Engine won't start (anymore)!

[wjb]

UPDATE: was able to do a A/B check with a mag from a friend who just pulled it to install a SureFly .. worked perfectly! I'm going to send in out for IRAN and we'll see what was wrong.

I've run into a engine starting issue that I would like your advice on:

I no longer can start the engine on my L mag; I might get a bit of ignition, but it doesn't persist, and pushing in the mixture didn't start the engine.

Flooded start protocol (throttle full open, mix out, crank till catch and then quickly adjust mix and throttle) did not improve the situation (ie, not just a flooded engine)

It now won't start on the L mag alone. Crank the battery into the grave; no workie.

Observation: while cranking for start, occasionally a mini catch would occur ... I found if I flip on the right mag then, it would catch and start Engine coughs, starts and settles in (my engine always takes a few seconds to get to a nice, purring ops state).

Mag check at 2000 rpm shows the typical 100-110 RPM drop L and R.

Just completed my annual condition inspection. Other than checking timing and cleaning/gapping the plugs, nothing was done with the mags.

Any thoughts on the cause from the VAF brain trust? Is my L mag hosed?


TL;DR content:

- Lyc IO-360-M1B, 370h, Dual conventional Slick mags, impulse on left.
- recent compression check in the high 70's on all cylinders
- borescope looks super clean (thanks LOP!)

- air filter is clean
- air ducts to the servo are intact, secure, clean inside and out.

- Fuel pressure good on engine pump and boost pump
- Injectors clean
- Fuel flow test to each of the flow divider arms are balanced.

- Plugs new-ish (<50h), cleaned, resistance checked (< 1kohm), and gapped,
- Timing looks good at 25-26 deg both mags.
- 1T, 3T, 2B, 4B show sparks in that order when the impulse coupler snaps.
- P leads appear sound; no sound from buzz box when mags are off (shorted) during timing checks

Normal starting process:

I have individual toggle switches for each mag; set up to only allow the starter to run when L mag is on, R mag is off, and starter button pressed.

• 5 sec prime with pump on, mix and throttle in
• mix to ICO,
• throttle cracked
• pump off
• engage starter

Typically, 2-3 blades go by before it catches .. once it does, mix goes full and throttle is adjusted. R mag on, and lean for taxi. Has always been reliable.

 

[Tracer 10]

How many hours on your magnetos since new or 500 hour inspection?
If you remove the plugs and pull the prop thru does the impulse coupling on the LH magneto “snap”. Turn the L/H magneto switch on and check to see if it develops a hot spark when the ignition lead for #1 cylinder is positioned close to a cylinder fin and #1 on compression stroke. The impulse coupling should produce a hot retarded spark after Top Dead Center to allow the engine to start easily.

 

[wjb]

How many hours on your magnetos since new or 500 hour inspection?
If you remove the plugs and pull the prop thru does the impulse coupling on the LH magneto “snap”. Turn the L/H magneto switch on and check to see if it develops a hot spark when the ignition lead for #1 cylinder is positioned close to a cylinder fin and #1 on compression stroke. The impulse coupling should produce a hot retarded spark after Top Dead Center to allow the engine to start easily.

370h since new on the mags. The impulse coupling does snap as I pull it through. It does create a spark on snap (1-3-2-4) but need to cross check the phasing (snap to TDC approximate rotation)

 

[Avanza]

Hi VAF,

I've run into a engine starting issue that I would like your advice on:

I no longer can start the engine on my L mag; I might get a bit of ignition, but it doesn't persistent, and pushing in the mixture didn't start the engine.

Flooded start protocol (throttle full open, mix out, crank till catch and then quickly adjust mix and throttle) did not improve the situation (ie, not just a flooded engine)

It now won't start on the L mag alone. Crank the battery into the grave; no workie.

Observation: while cranking for start, occasionally a mini catch would occur ... I found if I flip on the right mag then, it would catch and start (could be pretty exciting depending on the throttle and mix config). Engine coughs, starts and settles in (my engine always takes a few seconds to get to a nice, purring ops state).

Mag check at 2000 rpm shows the typical 100-110 RPM drop L and R.

Just completed my annual condition inspection. Other than checking timing and cleaning/gapping the plugs, nothing was done with the mags.

Any thoughts on the cause from the VAF brain trust? Is my L mag hosed?


TL;DR content:

- Lyc IO-360-M1B, 370h, Dual conventional Slick mags, impulse on left.
- recent compression check in the high 70's on all cylinders
- borescope looks super clean (thanks LOP!)

- air filter is clean
- air ducts to the servo are intact, secure, clean inside and out.

- Fuel pressure good on engine pump and boost pump
- Injectors clean
- Fuel flow test to each of the flow divider arms are balanced.

- Plugs new-ish (<50h), cleaned, resistance checked (< 1kohm), and gapped,
- Timing looks good at 25-26 deg both mags.
- 1T, 3T, 2B, 4B show sparks in that order when the impulse coupler snaps.
- P leads appear sound; no sound from buzz box when mags are off (shorted) during timing checks

Normal starting process:

I have individual toggle switches for each mag; set up to only allow the starter to run when L mag is on, R mag is off, and starter button pressed.

• 5 sec prime with pump on, mix and throttle in
• mix to ICO,
• throttle cracked
• pump off
• engage starter

Typically, 2-3 blades go by before it catches .. once it does, mix goes full and throttle is adjusted. R mag on, and lean for taxi. Has always been reliable.

To me it looks that engine is well cared for. I would open the throttle as little as possible when starting. A setting that would give 8-900 rpm.

Good luck

 

[jrs14855]

Do you have cooling air directed at the mags? Apples to oranges but my Bendix mag was near failure at just over 200 hours. Plastic portion of breaker points was melted to wher the points were barely opening.

 

[Stevea]

If this is a gradual change over time, something likely degraded (over time). Things that come to mind are mag/engine timing, ignition harness (continuity, resistance), and the internal condition of the L mag itself. Even at 370 hours, something inside the mag could be worn, loose, or mis-timed.

 

[scsmith]

My first Slick mag (not impulse coupled) had bad-enough breaker wear (on the plastic cam follower) at 350 hrs that I got much more mag drop. I changed out the breaker assembly and re-timed it and it worked normally.

 

[mahlon_r]

The left mag may engage when you are pulling through but may not when cranking with the starter. You definitely have ignition issue when cranking and my guess is the impulse is intermittent or non existent when cranking with the starter. Listen for it with the starter engaged and cranking. Good Luck, Mahlon

 

[rockyfatcat]

Pull the plugs and hook up the plug wires. Have someone crank the motor while you are watching. The plug shell must be grounded.

The only things in the system is magnetos, wires, and plugs.

The full shotgun would to be repair or replace all 3

 

[rvbuilder2002]

You mentioned you just completed your condition inspection (note, I did not say CONDITIONAL... there is no such thing ).

Did the left mag. require a timing correction adjustment by chance?

If so, that is an indicator that the magneto internal timing (E gap adjustment) has drifted.
When the internal timing drifts, the mag is no longer producing the highest output that it can.
With the timing readjusted, once running the engine can seem to operate normally, but the starting performance can be degraded. Sometimes severely.

Your quoted mag. check RPM drop of 100-110 RPM may be an indicator of degraded output as well.
From my experience, healthy, properly adjusted mags result in an RPM drop in the neighborhood of 50-60 RPM

What ever your answer, the problem definitely points to being ignition related. Impulse coupler springs are know to fail and become weak. This will also have an impact on the starting performance of the mag. but have zero impact on performance once the engine is running.

 

[blaplante]

I've modified my IO cold start procedure... it's a thought:

1) mixture cut-off, throttle idle: turn on pump, run until full pressure indicated
2) now advance the mixture and throttle, for whatever number of seconds. For me it depends on the outside temp....

If you don't do step 1, you can get inconsistent prime amount depending on how much residual fuel is in the system.

Probably not your problem, given the mag drop you reported.

 

[wjb]

Thanks everyone for your thoughts .. happily, my hangar neighbor just pulled the same mag from his 7 to replace with a SureFly. So we did a A/B test and swapped his in .. Fired up just like normal. Looks like the something happened to the mag. I did a timing check on the mags during the condition inspection, but did'nt have to adjust anything this year. At least the plane is back up now!

I'll send it out for IRAN. Any recommendations for a good mag shop?

 

[RV8JD]

I'll send it out for IRAN. Any recommendations for a good mag shop?

I've had good luck with Quality Aircraft Accessories (QAA) for Slick 500 hour IRANs:

Aircraft Magnetos & Aircraft Magneto Overhaul Service | QAA

QAA stocks aircraft magnetos in new and factory overhauled condition. We are the only Factory Authorized Service Center for Slick Magnetos by Champion

www.qaa.com

​

Aircraft Magneto Service has a very good rep also:

​

Aircraft Magneto Service

Aircraft Magneto Service Repair 500 Hour Inspection Overhaul Exchange Magneto Part Sales Magneto Sales, aircraft mag

www.aircraftmagnetoservice.net

 

[wjb]

Thread followup: Just got the IRAN report back from Aircraft Magneto ... the coil was failing; impulse coupler and points (common hard to start culprits) were fine per their testing. The "come in" speed was too high, meaning that the mag needed a higher rotation rate than nominal to make a good spark. Coil replaced and it now tests OK. It's coming home and will go on the shelf until I need to pull the replacement mag -- maybe next year for the non-impulse mag 500 hr inspection.