O-360 Starting Procedures

RyanB

RyanB

Super Administrator
Management Council Member
PoA Supporter
Joined
Jul 21, 2010
Messages
16,524
Location
Chattanooga, TN
Display Name
Display name:
Ryan
Some of you may know that I recently started flying an Archer II, and now that I’ve spent a little bit of time with it, I’ve got a couple questions.

For a cold start (or first start of the day) it seems to need about 4 shots of primer and it will fire right off.

If I shut down and re-load a few passengers and then go to start again, it doesn’t seem like it wants to start unless I give it 1 (or 2 shots max) of primer. After that, it starts right up, otherwise, it seems to just turn over and over.

Is this typical? I’m used to flying O-235’s and O-320’s and they would typically always start right up on a hot start without any primer at all.

Opinions?
 
My o-360 hot starts with no pumps. Just 1/4” throttle and turn the key. Once in a while it won’t kick right away and a small pump while it’s turning kicks it off.
 
The 360 in our archer 3 likes a fair bit of prime. It's electric, not a plunger, but in warm weather I hold it for 2-3 sec and 5-6 in cold weather. I gather that 1s with the solenoid is somewhat similar to a pump with the plunger. At least the Dakota and the warrior seem to like the 3-5 pumps depending on temp.

Eta: with the electric prime, it's easy to give her a little extra while she's cranking, which will usually salvage a failed starting attempt. I haven't tried this with the manual primer planes as I don't get to fly them much. I agree that pumping the throttle is largely useless, and led another club member to buy a new air filter...
 
Last edited:
Always prime. Slowly. Make sure the tube is full so it gets a good squirt.

Don't use the throttle as "extra prime" when it won't start. The primer fuel is delivered differently, so playing with the throttle can lead to worse than flooding, but fire.

Or so I've heard. Where's @Tom-D?
 
Ravioli said:
Always prime. Slowly. Make sure the tube is full so it gets a good squirt.
Don't use the throttle as "extra prime" when it won't start. The primer fuel is delivered differently, so playing with the throttle can lead to worse than flooding, but fire.
Click to expand...
Ehh, yes and no... if you have a primer (plunger type) use it for a shot or two. Or, then there's my RV-8 with a O-360-A1D; I have an electric boost pump, but no primer system at all, I didn't install one. The carb does have, however, an accelerator pump; my engine usually starts after a couple of blades and one pump on the throttle, hot or cold. Okay, maybe if it's cold, two pumps on the throttle. The key here is, only pump the throttle while the engine is cranking; the intake air sucks the fuel charge into the cylinders. If you pump the throttle without cranking, then you have a fire hazard as Ravioli mentioned. The accelerator pump will squirt fuel into the carb air intake but doesn't get pulled into the cylinders, instead it will pool in the airbox. Then, if you backfire the next start attempt you'll have a nice fire for a weenie roast... oops.
 
I never pump the throttle. I’ll just crack it 1/4” or so for the start.

Guess that leads me to my next question - Since fuel is delivered differently when using the primer vs. pumping the throttle, is the chance of having an engine fire a less when using the primer?

I def don’t feel like I over prime by any means (4-5 cold & 1 or 2 max when hot), but I’d still like to learn more about the mechanics behind the two methods.
 
Ryanb said:
Some of you may know that I recently started flying an Archer II, and now that I’ve spent a little bit of time with it, I’ve got a couple questions.

For a cold start (or first start of the day) it seems to need about 4 shots of primer and it will fire right off.

If I shut down and re-load a few passengers and then go to start again, it doesn’t seem like it wants to start unless I give it 1 (or 2 shots max) of primer. After that, it starts right up, otherwise, it seems to just turn over and over.

Is this typical? I’m used to flying O-235’s and O-320’s and they would typically always start right up on a hot start without any primer at all.

Opinions?
Click to expand...
Have the primer out for a hot start. If it's not firing, give it a pump; if it starts without the primer, wait until it's running smoothly, then slowly ease the primer back in (so you don't over-enrich the mixture) and lock it.
 
Ryanb said:
I never pump the throttle. I’ll just crack it 1/4” or so for the start.

Guess that leads me to my next question - Since fuel is delivered differently when using the primer vs. pumping the throttle, is the chance of having an engine fire a less when using the primer?

I def don’t feel like I over prime by any means (4-5 cold & 1 or 2 max when hot), but I’d still like to learn more about the mechanics behind the two methods.
Click to expand...
Yes, way, way less risk. Don't pump the throttle back and forth to prime unless you have the fire extinguisher ready in one hand.
 
My Cherokee required 6 shots cold, the first 2 were just priming the primer. Haha For a hot start I gave it 4 shots, mixture pulled all the way and throttle cracked. Start it and when it starts to catch advance the mixture.
 
The primer pump delivers fuel to 3 of the intake runners just before the intake valve, so fuel goes in as soon as the engine starts turning. Flooding is easy here, but fire is unlikely.

If you do not prime, expect 4 or 5 blades of the prop to go by before the first cylinder fires. On hot starts, be sure you turn on the electric pump, and wait for it to fill the carb float bowl, before cranking. The planes that I trained in usually started after 5 blades, hot and no prime. The owner discouraged priming when hot.

Ryan, you can download and print the POH for the Archer ll free, from Ram Aviation. I read the POH for all the planes that I flew, but the more recent ones are rather many pages. Good to know the details on system arrangement.
 
Ryanb said:
otherwise, it seems to just turn over and over.
Click to expand...
By "over and over" you mean 10 seconds, right? ;) #dontbeCrankenstein
Guess that leads me to my next question - Since fuel is delivered differently when using the primer vs. pumping the throttle, is the chance of having an engine fire a less when using the primer?
Click to expand...
Depends on a few factors, one of which is whether you have an updraft carb or a sidedraft carb.
I def don’t feel like I over prime by any means (4-5 cold & 1 or 2 max when hot), but I’d still like to learn more about the mechanics behind the two methods.
Click to expand...
Starting fundamentally comes down to finding a proper air/fuel ratio. My personal philosophy on hot starts starts with the shutdown. Set it for 900RPM then pull the mixture. When it comes time to re-start, don't touch the throttle. That sets the "air" portion of the ratio to a known quantity. From there it's a matter of finding the proper fuel portion.
 
Last edited:
asicer said:
By "over and over" you mean 10 seconds, right? ;) #dontbeCrankenstein
Click to expand...
Negative. 5 seconds on the starter or less typically. If it doesn’t start within a few blades, I don’t continue to crank.
 
David Megginson said:
Don't pump the throttle back and forth to prime unless you have the fire extinguisher ready in one hand.
Click to expand...
To summarize; pumping the throttle to "prime" the engine is ineffective and a bad idea. A throttle pump while cranking the engine is not so bad and has worked on every start of my O-360 for 1600+ hours.
 
Ryanb said:
I never pump the throttle. I’ll just crack it 1/4” or so for the start.
Click to expand...

There's your problem. Close the throttle all the way and then crank it. The idle fuel nozzles are just tiny holes in the carb bore right next to one edge of the throttle plate, and if the throttle is open some the airflow past them might be slow enough that little or no fuel is delivered. And the airflow through the venturi is too slow at your 1/4" throttle setting for the main nozzle to give anything. Every engine and carb is a little different, and it depends a lot on how the float level has been set.

hqdefault.jpg
 
The throttle pumping fire risk is much greater with an O-470 on a 180 or 182. Lycomings aren't immune but induction fires are less common. I know Cub guys with no priming system and they get by. The comment to engage the starter before pumping to establish the draft is good advice.
 
Stewartb said:
The throttle pumping fire risk is much greater with an O-470 on a 180 or 182. Lycomings aren't immune but induction fires are less common. I know Cub guys with no priming system and they get by. The comment to engage the starter before pumping to establish the draft is good advice.
Click to expand...
They'll all do it. I have found massive blue stains on Lycoming airboxes that weren't there 50 hours before at the previous inspection, and they weren't from leaky carbs. Pumping the throttle will do that. The pump nozzle doesn't atomize the fuel; it depends on rapid airflow through the carb to break it up, and at rest there isn't any airflow, and during cranking airflow is minimal. The jet of fuel hits the top of the divider and runs back down. It's the fumes that start the engine.

Continentals often have their primer nozzles lower down in the induction system, while Lycs have them right next to the intake valve. Priming without cranking immediately will have fuel running down the intake and out the carb much sooner in the Continental.
 
Ryanb said:
Some of you may know that I recently started flying an Archer II, and now that I’ve spent a little bit of time with it, I’ve got a couple questions.

For a cold start (or first start of the day) it seems to need about 4 shots of primer and it will fire right off.

If I shut down and re-load a few passengers and then go to start again, it doesn’t seem like it wants to start unless I give it 1 (or 2 shots max) of primer. After that, it starts right up, otherwise, it seems to just turn over and over.

Is this typical? I’m used to flying O-235’s and O-320’s and they would typically always start right up on a hot start without any primer at all.

Opinions?
Click to expand...

Honestly each engine is different and likes different things. Just do whatever works. I have time in LOTS of different planes and starting seems to be a little different in each one. Same type of airplane, same engine.... They will act different.
 
Yes, it is typical. My Archer II with an O360-A4M likes four or five prime shots cold and a few shots warm, just like you’re doing. Every now and then I have to do the throttle pump but try not to.
 
My Sundowner has an O360-A4K. Previous owner told me to go with 8 shots of primer when cold. Works like a charm. When warm, I'll usually give it 2-4 depending on my mood.
 
When I bought mine the previous owner said no prime just pulp the throttle 3-4 times and it starts right up. Over time I have read it’s a hazard. So here is my procedure , tested and validated till about an hour ago.

While shutting down set the RPM at 1000, don’t touch the throttle anymore.

Cold start

3 full shots of primer ( first one doesn’t count, I always hurry with the first one and then remember to slow down)

Start and it will catch instantly. A new lightweight starter definitely helps.

Hot start

Mostly in winter, I would need at least 2 full shots of primer, in summer usually one full shot will do. No idea why.
 
On my Archer II (for hot/warm start) I tried several methods already mentioned and they all work, some better than others. The best one I've found though is a bit unique. Full throttle and mixture before starting, hand on throttle to quickly pull it back. Starts on first or second blade every time. May sound risky but if you pull back as soon as it fires it'll barely be idling
 
geezer said:
The primer pump delivers fuel to 3 of the intake runners just before the intake valve, so fuel goes in as soon as the engine starts turning. Flooding is easy here, but fire is unlikely.

If you do not prime, expect 4 or 5 blades of the prop to go by before the first cylinder fires. On hot starts, be sure you turn on the electric pump, and wait for it to fill the carb float bowl, before cranking. The planes that I trained in usually started after 5 blades, hot and no prime. The owner discouraged priming when hot.

Ryan, you can download and print the POH for the Archer ll free, from Ram Aviation. I read the POH for all the planes that I flew, but the more recent ones are rather many pages. Good to know the details on system arrangement.
Click to expand...
Also download the Lycoming manual for more info on the engine.
https://www.lycoming.com/sites/default/files/O-HO-IO-HIO-AIO & TIO-360 Oper Manual 60297-12.pdf
 
My POH doesn't mention exact priming, but does list throttle 1/4" when cold and 1/2" when hot.

I do 5 shots of primer, 1/4" open cold. 2-3 shots when hot. Starts every time.
I also preheat with a tanis, as well as keep my hanger at 50F October though December, and 40F January and February. My T hangar is insulated and tight as a drum from mods that I added.
 
Flybuddy said:
On my Archer II (for hot/warm start) I tried several methods already mentioned and they all work, some better than others. The best one I've found though is a bit unique. Full throttle and mixture before starting, hand on throttle to quickly pull it back. Starts on first or second blade every time. May sound risky but if you pull back as soon as it fires it'll barely be idling
Click to expand...

Same experience on my Archer II. My goal is always to have the least amount of cranking and this full throttle (not pumping) technique works well for me on hot starts.
 
RV-8A, Aero Sport O-360-A1A with no primer installed: Boost pump on, ignition switches on (toggles). When fuel pressure is indicated, pump the throttle once. When it hits the idle stop, push the ignition switch.

Good start, boost pump off, check fuel pressure, check oil pressure, lean.
 
This is a video that I took, it is a common carb and shows how much is fuel is produced.
watch..when you stroke a carb.
 
Tom-D said:
This is a video that I took, it is a common carb and shows how much is fuel is produced.
watch..when you stroke a carb.
Click to expand...
That’s from pumping the throttle or using the primer?
 
Ryanb said:
That’s from pumping the throttle or using the primer?
Click to expand...
the carb does not activate the primer.. the primer is a separate system, and delivers about 100 CC of fuel.
 
Every engine is a little different, and the same engine will be different once it is refurbished. Experiment with prime cold and hot and you will eventually find the sweet spot for quick starts. My current O-320 likes 3 shots of prime cold, and starts on the first blade. Hot, it will take 1 shot and a 2-3 blades to catch. You can find what works by starting with no prime and adding one shot of prime each time you fly for each start until you discover the magic number. My previous engine didn't want ANY primer fuel hot, and no more than 2 shots cold or it would flood.
 
chemgeek said:
Every engine is a little different, and the same engine will be different once it is refurbished. Experiment with prime cold and hot and you will eventually find the sweet spot for quick starts. My current O-320 likes 3 shots of prime cold, and starts on the first blade. Hot, it will take 1 shot and a 2-3 blades to catch. You can find what works by starting with no prime and adding one shot of prime each time you fly for each start until you discover the magic number. My previous engine didn't want ANY primer fuel hot, and no more than 2 shots cold or it would flood.
Click to expand...
no engine should require 3 shots of primer fuel to start, son-tin-wong.

3-4 shots will be puddling some place. most like in the intake spider.

watch the engine stacks, see if they are producing black smoke when they start.
Remember the 0-320-360 primes the cylinder intake pipe at 3 or 4 places.

any excess fuel is simply draining down in the intake spider
 
Last edited:
Tom-D said:
no engine should require 3 shots of primer fuel to start, son-tin-wong.
Click to expand...
Funny, cause the mechanic who takes care of the Archer I fly, said you may need 4-6 shots of primer on a cold start. Usually takes 1-2 for a hot start.
 
Ryanb said:
Funny, cause the mechanic who takes care of the Archer I fly, said you may need 4-6 shots of primer on a cold start. Usually takes 1-2 for a hot start.
Click to expand...
how many primer nozzles do you have hooked up. has any one ever cleaned them?

have you ever tried to use the accelerator pump to start? (stroke the throttle method)

be ready to start, stroke the throttle while cranking, see what happens, stroke the throttle again.
when you use the throttle fuel goes to all cylinders.
 
Last edited:
You must log in or register to reply here.
Back
Top