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Old 01-02-2002, 02:46 PM
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Join Date: Apr 2000
Posts: 75
Angry Diesel cold starting weirdness.. anyone??

Here's some additional diesel starting weirdness..

1978 300D W123 154,000 miles....
No block heater(well, the new one is in the trunk)
Temperatures have been DAMN cold here (+10F in the mornings)

When I first glow to start.. car has been coughing and hacking like fuel is restricted or glow plugs are not working correctly. However, turn car off, re-glow immediately, car starts much more easily and gets to smooth idle right away. Any ideas? On the second glow, the glow light has been staying on for a few seconds as well after the car starts...... bizarre.

Also, for those who have slow cranking on cold mornings... A new battery and synthetic oil seems to make a HUGE difference. The car has been turning over almost as quickly as in warm weather. Nice.

Cheers and thanks to all.

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Old 01-02-2002, 07:20 PM
Kyle Blackmore's Avatar
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Join Date: Sep 2001
Location: almost beyond Hope...B.C.
Posts: 897
Smile let it glow

Try letting the glow plugs cycle twice.wait to hear the relay click off(takes about 45 secs),turn the key all the way off,then on to glow till you hear the relay go off again.Makes a big difference in cold running.
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Old 01-02-2002, 09:57 PM
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i live in sunny california, so i dont know much about cold weather. however, on cold mornings(relatively) after the glow plug light goes off, let it sit for another 10 seconds then crank the engine, i think the GP's stay energized for a few seconds after the light goes off.
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Old 01-03-2002, 06:30 AM
Neil Eglintine
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Why is this weird?

Why do you find this strange? The purpose of the glow plugs is to provide a hot spot in the combustion chamber. This helps to vapourise the fuel because liquid fuel will not ignite, only in the gaseous state doe scompression cause ignition.

When the engine is really cold, the heating of the glow plugs is not sufficient to increase the temperature sufficiently to ensure vapourisation. Cycling the process puts more heat into the chambers.

The other problem you get in really cold temperatures is waxing of the fuel. The lower fractions in the fuel turn solid ie into wax. This blocks up the pipes, filters etc. Modern fuels have anti waxing agents, but it still can happen.
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Old 01-03-2002, 06:45 AM
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TurboTurbine is right on. Just wait another few seconds AFTER the GP light goes off, it will continue to glow for 30 seconds or so afterwards.

Good luck,
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Old 01-04-2002, 11:17 PM
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Join Date: Jun 1999
Location: Los Angeles, Calif, USA
Posts: 521
Re: Diesel cold starting weirdness.. anyone??

Originally posted by 79300D
Here's some additional diesel starting weirdness..

....... the glow light has been staying on for a few seconds as well after the car starts...... bizarre.

Isn't that telling you a failing glow plug(s)? The service manual (for 1978 to 1980 system) says "If one or several pencil element glow plugs or lines are interrupted, the preglow indicator lamp will flash for aprox. 30 seconds after starting".


Last edited by be459; 01-04-2002 at 11:24 PM.
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