Could be electrical.

[jreacock]

I'm experiencing a strange fault with the Beta.

It's getting hard to start from cold. After 20 to 30 seconds in total of cranking, it starts to fire on one. Then after a bit longer, two are firing and it will run. After a minute or so like this, another joins in - followed by the last one a minute or so later. Once warm - it will start straight back up, but this issue seems to have got worse as the temperature in the garage has steadily got lower.
I've changed the leads, plugs, rotor arm and cap. I tried another coil just to eliminate that. Same with ignition unit. The pickup in the distributor looks to be working fine. Plugs have petrol on them - carb seems to be operating ok. As mentioned - it seems fine once it is running, but it's in a state now, where it's difficult to get it warm. I haven't checked spark quality yet, timing hasn't been fiddled with during diagnosis neither has the carb - but it was cleaned a while ago, new gaskets etc. The choke looks to be operating fine. The old leads were breaking down. 2 were 1k, 1 was 10k and the other was 140KOhm.

Any ideas of other things to check?

Thanks,
Justin.

[peteracs]

Hi Justin

Have you checked the earth and supply voltage under load for the ignition circuit?

Another thought is compression test the cylinders?

Are you sure the static timing is correct?

Just my two penny worth...

Peter

[jreacock]

Hi Peter.
Thanks for the reply. I need some input - and all suggestions are welcome.
I checked the coil for 12V on the side labelled B+, but it also seemed to have 12V on the second terminal as well but I think this depends on the magnetic pickup. I believe it only drops to ground when the pickup detects one of the 4 corners of the magnetic material passing by, which grounds the coil and steps up the 12V input to spark-making voltage level.

The compression was checked not so long ago (a month or two), and I've not altered anything timing related.

Thanks,
Justin.

[betabuoy]

Hi Justin

I'd start with all the plugs out and resting on the cylinder head whilst connected to their HT leads.  Crank the engine and check for a nice spark on all four.  If that's good, I'd move away from the electrics given you say it works well when warm.

Next, I'd l'd try to recall when I last put fresh fuel in the car.  If your car's been in the garage all year, it could be suffering the unreliable lawnmower effect; i.e., trying to cope with deteriorating fuel at the start of the cutting season.  New fuel is great.

Please don't be offended by my simple ideas... you have a great list of cars so you appear experienced and I'm sure you'll have already ruled my ideas out.

Chris

[peteracs]

Hi

Yes you will get 12V on both sides until the Ignition pulls one side low when it wants a spark. Given you changed the ignition unit check the earth is good from that unit as a poor earth will reduce the voltage drop on the coil and hence the spark energy. The comment re fuel is also very relevent as that will screw up any tuning

Peter

[jreacock]

Hi Chris and Peter.

All suggestions are welcomed. I've 'fixed' many faulty bits and pieces by checking things that were overlooked as being too obvious. The mains cables that weren't plugged in, the HT leads that were in the wrong order, getting the + and - the wrong way round on the battery etc. 

I do need to check the sparks as the next step, along with the earth on the coil. The fuel I think should be ok. I put a load of good stuff in to an almost empty tank this weekend, and it should circulate it around. It's an electric pump with a return.

I can't help thinking that it's got worse with the fall in temp in the garage, so I'm trying to identify what might be most affected by temperature fluctuations.

Maybe it just wants to hibernate.

[jreacock]

I had it running today and yesterday. It was a struggle to start yesterday where again it started firing on one cylinder after a fair amount of cranking, then two if I kept cranking after which it would free-run. Three started firing 30 seconds later, and then four another 30 to 60 seconds after that. Once running, it sounds fine - I just get a small backfire if the throttle is jabbed (choke still on), and the engine stutters / lags a bit from the sudden throttle change.

When it's warmer, the tickover oscillates slowly (2 to 3 seconds between waves). In time the oscillations decrease in magnitude (10 to 20 seconds following a throttle blip), and it revs at a constant rate again. Following a blip of the throttle, it nearly stalls then the revs go over tickover speed, then drop but not as low as before, then rise but not as high as the last time etc. getting less further away from tickover each time. In electronics, the effect is called overshoot and ringing.

Anyone got any ideas as to what might cause this kind of oscillation.

Thanks.

[peteracs]

Hi

I think you should get a timing gun on the engine and confirm what timing you have just to make sure it is what you expect.

Peter