Technical Bump Starting........2015 Ducato TD 2.3.

[corcai]

Is the Puma engine the Ford 2.2?
Please can you explain why bump starting is different to starter motor starting?

He did .. the bump

" the sudden release of the clutch can cause the timeing chain to jump the sprockets"

 

[Mohojo]

We seem to be going round in circles boys.......?
The starter motor turns the engine over to start it. A bump start turns the engine over to start it. How does the engine know what is turning it over? .....is it bothered as long as something is doing it?

 

[corcai]

We seem to be going round in circles boys.......?
The starter motor turns the engine over to start it. A bump start turns the engine over to start it. How does the engine know what is turning it over? .....is it bothered as long as something is doing it?

Starter motor has a stall torque of about 50-60NM. 2-3.5 ton van travelling x miles per hour turning 2m circumference tyres multiplied by gear ratio is at least one order of magnitude more.

 

[Mohojo]

I can see a problem if the vehicle is propelled up to say 50mph and the clutch is dropped in second gear.......you would expect a degree of mechanical protest and possible damage. However a typical bump start is carried out at low speeds of say < 10mph (because someone is pushing). If the clutch is engaged briefly at this speed, just enough to rotate the engine, and isdepressed immediately after it starts I would expect the chace of damage to be very low, bordering on the non existant.

 

[corcai]

I can see a problem if the vehicle is propelled up to say 50mph and the clutch is dropped in second gear.......you would expect a degree of mechanical protest and possible damage. However a typical bump start is carried out at low speeds of say < 10mph (because someone is pushing). If the clutch is engaged briefly at this speed, just enough to rotate the engine, and isdepressed immediately after it starts I would expect the chace of damage to be very low, bordering on the non existant.

It doesnt matter how long the clutch is engaged its the sudden application of masses of torque. Just google duratorq bumpstart. I'm not sure about the hydraulic tensioner theory though in the newer puma engine as the tensioner has a ratchet/pawl to prevent it going back, maybe the sudden pressure can push it back but more likely its the chain guides are worn and the tensioner is at the end of its limit.

 

[Mohojo]

Is the Puma the 2.2 chaindrive Ford? Do these dangers exist for the 2.3 belt drive Fiat?