Technical distributor timing 1982 Spider

[SuperHarley]

A few months ago, a mechanic said timing was perfect, i.e. 10 degrees BTDC at 850 RPM. Just failed California smog test because it is 27 BTDC and 1100 PRM. At higher RPMs, vacuum advance worked. I could not budge the distributor by hand, so I do not know how the timing could have changed. 1) Can timing at idle change other than by turning the distributor? 2) The clamp nut is underneath the distributor and appears to be 17mm, but the surrounding space is too small to use any of my wrenches. Is there a special tool for this? Thanks.

 

[bugsymike]

A few months ago, a mechanic said timing was perfect, i.e. 10 degrees BTDC at 850 RPM. Just failed California smog test because it is 27 BTDC and 1100 PRM. At higher RPMs, vacuum advance worked. I could not budge the distributor by hand, so I do not know how the timing could have changed. 1) Can timing at idle change other than by turning the distributor? 2) The clamp nut is underneath the distributor and appears to be 17mm, but the surrounding space is too small to use any of my wrenches. Is there a special tool for this? Thanks.

Ideally you need to check the timing marks are correct and the using a strobe light and rev counter to confirm.
If static timing correct and at idle then, then the most likely cause is wear in the distributor advance and retard mechanism and the springs controlling the bob weights.
What often used to happen is they never got oil during services so the shaft and mechanical advance side would seize.
Whether it is Electronic Ignition or still uses contact points the advance and retard mechanism principle is the same.
The only time it would be different is if some fancy electronic aftermarket kit has been fitted.
Normally to adjust most of the older Fiat distributors there is a 13mm nut which although it doesn't show in this photo it holds a clamp roughly where 15 is marked on the page in the photo to slacken and adjust basic timing.
If yours is similar to this design then when oiled and moving easily item 7 should move independently to item 9 within the range controlled by the bob weights 8 and the springs 10.
From memory we used to slacken the holding nut using a 13mm socket and flexible joint on a ratchet and extension.'
If yours is greatly different to this design possible to comply with smog laws where you are then send a photo, I am sure some one will recognise it.

 

[348azeus]

Mine has the distributor into the cam box with a 17mm nut. Can’t remember if I bent a spanner to fit but I had a similar problem with advance and in the end fitted a 123 distributor.

 

[s130]

What make / model is you fuel injection system?

It is normal, even for early Fiat systems to have the fuel injection system also deliver the timing for the spark plugs. It generates the sparks at the correct time and the distributor only directs the spark to the correct cylinder. There are probably NO points in your distributor.

Make and model of fuel injection system will confirm this.

 

[SuperHarley]

Thanks for the responses. I bought a 17mm crowfoot wrench for loosening the distributor nut, and rotated the distributor to 10 degrees before TDC. This reduced the idle to 850. So I should now pass CA smog test.

 

[bugsymike]

Thanks for the responses. I bought a 17mm crowfoot wrench for loosening the distributor nut, and rotated the distributor to 10 degrees before TDC. This reduced the idle to 850. So I should now pass CA smog test.

Sounds good.
Nothing seized on the advance and retard mechanism then?

 

[SuperHarley]

Nope. I just do not understand how timing changed on a seemingly tightened distributor.

 

[s130]

Nope. I just do not understand how timing changed on a seemingly tightened distributor.

Pretty unusual but here are some possibilities

1) Broken bob weight spring jamming the weight return
2) Sticking bob weight after maximum advance
3) Sticking vacuum advance shaft
4) Permanent vacuum
5) Loose points (highly unlikely as this would cause more issues than just high RPM