got a question it might be dumb but i have a 82 MB 240D and i just moved from GA (which is sea level) to AZ (about 4700ft above sea level) and the car is really sluggish to start now. i was wondering if the elevation has an effect on the car, like on carbureted cars? its mechanically injected so does the injection pump need to be adjusted to compensate for the elevation?

thanks.

 

At higher elevation you have less air, and therefore you're going to be able to burn less fuel and make less power. Naturally aspirated Diesels are affected more by high altitude than anything else, and even turbocharged Diesels see a rather large drop in performance.

Other than turbocharging the car, I don't think that you can do anything to help. Even if you added more fuel by tweaking the pump, you still wouldn't be able to get any more air to burn it.

 

As the saying goes...theres no such thing as stupid questions, only stupid answers (insert word people if you wish).

Diesels do need to be tuned for elevation. while I'm sure someone will post here with specific info for you shortly, the thinner air at altitude needs less fuel.

Edit: Doh! Begle beat me to it

 

That M-B probably has an aneroid compensator that reduces the fuel rate at high altitude to prevent black smoke and possible meltdown.

If it's not turbocharged there's not much you can do about it safely.

 

Hmmm. Sounds like a transplant is needed from a 300TD or SD.


MikeyB

 

I have owned a few of those things. If I remember right on the pump there is a control to adjust for elevation changes. Any way what ever you do it still only has about 70 hp.

 

You can make all the adjustments you want to the pump, but it won't help startup. It's just a matter of less compression at altitude. As long as it will start you're fine.

240s are especially sensitive to conditions because of the precombustion chamber design. Just make sure the glow plugs are working. If it starts on all cylinders and doesn't pick up the last one or two after a second or two, you can relax and know he compression is about the same in all cylinders and all the glow plugs are working.

A turbo will not help starting. All diesels, turbo or not, are naturally aspirated at startup. The injection pump does not have an aneroid compensator because it's naturally aspirated and a simpler design. So you might see a bit more smoke at full throttle but it wont hurt the engine.

Those 240s are great engines and will last forever. But they are really slow, especially at low speed. Mine seemed fine on the highway but was such a dog at stop lights. It finally got to where it was using so much oil that I dropped in a factory rebuilt from Mercedes. Wow, do they do a nice job. Then the car got bent up a bit and it now sits with a VERY nice engine looking for a new home.

Wetspirit

 

Lower air density at higher altitudes results in less mass flow during each intake stroke - less mass of air at the beginning of compression. With less air in the cylinder, compression pressure (and, therefore, temperature) is lower which means that the injected fuel is less likely to ignite. If the engine has a dirty air filter, worn rings (lower compression), etc., the problem is exacerbated.

Rusty