In Sept. 1999 and yesterday (7-18-02) on my 300SD turbo diesel, 1983, I had to replace glow plugs. The previous owner who had it for about 8 years never had to replace them (and the owner of its first 10 years or so, I don’t about its’ glow plug replacement history). The mechanic yesterday is trusted and has been providing reliable help on our vehicles for 10 years. They used Bosch plugs which he said M-Benz uses. The only habit I have that might be different than other users as a possible piece of diagnostic info., is that when there are wintry or cooler temps I quite regularly use the motor plug-in to pre-warm it, only about 15-30 minutes or so, (which I thought would be good for the engine but not the glow plugs?). Can you please advise me on this? It is very frustrating to have these kinds of repeated repairs when M-Benz is supposed to have a reputation of longevity and reliability.

Thanks, Peter Feneht

P.S. Another question is, do those magnets you can put on the fuel line actually increase power & mileage?

How did you come to the conclusion that you need new glow plugs?

Sixto
91 300SE
87 300SDL

Were the bad glow plugs (GP) open (infinite resistance) or shorted which would probably cause the fuse to open (blow out)?

Most of the time the GP go open like a burned out light bulb but I did have one that was shorted but that was the older loop style.

Could it have a problem with the connector on the relay or in the cable from the relay to the GP?

P E H

If you mean using the enging heater (motor plug in), there is no possible way this could damage the glow plugs.

One thing you might check is to determine the GP relay is turning off the GP as soon as the enging starts. If they are left on for an extended period of time, their life could be shortened. The relay should also turn off the GP after about 35 seconds if the engine is not started.

P E H

Peter,

I have had to replace mine 2 times in eight months and changed them all because I don't know how to test them. The first set I put in were autolites. And yes glowplugs are like lite bulbs and it could be somethig else causing the problem. Remember that your car is almost 20 years old and that ALL 20 year old cars need a repair or four. Stick with it, they are great cars. Welcome to the forum, there is a wealth info here and remember to use the search feature.


thebern

__________________
1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs

So you don't know if any of the GP were really bad. What made you think any were bad?

Here is a test that requires no electrical equipment: Remove the GP from the engine. Grip the GP with a locking plier (Visegrip) in the hex area. Touch the end of the GP where the wire attaches to one terminal of the battery and the opposite end of the locking plier to the other battery terminal. The tip of the GP should glow red hot in less than 10 seconds.

If the GP glows red hot, it is good. If not it is no good. Its that simple. I hope you didn't throw away your old GP. By the above test you can find out if they are still good.

NOTE: This test only applies to the newer pin type, parallel, 12 volt plugs and not to the older loop type, series, 1.2 volt plugs.