OEM Painted Rotor

[aktundra]

Did a routine plugs, wires, cap & rotor PM. Seems toyota had a cap & rotor, one box store had plugs, another box store head wires.

The rotor that I got directly from Toyota had a dab of some kind of paint on the tip of the rotor where it should be sending the spark to the cap & wires. I tested for connectivity, and the blob of paint was blocking current flowing from down the rotor to the top

Why does toyota put paint on the tip of the rotor ? Has anybody else seen this on a part directly from the dealership ? It seems to do nothing except I interfere with the function of the rotor.

 

[Grayscale]

My guess is that your distributor is the small-cap-type for an F engine. Later Nippondenso distributor rotors don't have this. It cleans-up/removes, if you ever feel inspired to clean your cap and rotor.

 

[B y r o n]

I've never seen it but my guess is it might have been put there to prevent corrosion while sitting on the shelf. Don't know if it was to be cleaned off before install or was designed to be chipped off by the contact when the rotor spun inside the cap.

 

[JohnnyC]

I dont think I had ever seen that.... you got a pic?

are you sure it's not carbon where the rotor contacts the carbon brush on the cap? I have seen rotors with the carbon on a spring that contacts the cap before

 

[aktundra]

The black rotor is new out of the box from the dealership. It came with a thin black line of paint on the tip. Probes on the end and the center, do not conduct.

 

[Grayscale]

Same here.

 

[JohnnyC]

That’s odd imho

 

[73FJ40]

It's not paint. The substance is a plasma coating intended to suppress radio interference noise on conventional distributor ignition systems.

The following is a link to the Toyota patent.

US4652705A - Ignition distributor with noise suppression electrode oxide coating - Google Patents

An ignition distributor having a radio wave noise suppressing function has a rotor electrode and counter electrodes. At least the cathodic one of the rotor electrode and the counter electrodes is provided at its end with a coating layer of a material which is a mixture of a metal oxide having a...

patents.google.com

 

[Engineer8000]

The DMM has a few volts that will not penetrate the coating. Several thousand volts will have no problem.