1989 Mercedes 300E 20mph topout

Check for any codes stored . this is an OBDI system .

Nowhere that I've gone has been able to check the system, and the box that is inside the vehicle to help me check the system is also unresponsive. I will mention that I'm apparently also spewing dark smoke

Most mechanic shops have an OBDI code reader. I have one that does both OBDI and OBDII but it is for American cars only. Be advised the system in your Mercedes is an analog system, not a digital system as in OBDII. You should have a box mounted to the upper fender called an impulse counter on the passenger side near the firewall. Some 1988-1995 Mercedes have built-in impulse code readers like this. Check to see if you have this impulse code reader. It will have a black plastic cover that when removed shows 16 holes numbered 1 -16 and a button to push and light. If so turn the ignition to the run position but don't start the car. Push the button on the impulse counter for 3 seconds only by pushing and counting 1/1000, 2/1000, 3/1000, and let go. The light will blink and you must keep count of the numbers of blinks. So let's say it blinks 10 times. Write that down . Now push it again for 3 seconds and release and count the blinks until it cycles back to 10 blinks. So let's say the second time it blinks 5. Write that down as now you have two codes number 10 and number 5. Push the button once again for three seconds, release and count the blinks. Let's say it blinks 10 times. You have two codes number 10 and number 5 only. Be advised it must cycle back to the original code retrieved to complete and read all codes stored and it could have more than just two codes stored. Once you have the codes you can google the OBDI code and see what may be the problem .Try this and let me know what you find.

watch this video.....https://www.youtube.com/watch?v=-wBysjMDVtI