Lycoming O360 hard start, mags?

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henryinparadise

Filing Flight Plan
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Henry
Its catches right off but will not fully start until after many attempts.
it kind of diesels, if that makes sense.
I had the mags timed and that helped.
The mags are 900 hrs old and i dont see a log book entry for an ARAN on them
ever.

Im thinking of ordering a mag with an impluse coupler,
swapping that out with the existing one.
sending that one in for an IRAN.
when that comes back, swapping it with the old non impluse mag.

then both mags would have impulse.
does that all make sense?

thanks for any feedback
 
Did this just start? What engine? Injected or carbed? Was priming and cranking/low rpm fueling ruled out?
 
900 hours is a lot of time on a magneto. It is likely time for an overhaul. I had my left mag fail shortly after I bought my airplane at about 650 hours ( I think ).

My IO-360 in my 64 Mooney has a "shower of sparks" ignition starting system. It is a system integrated into the ignition starter switch and left magneto with the ability to add a vibrating battery pulse to the magneto coil during starting, causing a retarded shower of sparks during starting. If you have one and it is not working properly that could be part of your problem.

My old O-320 Cherokee had an impulse coupling on the left magneto. It both retards ignition and increases magneto shaft speed during the firing pulse.

Your POH should describe what system is used for your particular application. Figure out what you have then TS accordingly.
 
henryinparadise said:
does that all make sense?
Click to expand...
What aircraft and year?
Is this a new problem or ongoing problem?
Why are you sure its the mags?
Once it is running how does it idle?
How is the mag check?
What are the condition of spark plugs?


I troubleshoot a bit more after a complete check of the entire engine for anything out of the ordinary or loose, etc. But its your money.
 
William Pete Hodges said:
900 hours is a lot of time on a magneto. It is likely time for an overhaul. I had my left mag fail shortly after I bought my airplane at about 650 hours ( I think ).
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It's time for a mag internal inspection, not an overhaul. Slick calls for the inspection at 500 hours, TCM/Bendix at 400. At engine TBO the mag gets overhauled.

There is a big difference between the internal inspection and an overhaul. In an overhaul just about everything in the mag except the case and magnet rotor gets replaced. Might as well buy a new mag. An inspection will sometimes need new points at 500 hours, most definitely at 1000. If the mag was properly assembled at the last OH or when new, the rest of the stuff will likely be OK. I replaced the distributor and its rotor once in all the inspections I did. Replaced a condenser once. Replaced the points many times, usually at the second inspection. Never had any troubles with the bearings or coils. The manuals give all the details for testing that stuff.
 
My O-360-A4M uses Slick 4300 series mags. These have 2 critical SBs related to the impulse coupling. One (SB2-19A) is that the rivets work loose and worst case, can fall inside the engine. The other (SB1-19) is that the stop pins work loose and shift, worst case, can come loose entirely and fall inside the engine. You should definitely send those mags out for the 500 hour inspection and have the IC replaced to comply with these SBs.

One place I recommend is Aero Accessories in Van Nuys (http://aeroacc-vny.com/). They did mine in 2-3 days, I had less than 2 weeks of downtime including shipping both ways. Cost about $450 per mag which seems to be the going rate these days.

PS: you don't need the IC on both mags, and the IC offsets the drive gear, so I'd advise sticking with the stock configuration. Mine has the IC on the left (pilot) side only and after you remove the mags you can see that engine drive gear is deeper/further into the hole.
 
henryinparadise said:
then both mags would have impulse.
Click to expand...
I believe some a/c ground out the non-impulsed mag when the key is in the start position, so might need to check on that before (what I believe you are saying) turning a one-impulsed engine into a two-impulsed engine.
btw, does the engine TCDS allow such a change?
 
TCDS ( ?) says any engine eligible for 1 IC can also have 2 IC’s.

My recommendation is for flight schools to go this way as it is much more

cost effective than burned out Starters and cancelled flights.

But there is more to it than adding an IC mag. An adapter is required on

the engine as well as longer studs. A new drive gear is $$ too.

If a simple mod on your Ignition Switch is not done you may still

starting on one mag after all this.

Take Dan’s advice and go with the 500 hr at the shop of your choice.

I can almost guarantee that your E-gap ( INTERNAL timing ) has drifted.

If you are proficient with starting procedures the 500 will work fine.
 
Thanks for all of the posts.

fuel is not an issue.
it runs and idles fine once running.
plugs look good. i inspected them recently.
mag check is real good.
its carbureted - a 2005 rv7 .

i think i will take them out and send them to
van nuys on monday.
ill also just leave the set up as is.
makes sense to me.
 
henryinparadise said:
plugs look good. i inspected them recently.
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What did that inspection involve? Did you check the resistor resistance? Were the plugs spark-tested in a proper pressurized tester? Were the gaps all correct?

Spark plugs, especially the older Champions, are responsible for an awful lot of problems. Just because mag drops are normal doesn't mean that they're sparking well during start. That applies to the mags, too.
 
Dan Thomas said:
... Just because mag drops are normal doesn't mean that they're sparking well during start. That applies to the mags, too.
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True, the IC is critical to starting and there's no way I know of to ground test it with the magnetos installed.

Incidentally, a better magneto function test is done in flight, well leaned at cruise power. It's more demanding and revealing than a run-up ground test. If you're antsy about in-flight magneto tests, do it while overflying an airport.
 
Feedback

I did take Dan's advice, took out the mags and mailed them to arrow accessories in Van Nuys, California. I was very happy with them, quick turn times, and the technician was very helpful. as I suspected the mags had never been inspected in 900+ hours. he said that the mags were on their last legs and the impulse coupler was just about dead. I got the mags back yesterday installed them, timed them and the engine started up immediately. Did a run up --mag drop was 50 RPM or so, flew around the patch, hot started the engine and that was not a problem at all.

Its like my birthday!

Thanks for all of the advice.
 
henryinparadise said:
Feedback

I did take Dan's advice, took out the mags and mailed them to arrow accessories in Van Nuys, California. I was very happy with them, quick turn times, and the technician was very helpful. as I suspected the mags had never been inspected in 900+ hours. he said that the mags were on their last legs and the impulse coupler was just about dead. I got the mags back yesterday installed them, timed them and the engine started up immediately. Did a run up --mag drop was 50 RPM or so, flew around the patch, hot started the engine and that was not a problem at all.

Its like my birthday!

Thanks for all of the advice.
Click to expand...
What was the current IRAN pricing? What ended up being replaced? I just had me IC left mag sent out to Aircraft Magneto. IRAN is $450. Waiting to see what needed replaced.
 
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