Ignition confusion - Page 2

bjdecker · #11 01-09-2022, 02:35 PM

See schematic from emag installation manual. Ignore the the typo ("tack". ugh)...Note the connection of the P-Lead (pin 4)

My question about the other connections to the P-Leads on the key switch (Left Mag - Blue Wire/Yellow Wire, Right Mag - Black Wire/Yellow wire stands.

Just a quick refresher:
The key switch will ground the P-leads when in the OFF position, and will ground the opposite P-Lead (R will ground the L p-lead, L will ground the R p-lead), and if the jumper is installed between Terminal 1 and GRD, the Right P-lead will be grounded when the switch is in the START position.

Connecting something else to the P-leads, *could* cause problems with magneto operation, especially if that connection was a ground path.

cdeggz · #12 01-09-2022, 08:12 PM

Thanks BJ decker. I confirmed with the ohmmeter I have the p-lead grounded when off and when the other side is selected. p-leads are not grounded in both, start, and appropriate L/R is selected.

On the 200 series mags (which I have) it calls for an optional mode switch so one can turn off variable timing. This gets wired to the p-leads through 1k resistors. I keep the mode switch open for now (it won't fire at low RPM in fixed timing mode).

bjdecker · #13 01-10-2022, 07:17 AM

Quote:

Originally Posted by cdeggz

Thanks BJ decker. I confirmed with the ohmmeter I have the p-lead grounded when off and when the other side is selected. p-leads are not grounded in both, start, and appropriate L/R is selected.

On the 200 series mags (which I have) it calls for an optional mode switch so one can turn off variable timing. This gets wired to the p-leads through 1k resistors. I keep the mode switch open for now (it won't fire at low RPM in fixed timing mode).

Ah, my mistake on the type of ignition...

So just for grins and giggles - leave the P-Lead disconnected at the 200's and see if you have the same issue.

As always, treat the engine/propellor as "LIVE" and ready to fire - don't touch the propellor, etc. etc...

lr172 · #14 01-10-2022, 07:30 AM

The fact that the same problem exists with both your old mags and new P mags would indicate a problem outside the ignition itself. I would be looking at the switch or the wiring between the switch and ignition as well as the grounds. The fact that the your measurements don't show a problem is not a 100% confirmation that your switch is working correctly. I would run some temporary wires and switches for the P mags to confirm operation, if unwilling to replace switch.

My first guess is that the switch is intermittently grounding both the L and R mags in the start position (only R should be grounded in start position when working properly).

Larry

bjdecker · #15 01-10-2022, 08:11 AM

Quote:

Originally Posted by lr172

My first guess is that the switch is intermittently grounding both the L and R mags in the start position (only R should be grounded in start position when working properly).

A good guess, and probably correct.

However, neither of the mags should be grounded in the START position, except for the Right and ONLY if the jumper is present between #1 and GRD.

cdeggz · #16 01-10-2022, 08:54 AM

Thanks Larry and BJ decker. In this case both pmags are starting ignitions so both p-leads should be ungrounded in start and both positions. I agreed that it makes sense to be an issue with the switch. On Saturday I used some alligator clips from the ignition switch to check ground continuity to the L and then the R p-lead. I moved the key and pushed on things and shook things for several minutes trying to find a condition that would show the p-leads grounded, but could not get anything.

I like the idea of alternate switches. I might first just keep the volt meter tied to the L or R p-lead every time I do an engine start for awhile and see what is going on there.

Mike S · #17 01-10-2022, 10:28 AM

Craig------as you are also having alternator issues as posted in another thread, I would look for any common link between the two.

Start with the grounds, my $0.02.

It might be time to bring in someone experienced in electrical systems to take a look at your plane.

Good luck, let us know what you end up finding.

lr172 · #18 01-10-2022, 10:40 AM

Quote:

Originally Posted by bjdecker

A good guess, and probably correct.

However, neither of the mags should be grounded in the START position, except for the Right and ONLY if the jumper is present between #1 and GRD.

Admittedly I have no idea how a Pmag is wired. However, the symptoms tell us that the switch or wiring is somehow preventing the pmags from firing with the switch in the start position. OP needs to fully understand how they are supposed to be wired and then confirm actual continuity. Given the symptoms, intermittent problems MUST be considered. This is why I suggested temporary, bypass wiring to confirm.

Larry