Petrol - warm starting problems

Just started having problems starting from warm. Will start on the button from cold (if I remember to charge the battery each night), but yesterday it refused to fire up after a stop of only ten minutes. It turned over OK, seemed to be coming into life if I 'played' the throttle, but in the end wouldn't fire up and drained the battery.

Ten minutes later, on a jump start, it fired first time albeit it seemed a little uneven and down on power a little. Charged the battery to the max last night, fired up fine from cold, but almost a repeat after 30 mins rest. Turned over fine, pumped the throttle and eventually it caught and fired.

The battery is definitely on the way out, particularly as it is an ancient halfrauds 550ca diddy thing.

Any suggestions very welcome.

First I would deffo change the Battery....

Then when you get it running - disconnect the MAF, if the running goes lumpy MAF is fine, if it stays the same the MAF could be suspect....

Also check the stepper motor on the side of the plenum chamber....this acts like the ye olde choke fitted to carbs....the stepper motor winds in and out to open and close a small airway to enrich or lean the mixture....it could have stuck in one position which permits fine cold starts but not warm starts (as it could be stuck in the cold start position).....

Worth a shot...

Another thought- this all stared immediately after I refuelled and I had a strong 'blow-back' of fuel as I was filling.

Any connection? Will have a look under the bonnet if it ever stops raining.