johndtitus

Symptoms are as follows:

Occasionally, my SL600 will not crank. It is getting progressively more frequent. It seems to be weather (temperature) related, although that is purely anecdotal.

I do not get a "start error" message, so I do not believe it is the anti-theft system.

Stepping on the brake and moving the gear selector to neutral has no effect.

When the car does start in the morning (cold) the starter motor sounds fine and cranks the engine as fast as always. Once it does start in the morning, the failure does not repeat itself for the rest of the day. On warm days the no-crank problem does not seem to happen.

Is there a starter relay somewhere I should be looking for? If so, where is it located. What other things should I be testing?

miike

Check the power to the starter. Clip a wire to the biggest positive lead to the starter and then to a meter. Have someone start the car and see how low the voltage drops.

Jim's500E

Bad solenoid...or time for a new or rebuilt starter, they are, after all, getting to be "old" cars.

johndtitus

New symptom. Today, after several tries I got it to crank and it started, but then the engine stalled just as the rpms were dropping down to idle. I could not get it to crank again. I am wondering if the battery is failing and the fuel injection and/or ignition cut out. It is at least a plausible theory. Battery voltage is lowest after the car sits overnight and voltage is lowest when it is cold. Once the car starts and the alternator has a chance to charge the battery, the car works fine and starts every time? Also possible the electrical contacts in the ignition switch is failing. I would think that if it were the starter failing, there would be an audible "click." When it won't start, it is completely silent.

I have ordered the carsoft multiplexer software so I can hopefully get some information from the 38 pin conector, but it won't arrive until mid-March. If it is simply the starter motor that is great, easy to replace, but if the car has logged some comm errors I need to know.

Jim's500E

Do you have a multimeter? Or take the battery to a Pep Boys or Autozone type of joint for them to check. Is it a sealed battery or can you check if the water is low in the cells? Def. worth a new battery regardless to cross out that as an issue if in doubt to its age and capability.

Checking the battery with a multimeter in the morning would answer a lot of questions on the available start-up juice....

johndtitus

I have a multimeter so I can easily check the voltage. Right now I have it sitting on a float charger to see if that changes anything. I am, however, beginning to suspect the ignition switch. I would think that with a low battery or bad solenoid it would still give some audible clicks or groans. Also, a failing ignition switch might explain the engine unexpectedly shutting off this morning after it started.

Is there a convenient way to apply voltage directly to the starter solenoid post? That would yield valuable information. There is not a lot of room to reach down to the starter itself on an SL600.

By the way, is this the correct part for the electrical part of the ignition switch? It;s confusing because it's labeled "ignition lock shield"

Part #: 210-460-12-97-MBZ

http://www.pelicanparts.com/cgi-bin/...ion%2520switch

(Still waiting to get the WIS/EPC disc I ordered)

miike

You need a real charger. A float charger will never bring back a seriously discharged battery. I've tried it and had the battery shop tell me it needs real amperage to put on a proper charge. Even if it shows 13 volts after the float charge, that voltage can fall flat on its face when a load is put on the battery.

So, get a proper charge on that battery. Then using your multimeter and a jumper wire with alligator clips, test the starter. If there is good voltage to the solenoid and bad voltage to the starter motor, the solenoid could be bad, or the wiring from the battery could be bad. If the solenoid doesn't have good voltage, it's the battery or battery wiring/grounds etc.

If the battery is real dead, it won't even click in my SL.

johndtitus

I would think that if the battery were completely dead, this would not be an intermittent problem, remember, my symptoms were dead silence (no clicking) then after a few more tries the typical fast cranking of the V12 starter. I can't imagine that being consistent with a flat battery.

miike

I agree but since you are trying to determine the condition of the starter motor and solenoid, you should do it with a strong battery. Misleading info because of a bad battery could cause you weeks in delay of finding the problem. If your car was at a shop and having trouble starting, the first thing they would do is put it on charge before testing the starter.

Also, if it's the ignition you want the battery to be strong when hunting down the bad connection or switch.

bobterry99

There is a starter relay -- K38/3. Unfortunately, it is located in the center of the dash on top of the transmission tunnel and not very accessible. Fuse #10 also figures into starter operation.

Due to the difficulty of reaching K38/3 I believe I would first check that fuse #10 is making good contact. If it is, I would then check for voltage on the starter solenoid.

johndtitus

Yes, I have read about the infamous K38 starter lockout relay. It doesn't seem too inaccessible once you have the radio, ventilation tubes and upper compartment out :-)

According to my fuse chart (MY1999) #10 relay is for the stop lights, dome light, cruise control and the instrument cluster. Does "instrument cluster" include power to the ignition switch?

johndtitus

OK, it is definitely temperature related and I am ruling out the battery. It was on a 10 amp charger until the charger said the battery was charged, then it was on the battery tender overnight. This morning, 60 degrees F the car would not start. Same symptoms. The battery showed 12.5 volts with the key off, about 12.3 with the key on and 12.2 when I tried to start. No clicks or other noise. That tells me nothing is trying to draw any significant current. Tomorrow is Saturday, so I will be able to get under the car to test the starter....

robertstjo

The K38 relay in my 2002 SL600 is in the relay box just aft of the fuse box. I couldn't tell you when the design change took place but it's very easy to access. You might give it a look before tearing into the dash.

miike

Yes it sounds like the ignition isn't sending power to the starter. Typically you would expect a volt or two drop if the starter was getting what it needs to crank. I'd chase those relays and ignition switch.

bobterry99

Great to know. No doubt the OP's K38 is also located there.

No.

johndtitus

More data. It is definitely temperature related. When the car didn't start, I left it in the driveway, not on the battery charger anymore. When I got home from work (70 degrees F, cabin temperature about 75) the car started right up.

johndtitus

I did indeed find the K38 relay in the relay bank on the drivers side behind the fuses. From the research I did elsewhere, this appears to be the configuration for MY 1996 and later. Having no chart to go by, I determined by process of elimination that K38 was the green Hella cube second closest to the front. By the way, it is important to realize that the green Hella cube is not a standard DIN SPDT relay, but is in fact an SPST relay. The 87a terminal of the K38 is shorted to ground in the relay bank and the relay has an internal diode. Presumably this arrangement is to avoid arcing of the relay contacts from the flyback of the starter solenoid.

Anyway, I determined that it was not the K38 relay or the starter itself. When it is cold and I would otherwise get a no-crank condition, putting a different relay in the relay box has no effect, but putting a test relay (with contacts permanently closed) causes the starter to crank right away. It also is not the ignition switch itself. I replaced it with a new switch last week.

That leaves the Neutral Safety Switch (which I had previously ruled out since moving the gear shift lever had no effect) and what else?

robertstjo

Very interesting. I had exactly the same symptoms - cold, start every time - hot, intermittent no start. Replacing the K38 solved the problem. I also found out while in to no start condition I could get it to start by just holding the key in the start position for 2 to 5 seconds and it would start.

johndtitus

Actually, you had the opposite problem. My problem is warm/hot starts every time. When cold, intermittent no crank.....

robertstjo

OK, my bad. I should probably learn to read more carefully.

bobterry99

There is no neutral-safety switch. The shifter signals the selected position on the CAN communication network.

If I am not mistaken when you turn the ignition key to position 3 a hard-wired signal to the right-bank engine management computer (N3/12) tells it to start the engine. If the shifter is in park or neutral and the Drive Authorization (DAS) module has signaled to the CAN that the ignition key is correct, then N3/12 grounds K38 to actuate the starter.

Things to check:

• K38 coil is not open-circuit
• All fuses are okay
• With key on 12-volts is at (+) side of K38 coil.

If those checks are okay, then I would presume that N3/12 is defective or is not getting the statuses it needs from the shifter and DAS. To evaluate those possibilities I believe you need a Star Diagnosis computer or its equivalent.

johndtitus

K38 coil is not open circuit. I can hear it click if I put 12V across 85-86.
Have not checked all fuses, but the problem only occurs when temperature is below 55F. I suppose it is possible, but unlikely, that fuse heals itself above 55F.
When the no-crank condition occurs, there is +12V power to terminals 30 and 85 when the ignition is on.
Although not a neutral safety switch per se, is it possible the shift position sensor is failing?
I thought if DAS was intervening I would get a "start err" message on the instrument panel?
I just got my Carsoft 7.4 multiplexor, but the software disc that came with it was blank. I am working with the vendor through Amazon to get it working.

johndtitus

If the shift position sensor is a rheostat, does anyone know what the resistance values are for neutral and park? Or, is the reference voltage 5V (or some other value) and what are the voltage values for neutral and park?

bobterry99

I believe this is correct, but I don't think you get any indication for the shifter being out of park or neutral. I suggest you verify that by trying to start the engine with the selector in reverse or a forward gear.

Internally I believe it uses optoelectronics. The output signal is a CAN message. I suppose you could look at the messaging traffic on the network and discern the status being output by the shifter but would not bother because of the ease and simplicity of using a diagnostic computer.

johndtitus

OK, so I got Xentry working enough to poll the car. The quick test yielded a lot of -f- results (does that mean fault?). There were several intermittent CAN communication faults ESP - C1022 Fault in CAN communication with control unit N3/10 (ME-SFI [ME]
control unit).
Instrument cluster - B1040 Fault in CAN communication with control unit MR engine control.
Transmission control - 135 CAN communication with the engine system is sporadically disturbed.

The one that got my attention, however, was this one:

132 CAN communication with engine system is sporadically disturbed or
engine temperature is sporadically implausible.

This seems to be consistent my observation that the no-crank condition is temperature related. Will an implausibly low engine temperature result in a no-start authorization? Are we talking about the Coolant Temperature Sensor(s) or some other sensor?

So far, I can't get any information from the ECUs. When I try, I get the message "DAS automatically selects HHT-WIN" Then I get an error (in German). "Not an HHT Application"