Serial Glow Plug Questions

The ol' 240D just ain't what she used to be. My son has driving my ol' 240D. Fall hit and it doesn't want to start.

I have an "interim" motor in the car which is a serial glow plug motor. When the temp went to the thirties, it wouldn't start. When the temp hit 60 F yesterday, I managed to get it started to bring it home. After getting it home and at operating temperature, sitting for five minutes, I had to glow plug the heck out of it to start it again to move it. The old engine is really tired. As soon as I can, I'm going to do a compression check to see if I can patch the old motor, and squeeze just a little more winter life out of it.

If this were a parallel glow plug engine, I would have already replaced the glow plugs. I had a serial glow plug engine one time that I took them out and cleaned the bores pretty well and replaced the plugs. It was still difficult to start but got by.

My question is, is it necessary to replace these plugs? All they are is a heavy filament. It just seems that as long as they're not open, they should work okay, if everything else is okay. I know they're getting voltage, and the voltage is divided evenly across them. The issue is the plugs, the plug bores and the compression.

Is there anything to gain by replacing these loop type plugs?

Have a great day and thanks for the help,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

[mbdoc]

Of course both Bosch & Beru make QUICK glow kits for this car. This allows much faster starting on these style systems. VALVE adjustment is also very important!

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MERCEDES BENZ MASTER GUILD TECHNICIAN (6 TIMES)
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 16V ITS SCCA racecar

[123 300D driver]

If you're considering replacing glow plugs, the new parallel plugs cost the same as the old serial ones. I switched over to parallel plugs and am impressed with the improvement in cold starting...5 sec glow in cool weather, 10 sec in winter.

123 300D Driver,

How did you switch to parallel plugs, did you use a bushing or something. The serial plugs are much larger in diameter. If I can do this, I'll do it in a heartbeat. The relay and everything is on the car still, the car was originally a parallel glow plugged engine. The engine I have now is an interim engine for use until the original is ready to go back in.

Thanks everyone for your responses,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

MBDoc,
Just a ball-park figure, what's the quick-glow kit cost? Will it work on MY W123, it has a '81 engine?

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William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles

[mbdoc]

The 1981 engine has a QUICK glow systen with small pencil style glow plugs.

Well, I think that the ol' engine is beyond the help of a quick glow kit. The compression was, front to back; 230, 230, 280 and 245. The back cylinder had an exhaust valve that was slightly too tight, but the others did not require adjusting.

The glow plug bores were not crudded up, and the loop type plugs all checked okay, not shorting to shell or bore.

I got it mostly back together last night before it was dark, and was too tired to do any more anyway, so I didn't even drag out a droplight. My shop is full, between the 300E being torn down, and the Vette and C taking up most of the rest of it, the ol' girl is stuck outside, and now I suppose will be left to Rest in Peace.

I will finish putting it together, but I'm sure it will still not start when it cools below about 60 degrees.

My son has been driving it as an interim car, he'll just have to find something else.

Thanks for your help, and I'll let everyone know if any miracle healing takes place. After I get the 300E back on the road, I'll get back to tearing apart the original 240D motor and do exploratory surgery.

Thanks and have a great day,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

[123 300D driver]

Larry, I got the series-to-parallel glow plug conversion kit from George Murphy a couple of years ago. The new plugs have exaclty the same threads as the old series ones. I am sure that George got the plug set from another supplier and then resold them. Anyway, I am very satisfied with them.

Gary