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C126 500SEC shutting off when shifting to D/R.

2K views 15 replies 5 participants last post by  speed9644 
#1 · (Edited)
My friend has recently bought a nice, low mileage C126 500SEC, that was originally sold in Italy and then sold to Germany and then i bought it :smile

So, today he started the car, started perfectly, idled as it should 750+- 50 rpms, however, he said as soon i put it in D/R the engine shuts off immediately, I need to mention too that the old plugs were very black looking, like it is running rich on fuel.
similar to this plug on the right:


And also, a fuel leak has occured since this problem started. it is leaking from the back fuel pump, where the fuel line connects to it, the one that is close to the wheel, i have marked it in the red circle, it is drippig one drop in two seconds, only when the engine is running, i tried to turn ignition on and off a couple of times to let the fuel pump run, it ran but didn't see it leak. However, it will start to leak a couple seconds after i start the engine. Here is a picture:



I took a video showing what is exactly happening when I shift to Drive/Reverse:

Any idea what is wrong ? what should i start checking ? the local mechanic also didn't know what is the problem...

Any help is very appreciated
Thanks :grin
 
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#2 ·
If this is an early 126, then the car has 2 ECU's the main one and the idle ECU. when in D or R or if you turn the aircon on the RPM should increase by 50 RPM. There is a switch on the throttle body that selects the idle relay, the can go out of adjustment or fail, or the idle ECU could be at fault, its placed in the car in front of the gear shift under the dash.
 
#4 ·
It would help to add the car and year to your profile. Yours is a GenII. On my Gen I the rubber/metal fuel line had to be replaced from MB ($$$).
Without repair history of the car, you need to establish some sort of base line to work from / test components in the fuel delivery system incl vacuum leaks.
If one or more of the spark plugs look wet, either the injectors are bad, or your fuel distributor is shot and dumping fuel (the latter is $$).
Search, and read up on threads in the forum archive.
 

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#5 ·
It's actually my friends car, that's why i didn't add it before to my profile.

It has the history service book, he told me that, all the ignition system is new, vacuum lines have been checked and all is connected as it should be, and there's no leaks in the joints / connections.

Haven't asked him about the fuel distributor, if im not wrong there's a certain amount of fuel that should be delivered to each injector, and all of them should be similar... Does anyone know what is the exact amount of fuel per x seconds ? I have checked the service manual from StarTek, but didn't find... And if there's some info on the amount of fuel that should be delivered back to the tank that would help me too....

Sent from my Redmi Note 3 using Tapatalk
 
#11 ·
Problem is still existing...

Symptoms:
-When engine is cold, idles good, as soon as i shift into D, it will misfire and shake but doesn't stall.
-When engine is on running tempreature, it will stall as soon as i shift in Drive.

What have been tried ?
1.Replaced EHA with a brand new Bosch unit, old one was leaking.
2.Replaced fuel pump with a brand new one.
3.Checked the ignition system, all good.

I'm thinking that it is the fuel pressure regulator, does anyone have a guide on how to check the fuel pressure regulator ?
 
#12 ·
Update, brought the car to another mechanic, he checked eveythings, nothing... everything is as supposed to be and still can't tell whats the culprit. Untill he removed the vacuum line that connects to the EZL ignition module, and blocked it. Can runs as it should be. not stalling anymore... now my question is how does that vacuum line affect the system and what is the problem ? the EZL ? a Vacuum diagram would help me a lot...
 
#13 ·
In theory now it's missing some enhanced features but should be fine to drive. I've disconnected that line to the EZL to reduce a high idle temporarily & didn't notice any difference in performance or economy.

I'm not sure what the problem with yours might be but there might be a vacuum diagram in the DIY sticky section - don't know if the right one for your year is there, I'm not at the PC to search.
 
#14 ·
In theory now it's missing some enhanced features but should be fine to drive. I've disconnected that line to the EZL to reduce a high idle temporarily
The ELZ controls spark, right? So, the vacuum line would be for the vacuum spark advance, right? If so, highway mileage should suffer as it'll be timed for full throttle operation all the time.
 
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