Ignitions, Wire Routing, etc

The blog post is going to be quick tonight so I can get to bed. Today I started by verifying the spark plug connections on the ignitions. While doing that I decided that I wanted to swap one of the shorter and longer wires to allow for better routing. That turned into completely re-running all of the spark plug wires to try to give them a clean routing and not have any wires that end up too short or to long. I came up with a routing I was happy with.

Then it took a significant amount of time to secure all of those wires, fabricate stand offs where they route close to hoses, etc. In the end, I am pretty happy with how it turned out.

Once that was done, I went through the timing procedure for the P-Mags. To borrow a line, it is so easy, even a caveman can do it. The LEDs on the ignitions tell the whole story. I should note, that after my dissertation of my confusion over timing in my post yesterday, James left a comment on the post. Turns out that there are marks on the engine side of the starter ring gear as well, which are the ones you align with the case split. So either timing method will work on my engine, and I don’t need the special tool. So I timed the engine using that reference. Thanks James.


After I had the ignitions timed, I did the pull through test detailed in the P-Mag manual. Basically you verify that the proper plugs are sparking in the proper pairs and at the proper time. This verifies many parts of the system as well as the timing and installation. When I did this, the left ignition worked, and the right ignition did not work. (I am using aircraft left and aircraft right for a naming convention so it is opposite of a normal tractor airplane engine configuration.) I thought about it and did some troubleshooting. I verified the switch wiring by using a continuity check with each switch terminal. I verified all the wiring at the ignition. I also verified that the plug housings were grounded to the engine. I got to thinking what could cause one ignition to be completely dead, but store the timing, and show it was at top dead center the whole time. I had a theory, and called the manufacturer who knew exactly what it was. Apparently they have seen this problem before.

Turns out that I didn’t realize that my engine accessory case had a spacer for an impulse magneto. This spacer won’t allow the gear on the ignition to mesh with the drive gear in the accessory housing. So the ignition wasn’t spinning when the prop rotated. I had figured out what was happening via my trouble shooting (ignition isn’t spinning), but thankfully Brad knew about the spacer issue and could tell me exactly what I did wrong. The ‘educational” part of experimental airplanes is really the biggest piece.

So i removed the ignition so I could remove the spacer. Since there was a spacer, the mounting studs were extra long and had to be replaced so that the didn’t conflict with the ignition housing. All of this should be simple, but working in an 8 inch area between the engine and firewall around tons of wiring, hoses, and an engine mount makes it time consuming and uncomfortable. Something about only being able to get 1/8 of a turn on a wrench that is frustrating. I don’t know how this happened, but I had the exact length stud that I needed as well as a gasket. Thank god for keeping removed parts and ordering extra gaskets.

Long story short… ignition removed, remove spacer and gaskets, remove studs, install new studs, new gasket, mount ignition, re-seat ignition wiring connector and plug wires. Done.

IMG_3772 IMG_3773

Then it was re-time the ignition and do the pull through test again. This time both ignitions worked. All the plugs are firing in the proper sequence. So I am pretty convinced that all is well with the ignition system. Groovy.

Lastly we removed the fuel filter and disassembled it. It was pretty much clean as can be. I did find some debris in there, but it appeared to be a little bit of dirt or dust. It was in the threads of the filter housing, so I am not sure if it was present before fuel went into the filter or if it came from the tanks. But in any case, the amount is so minuscule as to not be considered at all. I will continue to check the filter often in the first hours of operation. But I think our efforts at keeping debris/dirt/dust out of the fuel system were successful.

IMG_3774 IMG_3775 IMG_3776

That filter photo is without any cleaning. The photo of my finger is the little bit of debris taken from the filter housing.

Oh, Almost forgot. We also tensioned the alternator drive belt. I just need to safety wire the bracket bolts.

For those of you keeping score at home… we have fuel, air, spark, lubrication…. whats left?

2 thoughts on “Ignitions, Wire Routing, etc

  1. Suggestion on fuel filter checks: – do all your ground tests, taxi, nose lift, and crow hops (all low fuel quantity, 10-15gal) – check filter again before 1st flight – check any other filter down stream at this point including servo inlet screen (to verify no line contamination has shaken loose) – check filter/leaks after 1st flight – check filter after each flight if any material is found or 5hr increments if nothing is found for the first 15hrs and up to full tank flights – once pattern of no debris established, check at phase 1 completion, then each 100hr or annual

    Excellent filter, by the way. -James

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