The "correct" way to start a diesel engine.

Discussion in 'Tech/Mech General' started by GeriatricWanderer, Sep 25, 2016.

  1. GeriatricWanderer

    GeriatricWanderer Funster

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    Now back in Sarfend for a couple of months.
    I've run numerus vehicles in my lifetime, some petrol engined and some diesel. Some straight off the production line and some middle aged.

    From somewhere in that time I've picked up the understanding that the correct way to start a diesel engine is:
    Right foot off the gas pedal.
    Left foot hard down on the clutch pedal.

    I've never really understood the technical logic of the clutch pedal process but assumed it was something to do with taking some pressure off the flywheel while the engine is turning on the starter.

    I've recently bought another car, 10 year old diesel engined, and was browsing the User Manual expecting to see some precise instructions re starting and there is but only to keep that right foot off the gas pedal - but no mention at all of the clutch pedal depression process.

    Somewhere amongst this vast membership must be someone who knows, or think they know :) , the "correct" process.

    As always, your contributions will no doubt be varied - and welcomed.

    And before you are tempted - yes, I know, some of you drive automatics :)
     
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  2. BreweryDave

    BreweryDave Funster Life Member

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    I find that turning the ignition key often works .............;)
     
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  3. mike mcglynn

    mike mcglynn Funster Life Member

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    My car is a diesel and will not start unless clutch is depressed, 2013 model
     
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  4. wizzer59

    wizzer59 Funster

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    Never heard of it, all my cars and vans have been Diesel and all started without depressing the clutch(y)
     
  5. milliethehymer

    milliethehymer Funster

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    Had one car which needed the clutch pedal depressing to start.

    But in a manual I always start the car with clutch pedal down, having driven a lot of multi user cars where last person has left it in gear...certainly wakes you up as you lurch forward :eek:
     
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  6. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    I think the clutch pedal down was more to do with preventing accidental movement if left in gear rather than being a major help to the starter motor.
    The important bit when starting a Diesel engine is to give the glow plugs (when fitted) time to heat up before engaging the starter motor.
     
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  7. jollyrodger

    jollyrodger Funster Life Member

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    TD I was tought foot off throttle ,clutch down to ease pressure on f/wheel & no drive .let it tick over for a while to let oil flow.
    When switching off .out of gear let tick over before switch off.helps prolong life of turbo,maybe not so on more modern engines
     
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  8. mikebeaches

    mikebeaches Funster

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    Manual gearbox vehicles I've always pressed the clutch before starting, to minimise the load on the battery and give the engine maximum spin. Not to mention the risk the vehicle was accidentally in gear. Habit began as a teenager, when all my old cars had dodgy batteries, especially when it came to the winter.

    Rarely drive manuals now, car and van both have auto boxes.

    In the case of diesels, it was my understanding the ignition should be turned on for a few moments before starting to allow the glow plugs to heat up.
     
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  9. mikebeaches

    mikebeaches Funster

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    Duplicate post deleted
     
  10. chatteris

    chatteris Funster

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    years ago when gearboxes used EP90 oil depressing the clutch reduced the drag of the gears turning in cold thick oil,these days the oils are much thinner so not needed now
     
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  11. philw111

    philw111 Funster

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    I'm the same. Many years ago I worked for a car rental firm and quickly got into the habit of dropping the clutch before starting.
     
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  12. Snowbird

    Snowbird Funster Life Member

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    Holding the clutch pedal down is the correct way. It relieves stress on the battery and starter motor as it is not turning anything in the gearbox. I still see people starting a turbo diesel engine and driving off immediately without allowing the oil to circulate around the turbo. Same with shutting a turbo diesel engine down when hot. Always allow it to cool down a little before shutting down. Doing anything different in my day was a dismissable offence.
     
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  13. pyro

    pyro Funster

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    Originally I was taught to depress the clutch to take the flywheel out of the chain, and make it easier to turn over. The fact that it also safeguards against leaving it parked in gear is a bonus

    On diesels, I was taught to allow 20 seconds with ignition on, before turning over, especially if the engine/weather was a bit cold. A few years back I was told by a mechanic always to keep the foot off the accelerator on a diesel as you could damage the turbo if you revved high from cold (oil pressure)
     
  14. mjltigger

    mjltigger Funster

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    My van has been parked up a few weeks so when I came to start it a few weekends ago it went like this..

    Turn ignition on, check gear, wait for coil light, turn key
    Swear
    Clutch down, turn key
    Swear
    Clutch down, turn key, hold for 30 seconds
    Swear
    Turn off ignition, walk up the road and collect car, drive to van, connect jump leads, run car engine, turn ignition on, wait for coil light, turn key
    Connect jump leads properly, ignition on, wait for coil light, clutch down, turn key
    Swear quite loudly
    Examine exposed fuel pipes.. No air bubbles
    Turn off all ancillary devices and listen for fuel pump - heard
    Lick up vehicle and drive to halfords for a can of cold start (swearing all the way)
    Return home and collect SWMBO
    Return to van with SWMBO and cold start
    Start van
     
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  15. jonandshell

    jonandshell Funster

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    In theory, modern engine management should make it foolproof.
    Turn key and go! There is nothing to discuss, it is all done for you. The only thing to watch is that your glow plug light has extinguished before operating the starter.

    In practice, with a properly cold diesel engine, it isn't so easy.
    At minus ten (or less!) with a completely cold engine I find the following works best-

    Turn key, watch glow plug light go out, turn off, heat again, turn off, heat again. Clutch down, accelerator to floor, turn key to start position. Keep turning starter, keep accelerator to floor until the engine is firing on all cylinders. Ignore all the white smoke and misfiring at all times and keep that accelator planted until the engine runs cleanly otherwise the moment you lift off, it will stop.
    Please note you do not rev the nuts off the engine from cold, all this takes place below 1200 rpm.

    Something like this-

     
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  16. Enword

    Enword Funster

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    I was taught to always depress clutch when starting, as was said before (EP 90) some of the plant was EP 120/140, in the depth's of winter it made the difference between starting or not starting, feels wrong with no clutch peddle, robotized manual gearbox.
     
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  17. Boringfrog

    Boringfrog Funster

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    What's a glow plug light grandpa? ;)
     
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  18. jonandshell

    jonandshell Funster

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    Not sure what you are saying. I am 45 years old and both my diesel vehicles, a 62 plate Nissan and a 10 plate Transit have a preheater light on the dash.:)

    20160925_122859.jpg
     
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  19. PP Bear

    PP Bear Funster Life Member

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    Starting a diesel takes a lot from a battery, for that reason they're bigger and better than those batteries fitted to most petrol engines.

    You can't take the flywheel, or clutch out of the chain, as its the flywheel that has the starter ring on it. The flywheel also houses the clutch assembly. On an automatic, it houses the impeller and vane assembly that allow for drive, once sufficient rev's are reached.

    By depressing the clutch pedal (our military Kia's only start with the clutch depressed) you reduce the drag and effort that both the battery and starter motor has to endure by not turning over any internal components of the gearbox and drive assemblies.
    You are turning over the flywheel and clutch.

    It's good practice on all engines regardless of fuel, to depress the clutch while cranking the engine.

    Turbos have a number of systems fitted to try to help prevent the bearings running without oil. Best practice is to run the engine for a very short time to get the fresh oil around all internal parts (consider something like Slick50, as it does extend the life of internal components).

    On closedown of an engine, you should let it ideal for a while to allow for cooler oil to circulate around and it assists in extending the life of the turbo.

    One of the things that make me cringe the most, is those that drive the motorway at high speeds, then pull into a service station and switch straight off. With an engine doing say, 4500rpm, a turbo will be nearer 150,000 rpm and requires to slow down, cool slightly and have fresher oil delivered to the bearings :)
     
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  20. jonandshell

    jonandshell Funster

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    Both PP and I have seen some proper diesel engine starts.
    Remember the clouds of smoke in Heavy 'A' at Bordon on a winters morning PP?:)

     
    Last edited: Sep 25, 2016
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