Hi all, this is my first post here but hopefully someone can help me out with this. As ofFriday, I've been unable to start my 85 300D Turbo. Wednesday morning, I had trouble starting it before going to class; it was about 20 degrees Foutside, but I usually have little trouble getting the engine to fire at that temp. That day it did fire for me the first time I turned the key (waited for glow plugs, of course), but I had been giving it a little fuel to help the engine warm and I let off the throttle too soon, and the car died as it would normally do in such a situation. But usually it would fire almost immediatelywhen cranked again, and that day it took me about twenty minutes to get it to finally turn over. Later that day, at a similar temp(maybe after the battery had recharged from driving) it started fine.

I did not try to start the car again until Friday afternoon; it was about 40F then, and the starter would turn over but the engine would not fire. I thought it might be the battery, so tried to jump it off another car with jumper cords. Even after leaving the batt charging from the other car for a half hour or so, it still would not start. I bought jumper cables, heavy duty, hoping they would work, but the car still would not start after trying to charge the batt.I replaced the fuel filter, thinking that might be the problem, but the car still would not start, so I took the battery to AutoZone. They tested it and told me that it had a dead cell, so I bought a new one, brought it home, installed it. Thought all would be good but when I tried to start the car it went the same as before: nothing. The starter will turn overnormallybut the engine won't fire.

What could be the problem or where should I look next? Could the glow plugs be bad? I recently replaced the glow plug relay but I don't think the plugs have been replaced since I've owned the car (about two years). Thanks!

 

The car will start fine with 2 plugs dead, little bit harder with 3 dead, but you will struggle you but off to get it started with 4 dead, and that is probably what the problem is. Take the plugs out, connect a wire to your battery and hold it on the thread at the cold end of the plug, then lay the thread that goes into the block, on the negative of the battery, you will see it get hot, then it is OK, if not, toss it in the bin.

Once you have replaced all five, you will be amazed at how it starts... replace them anyway, takes about 30 minutes, all the tools you need is an 8mm spanner, to get the wire off, and a 12mm ring to get the plug out. just put the new ones in, they are probably about $10 each there in the US.

 

After further research I don't think the problem is with the glow plugs. The glow plug light comes on and stays on the normal amount of time, then goes off. I unplugged the glow plug relay and tried to start the car with ether but it still will not fire. I'm going to replace the primary fuel filter today to see if that helps, but in the meantime, any other ideas on what could behappening?

 

When that light turns on then goes off, it onlymeans that power is getting to the glow plugs correctly. It still leaves out the possibility that the heating element in some of the glow plugs have gone bad.

I would suspect bad glow plugs because they usually are the problem. They're fairly easy to replace and with a multimeter you can testthe plug connected ontothe relay going toeachindividual plugfor correct installation so you don't blow the relay fuse. My 190D had similar problems and after changing the glow plugs it starts perfectly in 18 degree morning weather.

 

But if it is the glow plugs, why wouldn't the car start when I disconnected them and tried to start it with starting fluid?

 

Do yourself a favour, take them out, take a length of wire, connect it to the + of the battery and hold the other end of the wire on the threaded part where the "wire" goes on, then hold the Threaded part of the glow plug, that turns into the motor on the - of the battery, if it gets hot, get's hot means RED HOT 850 degrees C, then it is working fine, else it is kaput. Promise you light on etc etc, and will not start if there is not at least 2 GPs working....

 

even easier... if you have a multi meter (which every tech should) check resistance on each plug. if you have a meter that shows continuity, connect negative to ground, unhook wire going to each plug, and touch the glow plug. If continuity, it may beep. if good it will show a resistance. If it shows infinity then the plug is dead. hope that helps.