Starter delay in cold weather.........???

[MarkM]

This morning, rather than crawl under the car and put a clamp on the wire from the ignition switch to the starter solenoid to test for delay in voltage to the solenoid, i did another test that essentially accomplishes the same thing....

I took my momentary-on push button switch with two wire leads with alligator clamps (used for jogging the engine when adjusting valve clearances) and attached it to the two connectors in the connection block on the passenger side front wheel hump (the little black plastic box with the cover held shut by two tabs)...same routine for jogging engine during valve adjustments. By doing this, you can close the circuit to the solenoid and bypass the ignition switch (the ignition switch does need to be in the "run" position). It was in the 20's F this morning. When i started the car with the ignition switch, there was the expected 1 to 2 second delay. But when I started with the push button switch (after standard glow plug cycle), the car started immediately upon pushing the button...no delay whatsoever. Then I repeated with ignition switch again and it had the delay again. I repeated the procedure in both park and neutral with no difference, thus eliminating the neutral safety switch. So the culprit is the ignition switch, or possibly a short or corrosion in the wire harness to the ig. switch. (Looking at the electrical diagram for the starter system, there is no other possibility).

THEREFORE: The mysterious delay problem is without a doubt one of the following:

1. Crud buildup on the external connectors (pins and sockets) of the electric portion of the ignition switch (diagnose by visual examination)

2) Deteriorated insulation/corrosion in the wire harness to the ig. switch (diagnose by checking continuity/resistance of the appropriate wire from the ignition switch harness connector to the connection block on the wheel hump),

3) Internal problem in the electric portion of the ignition switch, (diagnosis based on elimination of the two possibilities above)

I will check it out over the next couple of days, and take pics.

Regards,

Mark

[kerry]

Here's something I hadn't thought of before. I changed keys between the occurence of the problem and the solution. My old key had the plastic end that detached from the metal so I had an all metal key made. Perhaps this is what solved my problem.

[JimmyL]

Excellent diagnosing Mark. I will be riding your coat tails to the finish!
Do these wheel-hump terminal blocks have a cover that goes over them? Never seen one with a cover.
The possibility of not having to replace the starter has certainly brightened my outlook the wagon.
I'm hopeful, and awaiting your results.
Thanks so much!
Jimmy

Originally Posted by JimmyL

Do these wheel-hump terminal blocks have a cover that goes over them? Never seen one with a cover.

Mine both have covers.

[MarkM]

I previously described the sympton as a delay in actuation of the starter after you turn the key....he colder the weather, the longer the delay. Even in mild weather, there is a slight but noticable half second delay, but in very cold weather, the delay is sometimes as much as 10 seconds!! The symptom is usually thought to be a faulty starter solenoid....it behaves as if the solenoid is gummed up, and the gum gets thicker with cold weather.

In the last post, I described how my car had this symptom and I proved that the starter solenoid was NOT THE CAUSE..see that post for further discussion.

The neutral safety switch is not the cause, verified by "jumping" the contacts to the leads from that switch, completely bypassing that part of the starting circuit, and the car still had the starter delay.

All indications were that the cause was the electric portion of the starter switch. I just replaced that switch on my car tonight, and voila, absolutely no hint of a delay!!! Solved! Done!

I took apart the old switch, and inside there was a lot of heavy oil lube...not white grease or similar non flowable grease, but messy heavy flowable oil. I don't think the increase in viscosity of this oil with cold weather is the cause, though, because there is no freely sliding switch component that would explain the symptom. What I DID see inside the switch was that two of the several contacts (relay type contacts) were severely carbonized, and one of those carbonized contacts had a lot of oil on it. The remaining contacts were nice and clean.

I don't have enough technical knowledge about current flow through carbonized contacts to explain why variation in temperature would cause delay in current flow, but I suspect that the symptoms (delay start) have something to do with attraction of moisture to the carbon, freezing of the moisture in cold weather, high resistance of the contact point, insufficient current flow to engage starter solenoid when first contact is made, but after the contact heats up, current flows.....maybe someone else could explain this phenomenon.

The bottom line is that the common delay start symptom is absolutely, positively caused by internal malfunction of this switch....seems to be bad contacts. This switch is easily opened by pressing the three tabs and sliding the internals from the metal case. It would be very easy, I believe, to repair the switch by cleaning out the oil, cleaning the contacts, re-lube with better grease, and reasemble. However, you can get a new switch for about $30 through Phil with Fast Lane. My own experience is that once contacts are severely carbonized, even when you clean the contacts, the carbon problem reoccurs quickly. Therefore, given the price, I think the new switch is the better option.

Note....in order to gain access to replace the electric switch, it is best to remove the entire ignition lock from the car with the switch attached, and then replace the switch. This procedure is really very simple and easy (you do need to remove the dash cluster and the footwell trim panel)....easier than trying to get your hands into the dash an unscrew the three screws that attach the electric switch to the ignition lock housing.

Procedure for removal of the ignition lock is described in detail in other strings on this site...note that Diesel Giants writeup says that you need to unbolt and lower the dash as you extract the ignition lock in order to provide enough clearance....this is NOT the case...you just twist the lock housing as you extract it and it comes out no sweat.

Another note, you can only remove the harness plug from the back of the switch if the ig. key is in position 1...there is a little gizmo that holds the plug in there when the key is turned to OFF.

I can post a pdf of the Mercedes manual procedure for ignition lock removal if anyone would like,

Regards,

Mark

[kerry]

Well done. A longstanding mystery solved. Any speculation on why the problem magically disappeared on my 85 TD?

[pawoSD]

Out of both of our cars, only the '83 has had a "turn the key with no sign of starting" issue. It was the solenoid on the starter...and it was when the engine was hot! Right off the freeway, went into the bank for 5 mins...came out, turn key, no go. Hit it with a wrench from the trunk... tried again, voila, started right up. Has never happened again, hot or cold. Weird.

[MarkM]

Other than that, I can only suggest that since the delay start symptom is not the result of a specific, discreet, irreversable failure (e.g. something breaks)., but instead due the gradual buildup of carbon, and several related factors: number of starts, age of vehicle, presence of cold weather, humidity, and so forth, there will likely be variations in the occurance of "clinical symptoms". Perhaps in your car, you had a little carbon buildup only to be reversed when the contact arced and blew out some of the carbon (self cleaned).

Mark

[compress ignite]

Kerry,

I've had and old, wisened (and decrepit) starter "remaner" tell and show me
on the '84 SD's starter the incredible carbon buildup over 20 years of use.
Then he blew out the components (and bead blasted one or two) , reassembled
and said,"No new parts...Well not for another 200k miles".
Heat affects all the built up carbon , which acts as an insulator.

So, The inverse is also correct.
Cold "Shrinks" the heavily carbonized contacts away from each other,just
enough to reduce electrical transmission across the gap between the
contacts(until they "Warm Up" enough) to close the gap.

[JimmyL]

WOW!! I finally know what is wrong with my wagon. My symptoms couldn't have been more exactly like yours. Hmmmmm
I certainly wish you could have snapped some pics of the whole process, but just the info itself is such a huge help, and it saved me from replacing my starter.
So, is this electrical portion of the switch the same on a 240 as on a 300? I can swap the one from Scar to the wagon if they are the same. I need to look up the procedure for removing the whole assembly I guess.
Thanks again, and a job very well done!

[MarkM]

Originally Posted by pawoSD

Out of both of our cars, only the '83 has had a "turn the key with no sign of starting" issue. It was the solenoid on the starter...and it was when the engine was hot! Right off the freeway, went into the bank for 5 mins...came out, turn key, no go. Hit it with a wrench from the trunk... tried again, voila, started right up. Has never happened again, hot or cold. Weird.

Absolutely!!!! The most common cause of a delayed start after turning the ignition is a faulty starter solenoid. Hey, I pulled the starter and replaced the solenoid! I assumed that would fix the problem! The perplexing thing is that there is not much difference in symptoms to distinguish an ignition switch fault from a starter solenoid fault. However, when the starter solenoid is at fault, you often get some kind of noise from the starter (click, flutter, etc.). But with the ignition switch problem, after you turn the key there is NO sound anywhere, then all of a sudden, boom, the car starts. The other kind of unique characteristic to the ignition switch problem is the very clear correlation between longer start delay and colder weather...I lived with the several-second delay all last winter, then when weather got warm, the car was almost normal...only a split second (but noticable) delay all spring, summer and fall...and the car always starts. Then with the onset of colder weather again, the delay is more pronounced again. A bad starter solenoid will not likely correlate with cold weather that way.

Another distinguishing characteristic is that it seems the faulty ignition switch delay problem can persist for many months or years, and never result in a no start condition. On the contrary, when a starter solenoid starts to "act up" you can be pretty sure that you will soon (days or weeks at the most) have a failure to start condition.

Bottom line is that it is VERY EASY to distinguish between a faulty starter solenoid and a faulty ignition switch by a TEST: if your car exhibits the delay problem, turn the ignition to the "run" position, then "jump" the contacts in the connecting block on the passenger side wheel hump forward of the battery (jump one of the big screws to the small screw)....if the delay occurs, you know its not the ignition switch because you bypassed it...thus, the problem is likely the starter. If there is no delay when you jump the contacts, but there is a delay when you start with the ignition switch, then you know you have the ignition switch problem.

Mark

[JimmyL]

I had almost forgot about the starter delay as we haven't had any cold weather yet. Went to go somewhere in the wagon today and had my 2 second starter delay again.
I really need to replace the electrical portion of my switch this winter. Just not looking forward to dash removal again.....
Mark, I am still appreciative of your fine investigative work last winter. A job truly well done, and another example of helpful folks on here.....
I'm guessing this is the part?

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=27R1AUDQC28H16YA6N&year=1985&make=MB&model=300-TDT-001&category=M&part=Ignition+Switch

[kerry]

Just leave it alone and use those 2 seconds for a silent meditation on the wonders provided by the harnessing of electricity. Had you been born 50,000yrs ago you would have been denied the experience. Relish it while you can.

[compress ignite]

JimmyL,
That's the electrical portion of the ignition switch that you want!

[Carrameow]

Is this the switch--I need it!

Originally Posted by JimmyL

I had almost forgot about the starter delay as we haven't had any cold weather yet. Went to go somewhere in the wagon today and had my 2 second starter delay again.
I really need to replace the electrical portion of my switch this winter. Just not looking forward to dash removal again.....
Mark, I am still appreciative of your fine investigative work last winter. A job truly well done, and another example of helpful folks on here.....
I'm guessing this is the part?

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=27R1AUDQC28H16YA6N&year=1985&make=MB&model=300-TDT-001&category=M&part=Ignition+Switch