PI engine hunting at tick over

[Pete R]

I recently had to change the distributor drive shaft and although I think I timed the MU and dizzy correctly the engine has been hunting or pulsing at tick over. It starts ok and once I get a few more revs it pulls away well, plus fuel economy on a recent 200 mile run was about 27mpg, which is excellent. It has twin sports exhausts, which i know don't sound as smooth as a standard single one.

 

I have so far done the following:

 

1. Timed distributor with adjustable strobe light and all ok, inc advance retard

2. Checked number 6 MU port is just opening at number 1 tdc (assuming that is correct!)

3. Tried both points and electronic ignition, no change

4. Tried a different coil, no change

5. Cleaned the Bosch fuel pump pre-filter

6. Checked and balanced the butterflies

7. Blown through the injectors

 

Before I replaced the drive shaft, the advance retard shaft used to point to 10 o'clock but now points to 8 o'clock, although I have seen pictures of both on other engines. The shaft within the dizzy has a bit of vertical play, but I am sure it was always like that, plus it seems to make a clicking noise when running. I thought it was the points, but it makes the same noise with the electonic module.

 

Any ideas please?

 

Pete

[Peter Cobbold]

Hunting is a symptom of an over-rich mixture. Maybe the 'choke' lever on the MU is not going fully home , or the outer cable has jumped forwards out of its clip on the MU, also leaving the mixture rich at tick over.

Peter

Edited April 24, 2014 by Peter Cobbold