ok, so I have an intermittant no start issue with my 1998 E300TD. and I have done quite a few tests, sometimes it starts just fine, but I have noticed that when it doesnt start, the SOV is not clicking. I can jumper pins 2 and 3 with batt. voltage and get it to start. I have kind of singled the problem out to the K40 relay based on all my research. However, sometimes at key position 2, there is no click from the SOV, but it will start anyways, I have tested voltage at SOV plug when this is happening and found that the SOV gets battery voltage at crank position, so it will start. so my question is this: Does the SOV also operate from another sensor? (crank pos./cam pos.) and is the K40 relay the ultimate source of SOV control? or is this just a fail-safe built into the K40 relay and or a clear symptom of a failed K40 relay? Wiring diagrams should be more available for free online!!!

so, no one here has actually electrically diagnosed these things? just replace with symptoms?

complete Wiring diagrams for the k40 and associated controls/devices really needs to be a sticky. anyone have wiring diagrams?

PM jay_bob... If anyone knows he will.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

From what I understand about the 210 Diesel electronics is that the "K40" assembly is the same function as the OVP relay on the older models.

I know that if the system is not satisfied you are not going to get the permissive for the fuel solenoid.

On the other hand the starter and glow is pretty much straight wired to the key so even if the K40 is not working I believe you will get crank and glow but no fuel.

There are many things that have to come together in order for the fuel solenoid permissive to happen.

- the DAS has to do the happy dance with your key, the permissive message goes over the CAN bus from the EIS (key switch) to the ECU.
- the crank position sensor has to see RPMs - does your auto crank function work? This uses the CPS to know that the engine is turning and sense the surge in RPM when it fires to know when to release the starter.
- I'm sure one of the relays on the K40 assembly has to be the one that drives the fuel solenoid.

Unfortunately MB has not seen fit to post the 210 information online like they have with the older models. However there are DVD copies of the service manuals floating around eBay that have all the service info. Or if you get a clone Xentry diagnostic system, the hard drive image they give you will include all the service data as well. Xentry literally makes it point and click, you plug in the car, it tells what is wrong, and it hyperlinks to the right procedure for how to test and fix it. I just wish I had $1000 burning a hole in my pocket right now.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

thanks for the replies folks, another quick question, does the SOV get commanded open at key position 2 only? I have noticed a few times that the connector at the SOV does not get battery voltage until I crank. Maybe by testing with the connector un-plugged it does not work correctly?.

what I have done is to unplug the connector, and I determined that pins 1 and 2 are grounds, pin 3 is hot to the solenoid, and pin 4 is the other half of the fuel temperature sensor in the SOV. If I put batt. voltage to pin 3 and ground pin 2, I can open the SOV. I have also had a Volt meter hooked up between these two pins on the wiring side and I get battery voltage only when cranking. should I get battery voltage at these pins at key position 2? I have not yet jumpered all the connections to have the meter in line with the circuit, only tests with the SOV unplugged....maybe this is throwing things off? I will promptly test this and let you know.

I also took the relay off the top of the K40 unit, took it apart and cleaned the contact points, maybe this relay controls the SOV?

and yes, my auto crank works as it should...."flick test?" i think i have seen it referred to. stops after about 5 seconds if no start.


does anyone have solid resistance values for the internals of the SOV? i'm sure the temp side changes accordingly, but there should be a base reference, or table, and the solenoid part should have a solid range. anyone able to test a known good SOV for resistance values between pins?

I have a couple of them sitting around. I'll do a test when I get home this evening.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

OK, so I tested two of the SOV's and came up with different results. If you look at the connector, and imagine the pins are numbered 1, 2 across the top and 3, 4 on the bottom, the results are this:

SOV #1 currently working on my car: Pin 1-3 = 16k ohm. Pin 2-4 = 7.9 ohm.
SOV #2 my spare: Pin 1-3 = nothing. Pin 2-4 = 7.9 ohm.

Not sure what it means but there's the readings.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

cool! so that is looking at the SOV as it is installed in the car with top left being pin 1, top right pin 2 then bottom left pin 3? and bottom right pin 4?

on the harness side of the vehicle, i believe the pins are labeled 1 through 4 starting at bottom left and moving counterclockwise

Thank you so much, i believe the 7.9 ohms is what I am after, it will allow me to verify if mine is ok

Exactly...

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

so I have 8.3 ohms where you have 7.9 twice.

do you suppose that is enough resistance increase to create a problem?

That is not a significant difference.

(8.3-7.9)/8.3 = 4.8% which is within the margin of error when measuring something that low with a common multimeter.

Evan, I would say one of your solenoids has a bad temperature sensor.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

thanks guys, I think I will be buying a K40 unit

Ok, I give up, what is an SOV.

But seriously, I think this may be related to my problem as my 1995 E300D won't start. The battery reads 12.75 volt on my DVM. With the DVM connected, when I turn the key, the voltage drops to 11.5 volts until the buzzer for the glow plugs stops.

Now, when I try to start the car, nothing happens and the voltage remains the same. Btw, I replaced the ignition about 2 years ago, so I doubt if that's the problem.

Any diagrams or ideas?

Bjoern

__________________
Regards,
Bjoern

_________________________________
'08 E320 Bluetec - 101k
'95 E300 Diesel - 241k
'92 300D 2.5 Turbo 321k (Rear-ended by negligent driver and totalled)
'06 Jetta TDI (Sold in 2010)

SOV is the shut off valve and it is what stops, or allows fuel to enter the injection pump.

in your situation, are you simply measuring over-all system voltage? if there is no change at all when your glow plugs are supposed to be getting hot, then I would think you have a bad relay. i believe the GP system pulls quite a draw on the system.