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93 300sl starts fine but does not drive

1929 Views 52 Replies 7 Participants Last post by  rayhennig
I’m not sure if I’m in the right place. I’ve looked everywhere on the internet and in your forum for similar cases to my car, and so far nothing like it. So I bough this 93 300sl not running. Looked really good and complete minus the ignition control module. I found a used module online and bought it. Connected the different sensors to it and the car turn on like clockwork. It idle a bit high but I figure that was normal since the car had not ran for a long time. The po mentioned it hadn’t ran for about a year. So I let it idle for a bit, after a few minutes I put it in drive and that’s when I noticed the car would not engage into gears. It drove super slow and as I tried to accelerate harder it would kind of just want to turn off. To the point it just turns off randomly. I’ve replaced dristributor cap, rotor, cables and some rubber hoses. Still have the same symptoms and I just don’t know where to start looking. So again, the car will start fine, idle ok, and after a few minutes will just die out randomly or if I try to put it in gear and drive off it has no power and shuts off as well. Any help or suggestions would be much appreciated. Thank you in advance.
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To me, this screams bad EHA. Is it leaking?

That said, it could be anywhere in the KE-jetronic system. And if the EHA isn't leaking, start elsewhere. Bad OVP. Bad fuel injectors. Mis-adjusted 3mm tower or air flow plate. Bad air flow potentiometer.
The EHA will be leaking gasoline out of its weep holes. This is a picture of mine.
Motor vehicle Automotive tire Automotive exterior Hood Automotive fuel system

Here's a pdf on the KE-jet tonic system. You'll want to study up on it.


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Your best bet is to search the w124 forum. They have a lot more information on the m103 (and m104) engine(s).
You can try and replace the o-rings. That's what I did. In my case, that didn't work. And I bought a new EHA. And I bought like 10 of those o-rings. Because you can lose them.

Oh, and if you're new to MB, I'd suggest buying the EHA from fcpeuro. They have a lifetime warranty. And my EHA which is 18 months old just tested as "bad." So I'll be sending it back using that warranty.

And everyone will say don't buy a used EHA. I tried it. Didn't work. It was bad. Bought new.
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So updating, I put new O-rings. Didn’t change much, except it is not idling as long as it was before. It starts idling really high and bouncing between 1000 and 2000 as if I was trying to rev it up but I’m not even pressing the gas pedal at all? I’ll definitely have to get the new eha, but was wondering if the symptoms meant anything?
Is the EHA leaking gasoline? If not, there are other things to look at. And there's a way to test the EHA.
To test the EHA, you're testing mAmps. You first need the engine at operating temperature. Then, you turn off the engine and unplug the EHA. Then you add your multimeter (set to mAmps) to the circuit. You restart the engine and check the multimeter value(s).
Motor vehicle Electrical wiring Auto part Electrical supply Automotive exterior

In my picture, you can see my yellow alligator clips run from the front EHA prong to the front connector on the wiring harness. Then you'll see the red alligator clip runs from the rear EHA prong (the prongs are numbered 1 and 2, but I can't remember which is which) to the multimeter. And the black alligator clip runs from the multimeter to the rear connector of the wiring harness. So, the EHA's front connection is normal, you add the multimeter to the second connection.

You'll need to verify what your value should be. I expect it will fluctuate just above and below 0. In my car, I think it's supposed to be 0.3 to -0.3.

There are great videos on YouTube by FixMyMercedes and MMWA on your engine. You'll want to watch them. MMWA has one showing the set up I gave you here. FixMyMercedes goes through all sorts of diagnosis techniques and repairs.

EDIT: It's FixYourMercedes
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Have you looked at the OVP? Idle bouncing like that is notorious for a bad OVP
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You're going to want to verify the part number, 201 540 37 45, is the correct one for your car. The prong numbers might not match. For example, my fuel pump relay has extra prongs.

OVP's can test as good but still be bad.
Let's get back to basics. Are you getting fuel? Have you tried jumping pins 7 and 8 on the fuel pump relay?
No, the car used to start and stay on for a while before it just fine, before it would unexpectedly cut off. After the ovp issue, it starts and dies right away. Correct me if I’m wrong, I’ve looked for fuel pump relay location here and it shows me that there is no relay for my car. It’s points me to a box that looks more like a module. Is this the correct part? And if not, where is the fuel pump relay located on a 93 300sl? Thank you again
That I can't help with. Though I do believe my '96 SL320 had a fuel pump relay or something in the trunk, near the battery.
The fuel cut off due to the fuel relay will be immediate. The crank position sensor can cause the same thing. They rarely go bad on the I-6 engine, but it does happen. Have you tested that?
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