2000 E320 K40 relay (or is it???) - Mercedes-Benz Forum

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post #1 of 22 (permalink) Old 06-15-2017, 08:35 AM Thread Starter
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Question 2000 E320 K40 relay (or is it???)

I've been looking into an issue with my father-in-law's 2000 E320 that started this Sunday, June 11. We had driven the car without any issues in the morning and early afternoon, but in the late afternoon after making a stop and removing the key from the ignition, we were unable to get it started back up. There weren't any signs that something was about to go wrong as far as I know. If it's relevant, the atmospheric conditions were a temperature of 83F and humidity of 44%.

We are able to unlock the car normally with the key fob. When we put the fob into the ignition and turn it to the on position, all cabin electronics come on and operate normally. When we turn the key to the ignition position, however, we can't hear any of the normal responses we'd expect from the engine - starter motor or engine crank. However, from inside the engine compartment, we can hear a few brief clicking sounds.

We've tested the battery - it shows 12.6 volts when the car is inactive, and 12.3 volts when the ignition is in the on position with electronics running. There is no voltage change at the battery when we turn the key to ignition.

One of the suggestions I found in this forum to fix this and a variety of other issues with W210 cars was to remove the K40, redo the solder points on the PCB, and replace. I want to try this repair as a first step, since it doesn't cost anything.

I found what appeared to be the right compartment in the engine - it was on the right hand (passenger) side of the car, marked with an air conditioner label. It was covered by a plastic top with four captive phillips screws. Inside the compartment were three computer-ish looking devices, plus what appeared to be a fuse box with lots of cables coming out. However, when I had disconnected the cables and removed the box, the relay looked significantly different than the ones I had seen on various YouTube videos and photos I found online.

This is what I was expecting: external link to large image


But what I found looked quite different:

From the top:

2000 E320 K40 relay (or is it???)-relaytop.jpg

From the bottom:

2000 E320 K40 relay (or is it???)-relaybottom.jpg

There were also far more cables attached to the top than I was expecting. Not sure if I removed the wrong part, or if it's just a different version on this particular model. I've also seen some other people mention that there are *two* K40's, and the other is on the other side of the engine compartment. But I don't see anything that fits that description over there, just the main fuse box (unless it's hidden under the back of the fuse box).

Any idea if what I'm looking at is the right part, or if I should be looking elsewhere? I just want to make sure it's right before I go resoldering anything.

Thanks!
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post #2 of 22 (permalink) Old 06-15-2017, 09:18 AM
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Hello

The fuse panel you show in the picture is for the 1998+ E320 cars and the one in the external link is for older models.

The older fusepanels had soldering PCB track cracking issues, and the newer ones do not seem so suffer from this as such.

There is another K40 relay / fuse panel at the driver's side (which is called K40/2) which is not relevant at this point.

1) With the above fuse panel installed, the first things I would check are the fuses, especially the the 10 amp fuses, and the voltages on them with the ignition switch in "run" position. This would make sure you get the power to the engine computer, and transmission computer.

2) Then, have someone turn the key to start the car and listen to the black relay that looks like a big ice cube on the K40 module next to the 40 amp orange fuse. If you hear the a click, and the starter does not turn, then you either have a bad starter relay, or bad starter / starter wiring. If you do not hear a click, You may have a problem with the electronics or switches (can you shift between gears with the ignition ON ? Try starting in Neutral, and move the shifter between gears several times, and re-try in P and / or N). If the start is not "enabled" by the engine computer, your car will not start.

3) With the key OUT, remove the starter relay, and put a jumper wire across the relay contact terminals on the receptacle on the K40. Terminals A and C, marked as circuit 30 and 87.

4) With the jumper installed on the K40 relay board, insert the key and turn briefly to "run". If the starter engages, turn and remove the key immediately. You have a bad starter relay, or wiring / connector between the starter and the relay.

5) If the starter does not engage from 4), then have the starter / wiring checked. Few posts similar to yours had problems with the starter wiring damage (between the starter solenoid and the starter motor) due to corrosion.

You can check this link for generalized start issues.

http://www.mercedesmedic.com/mercedes-wont-start/

Last edited by mrboca; 06-15-2017 at 10:17 AM.
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post #3 of 22 (permalink) Old 06-15-2017, 09:26 AM Thread Starter
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Thanks very much for your reply! I will try these tests when I get home tonight.

Also, I just found this thread... seems to be fairly similar symptoms to what I've seen, and it's the same year and model:

http://www.benzworld.org/forums/w210...ont-start.html

Quote:
Originally Posted by mrboca View Post
Hello

The fuse panel you show in the picture is for the 1998+ E320 cars and the one in the external link is for older models.

The older fusepanels had soldering PCB track cracking issues, and the newer ones do not seem so suffer from this as such.

There is another K40 relay / fuse panel at the driver's side (which is called K40/2) which is not relevant at this point.

1) With the above fuse panel installed, the first things I would check are the fuses, especially the the 10 amp fuses, and the voltages on them with the ignition switch in "run" position. This would make sure you get the power to the engine computer, and transmission computer.

2) Then, have someone turn the key to start the car and listen to the black relay that looks like a big ice cube on the K40 module next to the 40 amp orange fuse. If you hear the a click, and the starter does not turn, then you either have a bad starter relay, or bad starter / starter wiring. If you do not hear a click, You may have a problem with the electronics or switches (can you shift between gears with the ignition ON ? Try starting in Neutral, and move the shifter between gears several times, and re-try in P and / or N). If the start is not "enabled" by the engine computer, your car will not start.

3) With the key OUT, remove the starter relay, and put a jumper wire across the relay contact terminals on the receptacle on the K40. These terminals are parallel to each other, NOT those that form a "T". The T contacts are the coil side which are connected to the engine computer.

4) With the jumper installed on the K40 relay board, insert the key and turn briefly to "run". If the starter engages, turn and remove the key immediately. You have a bad starter relay, or wiring / connector between the starter and the relay.

5) If the starter does not engage from 4), then have the starter / wiring checked. Few posts similar to yours had problems with the starter wiring damage (between the starter solenoid and the starter motor) due to corrosion.
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post #4 of 22 (permalink) Old 06-15-2017, 09:35 AM
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Yeah, make sure the gear is in Park with the Parking brake is engaged prior to jumping the starter

Make sure your brake switch works, and you can shift between gears.
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post #5 of 22 (permalink) Old 06-15-2017, 06:39 PM Thread Starter
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Quote:
Originally Posted by mrboca View Post
Hello

with the ignition switch in "run" position
Just to clarify, in your testing instructions, you referred both to a "run" position and an "on" position. I want to make sure I understand those correctly. Could you specify which numeric positions those correspond to, based on a numeric order where:

0 is the position the key is in when first inserted
1 is the position 1 click to the right of 0 (minimal dashboard info displayed)
2 is the position 1 click to the right of 1 (all accessories active)
3 is the position 1 click to the right of 2, where ignition occurs, and from which the key automatically flips back to position 2 unless held

Thanks!
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post #6 of 22 (permalink) Old 06-15-2017, 06:57 PM
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run = ignition position 2.

--1998 MB E300TD 285k
--1997 MB E320 198k
--2004 Dodge Ram 5.7L 212k and holding (damn gas guzzler)
--2011 Suzuki DL650 44k
--1997 MB E320 161k. SOLD...loved that stupid car.
--1998 MB ML320 207k. SOLD, thank heavens!
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post #7 of 22 (permalink) Old 06-15-2017, 06:57 PM
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Yeah, position 2 is run, position 3 is start.
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post #8 of 22 (permalink) Old 06-16-2017, 06:52 AM Thread Starter
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To answer your testing steps:

1) All fuses in the K40 box tested 12.2v EXCEPT for the big orange 40amp one, which had zero voltage. All fuses tested ok for resistance.

2) Definitely no sound coming from the black cube/relay when attempting to start. There are, however, other sounds (cicks and buzzes) that come from the engine during this time. I had a helper turn the key gradually through the positions and made note of the under-the-hood noises at each one:

Begin:
  1. Insert to position 0: light "chunk" sound from key receptacle when the key is inserted and engages
  2. Turn 1 right to position 1: no sound
  3. Turn 1 more right to position 2: no sound
  4. Turn 1 more right to position 3, and hold: first a loud double click, and almost concurrently a loud buzzing starts, followed one second later by a softer single click. The buzzing sound continues.
  5. Release from position 3 and return to position 2: The loud buzzing sound that started when first turning to position 3 continues during position 2
  6. Turn 1 to left back to position 1: Buzzing sound from position 3 stops
  7. Turn 1 to left back to position 0: No sounds stop or start
  8. Remove key: Light "chunk" sound from key receptacle as key is removed

End

2 (continued) When I hold the key in position 3 (start), I am able to shift through gears from Park through Drive several times. I see the indicator on the dashboard change. I also confirm that the car remains stationary except when I shift to neutral, at which point it rolls.

3+4) Not sure if I should have continued at this point, but I found a short braided copper wire and used it to jumper the specified points after removing the relay. No change in anything with this setup.

Can we draw any conclusions based on the information above, or are there further things to try?
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post #9 of 22 (permalink) Old 06-16-2017, 09:38 AM
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Worth looking into the ECU cooling fan short/blown fuse issue?

Regards,
Al Savage
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post #10 of 22 (permalink) Old 06-16-2017, 11:26 AM
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Quote:
Originally Posted by prwood View Post
To answer your testing steps:

1) All fuses in the K40 box tested 12.2v EXCEPT for the big orange 40amp one, which had zero voltage. All fuses tested ok for resistance.

2) Definitely no sound coming from the black cube/relay when attempting to start. There are, however, other sounds (cicks and buzzes) that come from the engine during this time. I had a helper turn the key gradually through the positions and made note of the under-the-hood noises at each one:

Begin:
  1. Insert to position 0: light "chunk" sound from key receptacle when the key is inserted and engages
  2. Turn 1 right to position 1: no sound
  3. Turn 1 more right to position 2: no sound
  4. Turn 1 more right to position 3, and hold: first a loud double click, and almost concurrently a loud buzzing starts, followed one second later by a softer single click. The buzzing sound continues.
  5. Release from position 3 and return to position 2: The loud buzzing sound that started when first turning to position 3 continues during position 2
  6. Turn 1 to left back to position 1: Buzzing sound from position 3 stops
  7. Turn 1 to left back to position 0: No sounds stop or start
  8. Remove key: Light "chunk" sound from key receptacle as key is removed

End

2 (continued) When I hold the key in position 3 (start), I am able to shift through gears from Park through Drive several times. I see the indicator on the dashboard change. I also confirm that the car remains stationary except when I shift to neutral, at which point it rolls.

3+4) Not sure if I should have continued at this point, but I found a short braided copper wire and used it to jumper the specified points after removing the relay. No change in anything with this setup.

Can we draw any conclusions based on the information above, or are there further things to try?

Great observations

1) your key unlocks the steering wheel and turns, so your ignition is properly authorized.
2) you can shift the gear selector and observe the correct gear indication, so your transmission computer is powered up and can register the brake switch and the gear shifter module signals. So you should have start enabled.
3) You removed the black relay (key out), and put a jumper on the RIGHT set of contact sockets on the K40 module (marked as 30 and 87 which are the terminals for the relay switch side, NOT the coil side) see picture attached. After you did this with gear in Park, you inserted the key and put it in run position for 5 seconds, and nothing happened (no crank).

Based on the above, I would just make sure that the relay switch itself gets 12V from the ignition switch when the key is in run position. With the relay out, measure the voltage between the terminals that you previously put the jumpered. You should read 12V (with key in run). If you do not, then there is a problem with the ignition switch contacts that is supposed to provide this voltage when you turn the key (circuit 15u). If you read 12V, and jumpering does not work, you then have a confirmed problem with the starter or wiring to the starter or wiring between the starter motor and the solenoid (mounted on the starter).

When the engine module fan fails, it typically blows one of the 10 amp fuses out which is shared with the transmission control module. You checked the fuses and the voltages on the fuses and they seem to be fine. The 40 amp fuse is for the air injection pump, and will have voltage on it when the engine actually starts, so no problem there.
Attached Files
File Type: pdf e210_starter circuit.pdf (54.8 KB, 13 views)
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