Cold Weather Starting Difficulty

I have a RV-7A equipped with the TMX-O-360, a MA4-5 carb and Slick mags with impulse coupling on the left one. When it gets down to 40-50 degrees, I have considerable difficulty getting the engine to start. I have tried leaving the primer pump on for 5 seconds and also 8-10 seconds. With about 10 seconds, it will cough, sputter and then die. When I do get it running, even up to regular idle speed, it dies about 3-4 seconds later. It seems to be running just on prime and is then starving for fuel. After a dozen attempts, it will finally stagger to life, and then idle just fine if I can keep it running at least 5-10 seconds. But I once ran a battery down in the process. Since the engine doesn't seem to want to stay running once it does start on the first few attempts, it makes me wonder if idle mixture is set too lean or if float level is low. Maybe it wants more than 10 seconds prime at lower temps? In warmer weather, the engine starts immediately. Any thoughts/comments appreciated.

Sounds like a lot of priming. My O-340 takes 2-3 seconds prime and that's enough. (My primer goes into cylinders 1&2 only.)

Is there a chance you're making it too rich by over-priming?

Could be bad advice, please read rest of thread later.I don't have a primer on my O-360 MA4-5, I found 2 shots of throttle and pulling the throttle all the way closed to the stop works best for mine. I was in the habit of only pumping the throttle if the prop was spinning, on the RV it didn't work as well. I believe close the throttle all the way helps richen my mixture, after it starts I bring the idle up to a normal 600-800 RPM.

crabandy said:

I don't have a primer on my O-360 MA4-5, I found 2 shots of throttle and pulling the throttle all the way closed to the stop works best for mine. I was in the habit of only pumping the throttle if the prop was spinning, on the RV it didn't work as well. I believe close the throttle all the way helps richen my mixture, after it starts I bring the idle up to a normal 600-800 RPM.

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I just want to point out that pumping the throttle with the engine NOT cranking is a significant fire hazard - you end up with a pool of gas in the FAB, and a backfire is likely to set your pride and joy on fire. Yes, you can get away with it a long time, but if it happens - you can't get an RV cowling off fast enough.

If it won't start without doing that - I'd find out why. Pumping with the engine cranking works really well for most everyone that does it, and if not, you might have an accelerator pump problem.

Cold Start

Get a couple light bulbs and hang inside the cowling via the oil door. That provides about 60 F of heat for a quick start on the coldest morning. Of course, use caution so they're not touching the cowling or other heat sensitive areas. As Paul noted, never pump the throttle without cranking.

Jim Diehl 7A
Lycoming 0-360
Lock Haven, Pa.

All lycomings start easier with warm air in the bottom end and intake tubes. The easiest way to do this is a 110V oil pan heater strip siliconed onto the bottom of the sump. 100W is plenty of heat. There is no need to leave it plugged in all the time, only for 1-2 hours before start up. With cowl plugs in the cooling intakes or a blanket over the cowl, you can even be outside in the wind and get good pre heating.

A hot air pre heater like "The Hornet Heater" from aircraft spruce is also an excellent, safe and easy way to make life much easier on the Lycoming. They have proper temp limits and won't blister your cowl or paint.

If the oil is cold and stiff, the impulse mechanism on the LH mag might not always function as intended, only adding to longer than needed cranking.

Warm oil on start up also extends the life of any engine.

Preheat when cold as mentioned by Jim and F1R. Any method is good as soon as oil is warm and battery preconditioned. I am parked outside and don't have a luxury of an electric outlet so I use a propane heater loaned by a fellow RV builder. Works like a charm at ANY low temps.

Ironflight said:

I just want to point out that pumping the throttle with the engine NOT cranking is a significant fire hazard - you end up with a pool of gas in the FAB, and a backfire is likely to set your pride and joy on fire. Yes, you can get away with it a long time, but if it happens - you can't get an RV cowling off fast enough.

If it won't start without doing that - I'd find out why. Pumping with the engine cranking works really well for most everyone that does it, and if not, you might have an accelerator pump problem.

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I should've been much more discretionary on my reply. I once caught a C150 airbox on fire using someone else's over priming procedure. I couldn't get out of the airplane fast enough much less continue cranking the engine with the mixture in idle cut-off or de-cowl the airplane.

My RV7 O-360 has dual EFII electronic ignition, everything seemed to run very well except the start. On the first start of the day I watched the prop spin for 7-10 seconds (pre-heated to 50 degrees or 80 degrees OAT) as I pumped the throttle 3-5 times as the starter spun the blades for a normal start. Initially I thought the ignition may be browning out during start. Long story short I found that 2 pumps of the throttle followed by a quick start button push (1 one thousand count for 2 pumps and starter hit) with the throttle at the idle stop fires the engine within a couple blades. Emphasis on the quick pumping of the throttle and spinning the engine to minimize any fuel pooling in the airbox.

I suspected the carb was a little lean for my RV because my idle mixture screw was 4 turns out instead of the initial 1 1/4 turns out. 4 turns out gave me about 10-15 rpm rise at idle cut off, Further turns out didn't seem to enrichen the idle circuit any more and very little residual resistance to hold the screw in place. At full power My leanest EGT at cold temps was only 80-100 degrees ROP, warmer temps yielded about 150 -180 degrees from full rich to peak EGT.

I'm currently in process of my first condition inspection, since my carb (MA4-5 3858) was still within the warranty period the fine folks at Marvel Schebler were willing to check it out. My carb flowed to within factory spec's, some throttle positions were closer than others. Marvel Schebler did en-rich both the idle circuit and main jet of my carb, based on my EGT and idle observations. I'm hoping to find out more specifics later. I hope to have some more real flying numbers soon.

You said your left mag has an impulse coupling, are you starting on just the left mag or on both?

One trick that works well for me. After you try starting a few times (with a normal start routine and normal priming), just wait.... sit tight for about a minute... then try again.

I can't explain why this works (for me), but it works (for me)

Two factors

LettersFromFlyoverCountry said:

One trick that works well for me. After you try starting a few times (with a normal start routine and normal priming), just wait.... sit tight for about a minute... then try again.

I can't explain why this works (for me), but it works (for me)

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Body heat and prayer

Gary

The words coming out of my mouth in those situations would never be described as "prayer".

Hard Start...

You know, the mag switch might be wired up "L" "R" in the wrong positions.
When you start it grounds the left mag. Just a thought...

Primer

I installed a primer solenoid system from vans catalog. When it's really cold, I use it and it works well. I use it when temps are below freezing. This I believe is better than pumping the throttle. The front two cylinders on my O360 are the ones being primed. Marvel carb installed. Starts about like most other planes. All planes seem to have their own way. Just remember, too much fuel can be a problem. The solenoid is fitted/plumbed just past the gascolator on the firewall and is switched on/open, then run your boost pump several seconds to inject raw fuel to the front cylinders. Shut off solenoid and crank engine. Mine will start normally after a couple blades on the crank cycle.

I have the same problem. It was bothering me more until this thread. I learned a thing or two here.

My first winter with the 0-375. It cold and hot starts quickly in the warm weather. But recently, it has given me trouble. I typically fuel with a single stroke of the throttle and then set the throttle about at the 1000 rpm position. Now, when it won't fire up, I don't know what to do. Typically, a little more advance on the throttle. That usually doesn't help so in fear of flooding the engine I pull the throttle back and try a quick shot with the primer. After that doesn't work, I shut it down and give the starter a rest. If I am lucky, the next go around will get it to fire, but twice I've had to get out and recharge the battery.

One thing I did notice this weekend is just how much more robustly the starter turned the prop with a full charge on the battery. That seemed to fire the engine right over but it may just have been the fact that I had already tried for a while. My gut feeling is that the battery had a lot to do with it. I try to fly my plane every weekend but it had been 5 weekends since I had a chance to start the engine this weekend. The battery still had enough power to turn the prop, but you could tell it was struggling. Even on successive weekends, the battery is not typically as strong as it was after a charge yesterday.

I am going to work the closed throttle start position into my procedure and see if that helps. I hate to use the primer though because I worry about wearing on the cylinder wall from the fuel. Also, I am never sure if it works like the rear wiper washer on my car...takes a few seconds to start flowing. I am never sure how much fuel I just injected into the cylinder. A frustrating process for sure. But I am glad to see we are not the only ones with this issue. For what it's worth, I preheat the engine with forced hot air for a good 1/2 to full hour. I still have all the issues above.

In light of recent chats about spark plugs, by chance, are you using Champion plugs? Long shot....

Interesting read. And another thing I have to worry about now.

I have had good results by completely closing the throttle during start. But the pre-requisite is that the carby's fuel bowl has fuel, so I run the electric pump for 20-30 seconds before and during start.

Also, consider pumping the throttle empties the fuel bowl.

I believe that the idle enrichment circuit works best when the butterfly valve is closed. Note the small hole in the side of the carby throat above the throttle plate is where the enrichment circuit emits the fuel (and air) mix. If the throttle is opened then there is insufficient pressure differential to get the fuel flowing through this secondary circuit plus the ventruri & main jet has insufficient airflow to draw fuel to start the engine.

I have no primer on my engine and rarely need to pump the throttle. This is on an O-320, not sure if the larger caby has the same features.

One throttle stroke and back to closed and she started right up. And without that hi rpm burst from the extra fuel. Great tip. Thanks. Andy

I am running an IO 360 in my RV so the follow is from what we use on a friends RV6, C 172 and a few others when it gets into the 20.

We preheat... Not a fancy preheater but one of those ceramic heaters which we fit with duct work from the aviation dept of Home dept. Usually for an hour.

The next step is one you might not do... but if you check the mags grounding out at idle rpm you have a pretty good confidence that with the mags off and the key hanging up.. we pull the prop through about 10 revolutions... ( If you do not check your mags grounding on a daily basis do not do this until you know your mags ground out with the key off.)
Use the same technique you would if you were propping the engine except
Mags. Off, Fuel OFF, Mixture idle cutoff, and throttle to idle and someone on brakes.

Starting.
Mixture rich, 3 pumps of the primer, we generally leave it out,
Throttle 1/4 open or less. Clear and engage starter. If the engine sputters
we slowly advance the primer. We do not pump the throttle...
99 percent of the time the engine just starts fine...let the engine idle near 800 rpm until the oil pressure comes up and the oil temp start to move. Don't get in a hurry.

Like I said.... as far as pulling the prop through I have done this most of my 45 years of flying in cold weather instructing in Angola Indiana or Ohio. Before I came down south. On radial engines I flew we had to pull the props every first start of a day... Assume the engine can fire and start.. so take precautions...

I see more damage done to engines by folks starting even in warm weather when they start and the engine revs up to about 2000 rpm instantly and blows everything and everyone around... and they start taxing almost immediately... a extra minute or two at idle will be pleasing to your engine.

Jack