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1987 560SL
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46 Posts
Discussion Starter #1
I've been loving my 560 — just drove it out from NY to Detroit — but unfortunately I can't trace an intermittent stalling issue.

Sometimes it happens 10 minutes after a cold start, sometimes it doesn't happen at all, and a few times it's tried to stall on me on the highway. The tach jumps around and then quickly stalls out. When I first got the car it happened very frequently (every drive), and my shop checked and replaced some leaky fuel injectors along with a few other things, and the stalling became much less frequent -- but still there.

Lots of reading on similar problems has pointed to the EGR valve. I tested to see if it held vacuum with a handheld pump - and it did not - so I'm going to replace it.
However, I can't find the right part anywhere (autohausaz, peachparts, rockauto, etc)...

Has anybody had luck finding and replacing this part? Or resolving a similar issue?

Cheers
 

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1987 560SL
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46 Posts
Discussion Starter #3
Might be the fuel pump relay.
I'll look into some bench testing on the relay. But since the EGR is leaking vacuum I'll start with that (y) — I just need to source the part.

Is it possible to bypass the EGR entirely by plugging the vacuum line and seeing if the stalling goes away?
 

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1984 380SL
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2,366 Posts
I'll look into some bench testing on the relay. But since the EGR is leaking vacuum I'll start with that (y) — I just need to source the part.

Is it possible to bypass the EGR entirely by plugging the vacuum line and seeing if the stalling goes away?
Yup plug away.
 

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1986 560SL
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51 Posts
A jumping tach more likely means an ignition system fault. I really doubt the EGR is going to cause that, especially as the EGR valve (on most cars IMHO) opens to allow exhaust into the intake manifold, during cruise. I'd suspect a contaminated electrical connection somewhere.
 

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1987 560SL
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46 Posts
Discussion Starter #6
A jumping tach more likely means an ignition system fault. I really doubt the EGR is going to cause that, especially as the EGR valve (on most cars IMHO) opens to allow exhaust into the intake manifold, during cruise. I'd suspect a contaminated electrical connection somewhere.
Somebody brought up that point before -- i'll do my homework on common ignition system faults
 

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1987 560SL
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46 Posts
Discussion Starter #7
UPDATE:
Replaced ignition coil with OEM Bosch because I found one on sale for only $30 (so why not). Hasn't stalled yet but only driven 15 minutes.

Inspected distributor cap and rotor, looks used but nothing crazy -- replacing today with OEM Bosch cap and rotor and will update.

EGR valve is not holding vacuum. When I removed and plugged the vacuum line she still ran rough and idled. I'd still like to replace this but damn they're expensive even used on eBay. Considering taking it off just to clean it, but if it's not holding vacuum does that mean a rubber seal/diaphragm is busted?

Other culprits -> Ignition: EZL (don't know what an EZL is, need to do my homework on that), Engine control module?
Fuel: Fuel pump relay?

note: the car always starts right back up after stalling. It usually happens at idle or accelerating out of a stop. On rare occasions it tries to stall at highway speeds and the tach jumps down but immediately recovers.

Cheers
2606257
 

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1987 560SL
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46 Posts
Discussion Starter #8
UPDATE:

Still stalled after replacing the coil.

Has not stalled after replacing cap and rotor, and seems to be idling smoother. It has only been 2 days, so I'll be watching.

Unrelated pics -- but can anyone tell me what these disconnected wires are?
1. 2 disconnected plugs going up into the hood -- my wiper fluid works fine
2. black/yellow wire on passenger side by the firewall
3. driver side firewall -- looks cut or broken.


2606720

2606721

2606722
 

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Premium Member
560SL 1986 244k miles astral grey / black
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404 Posts
First photo: electricity supply for the heating element in the window washers.
Second photo: see page 23 of the attached pdf
Third photo: don't know sorry

B
 

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Registered
1987 560SL
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46 Posts
Discussion Starter #10
Thanks Bauk,

Update 7 days later: Car is idling much smoother for the most part, but i have experienced the same stalling issue with the new coil + cap/rotor. It is hard to recreate but seems to happen after the car is warmed up, and when I'm driving very slowly. Tach usually jumps around, idle surges like it's catching itself, then either smoothes out or dies. Always starts right back up.
 

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Outstanding Contributor
1988 300CE
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1,489 Posts
jreina, I‘m actually not active in this R107 forum anymore, but I just paid a quick visit to it and seeing no one in your thread after one and a half months suggesting to check what should have been checked first in your case … (before wasting any time & money on unnecessary part replacements !) … I thought I should.

First of all, check the CPS (Crankshaft Position Sensor) !

If
the CPS is in order, check the TD-signal, which is generated by the EZL-ECU (based on input from the CPS), and its wires !

BTW jreina, “EZL“ is not a part, despite the fact that at Benzworld most people, if not all, think it is. “EZL“ is an abbreviation of the name of the whole ignition system of your car. It stands for “Elektronische Zündanlage mit Zündlinienverstellung“, which in English means “electronic ignition system with variable characteristics“. ;)

I‘m currently quite busy with other things, but other forum members should now be able to show you in detail how to check these (above mentioned) things up from this point.

:)

H.D.
 

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1987 560SL
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46 Posts
Discussion Starter #12
jreina, I‘m actually not active in this R107 forum anymore, but I just paid a quick visit to it and seeing no one in your thread after one and a half months suggesting to check what should have been checked first in your case … (before wasting any time & money on unnecessary part replacements !) … I thought I should.

First of all, check the CPS (Crankshaft Position Sensor) !

If
the CPS is in order, check the TD-signal, which is generated by the EZL-ECU (based on input from the CPS), and its wires !

BTW jreina, “EZL“ is not a part, despite the fact that at Benzworld most people, if not all, think it is. “EZL“ is an abbreviation of the name of the whole ignition system of your car. It stands for “Elektronische Zündanlage mit Zündlinienverstellung“, which in English means “electronic ignition system with variable characteristics“. ;)

I‘m currently quite busy with other things, but other forum members should now be able to show you in detail how to check these (above mentioned) things up from this point.

:)

H.D.
I really appreciate your reply. CPS is something I would love to look into but it's difficult to bench test since the problem is intermittent. Not to mention I can't find a good working CPS for sale anywhere.

1. A few days ago I plugged the vacuum line to the EGR to effectively delete it from the system. The car was actually running great over the weekend (which may not mean anything, as the stalling had always been very intermittent), but this morning was in complete limp mode to get back home. Could the limp mode have been initiated by the EGR delete?

2. Usually the car starts right back up with almost no cranking, but not this morning. It would crank ~8 seconds before catching and starting. When cranking, I noticed the tach barely moves (but does vibrate a bit). How should the tach move with a proper startup? Could little or no movement point to the CPS?

Video of my tach movement when cranking
 

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Outstanding Contributor
1988 300CE
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1,489 Posts
Could little or no movement point to the CPS?
That points to what I mentioned in my last post, namely to a problem with the TD-signal, which is generated by the EZL-ECU based on input from the CPS.

So I repeat the suggestion I gave you in my last post:
First of all, check the CPS (Crankshaft Position Sensor) !
If
the CPS is in order, check the TD-signal, which is generated by the EZL-ECU (based on input from the CPS), and its wires !

I‘m still very busy with other things and, as I said in my last post, actually not active in this R107 forum anymore. So please let other forum members show you in detail how to check these three things (CPS, TD-signal & TD-signal wires).

H.D.
 

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Registered
1988 R107 560SL
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66 Posts
This sound like hair line cracks in the fuel pump relay. My 87 and 88 did this too. After a new fuel pump relay and a new OVP relay (why not, I’m already in the pass side) the Problem never showed up again.
rudiger
 

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1987 560SL
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46 Posts
Discussion Starter #15
Just got a new (used) EGR valve. When given vacuum the valve very slowly loses vacuum -- while the one on my car now very quickly loses vacuum.

Are these things supposed to completely 100% hold vacuum or is a very slow leak normal/acceptable?

And as much as I'd love to just throw in a new fuel pump relay I hate just throwing money at the car to see what works.
 

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1987 560SL
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46 Posts
Discussion Starter #17
Still working on this one. Is anybody able to deduce anything from these two videos?

1. One of the stalls, quick surge in idle before it drops to zero. This is intermittent and hard to reproduce. Usually happens at full operating temp, but not every ride.

2. Difficult to restart after a stall (this is very rare, it usually starts back up immediately) -- it looks like the tach isn't moving on the cranks, if that's indicative of anything.
 

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1987 560SL
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46 Posts
Discussion Starter #18
Closing the loop — replaced the EZL with a used one and haven't stalled in over a month. Problem solved :)
Thanks to all who helped out.
 

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Outstanding Contributor
1988 300CE
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1,489 Posts
Closing the loop — replaced the EZL with a used one and haven't stalled in over a month. ...
You could‘ve closed this loop more than 4 months ago already ;) … if you would‘ve tested what I recommended to test in post 11 (and repeated in post 13) … which could‘ve been done within less than 5 minutes.

Thanks for the feedback!

H.D.
 
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