1098 cc getting more difficult to start from cold

[ndevans]

If it's an electronic ignition it's difficult to check coil voltage with points closed, unless it's the type where the points are assisted by a transistor. My Powerspark distributor does not provide more than a momentary pulse in each position as the crank handle is turned over.

[mike1864]

Good point, Neil. I hadn't clocked the OP's electronic ignition. My own electronic ignition (home-built and installed over 50 years ago!) is indeed transistor driven. In those days, semiconductors were rapidly superseding thermionic valves!
That said - and not knowing exactly what unit the OP has - no (valveless!) electronic ignition should be taking so much current (in addition to the coil's) that it drops the battery voltage to the same extent as a 120Amp starter motor. You'd quickly notice this 1.2kW cooking something!
So I don't think we are looking at (just?) a faulty electronic ignition.
My money is still on spurious ohms in the feed.
Afterthought: Taking the coil's SW wire off, and connecting SW to earth would emulate closed points for metering purposes. Expect a spark. And maybe fully isolate the electronic module in case it's terminally upset by not seeing the coil.

[ndevans]

I still say fitting a (known good) mech distributor if available would prove or disprove the electronic ignition and any associated faults. Would need a bit of setting up but would eliminate one unknown.

[mike1864]

The advantage of an electronic ignition that retains the points is that you can revert to standard ignition with just a few wiring changes. In the past I achieved this changeover with two alternative multipin "blind" plugs, with their pins differently strapped inside.
My project for the dark winter nights is to replace this "configuration key" with a multipole relay. This would enable reversion via a dashboard switch.
As the module requires only a tiny current to switch the base-emitter junction, the points don't suffer sparking or the associated wear and gap change.
But I digress
I'd suggest the OP concentrates on finding and eliminating the apparent inline resistance between the battery and the coil; ohms that even a new distributor would experience.

[eng622]

When you have electronic ignition you cannot do many of the tests suggested eg no points. Today it started instantly but will check the solenoid voltage. Cannot get at the coil terminal as on the underside coil mounted on the inner wing and servo housing is in the way.

[svenedin]

The advantage of an electronic ignition that retains the points is that you can revert to standard ignition with just a few wiring changes. In the past I achieved this changeover with two alternative multipin "blind" plugs, with their pins differently strapped inside.
My project for the dark winter nights is to replace this "configuration key" with a multipole relay. This would enable reversion via a dashboard switch.
As the module requires only a tiny current to switch the base-emitter junction, the points don't suffer sparking or the associated wear and gap change.
But I digress
I'd suggest the OP concentrates on finding and eliminating the apparent inline resistance between the battery and the coil; ohms that even a new distributor would experience.

I have electronic ignition (Lumenition Optronic) but I carry a spare distributor in the boot that is set up with points for trips far afield. It is quite straightforward to switch over the entire distributor complete with its bracket. If the spare distributor has been properly set-up in terms of the ignition timing, this is not disturbed if the distributor is removed with the bracket pinch bolt undisturbed.

Stephen

[simmitc]

Or not disturbed too greatly - the bracket has elongated holes for the retaining bolts (machine screws) and so can rotate slightly, but should be close enough for the engine to run.

[svenedin]

Or not disturbed too greatly - the bracket has elongated holes for the retaining bolts (machine screws) and so can rotate slightly, but should be close enough for the engine to run.

Yes the bracket holes are elongated which does allow a small movement but if the distributor is fitted so that the holes are hard over in the same direction every time then the effect on ignition timing is absolutely negligible.

Stephen