Refuses to Hot Start

[bob865]

Hello everyone.  It's been a while since I've posted, but I need some help from the brain trust.  We just our 75 M20E back from being down for a prop strike inspection.  Field in PA had a pothole that was big enough that the prop hit the ground when the nosewheel dropped in it.  Plane runs well coming back with one big exception, she will not hot start.  The engine is equipped with a surefly ignition and since we converted from SOS to the surefly, hot starts have been a non-issue.  However coming back from the prop strike, the engine will not hot start.  Normal procedures won't work.  Flooded procedures won't work.  Intentionally flooding and trying a flooded start won't work.  Nothing.  Checked the timing and it's spot on.  Checked wiring, all seems good.  Mag checks all check good.  Checking for a hot mag checks good.  Right now we have to wait over an hour before we can get it to start.  Battery passes load check and when cranking the engine, the engine monitor doesn't drop out which I interpret as the battery is in good shape.

During some early troubleshooting it appeared to be working find with the cowling off.  I could start it, let it get as hot as possible without the cowling, shut it down, and hot start it.  However when I put the cowling back on, it stopped working.

One observation is that it sometimes feels like a Hard Start or Kick Back like you would get on a SOS system when you released the key.  This makes me suspect the surefly is not working after it hot soaks after an engine shutdown, but that seems unlikely.

Any thoughts on things to try or check?

[Ragsf15e]

51 minutes ago, bob865 said:

Hello everyone.  It's been a while since I've posted, but I need some help from the brain trust.  We just our 75 M20E back from being down for a prop strike inspection.  Field in PA had a pothole that was big enough that the prop hit the ground when the nosewheel dropped in it.  Plane runs well coming back with one big exception, she will not hot start.  The engine is equipped with a surefly ignition and since we converted from SOS to the surefly, hot starts have been a non-issue.  However coming back from the prop strike, the engine will not hot start.  Normal procedures won't work.  Flooded procedures won't work.  Intentionally flooding and trying a flooded start won't work.  Nothing.  Checked the timing and it's spot on.  Checked wiring, all seems good.  Mag checks all check good.  Checking for a hot mag checks good.  Right now we have to wait over an hour before we can get it to start.  Battery passes load check and when cranking the engine, the engine monitor doesn't drop out which I interpret as the battery is in good shape.

During some early troubleshooting it appeared to be working find with the cowling off.  I could start it, let it get as hot as possible without the cowling, shut it down, and hot start it.  However when I put the cowling back on, it stopped working.

One observation is that it sometimes feels like a Hard Start or Kick Back like you would get on a SOS system when you released the key.  This makes me suspect the surefly is not working after it hot soaks after an engine shutdown, but that seems unlikely.

Any thoughts on things to try or check?

If you get it running, nice and hot, then do a mag check, SF is fine, no?  If so, I’d think it’s unlikely the SF.  Was the engine completely off for the prop strike check?  Are the mag grounding wires on the correct mags?  Because it sounds like it starting on the right mag…

Also, it sounds like you had a good workable hot start technique before, but it might help to say exactly what you’re doing to hot start it just to help the troubleshooting.

I have same setup with SF on the left and hot starts are pretty easy as you saw before, so clearly something is amiss…

[MikeOH]

Curious if prior to the prop-strike you had performed hot-starts in HOT weather post SF installation; i.e. is this the first summer since your SF was installed?

Admittedly, I know nothing of the particulars of a SF but I'm not convinced that it matters if the SF passes mag checks with the engine running.  If the SF is involved in starting itself then I can see it being possibly the problem if it was somehow miswired on reinstallation (if it was removed for prop strike inspection)... or, if this is the first time the SF has been exposed to hot ambient temperatures.  High temps and electronics often don't go well together

[Shadrach]

1 hour ago, bob865 said:

Hello everyone.  It's been a while since I've posted, but I need some help from the brain trust.  We just our 75 M20E back from being down for a prop strike inspection.  Field in PA had a pothole that was big enough that the prop hit the ground when the nosewheel dropped in it.  Plane runs well coming back with one big exception, she will not hot start.  The engine is equipped with a surefly ignition and since we converted from SOS to the surefly, hot starts have been a non-issue.  However coming back from the prop strike, the engine will not hot start.  Normal procedures won't work.  Flooded procedures won't work.  Intentionally flooding and trying a flooded start won't work.  Nothing.  Checked the timing and it's spot on.  Checked wiring, all seems good.  Mag checks all check good.  Checking for a hot mag checks good.  Right now we have to wait over an hour before we can get it to start.  Battery passes load check and when cranking the engine, the engine monitor doesn't drop out which I interpret as the battery is in good shape.

During some early troubleshooting it appeared to be working find with the cowling off.  I could start it, let it get as hot as possible without the cowling, shut it down, and hot start it.  However when I put the cowling back on, it stopped working.

One observation is that it sometimes feels like a Hard Start or Kick Back like you would get on a SOS system when you released the key.  This makes me suspect the surefly is not working after it hot soaks after an engine shutdown, but that seems unlikely.

Any thoughts on things to try or check?

This reads to me like the Surefire ignition module is not delivering spark at the specified timing (TDC at 400rpm and below).  Has someone physically verified spark to the plugs at TDC?

[bob865]

17 hours ago, Ragsf15e said:

If you get it running, nice and hot, then do a mag check, SF is fine, no?  If so, I’d think it’s unlikely the SF.  Was the engine completely off for the prop strike check?  Are the mag grounding wires on the correct mags?  Because it sounds like it starting on the right mag…

Also, it sounds like you had a good workable hot start technique before, but it might help to say exactly what you’re doing to hot start it just to help the troubleshooting.

I have same setup with SF on the left and hot starts are pretty easy as you saw before, so clearly something is amiss…

Yes.  In flight mag check is good (nice and hot).  I haven't thought about checking it again after I finally get it started following a hot start.  The engine came completely off and went to Triad in NC for the prop strike inspection.  I cam going to check the P-leads this afternoon.  I'm also going to disconnect the started and check the correct mag is firing when the key is in the start position.

Edited July 9, 2024 by bob865
typo

[bob865]

17 hours ago, MikeOH said:

Curious if prior to the prop-strike you had performed hot-starts in HOT weather post SF installation; i.e. is this the first summer since your SF was installed?

Admittedly, I know nothing of the particulars of a SF but I'm not convinced that it matters if the SF passes mag checks with the engine running.  If the SF is involved in starting itself then I can see it being possibly the problem if it was somehow miswired on reinstallation (if it was removed for prop strike inspection)... or, if this is the first time the SF has been exposed to hot ambient temperatures.  High temps and electronics often don't go well together

It's not our first summer and so far we haven't had any issues.  Admittedly, the SF came off and went to them for inspection for the prop strike.  I'm going to check serial numbers this afternoon to see if maybe we got a different unit back.  I'm curious if they just exchanged the unit and maybe we got a 'repaired' unit that potentially had an issue.  I'm grasping at straws here if you can't tell.

[bob865]

17 hours ago, Shadrach said:

This reads to me like the Surefire ignition module is not delivering spark at the specified timing (TDC at 400rpm and below).  Has someone physically verified spark to the plugs at TDC?

No.  I haven't thought of a safe way to do this.  Any guidance you can offer to check for spark safely?  I'd love to be able to confirm or deny spark to move on to something else if it's not ignition related.

[N201MKTurbo]

To check your spark, remove all the top spark plugs so there is no compression. remove all the bottom spark plug wires so there is no chance of spark in any cylinders. then blow compressed air into all the top spark plug holes to flush out any fuel vapor. Then you can hook a spark plug to a spark plug wire, lay it on top of the cylinders. Turn the mags on and spin the prop by hand and check the spark.

If you don't flush the fuel vapor out of the cylinders, the spark may ignite it. It won't hurt anything, unless you are in front of the spark plug hole, but it will scare the bejesus out of you.

[Shadrach]

1 hour ago, bob865 said:

No.  I haven't thought of a safe way to do this.  Any guidance you can offer to check for spark safely?  I'd love to be able to confirm or deny spark to move on to something else if it's not ignition related.

Rich gives good advice above and is very thorough in his instructions.

While there is no legal requirement that your mechanic be there for this type of troubleshooting, it’s probably a good idea given it’s your first time doing this.

I am not an expert on the Surefly system. I do not know if the switch needs to be in the start position for it to Fire at TDC. If ignition timing is purely driven by RPM, you should be able to do the following with the ignition switch set to the left mag (Surefly).  Perhaps someone more familiar with the system can verify.

I remove all of the spark plug leads and then remove the top plugs. Remember that you are only testing the Surefly leads. Extend a straight edge from the parting flange of the crank case out to the back of the starter ring. The TDC (0°) mark on the starter ring is for cylinder #1.  Verify #1 is on the compression stroke by covering the top spark plug hole with your thumb and cranking the prop through by hand until you feel pressure at the plug hole.  With the ignition Switch in the appropriate position (which would be left mag) hold the lead close enough to the cylinder for the spark to jump and move the prop through top dead center.  You should see a spark at TDC.  Alternatively, you can put a spark plug back on the lead and hold it against the cylinder and look for a spark at the electrode as you move the prop through TDC.

[Ragsf15e]

12 minutes ago, Shadrach said:

Rich gives good advice above and is very thorough in his instructions.

While there is no legal requirement that your mechanic be there for this type of troubleshooting, it’s probably a good idea given it’s your first time doing this.

I am not an expert on the Surefly system. I do not know if the switch needs to be in the start position for it to Fire at TDC. If ignition timing is purely driven by RPM, you should be able to do the following with the ignition switch set to the left mag (Surefly).  Perhaps someone more familiar with the system can verify.

I remove all of the spark plug leads and then remove the top plugs. Remember that you are only testing the Surefly leads. Extend a straight edge from the parting flange of the crank case out to the back of the starter ring. The TDC (0°) mark on the starter ring is for cylinder #1.  Verify #1 is on the compression stroke by covering the top spark plug hole with your thumb and cranking the prop through by hand until you feel pressure at the plug hole.  With the ignition Switch in the appropriate position (which would be left mag) hold the lead close enough to the cylinder for the spark to jump and move the prop through top dead center.  You should see a spark at TDC.  Alternatively, you can put a spark plug back on the lead and hold it against the cylinder and look for a spark at the electrode as you move the prop through TDC.

SF senses rpm (i want to say less than ~400?) to fire at TDC so your method should be good.  No “switch” other than the advance settings and the setting for timing.  He should probably check those but they shouldn’t play a part in starting…

Edited July 9, 2024 by Ragsf15e

[bob865]

Time for an update and resolution.  Thanks for all the help with the troubleshooting and conscience checks as we were working the issue.  We were able to narrow it down to the surefly.  No spark.  By the time we were testing it, it even struggled to start cold reliably.  My mechanic worked with their support on the phone and they ultimately gave us an RMA to return it.  With Oshkosh coming up, we got them to do an advanced exchange so we could get the plane going.  The surefly was installed and all of our woes came to an end. 

 

Oh and one additional note.  The sn of the 'bad' unit was the same as my original.  The unit went back to surefly right before our issues for a prop strike inspection.  The only thing worth noting was the revision number on the case went from an A to an F.  I'm guessing maybe they did a software update that failed during the inspection?

Edited July 30, 2024 by bob865