glow plug relay conversion 6 cyl engines - PeachParts Mercedes-Benz Forum

#1 10-02-2002, 05:42 PM

Hello group,

It has been a while since my last post. I have learned recently that it is possible to use a Glow Plug Relay from a 90-91 350SDL 6 cyl in the 87 300D turbo . Can anyone confirm this ?
Is the relay in the 350SDL's a pre+post glow unit ?
The Duraterm glow plugs are available for about $ 13.00/ea
Since nobody offers a conversion kit for the 6 cyl 300d, would this be an alternative ?
The relay is $ 99.00 but being an electrical part is not returnable.
I would appreciate any advice on the matter. Would it plug into the harness or would it need a new plug ?
The most important issue is, however, to be a pre+post glow relay to smooth out the cold starts and smoke.
Thanks

Marius
South Bend IN
342,000 mi 1987 300D turbo

#2 10-07-2002, 10:36 AM

No one knows ?

#3 10-14-2002, 10:07 AM

Any members with '90-93 MB 350 SD or SDL's on this board ?
Could someone help me determine if this is feasible ?
I would appreciate a picture maybe of the Glow relay that shows the electrical connections.
Anybody has an electrical diagram that shows the glow relay connections so that I can determine if I need to make changes to my system to adapt the new relay ?
Thanks in advance.
Respond to my email mariusg@sbt.infi.net

Marius

psfred · #4 10-14-2002, 10:29 PM

Marius:

I would expect the relay to be the same item. If it is working, try waiting a few seconds after the lamp goes out before cranking, as the plugs stay on for a while (up to a minute, depending on temperature).

Most likely you have bad glowplugs rather than a bad relay, as they are identical. You can check part numbers to be sure (look on FastLane), but the 87 has glowplugs that stay on for a while after the engine cranks, too. Rough idle and while smoke indicates to me that you have one or more plugs out -- the engine will start nicely on four cylinders, but won't idle smoothly until it warms up.

Peter

#5 10-15-2002, 10:50 AM

The part numbers are different:
'87 300D - 36140
'91 350SD - 70431

I had new Beru plugs put in last summer ( 15K ago) and tested the juice going to them. It is 11 V consistent to all of them.
After about 3 seconds after the key is turned the light goes off, I keep on heating them about 25 sec. then start the engine. It doesn't run very good unless I had the heater plugged in.
I timed the glow relay and it kicks the power off after 25 seconds.
I also tested the relay and the power is cut of to the plugs the instant the engine has fired. No post glow. That is why I am loking at the new type relay. The new pencil type Duraterm plugs are also different they say.
So what do I do ?

Marius

psfred · #6 10-15-2002, 07:42 PM

Let me check mine -- I'm sure the glow after the engine starts. I'll also try to talk to Hans soon and see what he says. If the relay fits in the harness, it should work.

Also, don't wait so long to crank -- the plugs may stay on longer with shorter pre-glow.

It is also possible that your relay is bad.

The other causes of rough idle cold are bad and leaking valves, or rings (in which case there is excess oil consumption) and worn out injector nozzles. Really shot tappets won't help, either -- have you changed the little o-rings on the center bolt of the oil filter housing cover recently?

Peter

#7 10-22-2002, 05:25 PM

Hello Peter,

Have you had a chance to look up the info on the relay and plugs?
BTW, I have 340K on this engine, I never had the compression tested but do you think The Engine Restorer additive could help a high mile diesel engine?
With every oil change I add 2 cans of the LubroMoly Engine Saver additive and the engine seems to run fine. I timed the 0-60 Mph and got 12.3 seconds. It puts out some smoke under hard acceleration but seems to run good. My only problem is the cold starts when the heater is not plugged in and I want to improve that by doing the pre+post relay conversion. The EGR is plugged and the trap oxidizer has been removed, actually I opened up the trap, took the ceramic out, welded back the window and put it back. The MB dealer showed my car with the conversion already done so I could not get them to do it again. I don't know what the previous owner did with that.
To come back to your questions, the injectors are new ( 15K), ran a can of LubroMoly cleaner straight from the can, return in the can, about 4 months ago. The O-rings on the shaft in the oil filter have been changed 2K miles ago - last oil change 15W40 Rotella.

Marius

psfred · #8 10-22-2002, 07:47 PM

Marius:

You should not have messed with the trap -- it is being replaced at the usually service interval (30,000 miles) unless plugged, in which case it is replaced then with a catalyst and usually new turbo. Since you opened yours, you have voided the warrenty and will not be covered.

Haven't had a chance to look at the glow plug relay yet -- just got the wood trim back in the 280 SE, trying to get THAT car running so I can work on the others......

Engine Restorer will help with a leaking rear main and will free up stuck rings, but my guess is it won't help if the compression is low. Before I got any further with it, I'd check the compression -- if it is in fact low, and a leakdown indicates worn cylinder walls, it will cost a bundle to fix, especially if the pistons need to be replaced -- about $5000 in parts, 50 hrs labor. A big deal.

A valve job will be considerably less, and if you have noisy lifters, they are probably not holding oil pressure. That means the valves aren't opening correctly, causing the rest of the troubles.

You probably need to replace the tappets at that milage, anyway. To do so, alas, you must remove the cam.

I'd also run Mobil 1 15W50 in it for one oil change, not additives, to see if it can work some magic for you.

Peter

#9 10-23-2002, 09:37 AM

Thanks Peter.
I only did the trap after 3 months of arguing back and forth with the dealer and MB Customer Service Headquarters. The computer records showed the trap being already changed in IL but it was still on the engine. The Service Mgr. said that it has been done already and if I want it done it will cost me something like $ 1800,00. He blamed the previous owner for switching it with another car's trap .....yada..yada...yada
I had no choice. The turbo runs fine, I didn't want to take the chance to ruin it with chunks of ceramic from the trap. Anyway, if you look at it you can not tell what has been done to it. It looks just like original. I had the shield taken off vary carefully and cut the window on the bottom side with a plasma cutter then argon welded the window back and pressure tested. Alittle more smoke with it removed but running fine.
There is a little chatter and valve noise when cold but it quiets down as it warms up. The engine seems to run fine, a couple of mechanics that work on european diesels said that by the way the engine sounds and looks, it should not have a serious compression problem. It is old, got a lot of highway miles but appears to have been taken care of also. Everything works on this car except the cruise which I don't need anyhow.
So, if you find the time, please let me know what you find out on the relay issue.
Thanks in advance.

Marius

Geezer · #10 11-16-2009, 03:04 PM

Sorry for reviving this old thread, but it would be cool if anyone in the 7 years since it died, figured out if this is possible. I'm very much in the same boat. 350k+ miles 87 300d trying to improve cold driving and starts.
Thanks

old goat · #11 01-26-2010, 02:12 PM

If you are still interested in knowing about the glow plug relay conversion, let me know as am about to do it on my 86 300SDL. I contacted Beru in Germany to get information on the switch over.

Frank

Hit Man X · #12 01-26-2010, 03:08 PM

WOW old thread.

Anyway, yes I installed (successfully and easily) the later afterglow system into my 300SDL.

You basically need the later plug relay, different cylinder head sender with two pins (other pin is for GP relay), few plastic connectors, solder, some quality wire, and a bit of time.

I believe Bosch only makes the afterglow style glowplugs now (80006 or something is the PN) and you would need those if you do not have them. GP life is shortened obviously, but not to a year or two. I have one or two plugs out since my install which was probably in 2005 or 2006.

old goat · #13 01-26-2010, 04:18 PM

Thanks for responding. Yes, a very old thread for sure.

By any chance do you have the part number of the cylinder head sender?? I have the wiring diagram for the 91 300SD and SDL but the darn thing does not show the wire to the T pin in the relay....so I did not know where they were picking up the temperature input.

I have a recommendation from Beru for the glow plugs but have not purchased them yet so another possibility sounds reasonable too. Do you have a preference for Beru versus Bosch??

It is winter in Michigan, so the car is put up out of the salt and I have time to play with it.

Thanks again

Frank

Hit Man X · #14 01-26-2010, 05:50 PM

Quote:

Originally Posted by old goat

Thanks for responding. Yes, a very old thread for sure.

By any chance do you have the part number of the cylinder head sender?? I have the wiring diagram for the 91 300SD and SDL but the darn thing does not show the wire to the T pin in the relay....so I did not know where they were picking up the temperature input.

I have a recommendation from Beru for the glow plugs but have not purchased them yet so another possibility sounds reasonable too. Do you have a preference for Beru versus Bosch??

It is winter in Michigan, so the car is put up out of the salt and I have time to play with it.

Thanks again

Frank

It was so long ago, I will check my records but I probably do not know anymore. Check out the FREE EPC

https://epc.startekinfo.com/epc/welcome.jsp

The temp sender is in the head under the intake manifold area. Semi difficult to reach, figure this for a good few hour job. The extra wire to the GP relay is obvious, it is the only new pin open.

Either glow plugs would be fine. Purchase whatever is on sale at the time. I even used :gasp: Champion plugs in my 300SD for years without a lick of trouble. I recently pulled them for afterglow style Bosch as I purchased the afterglow relay for the 617. All were still working after years of service.

Cannot remember the total cost for all the parts, but figure around a few hundred if you need new glow plugs. Plus the cost of the relay varies, I paid about $40 for mine used only.

Lastly, it really makes cold starts much cleaner. Now the car sounds like a Diesel on start up versus a top fueler at idle.

One of the best mods to the 603, next to removing the ALDA and hollowing out the cat on the '87s.

old goat · #15 01-27-2010, 01:24 PM

Thank you for all the information....as well as the knowledge that it works well in the car. I am not sure how I ran across that old post of yours but I have been looking for answers for quite a while before contacting Beru to get their advice.

If you are ever in Chelsea, MI, I am easy to find. I am assuming here your home listed as Hell is not Hell, MI!

Frank