78' 300D won't start - Mercedes-Benz Forum

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post #1 of 5 (permalink) Old 09-29-2009, 03:56 PM Thread Starter
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78' 300D won't start

Apologies for my diesel ignorance! This is my first one...here's where I am at.

Glow plug light on dash went out---wouldn't start.
I replaced the plugs and the strip fuse in the relay (it was frayed).
Light now comes on and the plugs and connecting wires are hot.
Still turns over but won't start.
I traced the fuel lines and replaced a cracked hose, replaced both fuel filters and cleared the line of air.
Same deal: it turns over but won't start.
Battery has a fresh charge.

I am stumped. What do I do next? The local M-mechanic suggested a cliff!

many thanks
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post #2 of 5 (permalink) Old 09-30-2009, 12:43 AM
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not sure what the history is--did it start before the glow circuit issue?

anyway, i would suspect that either you have not actually completely purged the fuel system of air OR you need to look at injection timing.

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post #3 of 5 (permalink) Old 09-30-2009, 07:39 AM Thread Starter
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yes, it was running great before glow plugs went out---Just repurged the fuel lines and turned it over until the battery ran out of juice. Not even a cough like it wanted to start.
Back to the manual to learn about injectors and charge up the battery.
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post #4 of 5 (permalink) Old 10-01-2009, 10:31 AM
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If your glow plugs are lighting and you have good Compression? and fuel with no air,,, have you checked replaced BOTH Fuel Filters? You will need a very STRONG Battery,, if you have all this , just try cranking on it while all the while holding the accelerator pedal all the way to the floor,, and see if it does not slowly sputter to life.... as you crank on it do not let off the key until it is runnning on all five....good luck..

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And Remember to always KISS, Keep It Simple Stupid!

Last edited by christopher1959; 10-01-2009 at 10:34 AM.
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post #5 of 5 (permalink) Old 10-07-2009, 06:50 AM Thread Starter
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Okay, Back at it today. I swapped out the battery and charged her up. Then went back and noticed when the plugs were heating that #2 was just warm and #1 was stone cold while the other three filaments were glowing red hot. I thought maybe I screwed up the install or the core was dirty so I took out the plugs and wire brushed inside the cylinders---made sure everything was CLEAN. Now same deal, #1 and 2 are not hot. Is it possible that the filament/wire between the plugs can go bad? Why would I not be getting heat to those two plugs when everything is new.
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