I have a 78 300SD and the glow plugs take forever. Especially since sometimes in the winter I have to glow them twice...

Is there are replacement glow plug for this vehicle that is faster than the original? If so, where can I get them?

The time that the glow plug light stays on is not the same time the glow plugs stay on I.E. the light goes off but the glow plugs are still on each time the key is turned to the run position and they stay on for about 35 seconds. The light is on a timer that senses the engine temperature and the colder the engine, the longer the light stays on.
The light on my '80 SD doesn't stay on long enough to make the enging start easily so I wait about 10 seconds after the light goes out and it starts instantly. The light on my '79 SD stays on longer than the '80 and it starts easily when the light goes out.
Second glowing shouldn't be necessary if you wait 30 seconds before cranking the engine on cold starts.
P E H

I agree with what you guys are saying. My glow plugs are original and will shortly need to be replaced. Part of my problem starting is the altitude that the car is at (7000 ft). The lack of oxygen doesn't help - when we are at sea level it is fine.

My concern was that if I had to replace the glow plugs is it worth modifying the system for a faster glow.

This car seems horrendously slow - but that is compared to my '97 E300D and my wife's VW TDI. I now it's different technology but when I had a 123 300D-T that car did glow faster.

Since the glow plugs are on for only a short time, the parallel combination shouldn't hurt anything. If a glow plug is shorted, it should still blow out both links. If you can find which glow plug is shorted, just disconnect the wire from that plug temporarily. IMHO
P E H

Speaking of high altitude: I was in Incline Village at Lake Tahoe (8000 feet). It was about 30 degrees F outside in the morning. When I attempted to start the '80 SD engine in my normal manner of stepping on the accelerator while cranking the engine, it wouldn't start. After trying to start it a couple of times in this manner without success, for some unknown reason I tried again without stepping on the accelerator and the engine immediately started.
Any explanations?
P E H

I know the manual states that you must depress the pedal if it's less than 0 C outside but I never touch the pedal and it always starts. Even during canadian winters. If i depress the pedal than she spins really fast after startup and that's not a good thing.

81 300SD

I replaced my series glow plugs with the parallel style a couple of winters ago. I got them from George_Murphy@compuserve.com. They cost the same as the serial ones. They fit right in to the existing large threads. No difficult rewiring necessary. I think Mercedes switched to parallels part way through the '79 model year. That's why the newer ones start better. With the parallel plugs in summer (cold engine) you have to glow for 4 sec. In winter, for 10 sec. In my case, they work fine down to -20C or -5F without preheating the engine. I can't think of any reason not to switch unless you want to keep your car original.

Gary

I went out to start my car a few mornings ago and it(1980 300cd)wouldn't start. It cranks but wont fire. I checed the fuse in the black box on the inner fender(glow plug relay or startin unit i think it's called)it was fine. That fuse went out on me one time and I had the same result.(cranks but won't fire)I'm trying to get the same glow plugs that were in it.(pin type large thead) but I'll have to wait until the dealer opens on Monday. If the new glow plugs don't fix it, Do you have any idea of another cause? I would appreciate any help. p.s. My car was a 1980 model built in late '79

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Originally posted by 123 300D driver:
I replaced my series glow plugs with the parallel style a couple of winters ago. I got them from George_Murphy@compuserve.com. They cost the same as the serial ones. They fit right in to the existing large threads. No difficult rewiring necessary. I think Mercedes switched to parallels part way through the '79 model year. That's why the newer ones start better. With the parallel plugs in summer (cold engine) you have to glow for 4 sec. In winter, for 10 sec. In my case, they work fine down to -20C or -5F without preheating the engine. I can't think of any reason not to switch unless you want to keep your car original.

Gary

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