Distributor Rotor Arm not Turning

[Stagless Steve]

Hi All,
I have been wrestling with a lack of spark for a couple of weeks now and decided to check if the rotor arm in the distributor is actually going round. Well, it's not. I got the wife to look while I cranked the engine. She said it just twitches but doesn't go round. Any thoughts on how I can diagnose the cause please?
TIA
Steve

[NeilR]

For a start, pull the dizzy out & see if the Jackshaft is turning & teeth on both jackshaft & dizzy are undamaged.

[wilf]

Also, it is possible that the pin holding the distributor (also the oil pump drive gear) onto the distributor shaft has snapped, But as Neil says, you will only br able to check by pulling the distributor.

Can you see if there is any oil pressure while cranking?

[Stagless Steve]

Thanks for the pointers guys. I've removed the distributor. The jack shaft does turn when the engine is cranked, and the gear teeth seem to ok (what I can see of them) as do the gear teeth on the distributor.
I assume that the pin that holds the distributor onto the shaft is the hex headed thing sticking up from below? I put a magnetic probe on it. It doesn't come out but it can be moved around in the hole. Does that mean it's broken?
I didn't look at the oil pressure while cranking. Presumably I would need the distributor in place for that to happen?

[Goldstar]

Hi Steve the hex head you can see is the top of the distributor drive shaft. It often comes out with the distributor but not a problem if not.

easiest check is did you have the distributor seated properly to engage with the drive shaft. First check if the very bottom part of the distributor where the teeth are turns the rotor arm when you turn it. If yes it’s likely that it wasn’t seated properly. The rotor arm usually turns a bit when you engage it.

if no there are 2 possibilities. 1. The shaft is seized (unlikely) or more likely the roll pin has broken as per wilfs post above.

[NeilR]

Dizzy needs to be in place to drive the oil pump, if it's just the roll pin in the dizzy drive gear, then thats an easy cheap fix.
Unusual for that to break though, unless something drastic has happened inside the distributor.

[Stagless Steve]

I have tried turning the gear at the bottom of the distributor. Sometimes it turns the rotor arm freely, but sometimes it jams. Also, when I move the distributor from side to side I can hear a clonking like something is moving around inside.
Also, I can see the head of the roll pin on one side of the shaft, but on the other there is just an empty hole. Does this mean that the pin is broken? See attached photos.

[NeilR]

Distributor needs to come apart then to find what's fallen off & jamming it. Has to be pretty substantial to shear that rollpin.

[Wheelz]

Sometimes a part like a screw can drop down into the dizzy advance mechanism, and can cause a sudden jam which possibly might break the roll pin, but also can break the dizzy casing!

[jbuckl]

New distributors are available.

Repairs are available.

Distributor spares are available

https://www.h-h-ignitionsolutions.co.uk/

https://ignitioncarparts.co.uk/

[022Dave]

New distributors are available.

Repairs are available.

Distributor spares are available

https://www.h-h-ignitionsolutions.co.uk/

https://ignitioncarparts.co.uk/

Don’t forget the Distributor Doctor; Martin really knows his stuff and gives excellent service

https://www.distributordoctor.com

[jbuckl]

Don’t forget the Distributor Doctor; Martin really knows his stuff and gives excellent service
https://www.distributordoctor.com

Ok.
I was sent a distributor that had apparently been under the doctors / surgeons knife at that place. (Apparently-Apparently)

It wasn’t working.

The vacuum capsule arm was fouling.

there were other baseplate misalignments and self tappers in lieu of threaded screws.

It had apparently cost a pretty penny too.

[Goldstar]

Ok.
I was sent a distributor that had apparently been under the doctors / surgeons knife at that place. (Apparently-Apparently)

It wasn’t working.

The vacuum capsule arm was fouling.

there were other baseplate misalignments and self tappers in lieu of threaded screws.

It had apparently cost a pretty penny too.

I’ve heard many positive reviews of the DD and this is the first negative, I can’t say for sure but I would bet there’s more to that story than you have been told Julian.

[Wheelz]

New distributors are available.

Repairs are available.

Distributor spares are available

https://www.h-h-ignitionsolutions.co.uk/

https://ignitioncarparts.co.uk/

In the past I had a lot of work done by both of these suppliers. They made the distributors look very nice, and some of them apparently worked, but some didn't. The more I looked into the problems the more I uncovered cases of very poor workmanship, and in one case a lack of understanding that there is a need for calibration to ensure that the overhaul/repairs actually work to specification.

I sent 3 'reconditioned' dizzies that were not working properly to the Distributor Doctor, and he did fix them, and calibrate them, but the work was more expensive than I had expected.

Ignition car parts now sell new dizzies (Motortronic on eBay) but I have not yet heard if they are any good.

[richardthestag]

if they are anything like the lucas 35d8 reproductions then caveat emptor.

there is a world of chinesium out there and much of it appears on an online auction site near you..

DD all the way for me