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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,151 Posts
The switch wears out, especially if the key is on a ring with other keys which accelerates the wear due to weight
 

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Premium Member
1993 300CE Cabriolet (mine) ; 1994 E320 Wagon (wife's) ; 1990 Benz 300E 2.6 (son's)
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7,031 Posts
the ignition switch is not a simple switch on these cars, it has 5-6 different rings, each with its own contacts. its possible for some of it to work while other outputs are erratic or fail completely
 

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W124
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4,898 Posts
Fuel pumps and filter have been replaced. Once I replaced the fuel pressure regulator the noise was gone.


The tachometer works fine and moves for the short time that the engine is running. And I already posted that I checked for spark and it all checked out.
Okay, I see in post #34 that you verified spark to each spark plug. Something to consider though is that the spark needs to be confirmed at the time the engine dies, not when you are trying to restart it. If you've already done that okay that's fine because Floobydust raised a good point about three required conditions to KEEP spark working.

Use one of those "neon" type spark plug testers that fit in line with the existing plug wires. You could put it on one of the coil wires. That way you can at least watch one coil and see if the spark goes away when the engine dies. Another method would be to put a timing light on a coil wire and do the same thing. A third method would be to spray starting fluid into the throttle body when the engine starts to die and see if you can keep the engine running on starting fluid. If you can, then you know for certain you don't have a spark issue that is causing the dying.
 

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'97 e320, '02 e430, '08 s550
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34 Posts
So my 94 E420 dies instantly right after starting. I thought it was the fuel pumps because I had seen my fuel pump leaking. So I replaced both pumps and filter. Primed the system and tried starting and the same thing keeps happening. The ASR light stays on and the car dies. Need some input on what the issues could be.
Try replacing the crankshaft position sensor or the camshat position sensor, can recall which one goes bad.
 

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'92 W124 230E Auto
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167 Posts
I'm not familiar with the E420, but on 'lesser' W124 models this usually points to low fuel pressure (possibly due to leaking injectors); enough fuel is delivered via the cold start injector/dribbling injectors to start the motor, but not enough to keep it running. I had a similar problem on my 230E. Have you done a fuel pressure test (bridge the fuel pump relay to keep the pump running)?
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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I'm not familiar with the E420, but on 'lesser' W124 models this usually points to low fuel pressure (possibly due to leaking injectors); enough fuel is delivered via the cold start injector/dribbling injectors to start the motor, but not enough to keep it running. I had a similar problem on my 230E. Have you done a fuel pressure test (bridge the fuel pump relay to keep the pump running)?
Completely different system. The E420 has electronic injection, while your 230E has mechanical injection. There is no cold start injector or any component that is shared.
 

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W124
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4,898 Posts
Of course, in addition to all the suggestions to date, pulling codes from the modules wouldn't be wasted time at this point.
 

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1987 560 SL, 1990 300E 4Matic
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465 Posts
Yes, a code, or codes may help to narrow down possibilities that have been suggested, and hopefully give you a more direct pathway toward a solution.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,614 Posts
Is there not an easy way to check to see if the ignition control module/ckt has power in the resting state of the ignition switch? I would assume that would be a low hanging fruit.
 

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2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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If it were my car, I would just use a little starting spray to differentiate between a loss of fuel or loss of spark. When the engine starts to die, spray (or have an assistant spray) a little in the intake and see if it picks up again. If it does, then you have a loss of fuel; if not, you have a loss of spark. Go from there. I have used this test on many engines in the past and it usually tells me what I need to know.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,614 Posts
Do we believe that the fuel system pressure drops in a split second after the car starts? Sounds unlikely to me.
Now I believe these to be electronic fuel injection (correct me if I'm wrong) so perhaps the signals to "inject" may disappear after he stops cranking.

Most likely though the circuits that enable fuel injectors and the ignition are the one and the same (or affect each other).
After all why would anyone design a system that is injecting without spark or sparking without injecting?

Let me know if I'm way off base here....

- Cheers!
 

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Discussion Starter #55
Apologize for the late reply, I've been out of town working so I haven't been able to touch the car at all. Did some thinking about the issue and how to better describe the situation of when it happened. I was driving down the street from my house and then it felt like my car ran out of gas, ASR light came on, steering got hard and then the car just came to a stop and shut off. I had a full tank at the time and still pretty much do. When I start the car and it runs for about 2 seconds at most and just shuts off, feels very similar to when a car runs out of fuel. So my guess is signal for fuel is being cut. You guys have been telling me to try replacing the ignition switch, but it doesn't feel like ignition failure because the car does start and run for a small amount of time.
 

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W124
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Are you just letting us know you are still here or are you looking for another suggestion to ignore?
 
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