Glowplug Change Rave!
 

For the past month in Northern California my otherwise reliable 82 300 SD has been either a pain to start or would not start. I changed the glowplugs and tested as I removed each gp . . . two were burned out and would not glow. This morning was 28 degrees, a good test . . . Car fired almost immediately! Back to normal and to think just two plugs created this condition! I did the job just before Thanksgiving dinner, now I am very thankful! Love the simplicity of my diesel!

That sounds about right. Mine will start and run rough with one bad plug, but it's a PITA to start with two bad plugs. With two bad plugs the indicator light should fail to come on.

Might as well step up and spend the other 30 bucks now... Birds of a feather type thing...

We are all thankful for this Forum, so...
 

Anticipating you will be with us for some time and back to ask questions and contribute as well, let me ask you to complete the "Signature" part of your profile so that your MBz's basic statistics are visible in ALL of your POSTS... something similar to what you see below on this POST!
Regards,

Having just done this myself, I strongly suggest always replacing all the glow plugs at the same time.

I had 2, 3, and 4 out. I had a used, but still functional, one left over from the last change, so I switched #2 with the used one and put new ones in 3 and 4.

3 days later, 1,2, and 5 were toast.
So I replaced those and now have all 5 new ones doing the job nicely.
I figured I'd save about $30. Nope.

Yes, I had replaced all five at time of removal and testing, it would be foolish and a waste of time to just replace the burned out gp's

Another believer.....
 

Replaced all of my glow plugs about a month ago......posted a thread here, commenting on the marked improvement in start/idle when engine is cold....

I, also, think it to be a waste of time to test and replace them individually!!

SB

Yes its best to do them as a set. When one or two have failed the others might not be far behind. Better use of your time to do the job one time.

Let me propose a sidebar topy to this GP discussion...
 

I propose that the life expectancy of a GP is directly related to how “long” power is applied to the plug… “long” in the sense of each cycle that the automated relay controls based upon temperature of the engine and of course “long” in the sense of total “powered on” time the plug accumulates over long use.

Thus IF/WHEN I am faced with a major expense with my GP system [e.g. a relay replacement], I will likely opt to “retro-grade” my GP system with a manual relay that allows me to control when and how long I use my GP(s). Such a manual relay “retro-grade” would also cost far less than the “Up-Grade” kit from Bosch.

P.S. - I just drove a 1.5L turbo diesel Renault "Megrane" for 3-weeks in Italy and not only do these new technology diesels have a very short GP cycle, but it is totally controlled by the engine control system and their electronic ignition key card. God bless these simple vintage MBz(s)!
Regards,

I bought an '85 300 TD back in August and she ran beautifully until the temperature started dropping. After the first toe dip into the 20's cranking for more than 30 seconds wasn't out of the ordinary. And even starting in the 40's wasn't easy. Tuesday it took a minute and a half to get her started when it was 25F.

So, I figured I'd replace the glow plugs and luckliy my local Napa had 5 Bosch plugs left. I hurried home from work (it starts getting dark around 4:30) and started to work. Except that I couldn't get the 1st plug loose and in trying broke the very old and brittle fuel return line. It was all I could do to clip off the end and get it back on before there wasn't enough light.

Needless to say, I wasn't surprised when I couldn't get her started the next morning with a temp of only 7F -- regardless of how much I cranked. I had her towed to a trusted repair shop. It turns out 4 out 5 plugs were dead and even the block heater died too. My repair guy said he can count on one hand how many block heaters have died. But now with new fuel return lines (so soft and supple!) and new plugs my diesel starts without ANY hesitation -- even this morning with a temp of only 5F.

Ok, I also ran the block heater for a couple of hours, but she purrs like a kitten and I no longer get the clouds of black smoke before she warms up. And this is with running 15W40.

I told my wife: "no offense, but hearing that diesel start in the cold is one of the sexiest things I have ever heard".

p.s. my mechanic mentioned that the plugs were very difficult to get out so I'm not completely emasculated!

You are kiding me...
 

... surely you have not been married very long and probably won't be much longer! When I purchased our 240D for what I now consider a steal, she told me it looked "like an old person's car!" Now she likes the compliments and horn "toots" she gets from people!
Regards,

AFAIK, your older vehicles function in an identical manner to the SD and SDL. When you turn the key to the start position, the glow plugs shut down. You control the length of time the glow plugs operate...........it's strictly dependent on the time with the keyswitch in the #2 position prior to the start.

The only reason to attempt a manual relay is for those with afterglow. Now, the afterglow time is controlled by the new relay and not by the driver.

Thanks Brian...
 

... despite testing and seeing this was the case, I had forgotten the reality that afterglow ends when you hit the starter with the ignition key. Unfortunately Bosch does not make it's relay/plug kit for either of our 1980 models... so when the relay goes, I'm looking at an expensive fix... and thus my serious consideration of a manual relay solution.

You stalking me again?!
Regards,

The 240D I just purchased had all 4 bad glowplugs. I got it to start once, and only once until I changed out the plugs. It was in the 70's at that time......

"Afterglow" is the condition where the plugs remain energized when after the vehicle starts. The later diesels ('90 and above??) have this feature. All of our older vehicles do not have "afterglow" and the plugs shutdown the moment you hit the starter.

Yes, if the relay goes, you can certainly substitute a manual relay. In fact, if you run heavy wires to the cabin, you can dispense with a relay altogether and just use a pushbutton for the plugs.

..........hardly.........