Roll starting an diesel

Hello all;

Has anyone here tried to start a Disco Tdi by letting it roll down a hill in

2L. I have a dual battery in mine but often wondered if a roll start is possible when needed as I am often camped in the bush in winter for lengthy times.

Frank

Reply to
Thesnowbaron
Loading thread data ...

4th low box or 2nd gear in the high box would be appropriate.
Reply to
EMB

Actually, the best gear is usually 4th high. Remember you want the motor turning at starter speed, not even idling speed - if you roll to, say,

10kph, 4th high will be quite suitable. If you use too low a gear the engine braking effect is likely to skid the wheels, and there is a real chance of breaking something if the clutch is engaged suddenly in an effort to start the motor turning.

I have not done it with a Tdi, but my 110 3.9 diesel roll starts readily at about 5kph in 4th High. You don't need to turn a diesel fast to start it unless it has bad compression - just get it over one compression, it fires and you put your foot on the clutch again.

JD

Reply to
JD

Mine will only do it in 3rd or 4th high - otherwise it just locks up all the wheels and stops! - even on steep downhills going at a fair rate.

Mine is a 2.5 n/a. I've managed to push start it once in a pub carpark (I had to buy a good 6 or 7 pints for that and it knackered all the pushers!). I have also done it rolling down a hill - though as above you have to be in high else the engine just stops it!

Reply to
Tom Woods

On or around Sat, 23 Feb 2008 14:33:55 +1100, "Thesnowbaron" enlightened us thusly:

If you use 2L and get any speed up you'll probably rip the engine off its mountings or break something else.

I'd personally reckon you want 3H for a diesel or even 4H as someone said. Let it get up a bit of speed and then feather the clutch in gently, don't jump off it.

Diesels tend to want a slightly different technique to petrols, due to the higher compression.

And remember that on modern ones, you need *some* electricity - even if it's only to operate the stop solenoid. Also, an alternator won't charge a totally flat battery. Newer ones with various EDC need more power - I reckon the reason the bus wasn't starting here was that the voltage drop was cutting the fuel off again, seeing as it did turn over albeit not very enthusiastically.

Might have a go at fitting both batteries, now I've got 2. Leaving the spare lying around the shed won't improve it.

Reply to
Austin Shackles

I've bump started my TD5 in 2nd or 3rd high a couple of times (as an experiment). Switch it on, let it roll up to a few mph, fast walking pace and release clutch not too quick not to slow (thats the hard bit...). One compression even at very low speed and a decent diesel will start. Stopping diesels is normally the problem if they have a fuel they will run. "Fuel" can be their own lubrication oil...

Reply to
Dave Liquorice

Perfectly possible, though you will want to use 2nd or 3rd High range .

Tim.

Reply to
Tim

4th high, Less damage to the main gearbox as it is in direct drive unless you've only a short run.

Martin

Reply to
Oily

Thank you all for your inputs.

Reply to
Thesnowbaron

+1 to that. The idea is to make it as easy as possible to turn the engine over, while providing enough speed to get the engine to "catch". Think of the transmission as a lever. 4H will turn the engine the slowest, and so be easiest to do. Diesels don't need a lot of revs to start - it's more a matter of getting over the compression and, as others have said, once one cylinder is over, the rest usually follow. Use of second or third gear (high range) is, however, correct for a petrol engine, as they seem to need turning over faster and for longer, and the lower compression makes this possible.
Reply to
Rich B

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.