Just a quick note in case anyone else gets this. Had starting problems which seemed to coincide with leaving the van for a few days (red herring). I initially thought that the twin carbs were emptying (syphoning, evaporation?) and it was therefore pumping the petrol back up and flattening the battery in the process. Then I thought the petrol was fine and I was just flooding it having waited and then it would start . Measured voltage on battery and there was a rise in voltage when the ignition went out so charging. Noticed that the engine would catch as I released the starter.... Finally sussed it when I had to call the AA when I flattened the battery at a petrol station. Friendly AA guy (came in 15 mins). We eventually tracked it down to a bad earth between the engine and the battery. Putting a jump lead between the engine casing and negative gave an extra 1.5 volts. So, made up a fat earth cable out of a bit of 10mm 'bonding' and a couple of ring tags, bolted it onto one of the alternator pillar nuts and battery negative and no more starting problems.
Bad Earth......now were have i heard that before Glad you sussed it.... probably worth putting another earth strap from the gearbox to the chassis while you're at it....if this is bad, you'd also struggle to do the Jump lead trick
I'm glad you have posted as I'm Having a similar issue and may not have known to check for this. I end up flattening my battery then charging it back up to start. My problem has also only started recently after being left a while. I had thought my dizzy cap might be at fault as wiggling it sometimes helps!
It could also be the ignition switch. These can sometimes fail such that the ignition live goes off when you turn the key to the start position. You can crank the engine all you like, but the coil has no juice so there's no spark. It might "catch" as you release the starter. You can check for this with a voltmeter or test lamp between the coil positive and earth whilst your mate turns the key.
