TR6 Crazy Ignition Failure in TR6 engine…

[Rocky_LC]

Yesterday I was driving my car (‘71 TVR Vixen 2500 with the TR6 engine) up Mount Lemmon with some friends. It’s a 26 mile uphill drive to a little town.

I was about milepost 14 when the engine just suddenly completely cut out, and I lost all power. I was able to steer over to the shoulder, and the engine died as soon as it wasn’t being driven by the wheels.

Of course, a failure like that seemed that it must be related to the ignition. So the first thing that we did was pop the distributor cap, check the rotor, and check all the wires going to my Pertronics ignition system. All was good.

We then verified that we had good spark from the coil (I accidentally shocked the heck out of my buddy!).

Since the ignition was obviously good, We took a look at the fuel. Even though it seemed to us that IF there was a fuel problem, the car would’ve cut out or stumbled, we convinced ourselves that it could be in the fuel pump. Luckily, I had one down in town, and we got it changed it out.

Still no luck! The car just turned over, and wouldn’t fire!

So we were back to ignition. We pulled the number six plug - it looked great! Then we decided to do an ignition check on the plug itself! No spark at all!

Luckily for me, I have been carrying a bunch of spare ignition parts, so we swapped out the rotor and the distributor cap. The engine immediately fired as soon as I cranked it!

We were both stunned, because the rotor and cap were nearly brand new.

Anyway, when I got home, I took a close look at the router. You can clearly see that there is a burn track where the spark was moving from the center of the rotor, from the river, and down the rotor body onto the distributor plate or shaft. I would never have believed it….

OBTW: This is the Lucas / Moss Motor “upgraded” rotor! Stick with the red ones!

Rocky

 

[Sarastro]

That's the problem in dealing with high voltages--they can be hard to contain. Whoever designed that rotor figured that there was enough spacing between the rivet and the distributor shaft to prevent arcing, but obviously there wasn't. A little moisture, a little crud on the rotor surface, or a crack, and voila--a path for a spark.

That rotor is a flawed design. The rivet should be deeply embedded in the plastic. Other rotors don't use a rivet at all and instead the brass piece itself is partially embedded in the plastic. Much better.

 

[Rocky_LC]

Absolutely you are right!

And I paid a two dollars extra for it!

 

[DrEntropy]

Anything for our "vintage" vehicles that's advertised as "improved" or "upgraded" needs to be viewed with the jaundiced eye.

RARELY is there a way to better the original design of the bits that served their purpose well for decades.

 

[bobhustead]

Expounding on Doc's point, electronic ignitions are a downgrade from original points and condenser systems (fiddly as condensers can be).
Bob

 

[mctriumph]

Perhaps if they had sealed the rivet with a bit of silicone?? Wow. This is why I never
trash good used bits,zip locked bag in the boot insures a happy ending.
Mad dog

 

[Rocky_LC]

I was happy I had 3 rotors, and my old distributor cap in the car with me! Saved me a tow!

Just wished I had been a little more thorough on the initial ignition checks the first time!

I would have made it to the top! As it was, I had to ride up in a Corvette for my lunch!

Rocky

 

[Rocky_LC]

Actually, now that I’m looking at the packages, the “premium” rotor is the red one without the exposed rivet.

The black one is the bad one with the electrical path to ground.

(And I know the red one (on the right) has a crack through it, but there’s a brand new one inside the white package)!

I couldn’t figure out how to edit my first post, but I thought I’d better correct myself if anyone is looking for parts.

Rocky