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  #1  
Old 02-10-2014, 01:32 AM
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W210 Glow Plug Issue - 97 E300D

I have had an intermittent issue with this for a long time, but now it seems it is a permanent issue. The glow plug dash light will not come on, and vehicle will not start - so I am sure glow plugs are not getting any juice.

I have replaced the glow plug relay - no effect.

So what else can I troubleshoot? The glow plug relay has one big wire (probably the 12V line) and the glow plug connector to the plugs and then a smaller connector with two wires on it. I am guessing that the small 2-wire plug is what delivers the signal for the relay to come on, so maybe I should check voltages there? Does it connect back to an engine module? If the glow plug relay is good (which it is), then is the engine module the culprit?

Thanks in advance for any help!

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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K

Last edited by treiberg; 02-12-2014 at 08:58 PM.
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Old 02-10-2014, 03:02 AM
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Go to Harbor Freight and get the about $6 Digital Volt/Ohm Meter (Multi Meter).
The Meter is best but if you have a 12 Volt Test Light you can use that.

I am assuming that the new Glow Plug Relays look similar to mine. There is a Flat Copper Wire and the Strip Fuse that should have Battery Voltage all of the time.
There was some Glow Plug Relays that had a Circuit Breaker built into it instead of a Strip Fuse.
Screws on the Strip Fuse have been know to be loose and the Strip Fuse itself can develop a Hair Line Crack.

You can use the Meter or test Lamp to determine if you are getting Voltage up to the Glow Plugs.

If you go to the Diesel Giant Website there is a Pictorial on a quick test using the resistance Function on the Volt/Ohm Meter listed under Glow Plug Repair. It looks like the Page is not opening up but you need to scroll down the page.

If you are not gettin Voltage to the Glow Plugs you will need to remove the Electrical Connector from the Glow Plug Relay and see if when you turn the Ignition Switch to Preglow that you are getting Voltag.
Unforunately I don't know what you Connector looks like, what color of Wire, or which number of hole on the Connector comes from the Ignition Switch.
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Old 02-10-2014, 05:02 PM
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What type of intermittent problem?

Check the 15 amp fuse on top of the K40 relay. Front most relay in the computer box.
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  #4  
Old 09-08-2014, 12:53 AM
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Back to this issue again. Car has been running fine for several months, with only a few times where light wouldn't come on, but usually if we just waited an hour or two, we would finally get the glow plug light and then car would fire up. But now I cannot get glow plug light on and engine will not start without it. Here is a tally of what I have investigated:

-glow plug resistance appears to be fine, all in the 0.6 to 0.8 ohm range
-glow plug relay seems to be fine, at least I see it providing 12V to output blades when I energize it, and you can hear relay click
-replaced the K40 relay
-problem appears to be worse when engine or ambient is hot

The problem appears to be that the signal to energize the relay is not working. I cannot consistently get 12v at the two input wires to the glow plug relay. My understanding is that this starts with the ignition switch, but it is also enabled by the temperature sensor located under the manifold. I wonder if this sensor has gone bad...??

Also, I need to start the car to move it. So I figured if I just apply 12V to the input side of the glow plug relay, then it will pass power to the glow plugs and I will be able to start it after 10-15 seconds - sort of bypassing the electronics that send the 12v. However, when I do this the relay only pops on for 1-2 seconds and turns right back off again, not nearly enough time to energize those plugs to allow me to start. Is that relay somehow super smart and know that my 12v is different than the one from the ECU?

If anyone out there has some input, or can even provide a wiring diagram for a 97 E210 E300D, that would really help.
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Old 09-08-2014, 02:44 AM
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Quote:
Originally Posted by treiberg View Post
Back to this issue again. Car has been running fine for several months, with only a few times where light wouldn't come on, but usually if we just waited an hour or two, we would finally get the glow plug light and then car would fire up. But now I cannot get glow plug light on and engine will not start without it. Here is a tally of what I have investigated:

-glow plug resistance appears to be fine, all in the 0.6 to 0.8 ohm range
-glow plug relay seems to be fine, at least I see it providing 12V to output blades when I energize it, and you can hear relay click
-replaced the K40 relay
-problem appears to be worse when engine or ambient is hot

The problem appears to be that the signal to energize the relay is not working. I cannot consistently get 12v at the two input wires to the glow plug relay. My understanding is that this starts with the ignition switch, but it is also enabled by the temperature sensor located under the manifold. I wonder if this sensor has gone bad...??

Also, I need to start the car to move it. So I figured if I just apply 12V to the input side of the glow plug relay, then it will pass power to the glow plugs and I will be able to start it after 10-15 seconds - sort of bypassing the electronics that send the 12v. However, when I do this the relay only pops on for 1-2 seconds and turns right back off again, not nearly enough time to energize those plugs to allow me to start. Is that relay somehow super smart and know that my 12v is different than the one from the ECU?

If anyone out there has some input, or can even provide a wiring diagram for a 97 E210 E300D, that would really help.
I went through this exact issue with my 97 a couple of weeks ago. First of all trying to hot wire the GP relay is not going to work because this GP relay is digitally controlled by the engine computer. Even if you manage to hotwire it, the computer won't allow fuel to the IP if it doesn't have clear communication with the GP relay. The GP relay has a PIC16 micro controller in it. There is a small 2 wire (3 pin) plug on the GP relay with a white and brown wire. Brown is ground and white is a data line from the engine computer. Grab that plug and wiggle it a bit. You'll see it has some play. The plug is poorly designed and intermittently cuts the data signal between the engine computer and GP relay.

The solution is fairly simple. Solder your own wires to pins 1 and 2 of the 3 pin plug on the GP relay and use standard off the shelf plugs to securely plug it into the car's wiring harness (brown and white wires). Leave everything else the same. You will also need to connect to the OBD2 port and delete the stored code (P0380 i think).

Heres an older thread where we discussed the issue and the fix.
GP relay help - 1997 E300 om606.912

My car went from intermittent no start to totally reliable starts after this modification. MB issued a service bulletin about this very issue.
Quote:
SUBJECT: DEALER TECHNICAL BULLETIN 31/98

31/98-1 RECALLS AND SERVICE CAMPAIGNS: WHEN REPAIRING ANY VEHICLE, ALWAYS CHECK THE VEHICLE MASTER INQUIRY FOR OPEN CAMPAIGNS

31/98-3 GROUP 07 - ALL DIESELS AS OF MY 96 (210.020, 210.025): For conditions of code P1482 (preglow control module) in engine ECU, in addition to the tests outlined in Diagnostic Manual 1.1 and 1.2, please check the electrical line and connectors between the preglow control module and the engine ECU (signal wire / ground and voltage supply) for possible intermittent contact, open contact, short to ground and / or power. If all checks OK, replace preglow control module. These additional tests are necessary to obtain a more precise definition of code P1482. In case of warranty, please use Damage Code according to identified problem.
H. Polz, Service Engineering
HPdg 12-18-98

Last edited by tjts1; 09-08-2014 at 11:37 AM.
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  #6  
Old 09-08-2014, 05:25 PM
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Excellent info, tjts1!

I had come to the same conclusion earlier this year when I did my original post. It ended up being that 2 wire plug. I even went to Mercedes and ordered a new one and the little pin receivers - but I never installed it because as long as I snugged up that connection every so often, it always started.

Man, even in 97 these cars were way to smart! No wonder I couldn't just apply that 12V and make it work. Probably could on a 1980's model, but not this one.

I think my recent problem may be something additional however. I now have a c-clamp on that connector to ensure it is plugged in nice and tight. I have found that it seems to be temperature related. Would not start yesterday in the ambient heat of 100 degrees. This morning a cool 75 and it acted perfectly. That is why I reasoned that maybe the temp sensor was messing with me.

OK, I will solder those wires/pins (I know exactly which ones because I had already cut them and resoldered them back once). That still could be it, maybe the old plug it affected by temperature.

Thanks for the great insight! And I will let everyone know what I find.
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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K
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  #7  
Old 09-08-2014, 05:32 PM
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If you suspect the plug in question is OK and the issue is somewhere else, you could try a temporary set of wires between the relay and the harness to create a secure connection. That way you don't create any unnecessary permanent modifications. I ended up with 2 good GP relays so I didn't have an issue modifying one.

When I got the car, the previous owner put a zip tie around the plug and GP relay to keep it tightly clamped down and that worked for a good long while.

I almost bought a new K40 relay as well but instead I re soldered all the joints in the old K40. It was causing a different stalling issue but maybe its related? I can't say for sure but the plug on the GP relay looks like the likely culprit to me. I don't think replacing the K40 relay is a good solution for anything because they were ALL very poorly soldered from the factory. Its only a matter of time before the new one fails as well and the fix is dead simple. Anyway, let me know how it works out.

good luck

EDIT:
Here's how to fix the K40 relay. It can be the source of a lot of different problems.

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