Question about 1984 Mercedes-Benz Mercedes Benz 300 Class

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As I go up hill at 70mph I lose power down to 55mph - the turbo is not kicking in. Is this a problem with my fuel filter? or air in the fuel piles or what? Any help much appreciated, thanks, ps even at lower speeds and gears the turbo does not seem to be kicking in... it does sometimes but seems rather hit and miss...

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It depends on the hill, too. Although the engine is rated at 125hp and 170 lb-ft of torque, the car weighs over 3,000 pounds. at low speeds you may have a lot of lag because of the turbo design. When this car was made, it was designed without an intercooler, so to keep the compressed air from the turbo as cool as possible, a larger, slower-spinning turbo was used. The slower turbo heats the air less as it passes through, but requires more engine RPM to produce useful boost, and also lags quite a bit along the way. I also have an 84 300D, and although the car runs almost perfectly, the turbo does not wake up until 2200rpm. You can pep up the turbo in a few ways. Make sure you change both fuel filters (both on the left side of the car, one down low that looks like it came from a lawn mower, and one mounted near the front, which looks like a big spin-on oil filter). Changing the air filter makes a big difference also. You may want to try an additive called Diesel Lube, which comes in a white jug with a red top (available at auto parts stores and most Walmarts). As for more mechanical things, adjust the valves, or get them adjusted. Also check out the ALDA, which is the device on the injection pump which adds fuel when the turbo kicks in. This is a hex-key type screw with a lock nut on it. Hold the hex key still, loosen the lock nut (but don't take it off!), turn the hex key 1/2 turn counterclockwise, and while you're still holding the hex key and keeping it from rotating, tighten down the lock nut. Take the car for a spin and see if that makes a difference. if it does, do that again. You'll find that it adds some power as you go, but it will increase your fuel consumption to a point, and when you pass that, all it does is make the exhaust sooty and waste fuel, so you'll have to turn the key back in the clockwise direction. Find a position you like that gives good power but doesn't soot up the back of the car, and you'll be in good shape. If you do all of these things, the car will be quieter, quicker, and probably won't lose as much speed on that hill of yours. To comment on the other answer, you'll know if the turbo is bad, because you probably won't hear it spin up when you accelerate, or if you do, the whistling sound will be rough, and the lag will be abominable. Good luck, and enjoy.

Posted on May 30, 2009

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That means your turbo's bearings are wearing out and the turbo will have to be replaced

Posted on Apr 24, 2009

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