A couple plugs down will make the whole thing not work.
I'd be concerned if its above freezing and the car won't start.
I drove my 240D for about 2 weeks one fall with no glow plugs, as long as it was
above freezing it would still start, it didn't like it but it'd still go.
I was amazed when I replaced the starter and battery how much more quickly the
engine cranked over...
-Curt
Date: Wed, 15 Nov 2006 10:01:01 -0500
From: "ned kleinhenz" <[EMAIL PROTECTED]>
Subject: [MBZ] 85 300D No Glow?
To: "Mercedes List" <Mercedes@okiebenz.com>
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<[EMAIL PROTECTED]>
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Situation:
Son's '85 300D glow plug light does not come on.
Outside temp is below 40F and car will not start.
The 80A fuse in the GP control box is OK.
I suspect it needs new glow plugs. But please help confirm my
diagnosis is
probably correct.
Two questions:
If my memory serves me correctly -
If the GP light does not come on, the following are the potential
causes by
priority:
1. Blown fuse.
2. At least one bad glow plug
3. GP control system is faulty
4. GP light is burned out.
Is this correct?
I expect this car probably has the newer parallel glow plug
configuration,
so I'm not sure how the controller behaves.
Other question - if the glow plug light does not come on, does that
mean the
glow plug circuit is not activating?
In other words, will one or more bad glow plugs prevent the entire glow
plug
cycle from happening?
Thanks,
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Date: Wed, 15 Nov 2006 07:29:38 -0800
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Subject: Re: [MBZ] 85 300D No Glow?
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> The 80A fuse in the GP control box is OK.
You sure? Remove it and see if it falls apart. They can
develop fatigue cracks.
> If my memory serves me correctly -
> If the GP light does not come on, the following are the potential
> causes by
> priority:
> 1. Blown fuse.
> 2. At least one bad glow plug
> 3. GP control system is faulty
> 4. GP light is burned out.
>
> Is this correct?
Perfect!
> Other question - if the glow plug light does not come on, does that
> mean the
> glow plug circuit is not activating?
> In other words, will one or more bad glow plugs prevent the entire
> glow plug
> cycle from happening?
Normally, no. The light is on a separate timer than the GP's.
A shorted GP (rare) will take out the fuse, so in that case
the answer would be yes.
Five minutes with a decent multimeter can tell you what is
wrong. You ohm out the GP's and make sure the relay is getting
power and that the fuse is OK, then you check that it's getting
the ignition and start signals (in the little plug), and that
the lamp has continuity (ditto). Then you see if the GP relay
delivers voltage to the GP's when the key is cycled.
After that round, you _will_ know what is wrong, except in a
small percentage of cases where, for example, a GP is not
entirely bad and is drawing out-of-spec current. But that
won't keep it from starting, usually. With the addition of
a high-current DC ammeter (of whatever stripe) you can even
diagnose those with surety.
-- Jim
