Help with O-360 starting problem

[Nitty]

I have a carbureted O-360 with Slick mags, C/S prop and cannot get the engine to start. Not even the hint of a spark. I've had the mags out and sent for inspection. I dont have a primer system and my technique is to engage the starter and give the throttle a couple of pumps. It usually started on the first or second blade after the throttle pump.

There is gas getting into the carb intake as evidenced by the puddle under the airplane, I've taken off the air filter so it's getting air. The only thing I haven't checked is the spark plugs but these Tempest plugs only have 70 hours on them. Visual inspection shows no fouling. I'll check their resistance nonetheless.

The only thing different that occurred two flights prior was that I went full throttle on a touch and go at sea level with the prop set to 2300 rpm so I'm wondering if the manifold pressure exceeded limits.

Compression seems normal but haven't had a gauge on it to verify.

Anything I should inspect internally given that condition? Any other ideas?

Spent yesterday trying to solve the problem of the engine not starting. With the P lead wire on, the mag was grounded and would not fire. Took the P lead wire off and the mag operated normally.

Started chasing the wire from the P lead back to the switch, nothing, checked that the shielding wasn't touching the P lead, all looks good.

Happened to shine a flashlight on the P lead post and saw this



It was extending from the P Lead pad under the phenolic disk to the magneto case.

In installing the magneto originally, the ring terminal broke and I had to put a new one on. In the process of either stripping the wire or working the conductor through the shielding, this little wire fell onto the magneto and found the perfect spot to hide and ground out the mag. It is a very fine wire and I doubt that we would have found it in normal daylight.

Put everything back together and the engine fired right up.

Gotta love aviation.

[krw5927]

Since you've had the mags off, make sure they're timed appropriately. And if there is an impulse coupling on one or both, that you rotate the prop past TDC where the coupling snaps, then backward to more than 25 degrees before TDC, then sneak up on 25 degrees in the direction of normal prop rotation (assuming your engine is supposed to be timed at 25 instead of 20 degrees before TDC).

Also, another poster reported recently that taking the air filter and air box off his carb caused it to run excessively rich on the ground.

[edsong]

Your mags can be out of time if you didn't use the timing pin. Theres a pin that you insert under the harness cap to correctly time your mags.

Eddy

[Turbofan]

What was OAT? And what type of fuel? I'm assuming Arizona is your location, but know temps can drop in the desert. With cold temps, no primer and the poor atomization of 100 LL, I'm not surprised you're not getting any hint of a start.

After flooding, did you try the flooded start procedure? Mixture cutoff, throttle all the way in, cranking? Flooding doesn't mean the fuel has atomized enough to start. If the flooded engine didn't fire with proper procedure, try clearing engine completely with no fuel, preheating( not near any raw fuel of course) and trying again.

I doubt you over boosted with prop set at 2300, some course fixed props only turn 2300 at takeoff with MP higher than rpm, although I would check your induction system, carb attach area etc. has your carb been looked at recently?

[BobRv4]

Fly it up to Falcon and I'll have a look. (Just kidding)
If you've had the mags off make sure they are timed correctly using the timing pin in the correct hole. The mag data plate will say "LH or RH" use the correct hole. Put #1 cly to top dead center, insert both mags, then use your timing box to verify 25' timing. I would also check the switch, mine went bad one time.
Switch in start you should have one lead open, one lead closed or shorted. The open lead goes to the mag with the impulse. If you don't hear the impulse click or snap right past top dead center, then you got something wrong, timed wrong or broken impulse. Good luck hope this helps. Bob

[Nitty]

Yep, did the pin in the mag on installation thing. Pretty sure I timed the mags correctly but will recheck my work on that.

OAT for the last start attempt was in the 50's with 100LL. Previous attempts though have been warmer (70 degs or so) I did a general inspection of induction tubes, carb, valve covers to see if anything was amiss. Nothing obvious came of that inspection.

To my knowledge the carb hasnt been looked over the life of the engine (790 hours) so that needs looking into. I did try spraying some carb cleaner into orifices but not really sure I did any good with the carb on.

[jetjok]

Originally Posted by BobRv4

Fly it up to Falcon and I'll have a look. (Just kidding)
If you've had the mags off make sure they are timed correctly using the timing pin in the correct hole. The mag data plate will say "LH or RH" use the correct hole. Put #1 cly to top dead center, insert both mags, then use your timing box to verify 25' timing. I would also check the switch, mine went bad one time.
Switch in start you should have one lead open, one lead closed or shorted. The open lead goes to the mag with the impulse. If you don't hear the impulse click or snap right past top dead center, then you got something wrong, timed wrong or broken impulse. Good luck hope this helps. Bob

I am sure that Bob meant to state...Put Cyl #1 to 25 degree BTC (on compression stroke), then install the mag with the timing pin in the appropriate hole.

[az_gila]

Originally Posted by BobRv4

Fly it up to Falcon and I'll have a look. (Just kidding)
If you've had the mags off make sure they are timed correctly using the timing pin in the correct hole. The mag data plate will say "LH or RH" use the correct hole. Put #1 cly to top dead center, insert both mags, then use your timing box to verify 25' timing. I would also check the switch, mine went bad one time.
Switch in start you should have one lead open, one lead closed or shorted. The open lead goes to the mag with the impulse. If you don't hear the impulse click or snap right past top dead center, then you got something wrong, timed wrong or broken impulse. Good luck hope this helps. Bob

Note that LH and RH refers to the direction of rotation, not the side of the engine the mag. is installed on...

[BCP Boys]

Can you provide more background info? Did this happen all of the sudden? When was the last time it was started? Since you don't have a primer system (most don't use it anyway) do you turn on your pump at all, even if it's for 5 seconds?

[Nitty]

It last started about 2 weeks ago. The problem arose suddenly. The over MAP flight occurred on a Thursday, I flew the airplane again on the following Monday with no start issue and went out the next morning and couldnt get it to fire..

Start procedure that I've used is mixture about an inch out of full rich, boost pump on prior to cranking, engage the starter, couple of throttle pumps to a cracked throttle open. It started within 1 or 2 blades of the 2nd pump.