Hard starting IO-360

Ed Haywood

Ed Haywood

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Big Ed
Really having a hard time with cold starts in my Decathlon, and it seems to be getting worse.
X
POH procedure is to turn on fuel pump, stroke the mixture in then out, open throttle a half inch, mags hot, turn over engine, and add full rich when it fires.

It never works on the first attempt. Engine will not fire. I have tried varying the length of prime, to no effect.

What did work for a while was to prime it, turn it over for about 10 seconds, then prime it again. But even that method seems to be struggling now. I am finding myself trying 5 or 6 times over a 5 minute period, and am running the battery down to the point where I am worried about getting stuck.

Aircraft was just in annual and had plugs and harnesses replaced and timing checked. Mags have about 250 hours.
 
My suggestion is to have the mag timing re-checked.
 
Ed Haywood said:
Really having a hard time with cold starts in my Decathlon, and it seems to be getting worse.
X
POH procedure is to turn on fuel pump, stroke the mixture in then out, open throttle a half inch, mags hot, turn over engine, and add full rich when it fires.

It never works on the first attempt. Engine will not fire. I have tried varying the length of prime, to no effect.

What did work for a while was to prime it, turn it over for about 10 seconds, then prime it again. But even that method seems to be struggling now. I am finding myself trying 5 or 6 times over a 5 minute period, and am running the battery down to the point where I am worried about getting stuck.

Aircraft was just in annual and had plugs and harnesses replaced and timing checked. Mags have about 250 hours.
Click to expand...
Open the throttle before you prime it, not after. The throttle controls the fuel flow, and with it closed you don't get more than a little dribble out of the injectors. You want an atomized spray.
 
Dan Thomas said:
Open the throttle when you prime it. Then close it to start. The throttle controls the fuel flow, and with it closed you don't get more than a little dribble out of the injectors. You want an atomized spray.
Click to expand...

I usually have the throttle a half inch to one inch open when I prime it. Should it be wide open?
 
Ed Haywood said:
I usually have the throttle a half inch to one inch open before I prime it. Should it be wide open?
Click to expand...
Try opening it further. What does the fuel flow gauge say when you prime it? Maybe the pump is getting weak.
 
Ed Haywood said:
Really having a hard time with cold starts in my Decathlon, and it seems to be getting worse.
Click to expand...
I would really consider checking your ignition system, with mags being suspect. If it’s getting worse, it could leave you stranded someplace inconvenient.
Ed Haywood said:
POH procedure is to turn on fuel pump, stroke the mixture in then out, open throttle a half inch, mags hot, turn over engine, and add full rich when it fires.
Click to expand...
Try this -

1. Throttle at 1/2
2. Mixture rich
3. Prime
4. Mixture ICO
5. Start
6. Advance the mixture once it starts

Nonetheless, if you’re doing everything like you always have and now it’s not to working, something needs attention.
 
Did the mag timing need to be adjusted at annual?
 
RyanB said:
…

Try this -

1. Throttle at 1/2
2. Mixture rich
3. Prime
4. Mixture ICO, throttle to 1/4”
5. Start
6. Advance the mixture once it starts

….
Click to expand...

I usually set throttle to 1/4”. If it doesn’t fire off in a few blades then I’ll stop. Hit primer again for a second (throttle / mix forward when re-priming), then try again. I never crank for more than a few seconds at a time. C172SP with IO360.
 
On my TIO-540 the throttle is wide open for priming.

my cold procedure is probably the same as most:

mixture full
Throttle full
Fuel pump on for a count of 3-5 sec
Mixture to cutoff
Throttle to 1/2”
Engage starter
Advance mixture as it fires
 
I agree, check mag timing. Then probably clean, check, service plugs. Check intake gaskets for signs of leakage.
 
Rgbeard said:
On my TIO-540 the throttle is wide open for priming.

my cold procedure is probably the same as most:

mixture full
Throttle full
Fuel pump on for a count of 3-5 sec
Mixture to cutoff
Throttle to 1/2”
Engage starter
Advance mixture as it fires
Click to expand...

The only thing I do different is crank it with the mixture full rich. I never put the mixture to cutoff starting a cold engine. My stuff always fires right up and I fly lots of different planes.
 
I just went through this, via expensive 350NM-away AOG, retrieval and two weekends of my time. I have the same engine series (injected 360, angle valve in my case, not sure if your Deca is parallel valve {180} or angle {200}).

From my experience, if the starting is getting harder, it's not due to poor technique. Something in the ignition system is worn out and bound to leave you stranded like it did me.

In my case, it was a straight up left mag (the impulse coupled one) contacts failure. Bastard started without hiccup in the morning, and failed in the afternoon's RTB start attempt...it was that sudden and impossible to predict. When they pulled it and inspected it, the worn out condition was obvious. Rebuilding the mag (new contacts, plus the usual odds and ends) fixed it. The thing started up right away without any magic vodoo or self-made starting checklist.

Don't dismiss this as an engine/installation reputation thing. They're not hard to start cold ime, owning two of them. When they give you trouble, something broke or wore out. In my case, the first one was a shot coupler, the latest one a straight up worn out mag. Rebuilding/repairing led to immediate resolution of the starting woes.

Good luck to ya.
 
I have an IO-360 in my DA40. POH states to run electric fuel pump, completely open throttle, then open mixture for 2-5 seconds (which I vary based on ambient temperature), mixture to ICO, then return throttle to 1/2 inch open, electric fuel pump off, then crank. When it fires, briskly advance mixture and adjust throttle. My engine has always been easy to start cold.
 
NavAir said:
I have an IO-360 in my DA40. POH states to run electric fuel pump, completely open throttle, then open mixture for 2-5 seconds (which I vary based on ambient temperature), mixture to ICO, then return throttle to 1/2 inch open, electric fuel pump off, then crank. When it fires, briskly advance mixture and adjust throttle.
Click to expand...
Weird. My DA40 POH says:
  1. Strobe light (ACL) ... ON
  2. Electrical fuel pump ... ON, note pump noise
  3. Throttle ... 3cm (1.2in) forward from IDLE
  4. Mixture control lever ... RICH for 3-5 sec, then LEAN
  5. Throttle 1cm (0.4 in) forward from IDLE
  6. Ignition switch ... START
  7. When engine fires: Mixture control lever ... rapidly move to RICH
 
tyndall said:
Did the mag timing need to be adjusted at annual?
Click to expand...

This is a good question. The OP stated the timing was "checked" during the annual. If the timing was adjusted at that time and the hard start problem began afterwards, it's a safe bet the adjustment was improper. The issue could also be related to the harness and plug replacement.

It's not uncommon for a grab bag of problems to occur after maintenance has been performed. When these sort of issues happen, always go back and verify the work was done properly.
 
I’ll agree with the previous comments on timing; sorta.

My assumption is this has the Left mag with an Impulse Coupling.

There are at least 3 timing points on the typical engine.

1 is magneto / engine timing that is adjustable and is about 25 degrees BTC for

most Lycomings.

Normally verified at inspections.

2 is what I call Static Starting Timing.

It is the point the Impulse Coupling clicks and provides the Starting Spark.

Typically this point is at about TDC .

I’ve found O & IO-360s somewhat critical that you don’t want this to occur after TDC.

The amount of retard ( lag angle) for a certain engine is determined by the

particular Impulse Coupling installed.

It is not independently adjustable. You can check this.

3 is Cranking Starting Timing . Starting with 2 ( Static Starting) and the Starter

is cranking the engine. The FASTER the engine turns the more the spark is RETARDED..

This is due to the Impulse Coupling action. Some engines are harder to start if they

have newer type Starters.

Some Lycoming engines have a chart that depicts the preceding.

So again assuming proper mags are installed ; what is the problem?

Setting the E-gap will set the Internal Magneto Timing and align the Spark with

the Impulse Action for optimum starting. E-gap will “ drift “ as the Contact Cam wears.


One way to check this is to TEMPORARILY adjust the Left mag to fire 5 degrees earlier.

( 30 degrees ?) Do not exceed 1000 RPM .

TEST ONLY - DO NOT FLY.
 
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asicer said:
Weird. My DA40 POH says:
  1. Strobe light (ACL) ... ON
  2. Electrical fuel pump ... ON, note pump noise
  3. Throttle ... 3cm (1.2in) forward from IDLE
  4. Mixture control lever ... RICH for 3-5 sec, then LEAN
  5. Throttle 1cm (0.4 in) forward from IDLE
  6. Ignition switch ... START
  7. When engine fires: Mixture control lever ... rapidly move to RICH
Click to expand...

Mine has the 3 cm index throttle position required for a warm start, cold is 1 cm. My POH is 20 years old (as is my airplane), there may have been revisions...
 
Regarding throttle position? Here’s what my Lycoming manual says.

7. Open the throttle approximately to 1/4 travel.
8. Turn the boost pump ON.
9. Move the mixture control to FULL RICH until a slight but steady flow is indicated
(approximately 3 to 5 seconds) and return the mixture control to IDLE CUT-OFF.
Click to expand...
 
Magman said:
The FASTER the engine turns the more the spark is RETARDED..
Click to expand...

No. The retard setting is fixed, not variable. Even if the timing was well off from what it should be, the engine should still fire and try to start. A spark in the air/fuel mix just about anytime should do something. I've seen an engine run with the timing mistakenly set near TDC. Not well, but it did start and run.

One way to check that impulse mag is to disconnect ALL the plug leads, turn on the mag switch, then hold one from the impulse mag 1/2" away from a clean ground point like an unpainted bolt head, and pull the prop though several times until you see a spark. If it can't jump that distance, the mag is weak, and even if the other (non-impulse) mag is strong, the engine will be hard to start.

If the mags have needed retiming several times since they were overhauled, it's a sign that internal wear is shifting the E-gap, and a shifted E-gap weakens the spark. Slicks have had considerable trouble with this, first with a bad batch of plastic points cams, then a bad batch of points themselves. Before that they had problems with misaligned coil tangs that wore the carbon spark brush in the distributor rotor.

If a modified start procedure doesn't work, the impulse mag, at least, should be taken off and opened up and inspected for problems, by someone who knows what to look for. https://www.championaerospace.com/assets/technical/SL_Magneto4300_6300_001.pdf
 
Magman said:
E-gap will “ drift “ as the Contact Cam wears.
Click to expand...
That was my first thought. Typical Slick nonsense. I just did a 500 hr for a customer with this same problem. He made it almost 300 hours before the starting problems got unbearable. If you have to adjust the timing on an impulse Slick at annual, just pull it and either reset the e-gap yourself or send it in.
 
“ Retard setting is fixed” is true ; within the mag.

However; as none other than the Lycoming folks state that the starting timing

will be retarded if cranking speed is increased.

Since the Impulse will engage, wind up and then release in a relatively constant

time the faster the Crank is turning the more it it will move during the

period and retard the timing.

When the 152 came on the scene 44 years ago it had major starting problems

using the Starter. Hand propping worked fine though.

You could almost taxi using the Starter.

They resolved the ignition issues 2 ways.

A slow speed Starter was introduced and became the Standard.

Also the Impulse Lag Angle was reduced from about 20 degrees to the current

5 degrees.

I’ve seen good starting engines have issues when a modern Starter is installed.

Almost acting as the recip equivalent of a “Hung Start”.

Adjusting e-gap always resolved the problem.

Some engines are critical in some regards; some not.

Just sharing what my experience with 360 is.
 
NavAir said:
Mine has the 3 cm index throttle position required for a warm start, cold is 1 cm. My POH is 20 years old (as is my airplane), there may have been revisions...
Click to expand...
For warm start mine says:
  1. Strobe light ... ON
  2. Electrical fuel pump ... ON (note noise)
  3. Throttle ... 3 cm (1.2 in) forward from IDLE
  4. Mixture control lever ... RICH for 1-3 sec then LEAN
  5. Ignition switch ... START
  6. When engine fires: Mixture control lever ... rapidly move to RICH
So in mine the only difference between warm/cold is step 5, move the throttle back to 1cm for cold and leave it at 3cm for warm.

Mine is Rev 5 (Sep 2001).
 
Magman said:
When the 152 came on the scene 44 years ago it had major starting problems

using the Starter. Hand propping worked fine though.

You could almost taxi using the Starter.

They resolved the ignition issues 2 ways.

A slow speed Starter was introduced and became the Standard.

Also the Impulse Lag Angle was reduced from about 20 degrees to the current

5 degrees.
Click to expand...

They also hung two impulse mags on it. It wasn't a timing issue; the O-235 can be a stinker to start anyway. We had a Citabria with it, and it had the normal starter and two impulse mags and still gave us hassles. I changed over to UREM37BY plugs and got rid of the usual plug fouling problems of the O-235, and got much better starts, too. The spark is farther out in the cylinder instead of being halfway buried in the plug well.

Like I said, retard timing won't affect the engine's ability to fire. Too soon and it will kick back. Too late and it should still catch. Weak spark is the issue, usually, if all else is OK.

Some of the newer PM starters turned too fast, so fast that the impulse disengaged. Weaker spark, and spark much too soon. Kickback.
 
The BY plug is what I put in all engines that allow it.

Also find it useful that they shortened the plug after initial production.
 
OP here, lots of good discussion and suggestions, thanks to all.

Here is what my POH specifies for technique:

1. Throttle - 1/4 to 1/2 inch open.
2. Mixture - full rich.
3. Electric fuel pump - on until fuel pressure indicated, then off.
4. Mixture - idle cut off.
5. Throttle - open 1/2 to 1 inch open.
6. Mags - hot.
7. Starter - engage.
8. Mixture - full rich when engine fires.
 
I must be really lucky. I’ve never had the starting issues people talk about on here.

would have been way more useful if I was good at guessing lottery numbers.
 
For cold starts i run my electric fuel pump for 5 seconds. This gets it started in 1-2 blades. In colder weather (<50°), I add about 1 second for every 10° below 50.
For hot starts I don’t touch the controls, just fire it up and give it full mixture or less if at higher altitudes, adjust RPMs to 1200 to get cool fuel running through the hot fuel lines to stop it from coughing due to fuel vaporizing, after it a few seconds of smooth operation I back the RPMs down.
 
Ed Haywood said:
OP here, lots of good discussion and suggestions, thanks to all.

Here is what my POH specifies for technique:
Click to expand...
I don't think the problem is technique. As @RyanB mentioned, if the same inputs worked before but has a different outcome now then something mechanical has changed and you should get it fixed.
 
I changed my technique today and got much better results. I opened the throttle halfway, ran the pump for 4 seconds after pressure indicated, closed mixture and set throttle to 1/2 inch, and cranked. It fired on the 2nd rotation. I guess I just wasn't getting enough fuel in there. Will repeat the process tomorrow morning and see if I get the same result.
 
Yup, it was bad technique all the time. Just needed to prime longer.
 
Ed Haywood said:
Yup, it was bad technique all the time. Just needed to prime longer.
Click to expand...

When cold you can’t flood a Lycoming…at least according to my mechanic. I never tested this theory, but his point was it needs fuel to start. Now hot starts are a different animal.
 
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