Bump starting

[will_]

I had to bump start my Octy the other day after leaving a portable fridge plugged in overnight. It didn't go quite as expected so I'm posting my findings in case it's useful to anyone else.

A friend and I first bumped it in second gear and the engine started but just ticked over slightly lumpily. None of the dashboard dials twitched (not even the rev counter), the alternator and airbag lights were on, and pressing the throttle had no effect.

I remember hearing once that alternators need "spinning up" to a certain speed before they start "working" (i.e. charging), and I guess we hadn't got it going fast enough. We still had clutch control so we gingerly turned the car around and accelerated up through first and second, into third - luckily it was a long car park! Once there, doing about 25mph, I dropped it back into first and everything sprung into life.

Weird, huh!

[cjb]

Probably the battery voltage was very low at first.

[KenONeill]

It's actually not recommended to bump start any car with a catalytic convertor, because when they first fire you get a slug of unburnt fuel past the lambda and cat, and it's possible for that to blow the cat.

[AndrewTait]

I had to bump start my Octy the other day after leaving a portable fridge plugged in overnight. It didn't go quite as expected so I'm posting my findings in case it's useful to anyone else.

Strange that - I did exactly the same thing last week - (Monday night/Tuesday morning) so it would have been very useful to me last week.

Fortunately the guy on the reception desk at the Premier Inn in Folkstone, allowed me to jump start mine of his car, and I still get to the Channel Tunnel on time.

By the way, is it possible to bump start deisels? I didn't try, as there wasn't enough room.

[KenONeill]

I've never tried to bump a diesel; I suspect it might not be possible on a cold engine because they rely on achieving a certain combustion chamber temperature to get the fire going.

[Octavia Vrs!]

I've bump started an astra deisel from cold a couple of times - its hard work, the first time as soon as the driver lifted the clutch I thought she'd pressed the brake peddle. The compression is so high get it rolling at a good speed first! Must admit I didn't know about CAT damage but if your in a pickle it's worth the slight risk IMHO.

[expostmanpat]

Bump started LDV deisals loads of times, just make sure your not behind the exhaust when they fire up

[RichieVRS]

It's actually not recommended to bump start any car with a catalytic convertor, because when they first fire you get a slug of unburnt fuel past the lambda and cat, and it's possible for that to blow the cat.

Agree

[Banana-Man]

I've never tried to bump a diesel; I suspect it might not be possible on a cold engine because they rely on achieving a certain combustion chamber temperature to get the fire going.

With the ignition on it should be possible to push start any diesel, as long as the glow plugs heat up. Diesels do not rely on combustion chamber temp really - the fuel and air is combusted under pressure on the power stroke of the engine not from ignition spark spark like gas cars.

The only danger jumping the car from under the hood on the battery is blowing fuses? Pushing it is OK because there is no serge in electrical energy

[richardsfavorit]

I woudn't think it warm if you bump started once or twice. I did with my Felicia and it didn't harm the emissions!

[ian110]

Bump started LDV deisals loads of times, just make sure your not behind the exhaust when they fire up

Ahh LDV minibusses and their interior lights that flatten a battery in an hour. It is possible to bump start a overladen minibus on a flat car park with enough people pushing. The trick is to use a high gear such as 4th and lift the clutch at running speed but drop the clutch again before it stalls. With practice it is easy!