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93 300sl starts fine but does not drive

1927 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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Sorry to hear that! The KE Jetronic is very funny sometimes. The fact it starts is good. That probably means the EZL you got is somewhat working, but since it controls pretty much the entire ignition system, it doesn't mean it is working correctly. If you have a 1993 300SL-24V, you need to check, if you have the proper EZL.

Please take a lock and confirm your BOSCH/Siemens part number is printed on it. If you have the M104.980 or M104.981 engine your acceptable EZL's should be: 0075457032, 0075457132, 0105459532, 0105459632, 0125452032, 0125452132. Make sure it has the round MAP controlling resistor 0155456728 plugged in.

Even if you have these installed, no guarantee it is a working one, other than you have a refurbished with warranty.

Next you need to start the car, idle it and then check the On-off ratio. If that is out of range, your car will not accept power and or stumble or die. The EHA does not adjust idle mixture ratio, but acceleration fuel pressure. If that thing is wacked, it will not drive properly. There are many protocols out there that can help you measure and adjust.
How old is the fuel? Is there enough fuel pressure coming from the fuel pumps, Do both work? Do you hear them humming when the car runs.

So many ways to mess up an M104. Since the car starts, you do have compression and spark and some fuel.
Go from there.

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Almost forgot, you mentioned it won't engage into a gear, but it does move slowly?! Try reverse, 4/3/2/1 maybe your torque converter is toast or low on transmission fluid and no matter what you do to the engine the car doesn't get the torque onto the rear axle. Idle the car and check the transmission fluid level when it is warm. It should be between the two markers. If it is too low, your car might not want to drive. If you need tranny fluid, go to Autozone and get Valvoline MaxLife full syn ATF (DexronVI, Mercon LV, DEX/MERC in a red bottle/red fluid). On the back it says Mercedes-Benz NAG-1 compatible. That fluid works well for our older 722.4 or 722.5 transmissions.
Yes, you are missing the resistor, that maps the EZL to the car/computer. Here a picture where it is and how it looks like. It's a plug-in, you might be able to buy one on Ebay.
Game controller Input device Video game accessory Gadget Font
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Here is what I found about the trim plug. Car should still be running without it, but you never know.

Here is the official MB guide as to what EZL trim plugs to use for specific conditions.

VersionFuel RONTrim Plug Connector
part number
Ignition timing correction
(crank angle w/o vacuum)
on plug
CATPremium 95015 545 67 282.4 kohms02
Without CATPremium 95015 545 71 28220 ohms06
CATRegular 91015 545 68 28$1.3 kohms-33
CATRegular 91015 545 69 [email protected]750 ohms-64
Without CATRegular 91015 545 70 28470 ohms-4

* If no adjustment coupling is available, the injection timing at full load is retarded by approx 3 degrees crank angle.
$ With frequent regular fuel operation
@ With pinging complaint using regular fuel
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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
It is incorporated in the MAS module, which is located in the ECM box on passenger side.
But if your MAS works, you will hear a short fuel pump noise (1-2 sec) from under the right rear axle when you switch the ignition on.
Sorry, I am not good at guessing.
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