W210 starting problem - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 07-16-2009, 12:29 AM

Our '96 E300D (W210, OM606NA) is becoming a "non-starter." Yesterday, my wife called to say that "the car won't start." After making sure she wasn't trying to start it in gear (which has happened), I drove to where she was. Indeed, although all the lights came on and the glow plugs cycled, the starter did nothing. I moved the shifter from Park into Neutral and voila, it started. Turned the engine off, went back to Park, tried again, now it would start in Park.

So--probably a flaky Neutral Safety Switch, right? Same problem repeated once in three starts today except now the wife knows about trying Neutral. She said it took several tries (moving the shift lever back and forth) but eventually it started.

Back at home, I pulled the belly pan and took a look. The pictures show what I saw. I need help with identification. Remember that this is a 722.4 4-speed tranny, not the new 5-speed that the '97 models got. I also played with the shift lever, moving it back and forth, trying to get it to misbehave. It did not, of course. Is the thing with the long plug in it the NSS? What about the plug at the rear of the tranny? The reverse light switch maybe?

The NSS should be fairly new, since about 18 months and 13,000 miles ago Santa Rosa Hydramatic rebuilt the transmission. I will ask them tomorrow but I would assume that the NSS was replaced at that time. Maybe not--anyone have experience in this area?

You'll also notice the repair job on the wiring, done when the transmission was overhauled. The environmentally-friendly insulation on that cable had disintegrated so they patched it up as best they could. This means that the starter problem could also be that wiring. That is something I can rebuild myself. I'm not sure I can replace the NSS--the factory DVD says something about "lowering" the transmission to get it out. Not sure I want to do that.

Is there anywhere in the 210 chassis to jump the starter, in case whatever is now intermittent turns into a hard failure before I can find it? I know how to jump the starter on the W123 and the W124 but don't see anything familiar under the hood of the W210.

As always, your advice is appreciated.

Jeremy

Jeremy5848 · #2 07-16-2009, 03:26 PM

This morning, the transmichigan shop told me that, in overhauling Mercedes automatic transmissions, they normally do not replace the neutral safety switch. [In Fords, they always do.] So, since AFAIK this car has never had this switch replaced, I would not be surprised in a failure after 13 years and 262,000 miles.

So I stopped by the dealer and ordered a new switch ($50 after MBCA discount). Monday the car goes to the tranny shop where the switch will be installed. Then we'll see how it does.

Jeremy5848 · #3 07-16-2009, 10:18 PM

The following applies to the '96 E300D, probably to the '97, maybe to the '98-99. YMMV.

Studying the schematics in the FSM (DVD version), I learned that the W210 cars have a "cycle module" (N65) in one of the three fuse boxes (the one in the engine compartment--see the first picture). There is a relay in this N65 that must operate for the starter to work. It is a mass of solid state and looks to be made of Unobtanium. I don't even want to know how much it would cost to replace, just hope that my car's problem is not there.

To start a W210 that has a faulty starter contact in its ignition switch, you separate the two halves of connector X22/1 (located between the pre-glow relay and the ABS pump) and jump pin 4 to the +12 volt connector (see second picture). The ignition must be on, the engine glowed for an appropriate interval, the neutral safety switch must be good and the transmission has to be in "N" or "P." If you just want to crank the engine for some reason, leave the ignition off.

Jeremy

nhdoc · #4 07-17-2009, 07:19 AM

I would hope there would be a way to test the NSS without having to replace it under suspicion, although it sounds like your is probably the cause of the problem you are having. I had an intermittent no-crank condition on my '98 when I first bought it but it would not be cured by moving the shifter like yours was - mine happened on hot days when the engine bay was hot. At first I thought it might be the NSS but it turned out to be a small black "cube" relay in the right-front electronics box under the hood.

I was able to isolate it to that part first by unplugging relays and trying to start the car...when I found the right one the car would not crank - same as the condition I had experienced. The next time the "no crank" occurred I tapped the relay while my wife held the key in the start position and sure enough the starter began turning.

I replaced that relay (around $15) and never had the problem again. Like I said, it sounds to me like yours is the NSS but I posted this for other W210 owners who might experience a similar no-crank issue.

Jeremy5848 · #5 07-17-2009, 11:13 AM

Quote:

Originally Posted by nhdoc

I would hope there would be a way to test the NSS without having to replace it under suspicion, although it sounds like your is probably the cause of the problem you are having. I had an intermittent no-crank condition on my '98 when I first bought it but it would not be cured by moving the shifter like yours was - mine happened on hot days when the engine bay was hot. At first I thought it might be the NSS but it turned out to be a small black "cube" relay in the right-front electronics box under the hood. . . .

Thanks for the information. It sounds like they changed the design for '98-99. Your ice cube relay is not in the '96. It would be a lot easier and less expensive to replace. Oh well.

I'll post results next week.

Jeremy

Jeremy5848 · #6 07-18-2009, 10:39 PM

It's not the neutral safety switch!

For the past couple of days, I have been taking the car for a drive and then letting it spend the day in the sun, sitting in the driveway rather than in the cool of the garage, trying to get it to act up. Finally today it refused to start and no wiggling of the shifter or anything else would get any action out of the starter.

The following diagram from the FSM, slightly edited by me, shows the path from the ignition switch, through the cycle module, through a connector under the hood, through the neutral safety switch (NSS), and thus to the starter solenoid.

Once I had the car in a "broken" mode I did some tests. First, I unplugged connector X22/1 and jumped pin 4 directly to 12 volts. That bypasses both the ignition switch and the cycle module and in the past would make the starter turn the engine over. No joy. Dead.

One difference from before: my jumper wire made sparks at the +12 volt terminal. I put an ammeter in the circuit and discovered that there was a draw of 25 Amps -- a lot of current for a circuit that's not doing anything!

I moved the shifter from Park to reverse -- no sparks, no current. I tried Neutral -- sparks and 25 Amps. Drive -- no sparks, no current. The NSS is doing its job. Crawled under the car, unplugged the connector at the NSS -- no sparks, no current.

That rules out everything except the wiring from the NSS to the starter motor and the starter itself. Although there could be a short somewhere, it would have to be in a place where a wire could short to ground. Given the wiring problems these cars sometimes have, that's possible. My main suspect is still the starter motor which, AFAIK, has never been replaced. I did try whacking the starter motor with a hammer -- no joy.

Monday, one way or another, the car goes to the mechanic.

Jeremy

Diesel911 · #7 07-19-2009, 01:08 PM

Quote:

Originally Posted by nhdoc

I would hope there would be a way to test the NSS without having to replace it under suspicion, although it sounds like your is probably the cause of the problem you are having. I had an intermittent no-crank condition on my '98 when I first bought it but it would not be cured by moving the shifter like yours was - mine happened on hot days when the engine bay was hot. At first I thought it might be the NSS but it turned out to be a small black "cube" relay in the right-front electronics box under the hood.

I was able to isolate it to that part first by unplugging relays and trying to start the car...when I found the right one the car would not crank - same as the condition I had experienced. The next time the "no crank" occurred I tapped the relay while my wife held the key in the start position and sure enough the starter began turning.

I replaced that relay (around $15) and never had the problem again. Like I said, it sounds to me like yours is the NSS but I posted this for other W210 owners who might experience a similar no-crank issue.

The intermittent nature of a lot of electrical problems often make them difficult to test; even when there is a test procedure in the manual.
As a test it is often easier to get a piece of wire and bypass a switch and see if the problem goes away.
Unfortunately some connectors are multi use and with out a Wiring diagram or if the wires can be traced bypassing can cause problems.
Example ; On a 123 I believe the Neutral Safety Switch also doubles as a Back-up Light switch.

Jeremy5848 · #8 07-19-2009, 04:10 PM

Quote:

Originally Posted by Diesel911

. . . Unfortunately some connectors are multi use and with out a Wiring diagram or if the wires can be traced bypassing can cause problems. Example ; On a 123 I believe the Neutral Safety Switch also doubles as a Back-up Light switch.

It is the same with the W210. Fortunately, I have the ETM and its diagrams (although the pinouts and wire colors do not completely agree with what is actually in the car, so I issue a caution here). I also have over 50 years of experience driving soldering irons.

There are actually two switches in the NSS. One closes in either P or N for the starter circuit, the other in R only for the reverse light circuit. I am in the process of rebuilding the plug and cable for that switch.

I do not see anything so far that would cause the starter to not work yet somehow draw 25 amps of current (and be heat sensitive: OK when cold, not OK when hot). This seems to point more and more to the starter solenoid.

The insulation fell apart on the original wires and caused the reverse light circuit to short and blow fuses. That was caused, found, and repaired when the transmission was overhauled. The mechanic did a good mechanic's job -- lots of butt connectors and black sticky tape. I am rebuilding properly with soldered connections and shrink tubing, a slow job.

Once that is finished, I'll run a new wire from the starter solenoid up to where I can reach it under the hood. Next time the problem repeats (hopefully today) I'll be able to jump the solenoid directly to 12 Volts as Marty suggested.

Jeremy

treetops · #9 03-20-2016, 10:20 AM

Quote:

Originally Posted by nhdoc

I would hope there would be a way to test the NSS without having to replace it under suspicion, although it sounds like your is probably the cause of the problem you are having. I had an intermittent no-crank condition on my '98 when I first bought it but it would not be cured by moving the shifter like yours was - mine happened on hot days when the engine bay was hot. At first I thought it might be the NSS but it turned out to be a small black "cube" relay in the right-front electronics box under the hood.

I was able to isolate it to that part first by unplugging relays and trying to start the car...when I found the right one the car would not crank - same as the condition I had experienced. The next time the "no crank" occurred I tapped the relay while my wife held the key in the start position and sure enough the starter began turning.

I replaced that relay (around $15) and never had the problem again. Like I said, it sounds to me like yours is the NSS but I posted this for other W210 owners who might experience a similar no-crank issue.

I know this is a very old thread, but I would like to know which relay is referred to in this quote. My e300 sometimes, too often actually, does not start and when this happens I hear a relay click from the area of the fuse box in the engine bay on the drivers side. Pushing on the shifter while in park clears the issue for a good bit as does some time, 45min+ between starts.

I've got a new FOB, battery checks out so I think I am narrowing it down to the NSS, Shift selector or whatever this relay is.

KarTek · #10 07-17-2009, 09:00 AM

Quote:

Originally Posted by Jeremy5848

The following applies to the '96 E300D, probably to the '97, maybe to the '98-99. YMMV.

Studying the schematics in the FSM (DVD version), I learned that the W210 cars have a "cycle module" (N65) in one of the three fuse boxes (the one in the engine compartment--see the first picture). There is a relay in this N65 that must operate for the starter to work. It is a mass of solid state and looks to be made of Unobtanium. I don't even want to know how much it would cost to replace, just hope that my car's problem is not there.

To start a W210 that has a faulty starter contact in its ignition switch, you separate the two halves of connector X22/1 (located between the pre-glow relay and the ABS pump) and jump pin 4 to the +12 volt connector (see second picture). The ignition must be on, the engine glowed for an appropriate interval, the neutral safety switch must be good and the transmission has to be in "N" or "P." If you just want to crank the engine for some reason, leave the ignition off.

Jeremy

That's some handy information. Thanks for the post!

aTOMic · #11 01-12-2011, 12:41 PM

Hi from snowy TN!
I am having NSS probs on my 96 E320 (it freezes and a long application of heat gun cures it enough to start in N). Your great NSS post was a great deal of help.

My question do you remember / know what color wires to jump to bypass the interlock?
Is there a way to access them without jacking up the car, because it would'nt be safe to do so where it is)

Thanks in advance,
Tom (aTOMic)

Jeremy5848 · #12 01-12-2011, 01:38 PM

To bypass the NSS, cross the violet and violet/white wires. Remember that you will then be able to engage the starter motor with the transmission in any gear.

The following info is from FSM (DVD version) for the 722.3 transmission in a 1996 W210 car with an M104 engine. I hope that's your E320.

The violet/white wire runs to the starter and then to pin 2 of X22/2, a connector in the "Engine compartment right rear, in Control module box, buried under wires."

The violet wire runs to pin 4 of X22/1, which is on the left wheel well next to the ABS pump. It is a black connector (plug/socket) with probably 6 pins and 5 in use. The heater hoses of the windshield washer bottle run near X22/1.

See pictures for these connectors.

Jeremy

Quote:

Originally Posted by aTOMic

Hi from snowy TN!
I am having NSS probs on my 96 E320 (it freezes and a long application of heat gun cures it enough to start in N). Your great NSS post was a great deal of help.

My question do you remember / know what color wires to jump to bypass the interlock?
Is there a way to access them without jacking up the car, because it would'nt be safe to do so where it is)

Thanks in advance,
Tom (aTOMic)

aTOMic · #13 01-12-2011, 05:49 PM

Thanks a million!
Looks a bit different than my gasser, but I'm sure the bits are all there!
Jeremy, your posts are exemplary! (I hate unsolved posts)
-Tom

aTOMic · #14 01-13-2011, 04:54 PM

Well using your first picture, today I easily located X22/1, which is a robust, thick-pinned connector, and separated the top from the bottom, jumped from #2 to #4 with a 1 inch long piece of 22 ga wire (looks to be the size coming out surprisingly) and it worked! Joy!
A pertinent note: the numbers are on the top (male) connector.

Also, as i tried to reconnect the M to F connector, the pins pushed the "lid" off the top which exposed a nicely corroded set of soldered attachment points and brittle insulation which I will need to address as soon as I finish my 2007 taxes and the billion other things I need to do.

I hope that the car doesn't "think" it's in P or N and cause some ABS, engine/transmission control, or other system to act up. I know these cars are quite complex. I'm sure we'll hear about it if there is a side effect.

I cannot tell you how much stress this has saved us, Jeremy. Thank you!

-Tom