Fendt 415, been spreading fert all afternoon, tractor running fine. Got finished and parked tractor up. Went back an hour later and it wouldn't start. Seemed like a flat battery, so I got another tractor to jump start it. Turned the key and just the same on first try, then it started on second go. Jumped off to take the jump leads off and noticed it was putting out quite a bit of blue smoke. I took the spreader off and stopped the tractor - still putting a bit of blue smoke out. I thought I'd try see if it would start again without jump leads which it did fine but still a haze from the exhaust. Engine sounds to be running smooth enough and I lifted the bonnet but couldn't see anything obvious. Will ring the dealer on Tuesday (why do these things always happen on a bank holiday), but thought I'd ask on here now see if anyone has any ideas. Exhaust has always run totally clear until this point.