my 84 300d starts only after 10 seconds or so. the glow plug light only comes on for a second or so. the glow plugs check good to ground. im assuming the voltage is not on long enough. anybody have any ideas?? relay? location?

Not an expert but have read about this
 

Greetings,

Seeing as I am not only new to the forum but also to diesels, but have done some reading on this. Where is it you live first off? The glow plug timing relay takes information from the coolant temp sensor of the engine that determines how long the glow cycle should last. Let's say the engine is warm to hot, it simply glows the light for a second or so telling you that the engine has suffient heat to cause combustion explosions to take place. If the engine is cold as well as outside ambient temps. and you are getting the same results, a glow light for only a second or so would indicate to me that the coolant temp sensor is relaying the wrong info back to the glow timer. Opening myself up to be beaten down by the techs, hell live dangerously. I would also check cyl. 1 glow plug to ensure it's not shorting out. It could be telling the timer that all glow plugs are hot and ready to start when in fact the others aren't even hot yet.

Just my thoughts on how the system works.

Charles

The duration varies...
 

and can be up to a minute or even longer. The glowplug light will go out before the relay shuts off. You should be able to hear a little tinny "click" when it does. (leave the door or window open, maybe even the hood too, when listening for it.
-Larry

The problem can either be the plugs or the relay. You have to check them out. If your plugs are old, I would just change them and clean the holes with a glow plug reamer before moving on. For older diesel, it is true that the system measures the coolant temperature. For the 84's, the temp sensor is inside the relay box, not the engine.

David

300d glow plugs
 

thanks for all the inputs. the glow plugs all check good to ground. where is the relay? i assume its one of the two on the left inner fender. im in texas and the car starts pretty good anyway but you can tell it has no glow plug assist.

Checking the resistance of the plugs is not a reliable way to verify the plugs. Current flow changes as time passes. Search this forum to find out the way to check the plugs. The relay box is located on the left side fender, about 1.5x3x4 inches with a cover, black with wires going to the plugs.

David

glow plug duration
 

itwas 30 degrees this morning so i thought id do a little test i waited about 10 seconds past when the light went out. the car started right up. problem solved, thanks for all the advice.