Bad MPG and slow shifts in 83 240D
 

I just bought a 1983 MB 240D and I only got a best of 28 MPG on a road trip. I was driving pretty fast and pushing speeds up to 85 MPH, but it still seems like a bad MPG for a 240D. Does it have something to do with the idle speed control being too low or too high? The car sounds really loud at that speed (80-85 MPH) and feels like it needs a higher gear, is it just geared low?

Also, the car does not want to shift down without manually moving the gearshift from "D" to "S", or from "S" to "L" at really low speeds. From a standing start, it does not feel like it's getting full acceleration and engaging in first gear. It does not slip, but shifts harshly. The downshift button beneath the gas pedal when the pedal is floored does not trigger a downshift either. Any advice?

i am no expert on auto trannys but your mileage looks really good for the speeds you are driving.

it is not a 1800# economy car with a 1200cc engine and six speed manual.

tom w

28MPG at 85MPH is good for the 240D. If you want better gas mileage slow to 55MPH. It will do much better. Add a injector cleaner to make sure the injectors are clean.

Your downshift problem is a vacuum issue. the 722.1 transmission uses vacuum signals to shift. It does not have a downshift cable as the 300D and 300TD does.

Do a search on vacuum systems. You want to replace all the vacuum connectors (2 way,3 way and 4 way connectors) make sure the other vacuum systems are not "stealing" vacuum and check the vacuum output of the vacuum pump. Make sure all those are working correctly, then if all is OK then you may have to look at the vacuum control unit on the rear of the Injection pump. this controls the transmission shift. But at $165 I would check all the other vacuum systems first.

To get the 240D to downshift we have to floor it, or make the car downshift. I drive the diesels differently then a gas car. Just the nature of the beast.

Dave

That 722.1 transmission should have a control pressure rod which is part of, attach to the angle lever on injector pump. It’s a push pull set up, look for the rod on the passenger side of the engine going down to the transmission, make that rod shorter by turning the ball socket. You may need to set up/ adjust the linkage rods.

To check the kick down solenoid and electrical circuit. Open the passenger door with the ignition on depress the throttle pedal to full throttle , you should a hear click at the side of the open door, if not , blow fuse or open wire to the solenoid, bad solenoid or the pedal is not fully contacting the KD switch or a bad switch under pedal.