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0-360 A1A Cold Start Issue

P

pjmRV8

Member
I have an RV-8 with a 1500 hour since new 0-360 A1A engine. I fly in southern Indiana and most of the year it starts on the first or second blade. I use preheat on the engine below 40 degrees and most of the time even if in the 50’s.
I am having issues when traveling and the temp is 45-55 degrees- the plane will not try to fire. I do not have a primer installed (on the list for this winter). I have used the accelerator pump while turning the engine over 2-3 times careful not to flood the engine. I have not observed fuel from flooding. My question is why does there seem to be a spark issue between at 45-55 degrees that doesn’t exist when temps or preheat is used to get the engine temps above 55 degrees? Is the fuel not atomizing at the cooler temps? Maybe the primer solves the issue? I have two mechanical mags that have been timed and overhauled. I have a new FT230 battery (works great). The engine runs great and have no other issues. Any advice is appreciated.
Thanks
Phil
 
It probably is a fuel issue, not a spark issue

You say you have used the Excelerator pump two or three times carefully so as to avoid flooding.
What do you mean by this?
The likelihood of you flooding the engine, using the Excelerator pump, as in the same context of flooding a legacy car engine is extremely remote, if not impossible, as long as you are cranking the engine, while you are moving the throttle.
Most often the cause of failure to start when it’s very cold, as long as everything on the engine is in good working order, is a failure to be aggressive enough with the throttle.
What generally works well is to cycle the throttle full range quickly, as in 1 to 2 seconds for each stroke, and the engine will usually fire on the third or fourth stroke as long as the battery is good and the engine is cranking at a good rpm.
 
Mags?

I had a 1500 hour O-360M that acted like that. It turned out to be the mags. You looked at that already........
Had a little oil behind the seals also. chased it forever.
 
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Same…

Phil,
I have the same engine, O360-A1A (ECI). Barely turned over below 40F. I ended up installing the anti-splat plug-in heater. I use my RV for business and travel quite a bit, to remote airports. I’ll park or tow it to any accessible outlet (within 200’) and plug-in for 2-3 hours before flight. Just did this at Tehachapi, CA, Telluride, CO, and Klamath Falls, OR. Works great.
Paul
 
I have the same engine and had very similar problems for a while, it would start very easy either cold or hot, but not warm. It turned out to be the spark plugs, I re-gapped all of them and problem disappeared. I don't really know or understand why.
 
Phil,
I have experienced the same with every carbed lyc I’ve owned. I had a primer system on one of my prior birds, but on all the others I’ve pumped the throttle (accelerator pump) to get it started. When you preheat your oil in the winter, it probably doesn’t warm the carburetor very much, so the fuel is cold, as is the air being sucked in through the carb and the fuel doesn’t atomize as well, so I need a couple extra pumps on the throttle. The important thing is to not pump the throttle until you are ready to engage the starter. You don’t want raw fuel that doesn’t get sucked up into the intake tubes dribbling down out of your carburetor throat and laying in the bottom of the air box. Airplanes have been lost in a fuel fed fire this way. A back fire can create big problems.
If I didn’t pump the throttle on my O-30-A1A / RV6 I would never get it started.
 
liuk said:
I have the same engine and had very similar problems for a while, it would start very easy either cold or hot, but not warm. It turned out to be the spark plugs, I re-gapped all of them and problem disappeared. I don't really know or understand why.
Click to expand...

Unlike a car, the mag has it's own generator to make power for the coils. Power is RPM dependant (low RPM=low power output). Coils are quite weak. larger plug gaps require more energy to jump the gap. THerefore, at cranking level RPMs (better stated at impulse generated RPM, as they are doing the spinning then), larger than specified gaps can exceed the coils energy capacity to make the spark. Once started, the power output goes up and enough power exists to jump the larger gap. In these cases, you are at the fringe, so sparking can be hit or miss.

To the OP, the setting of the egap inside the mag also influences power production (technically timed coil saturation level) and can create this same issue, even with properly gapped plugs.
 
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pjmRV8 said:
I have an RV-8 with a 1500 hour since new 0-360 A1A engine. I fly in southern Indiana and most of the year it starts on the first or second blade. I use preheat on the engine below 40 degrees and most of the time even if in the 50’s.
I am having issues when traveling and the temp is 45-55 degrees- the plane will not try to fire.
Click to expand...

Howdy Phil - I have the same motor/setup but with dual p-mags. No expectation that my technique (for that OAT) will work for you but if you'd like to try it. I typically preheat at least the oil at 45 degrees, that's less likely at 55 degrees.
1. Mixture rich.
2. Two pumps of the throttle.
3. Crack throttle open slightly (just barely off the idle stop).
4. Engage starter.

If the engine is cold (no pre-heat) and OAT is in the 45 degree range - I use three throttle pumps.

Mine usually fires within one blade.
 
I know you said that you had overhauled the mags, but this just sounds so much like a problem we had years ago with Louise’s RV-6 when she’d tie it down on the ramp in the winter in College Station. Temps about 50 - no problem, temps below 40 - not start.

Turned out that the impulse coupler was “gummy” at low temps and wouldn’t give a nice snap and good spark. So….something else to check. Not all overhauls are created equal - and some things suffer infant mortality.
 
Phil!

If the idle mixture is set too far lean, a difference of 1/8 turn will make or break cold starts. Just had to deal with this exact problem on a PA32. Slight enriching fixed it.
 
rvbuilder2002 said:
It probably is a fuel issue, not a spark issue

You say you have used the Excelerator pump two or three times carefully so as to avoid flooding.
What do you mean by this?
The likelihood of you flooding the engine, using the Excelerator pump, as in the same context of flooding a legacy car engine is extremely remote, if not impossible, as long as you are cranking the engine, while you are moving the throttle.
Most often the cause of failure to start when it’s very cold, as long as everything on the engine is in good working order, is a failure to be aggressive enough with the throttle.
What generally works well is to cycle the throttle full range quickly, as in 1 to 2 seconds for each stroke, and the engine will usually fire on the third or fourth stroke as long as the battery is good and the engine is cranking at a good rpm.
Click to expand...

Thanks for the advice. I will give it a try next time I am out.
 
Priming

This has been discussed here numerous times. Priming by pumping the throttle should only be done with the prop turning. There is a real risk of backfire and fire if the engine is primed with throttle before engaging starter.
 
Thank you all for the time to respond and for the ideas. That is exactly what I was looking for. I will experiment and do testing to see if I can uncover. I appreciate this group!!! Happy Holidays and RVing!!
Phil
 
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