Jump starting a VW van

forgotmyname

Quality cables capable of passing 50 amps which was more than enough to start your Austin Seven, Not the 500+
amps required from a modern high compression engine?

neilmcl

ElephantBoy57 said:

I have tried and failed. I left my car running probably over 30 minutes, it got power to the ignition, but not enough to turn over the engine.

It ended up just nothing, which is what happened last time, months ago. I think the computer must have sensed an issue, not a clue really. Something came up on the dashboard.

Looks like you'll either need to try and charge the battery or get a new one. Plenty of places online where you can pick up batteries fairly cheaply or try a local motor factor.

ElephantBoy57

I will get the works garage out. I didn't want to bother them, as we have loads of vans not moving with COV19 closing down places. They have loads of vans not starting, after being laid up for 1/2/3/4 weeks.

AdrianC

forgotmyname said:

Quality cables capable of passing 50 amps which was more than enough to start your Austin Seven, Not the 500+
amps required from a modern high compression engine?

I very much doubt anything this side of a truck pulls more than about 200A - and any jumpleads that can't cope with that are broken.

Mutton_Geoff

If the jump leads are good and your car battery in reasonable health, the van should turn over. You’re not disconnecting the leads before you try are you? Even if the van battery was completely dead, it should turn and start with a good connection to another decent battery. 

ElephantBoy57

Mutton_Geoff said:

If the jump leads are good and your car battery in reasonable health, the van shoukd turn over. You’re not disconnecting the leads before you try are you? Even if the van battery was completely dead, it should turn and start with a good connection to another decent battery. 

I am assuming that the problem was not connecting the jump leads directly to the battery. The leads look intact and did give a connection to power the battery and the ignition lights came on.

I do have a multimeter, but I don't know if it would test the jumps leads, I am not really very good with a multimeter.

AdrianC

If connecting the -ve to a good earth makes a difference, then you've probably got a fairly knackered earth lead between engine and body/battery. Far more likely to be the issue is the leads themselves not having a good bite on whatever you've clipped them to.

Mutton_Geoff

forgotmyname said:

Quality cables capable of passing 50 amps which was more than enough to start your Austin Seven, Not the 500+
amps required from a modern high compression engine?

Petrol engines have a compression ratio of 10 to 1 and diesel engines 20 to 1. Modern petrol engines have a lower compression ratio than engines of old due to lower octane fuel today. Old cars also had more mechanical stuff hanging off the engine, fuel pumps, distributors etc compared to today so the torque required to start them much higher.

AdrianC

Mutton_Geoff said:

forgotmyname said:

Quality cables capable of passing 50 amps which was more than enough to start your Austin Seven, Not the 500+
amps required from a modern high compression engine?

Petrol engines have a compression ratio of 10 to 1 and diesel engines 20 to 1. Modern petrol engines have a lower compression ratio than engines of old due to lower octane fuel today. Old cars also had more mechanical stuff hanging off the engine, fuel pumps, distributors etc compared to today so the torque required to start them much higher.

...and turbocharged engines have lower compressions than naturally aspirated. NA diesels could be near to 30:1. Add in the effects of thinner oil, too - 0w and 5w oils are MUCH easier to pump cold than 20w...

ElephantBoy57

The garage started it this morning. He plugged leads from the mobile jump starter, tried to start it and it only clicked the starter. He then connected the leads to something in the back of his van and it started straight away.

I do have a cigarette socket multimeter to monitor the voltage, but not sure it will be of any use. From the cigarette socket, the voltage reading seems lower, around 11.5v, 13.9v when engine running, started ok.