hi,
I am complete novice with cars and was having a discussion with a mate about bump starting a car.
If the battery is completely flat (no lights even flickering on dash board) can you bump start it or must there be at least a small charge left?
cheers!
| hi, | | I am complete novice with cars and was having a discussion with a mate | about bump starting a car. | | If the battery is completely flat (no lights even flickering on dash | board) can you bump start it or must there be at least a small charge | left?
It all depends.
On a good enough hill the engine speed may get fast enough to get the alternator going and it might get started, but I wouldn't guarantee it, since the alternator needs some voltage to tell it to start charging !
If you get the engine turning fast enough the alternator might supply enough current to allow it to start. Difficult to say without trying it.
Rob Graham
| hi, | | I am complete novice with cars and was having a discussion with a mate | about bump starting a car. | | If the battery is completely flat (no lights even flickering on dash | board) can you bump start it or must there be at least a small charge | left?
It all depends! What sort of car is it, Petrol, Diesel, manual, automatic?
I always carry a pair of Jump Leads. IMO better than bump starting.
Alternatively one of those power packs like:
I don't know about car alternators, but some ac generators that need dc excitation to start delivering, will often actually start due to the residual magnetism from the last time they were used - it only takes a small amount to start generating and then everything is self-sustaining.
Steve W
Yes. been there, done that, bought the T-Shirt. Get a BIG hill or a tow.
"Gav" wrote
Bump starting isn't recommended on catalytic converter equiped cars as unburnt fuel will harm the catalyst.
A jumpstarter pack is a good idea (I got a really good one from Maplins for about £30)
If you must bump start, it'd have to be moving quite fast for enough charge to come from the altenator to fire the spark plugs. If it's a diesel, there doesn't have to be so much charge as the only thing that needs power is the fuel pump (although you'll probably have a hard time starting it without the glow plugs working, not to mention the fact that needing so much compression in the cylinders is likely to make the car stall before it fires)
| > I am complete novice with cars and was having a discussion with a mate | > about bump starting a car. | >
| > If the battery is completely flat (no lights even flickering on dash | > board) can you bump start it or must there be at least a small charge | > left? | >
| > cheers! | | | Yes. been there, done that, bought the T-Shirt. Get a BIG hill or a tow.
IME Fine for old carburetor petrol engines. Bump starting is forbidden on my modern diesel. AFAIK Bump starting is forbidden on some automatics.
Before you try check the manual.
Jump leads are IOM much better, I have carried a pair for years.
The message from Dave Fawthrop contains these words:
On the size of the shoes, the draught of the ships and the colour and melting point of the sealing wax. The colour of the cabbages and which monarch is reigning matters, too, as does the temperature of the sea and the empennage of porcines.
The message from "Robin Graham" contains these words:
Only if there's enough charge left to energise the rotor.
The message from "fishman" contains these words:
Where does this crap come from? Why should there be unburnt fuel going down the pipe any more with a bump-start than with a starter-start?
AFAIK you can't bump start an automatic - period. But then, IKFA!
The message from Dave Fawthrop contains these words:
It's not so much forbidden as it won't work. Most autos have their internal oil-pump on the input shaft, so they have pressure to operate the gubbins only when the engine's turning. Making the output shaft turn won't make the engine turn 'cos there's no oil pressure to allow a connection between output and input.
There are autos with pumps on the output as well - and these can be bump-started.
Because there's a lot of shit talked about cars with cats? I have been told by many people that you can't go through a large puddle with a cat because it'll bite and scratch you. That's true, but they also say you can't go through a puddle with a car with a catalyst as it will cool down too quick and kill it.
So what do you do if you have a flooded road on your way home? Bed down for the night on the back seat? It's bollox, 'cause I've done that lots of times as well.
It's not normally forbidden, it just doesn't work.
Owners handbook. It's normally in reference to tow starting though.
Cos you can try & tow start something for far more engine revs & hence far more fuel. It's an arse covering exercise.
It's *impossible* on most - they won't engage a gear without hydraulic pressure, and this is obtained from an engine driven pump.
I'd also be interested to know how many engine revolutions you can manage from a failed bump-start as opposed to say a couple of minutes cranking over on the starter (which can also go through a pre-start routine of squirting in extra fuel each time the fuel pump is energised).
The argument is totally bogus, unless I'm missing something.
The message from DuncanWood contains these words:
Very likely.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.