Figuring out the plug order on your aircooled VW distributor

I’m a member of many aircooled groups and forums, one question I see at least every month goes along the lines of:

“I’m at cylinder 1 top dead centre but my rotor is pointing at {unexpected position}”

Caveats before we start:

I’m no expert, I’m just a weekend warrior that has made enough mistakes to learn a couple of things the hard way.

This may only be true for Type 1 upright engines. I have no experience on any others to comment.

Figuring out what’s happening

There are normally two things that jump into my mind when I see that question:

Are you actually at TDC on Cylinder 1 or are you mistakenly on TDC on Cylinder 3?

If you can’t be confident your distributor rotor is telling you the truth you can determine this by looking at the movement of the valves.

Pop off both rocker covers and while at TDC, move the pulley back and forth.

If {valves on cylinder 1 not moving} + {Intake and exhaust valves on cylinder 3 are crossing over} = You’re at TDC on Cylinder 1.

Have you changed your distributor?

When changing from a stock SVDA type distributor to a 009 or vice versa the rotor will point to a different position for cylinder 1.

This is really confusing (especially the first time) as wiring up your distributor cap exactly as it was will mean all your leads are 1 position out and your engine won’t fire up.

To help with this I have created a couple of illustrations which I hope will help somone diagnose their problem and get back on the road quicker:

SVDA type distributor HT lead positions. Usually cylinder 1 is at 1o’clock when the engine is at TDC on 1

009 type distributor HT lead positions. Usually cylinder 1 is at 4 o’clock when the engine is at TDC on 1

So you’re confident you are at TDC on Cylinder 1 and it’s in neither of these positions?

There are a few reasons why your distributor might not align exactly as described. I understand that in reality it could point anywhere based on how the distributor drive has been inserted.

However a common one is that it has been put in the wrong way round, which would cause your distributor to be 180 degrees out.

If you start with this assumption you still don’t know if it’s 180 degrees out from 1 o’clock or 4 o’clock.

So here’s the same illustrations if the distributor is 180 degrees out.

SVDA type distributor HT lead positions if the drive is 180 degrees out

009 type distributor HT lead positions if the drive is 180 degrees out

Still not working?

Remember my caveat… this is probably the extent of my knowledge.

If things just seem way off or not making sense, go back to the beginning. Make sure you’re on cylinder 1 TDC, wherever you’re rotor is pointing, wire it up to 1 and go from there.

The firing order is 1,4,3,2 so when wiring up clockwise that’s the order of the leads you want to follow once you know where 1 truly is.

A quick tip, if you wire it anti-clockwise from 1 the order is 1,2,3,4…this is also helpful to remember when adjusting your valves gaps, you can just turn the engine backwards and do one side at a time.

Hope this has helped you get your engine fired up!