Plug wires

[Skywalker]

Getting ready to drive to a fencing tourney, but I figure I'll get myself ready for tomorrow's big push.

I know the firing order. I've seen the diagram of the distributor and wires.

I have an early model Prestolite.

Just checking. Number one wire is at 9:00.

Correct?

New cap.

Thanks for putting up with me.

Chris

[ndutton]

Maybe but not necessarily. What determines the position of the #1 plug wire is the position of the rotor when the engine is at #1 Top Dead Center (TDC).

[Skywalker]

Ok,

So once I determine #1 TDC, i look at where the rotor is pointing and proceed clockwise, right?

[ndutton]

Correct but be advised, we've seen instances of very experienced guys who have had difficulty placing the engine at #1 TDC. It's the next time the piston reaches the top of the cylinder (crankshaft roll pin vertical) after the intake valve closes. There's a technique described on the forum where you feel for compression as an indicator of the proper stroke.

[Skywalker]

Gotcha

Thanks.

Time to get my boy ready!

[ndutton]

Good luck to you today Chris. For me, I'm outta here - heading off to my son's college graduation. Good times.

[Skywalker]

Congrats! Big day.

All the best!

[ILikeRust]

Originally Posted by ndutton

Correct but be advised, we've seen instances of very experienced guys who have had difficulty placing the engine at #1 TDC.

I have no idea what you're talking about.

[67c&ccorv]

180 degrees away from the block for an early model A4 - there are some clearance issues with the Prestolite distributor and this is the optimum position for it.

[edwardc]

How serendipitous.

I was just at one of our sailing association's events, and one of the members was recounting a story of his long ago days with an A4, and I just had to share it here.

It seems that after spring commissioning and a plugs-points-wires tune-up, he had a problem. The engine would start, but would only idle. Any attempt to put a load on it would cause it to die. Adding choke would slightly help.

At this point in the tale, I thought "Aha! Sounds like fuel starvation!".

But he continued to note that there was a large sheen on the water from the exhaust, and you could smell the raw gas in it! Too much fuel, not too little!

Well, to cut to the chase, after a lot of debugging, and a call to Don, he discovered two errors that partially cancelled each other out. It turns out that, for some reason, he had removed the distributor and managed to get it reinstalled 180 degrees out. But, in addition to this, he also managed to connect the wires back up in the right order but the wrong direction! As a result of this, two of the wires ended up in the right place, but the other two were 180 out. And as many of us know, an A4 will start & run (but just barely!) on only two cylinders!

So, yes, it is possible for even experienced folks to get TDC and/or plug wires wrong.

[ndutton]

Add to the mix the typical initial belief that it can't, simply CAN'T be the timing. I did the work personally, never had a problem before, put it all back the way it was (I've convinced myself of that) and yet here's a guy with a double whammy.

Good story Ed.

[ILikeRust]

Originally Posted by ndutton

Add to the mix the typical initial belief that it can't, simply CAN'T be the timing. I did the work personally, never had a problem before, put it all back the way it was (I've convinced myself of that)

I still have no idea what you're talking about.

[ndutton]

Originally Posted by ILikeRust

I still have no idea what you're talking about.

But Bill, do you have any idea how informative your episode was (and others, you're certainly not alone)? It was a great thread with tons of information.

[ILikeRust]

Yeah, I'm just being light-hearted about it. Easy to do ... now...