cold start 406 diesel

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greggig@greggig.co.uk - 03 Dec 2006 11:34 GMT

Just had my pog 406 2.1 looked at for a smoking problem It has on low
revs, been advised that it is the cold start mechanism is sticking on?
(What ever this is) So my question is! What is this cold start thing
is there such a thing on a diesel and if so can the average Joey in the
street fix it or is the garage after work!!

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Bob Minchin - 03 Dec 2006 13:52 GMT

> Just had my pog 406 2.1 looked at for a smoking problem It has on low
> revs, been advised that it is the cold start mechanism is sticking on?
> (What ever this is) So my question is! What is this cold start thing
> is there such a thing on a diesel and if so can the average Joey in the
> street fix it or is the garage after work!!

I expect they mean the glow plugs are staying powered up. This may show up
as the light being on all the time or if the relay has stuck on, there might
not be an indication.
Either pull the relay out and see if the smoke stops or better still measure
the voltage across the glow plugs and see if they are telling the truth or
not.

You will have to find out the way to do this yourself as I have neither a
406 or any other diesel pug but it should be straight forward especially if
you read the workshop manual covering the diesel engine.

Bob

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greggig@greggig.co.uk - 03 Dec 2006 14:03 GMT

Hi Thanks for info
sadley the glow plugs have been replaceced so cant be that?

> > Just had my pog 406 2.1 looked at for a smoking problem It has on low
> > revs, been advised that it is the cold start mechanism is sticking on?
[quoted text clipped - 14 lines]
>
> Bob

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Peter Chant - 03 Dec 2006 17:02 GMT

> Hi Thanks for info
> sadley the glow plugs have been replaceced so cant be that?

If the glow plugs are staying on when they should not it is no the fault of
the plugs but something like the relay.

Pete

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MICHAEL ROCHE - 03 Dec 2006 16:55 GMT

The cold start device on a diesel is the equivalent of a choke on a petrol
engine.
On my 98 406 1.9TD it is a cable between the fuel pump and a vacuum
diaphragm at the rear of the engine. The vacuum diaphragm is operated from
the vacuum line that is used for the servo . This is switched on via a
switch operated by the ECU. Common fault is the vacuum line splitting where
it joins the diaphragm this will also give poor brakes.
Mike

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Phil Cook - 04 Dec 2006 10:22 GMT

>> Just had my pog 406 2.1 looked at for a smoking problem It has on low
>> revs, been advised that it is the cold start mechanism is sticking on?
[quoted text clipped - 4 lines]
>The cold start device on a diesel is the equivalent of a choke on a petrol
>engine.

What? To start a diesel you need some heat in the cylinders to ignite
the fuel when it is injected. You can do this by cranking on the
starter alone, but usually it is done with glow plugs that are heated
for a short time before and after turning the engine over by means of
a prestart sequence controlled by a relay. Once a diesel engine is
started it will run until fuel is shut off.

>On my 98 406 1.9TD it is a cable between the fuel pump and a vacuum
>diaphragm at the rear of the engine. The vacuum diaphragm is operated from
>the vacuum line that is used for the servo . This is switched on via a
>switch operated by the ECU. Common fault is the vacuum line splitting where
>it joins the diaphragm this will also give poor brakes.

What most modern diesl cars have is a fast-idle setup so that they
reach optimum temperature faster. Once the engine is hot enough to run
the heater it drops back down to normal idling speed.

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