I have been having trouble this winter, since a cold snap six weeks ago, starting my benz. Now the glow light will not come on at all. And if it does it doesn't seem to heat the engine. My only recourse is to spray starting fluid in the intake (which I hate).
I have just performed a resistance check on the preglow system and found that plugs 2 and 4 show infinite resistance. If I replce these two plugs does anyone think this will solve my problem?

Paul Roberts

To answer your question, YES.

They certainly must be replaced, but this may not completely solve your problem.

It would be most helpful to know the year and model of your Benz.

Have a great day,

That would be 1983 240 D

Okay, now I know that your car has pin type glow plugs.

In the past I have had best results by replacing ALL the glow plugs at the same time. Even when one passes the continuity test it can be ineffective for several reasons. That, however was when glow plugs were less than $4 each.

If replacing the two bad ones, does not achieve good results, check to ensure that each plug has voltage. If one of the plugs that you replaced was not number one, then replace number one for sure. On the pin type systems, number one is basically used as a sensor by measuring current through only that plug.

If you are not getting voltage, check the bar fuse inside the glow plug relay.

Hope this helps,

I replaced mine about 2 weeks ago in my 83 240d.
All four new bosch plugs were around 43 dollars, and found them locally after calling around .
I was stuck at work and wanted to replace them there at night in the cold windy night , but I had the car flatbeded home and did it the next day.
It is easy , I found that a closed end rathet wrench worked best for me, as I left the fuel lines in place.
I figure for the cost it is worth it to replace these as a set.
Good luck.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.

Hey folks just wanted to let you all know that I replaced my glow plugs last night and the problem is solved. Thanks as usual for the fast response and good advice.

Printprocc,

How many did you replace?

P E H

I was all set to replace just the two that tested bad, but I figured waht the heck and replaced all four.

Great to hear about the four new plugs .
I bet it fires up very fast now, I know mine do and I should have not let it go so long , thats why I got stuck but hey its done and will see how long they last .
First time for me changing Glow plugs.

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A couple of Ford pickups F 150,250, 350 missed.
1983 240 D 256,000 miles ,auto, ac.

First time for me as well. But they were as easy if not easier than spark plugs. More and more as I do work on this vehicle, I find that I love it just that much more. As well as the technical help and rapid response times of the kind folks here.

Thanks a bunch, Paul Roberts

Printprocc,

Keep the old ones and put them in the glove compartment. You never know when you will need a spare.

P E H

Can glow plugs be tested by using a tester light at the plug where the glow plug relay is located? Checking plug by plug?

I saw my indy do it today and he determined that 3 of 5 plugs were bad on an SD.

Thanks

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Enough about me, how are you doing?

Plantman,

Yes. The ~2 mho conductance of the GP will light the test lamp if the GP is good. If the GP is open, the light should not light.

BUT, I think the GP connector should be pulled out of the GP relay to eliminate parallel circuits thru the other GP.

I have an open GP to replace in my 300SD soon. I will experiment to see if there is any difference in readings with and without the GP connector connected to the GP relay. I will let you know.

P E H

PEH said "keep the old one's."
Please test all four and throw the bad one's away.
No rason to hall around bad parts, but PEH having you save the others could get you rear out of a jam. And it doesn't cost you a thing.
Charlie