranking, re-prime and WAIT 10 MORE SECONDS
7. Uncharted territory....she always starts and I have never gotten this far

[carusoam]

Fuel evaporates at lower rates from warm days towards cold days.  Evaporation is required for fuel and air to mix...

At 60°F paying attention to the normal start routine is a good idea...  this isn't cold yet.

At 40°F is generally where coldness starts being considered...  more of an engine lubrication and tightness of parts issue... people start using engine heaters below this number.

At 30°F a lot of priming is used if preheat is unavailable...

At 20°F, 100LL doesn't evaporate appreciably.  This is where pre-heat is generally required....

At 0°F, this is cold start territory when lots of pre-heat and throttle pumping is used in an M20C... be ready for fires when using this method.

Get ready for winter. 

Best regards,

-a-

 

 

[Bob_Belville]

5 hours ago, mccdeuce said:

Appreciate the thoughts. Still no luck. Took cowling off to let ambient air warm up there. Seemed to want to catch but still won't turn over. 

Took a pic of the left mag. I had never heard term lag before. This is different than timing correct? 

A real mechanic may correct me but I believe the 15 deg lag implies that your left mag has impulse coupling (vs. Shower of Sparks). At operating RPMs the spark lead is 20 (25 for some engines) deg BTDC. At low RPM during starting the spark is "lagged" by 15 deg to get it close to TDC. Ms. Google can fill you in with the details. 

http://www.chiefaircraft.com/slk-4372.html

[kevinw]

From a guy who had similar starting issues (perhaps not quite as bad) I found two things that really helped. First, I had Champion massive spark plugs in my new FRM A3B6 engine and while changing my starting procedure helped some, I still struggled with it a bit. After installing Tempest fine wire plugs, I've never cranked with so much confidence; night and day difference. I truly think I had bad plugs from the get go.

But before you run out and buy new plugs there's one thing I would try when using both Bobs starting procedures. Increase the throttle a little more. My procedure is exactly like Bob-S50's except I increase throttle 1". Just seems like mine needs a little more air and I think my engine runs a little on the rich side; yours might too. I don't bring the mixture in all the way in once it fires either. Like Bob said, about half way seems about right. Give this a try and let us know if it helps. It's frustrating...I've been there.

Kevin

[Guest]

Anything below 40 degrees deserves pre-heating.  Remember that during all this cranking while attempting to start your engine, your camshaft receives no lubrication.

Fuel, air and sparks makes your engine run.  With Slick mags you're already at a disadvantage, add in some Champion spark plugs and you may never get going.

Clarence

[Hank]

Preheat is the secret, at least an hour, overnight is better.

After building fuel pressure, put some into the engine then put on and adjust headset, set the clock and dawdle a little so the fuel can vaporize. Cold fuel vaporizes slowly, the preheat only warmed the engine not the tanks. Wait longer as the temps drop. At 20°F I try to wait 60 seconds. Then crank.

Hey, it works for my C. But then again, hot starts are pretty easy without that fancy fuel injection thingy, too.  

[DVA]

Gut says you have a MAG issue, which might be intermittent.

With the ignition OFF, if you slowly hand-turn the prop do you hear a noticeable click occasionally? If so, that sound is the impulse coupler adjusting the timing lag to fire at a more optimal position for a start. If you don’t hear it, there is something wrong.

Bob_Belville is right on - In the picture you posted, the tag has a marking of 15 LAG - that is the amount of advance past the static timing that the impulse coupler will fire when the engine is turning at a low rpm, as with the starter motor. It means that if you have a static timing of say 20degrees before Top Dead Center, the impulse coupler will ‘lag’ that to 20-15 or 5 degrees BTDC; amore advanced spark makes it easier to get the engine started.

Impulse couplers do fail - they are mechanical - and they do fail intermittently. That could be the reason that on one day you start fine on the next, not so much.

To add, only one of the mags (normally the left) has a impulse coupler. I think I recall in that model, when you crank, the ignition switch grounds the right P-lead to the right mag so that only the left mag is firing in an advanced state. When you release the key, both mags fire but by then the RPM is high enough that the IC has normalized.  You could also have a bad ignition switch which could cause an issue.

Let us know what you discover!

DVA

[Guest]

7 minutes ago, DVA said:

Gut says you have a MAG issue, which might be intermittent.

With the ignition OFF, if you slowly hand-turn the prop do you hear a noticeable click occasionally? If so, that sound is the impulse coupler adjusting the timing lag to fire at a more optimal position for a start. If you don’t hear it, there is something wrong.

Bob_Belville is right on - In the picture you posted, the tag has a marking of 15 LAG - that is the amount of advance past the static timing that the impulse coupler with fire when the engine is turning at a low rpm, as with the starter motor. It means that if you have a static timing of say 20degrees before Top Dead Center, the impulse coupler will ‘lag’ that to 20-15 or 5 degrees BTDC; amore advanced spark makes it easier to get the engine started.

Impulse couplers do fail - they are mechanical - and they do fail intermittently. That could be the reason that on one day you start fine on the next, not so much.

Let us know what you discover!

DVA

It would be a delayed spark not an advanced spark.  The delay or "lag" caused by the impulse coupling brings the spark closer to TDC.

Clarence

[DVA]

Just now, M20Doc said:

It would be a delayed spark not an advanced spark.  The delay or "lag" caused by the impulse coupling brings the spark closer to TDC.

Clarence

Thats what I said - only different. 

I said that the IC “advances” the spark from the static timing point (-20) to (-5) which makes it fire closer to TDC. I could have been more clear now that I re-read.

[cnoe]

And as far as technique goes, don't dismiss what Cyril said earlier. If you let your fuel pressure rise and stabilize before going full rich on the mixture you may get a more consistent dose of fuel into the cylinders. I also prefer to do this with the throttle set (priming only) at the WOT position so that every start is the same flow rate. That's WOT, boost on until full/steady pressure, full-rich mixture for 3-6 seconds (then back to ICO), retard throttle to ~1,000-1,1000 rpm area, then crank. Has worked for more than 300 straight starts with my IO360-A3B6D. The only thing that varies is the time your mixture is full rich. Don't forget to pull the throttle back to high-idle before turning the prop over though.

Honestly, every reply I've read should get it running, so keep the Slick Mags in your zone of suspicion.

[mccdeuce]

2 hours ago, DVA said:

To add, only one of the mags (normally the left) has a impulse coupler. I think I recall in that model, when you crank, the ignition switch grounds the right P-lead to the right mag so that only the left mag is firing in an advanced state. When you release the key, both mags fire but by then the RPM is high enough that the IC has normalized.  You could also have a bad ignition switch which could cause an issue.

I am leaning towards ignition switch as a possibility too.  When I do my mag check when I go second off instant drop, first off I sometimes have to wiggle the key a bit to register the position I want.  

 

I am understanding the cold needs for preheat from the discussion and will look at adding it.  Only previously owned a piston in TX/FL/SoCal so it was never an issue.  

@kevinw    I have been reading your EI thread, will see how things go over the next couple of weeks - I have an electroair mag sitting on my workbench awaiting install but hesitating (already run hot and interested to what e-mag might come out with).  I also have the engine timed at 20 BTDC, so might have to send this emag back for retiming, or just swap everything back to 25.  

Finally - looking at the JPI results from one of the failed start attempts over the last 2 days.

Saturday (OAT 60s): 3 cylinders (1,2&3) came up to 300s but cylinder 4 stayed at OAT

Sunday (OAT 35): 2 cylinders (1&3) came up to 280s but the other 2 stayed at OAT. 

 

Also I still think I am running hot at 380-395 for cylinder 3 in level cruise but that could also be my gauge.

More tinkering to do.

[carusoam]

First thing that comes to mind...

That's not possible..?

The gauges seem to be misbehaving.

 Cylinders can't be running smoothly and show a temperature the same as OAT.

Did I mis-understand something..?

Retarded timing like 25°BTDC generally Heats the CHTs more than 20°BTDC.  The trade-off is it produces a touch more power in an appreciable way.

 

The nice thing regarding CHT probes, they are easy to find, grab, clean, tighten, determine if they are working,  easy enough for even the newest of Mooney pilots...

For homework, see if you can upload the JPI data here.  Sounds like a sensor may have gotten free.  How are the EGT sensors behaving?  You can't get CHT without EGT.  If a CHT has gone funky, it may be a function of the EGT.

realistically, there are a dozen guys here that can read your data, and put you on the right track.  That would be better than trying to type a book, and have the same dozen guys try and interpret your writing skills.

Best regards,

-a-