Caporegime
Can you bump start any car?
- Thread starter mark66
- Start date
Caporegime
if its in the way of the car then sure.
Permabanned
I think its just a tale - I can see why someone might say that - with the engine turning perhaps dumping some fuel into the exhaust, which is pretty bad for the cat. But I don't think its likely.
You can't bump a car with a completely dead battery... there's no power to create a spark. not rocket science
the alternator is there to provide the spark, fuelpump, injectors e.t.c you just have to push it fast enough that you can get the engine to turn over at 1000rpm or soyes bumping can be bad for the cat and the lamda sensor, but they dont see enough fuel to cause them insta damage. an hour or so running on 3cyclinders killed a new lambda on my car and the cat barely works. garage left it running to see if a misfire would clear n killed it.
Caporegime
Bump starting a newish car (1998 onwards) isn't a great idea, it allows unburnt fuel into the exhaust and can cause O2 and Cat problems, some car makers actually state in the manual don't bumpstart.
Soldato
An alternator won't energise if you're trying to bump start it, and certainly wouldn't turn fast, or for long enough, to generate any meaningful output
Bump starting a car with a dead battery usually results in nothing, if there's not enough power to run the dash lights then there's not going to be enough power to run the coils, injectors, or ECU - in a similar fashion with carburetted cars, if the battery is stone dead then there'll be nothing to make a spark and it won't start.
Same with diesels - if there's not enough charge left to open the stop solenoid (or run the electrics, depending on how old it is), it ain't goin' anywhere. You can bump start them but sometimes have to push them (or pull them) with a car - because obviously the compression ratio is usually twice that of the equivalent petrol engine
Some mechanical ones start very easily if pushed, others not so - and obviously if the battery is so flat that the glowplugs can't be heated then it won't be as easy to start. You can't bump start, in short, any car with an automatic gearbox either, although back in the 30s/40s/50s there were a few that had provisions for it and there's always the odd exception floating around
Bump starting in reverse is also a bad idea as it tends to end up damaging the transmission. Likewise, as mentioned, some cars specifically state not to bump start them as you may damage the emissions and exhaust system - although, of course, sometimes they're just covering all angles to avoid any potential damage.
That noise is most probably the starter solenoid - basically the battery is holding enough charge to run the electrics and, when you turn the key, attempts to turn the starter motor - but it doesn't have the ability to because it's run down - so you get that rapid clicking as the starter solenoid flicks back and forth trying to engage the starter.
Put some jump leads on it and it'll probably go straight away
Do the dash lights dim when you turn the key to start it? Usually a giveaway that the battery's flat
Last edited:
Don
Soldato
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- 26 Aug 2003
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I tired to bump start a cat once and it just flopped about and said miaow
Soldato
ugh, so much **** getting posted.
The deal with bumping is the alternator boosts the voltage to enough to run the systems on the car when the battery is too low, or the systems are broken.
On most cars a really flat battery can be overcome by bumping.
If the car has field coils in the alternator, the flat battery may not be enough to energize the alternator so it can generate electricity. Which is why you sometimes can;t bump some cars.
If for example the fuel pump is on the verge of ceased, 12V before cranking may not turn it to prime the rail, but 13V from bumping might.
The deal with bumping is the alternator boosts the voltage to enough to run the systems on the car when the battery is too low, or the systems are broken.
On most cars a really flat battery can be overcome by bumping.
If the car has field coils in the alternator, the flat battery may not be enough to energize the alternator so it can generate electricity. Which is why you sometimes can;t bump some cars.
If for example the fuel pump is on the verge of ceased, 12V before cranking may not turn it to prime the rail, but 13V from bumping might.
Soldato
Also most cars put unburnt fuel into the exhaust all the time, how is that bad for the cat? My car as standard floods fuel at 10:1 afr, and that doesn't damage the cat?