Over the weekend I had a situation where a 2010 VW Golf Diesel had a flat battery. I had a nice long but gentle hill to let it roll down, so I attempted a bump start, which didn't work.
When starting normally, after you turn the key, the dashboard display says, "Depress clutch to start." So you have to have the clutch in, for the starter motor to turn the engine over.
So rolling down the hill, in gear, with the clutch in, when the car got up speed I simultaneously turned the key and let the clutch out to engage the gear. There were some lurches of the car, but the engine didn't turn over. I tried this several times until I was at the bottom of the hill.
Eventually I got the car started with jump leads. No waiting or revving the host engine. Started straight away (Which I mention to indicate the battery wasn't dead as such, just flat.)
Is the "Depress clutch to start" mechanism preventing the car from being bump-started, or did I just not do it right?