An unusual problem (to me) with my 1976 300D has developed over the past few months. Engine 617.910. Body 115.114. I have owned this car since 1984 and it has 133,000 miles.When I turn the ignition key to #2 position the pre-glow indicator lamp comes on and stays on too long. The glow plugs do not heat and when I check plugs (input and Output) with volt meter the meter indicates they are all getting current. Then I replace each plug indicidually until the engine starts. The normal assumption is a bad plug. The next day I can put the plug back in the engine and the engine starts. I am bewildered.

The 115 300D has a relay up under the cowl and a temperature sensor/timer in the head just in front of #1 glowplug. Sounds like the sensor is bad and isn't grounding like is is supposed to -- it has a thermal swtich that is supposed to regulate how long the glowplugs operate according to temperature.

My brother's is shorted -- the plugs run until you crank the engine. Your's appears to be staying open. Check for voltage on the "back" side of the sensor and see if it is hot when the plugs are supposed to be on. The dash light is operated off the relay and the sensor -- when the sensor goes open, the light goes off.

You may also have a bad relay -- and I cannot tell you exactly how to check it. It's expensive, so I would not just change it out. Check for corrosion around it and a bad ground, too!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I have a problem with the glowplug system on my '95 300D too in as much as when starting, the glowplug light stays on for an age though if I start the engine after say 5 secs from cold, it fires perfectly. The light then goes out and doesn't return. Same when the engine is hot - lamp stays on but engine starts perfectly after a few seconds pre-heat.
I checked the glowplugs to earth and all have 1 ohm reading which I think is correct so, I checked the resistance on the water temperature sensor at the relay end of the cable.
At 68C, it was 325 ohms and at 20C, it was about 200.

I guess this indicates that the sensor is dodgy and needs replacement however, as this is reading lower than usual when the engine is cold, wouldn't that fool the relay into turning the glowplugs off more quickly and thus the light would go out too soon? How would this affect the afterglow??

It's my first diesel and loving the 'relaxed' and 'soothing' performance but this has me a little baffled and I don't want to take the inlet manifold to bits, replace the sensor only to find the same problem....!!

Any ideas guys???

Thanks


Paul

Paul welcomg to the forum!

This thread is 11 years old and really has nothing to do with your problems. You have a very different car than a 115 chassis. Might get more responces if you start your own thread.

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only thing in common with this ancient post is the word glow plug...

I'm going to move this section of the thread to a new thread and see what responses you get that way!

welcome to the forum!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!