What makes a 300SDL randomly shut off? - Page 2 - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #16 01-26-2009, 10:11 AM

This is getting really strange. Try removing the OVP relay when the car is running. I don't think the electronic idle control will send the engine to 0 RPMs if it is not working. I THINK there is still a screw adjustment to set a base idle. I could be wrong in this and I don't have the SDL near me for the week so I can't check it myself. Hving it shut off randomly, with the vacuum system disconnected is something I have no experience with. I can ask my MB guy to see if he has any ideas.

redassag00 · #17 01-26-2009, 10:15 AM

I had a W124 OM603 do this but it turns out it was leaky O-Rings in the fuel heater thingy, but you're saying theres no fuel leak.

Hmmm.

Jeremy5848 · #18 01-26-2009, 12:16 PM

Quote:

Originally Posted by LUVMBDiesels

This is getting really strange. Try removing the OVP relay when the car is running. I don't think the electronic idle control will send the engine to 0 RPMs if it is not working. I THINK there is still a screw adjustment to set a base idle. . .

I agree, at least as regards the OM603 engine in the W124 chassis (my car). The 300SDL should be the same. There is a base idle speed (about 500 RPM) set by a screw in the IP and the ELR holds the idle a bit above that (about 650 RPM).

This is sounding like there could be more than one cause. If there was something wrong with the mechanical idle and then ELR failed . . . this is something you can test for, as the hypothetical mechanical idle failure should be there all the time. To test: With the engine warmed up and idling normally, remove the 2-pin plug from the ELR controller at the rear of the IP. The idle should slow to about 500 RPM. If the engine immediately dies then the mechanical idle is not working.

Jeremy

bustedbenz · #19 01-27-2009, 04:16 PM

Quote:

Originally Posted by Jeremy5848

I agree, at least as regards the OM603 engine in the W124 chassis (my car). The 300SDL should be the same. There is a base idle speed (about 500 RPM) set by a screw in the IP and the ELR holds the idle a bit above that (about 650 RPM).

This is sounding like there could be more than one cause. If there was something wrong with the mechanical idle and then ELR failed . . . this is something you can test for, as the hypothetical mechanical idle failure should be there all the time. To test: With the engine warmed up and idling normally, remove the 2-pin plug from the ELR controller at the rear of the IP. The idle should slow to about 500 RPM. If the engine immediately dies then the mechanical idle is not working.

Jeremy

A question about this test: I was assuming that the ELR lost power with the rest of the car when the ignition switch goes off. Although the tachometer goes off too, when I was shutting the ignition off with the shutoff disconnected and then getting out to kill the engine, it was DEFINITELY idling at what sounded like about 500 - very reliably. I'll pull the plug to check but I'm pretty sure the ELR was shutting itself down anyway with the key.

Ether · #20 06-07-2009, 05:21 PM

Bustedbenz,

Wondering if there was ever a resolution to this problem? I have been experiencing a similar issue with my SDL.

In my case the car has stopped a couple of times in stop and go traffic after accelerating and then having to quickly come to a stop. Often, the idle will dive low briefly before recovering but has only completely stopped on me on 2 occasions. I have been able to re-start the car both times with no problem.

I should also note that the idle will sometimes settle in at around 1k returning to the typical 650 after the next acceleration/idle cycle. This doesn't occur often but it has done it a few times.

JohnS · #21 06-08-2009, 10:20 AM

Hi, I don't have a complete solution, but I've been having the same problem and I've traced it to the voltage stabilizer (terminology may be wrong). It is the plug in unit next to the klima relay, it has a fuse in its top underneath a little plastic cover. Try wiggling it while the engine is running, if it smooths right out and comes up to speed, you've got it. I have tried cleaning the pins on the unit to no avail, and it only happens intermittently, but every time I wiggle the device it corrects the problem. In my case, the tach drops to zero at the same time the idle problem arises and comes back on when I touch the unit.

John

TX76513 · #22 06-08-2009, 10:25 AM

My SDL starting doing this about a month before my vacuum pump went south on me. Never has done it since pump was replaced. Un-scientifically I attributed it to a weak vacuum pump in the failure stage. I suppose it was able to keep up at higher rpms but not at idle.

ohiomike · #23 06-08-2009, 10:29 AM

No one has mentioned that this acts like a fuel pump is intermittent. They act like this when they are going bad.

Ether · #24 06-08-2009, 10:49 AM

Quote:

Originally Posted by TX76513

My SDL starting doing this about a month before my vacuum pump went south on me. Never has done it since pump was replaced. Un-scientifically I attributed it to a weak vacuum pump in the failure stage. I suppose it was able to keep up at higher rpms but not at idle.

My vac pump seems to be fine. I checked it last week and I'm seeing 23" Hg at idle.

bustedbenz · #25 06-08-2009, 01:27 PM

I haven't officially resolved the problem yet, but it's also been several months since I had an episode, which further strengthens one of my previous observations, that the problem is mainly an issue on the hottest days under the hottest conditions. As we get into the worst part of the summer I'll keep an eye on it.

One piece of advice I haven't tried yet from the previous part of this thread was unplugging the ELR from the "back of the injector pump" to see how the car idles without it (to check the mechanical idle). Anybody have a pic or a description of which plug it is? Mine has at least two or three things plugged into it at various places.