BTW : the low fuel lamp just came on an hour ago, 408 miles .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Have a look for a fuel leak? Check engine oil for increasing? Odometer stopped working properly? Last item is not uncommon.

Who, Me ? .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I do drive it pretty quickly. Not in an abusive way, more in an I’m having a lot of fun driving kind of way.

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1981 240D 4sp manual. Ivory White.

Certainly pre-heating the air by running it past the exhaust will increase mileage. Indeed, I submitted a patent idea for that when I worked at Bendix back in the fuel crisis 1970's, though I think it languished because of prior patents. At that time, gas engines had exhaust shield heaters w/ an inlet air diverter valve on the air cleaner, but it was used only when cold. If it stuck in the pre-heat position, mileage actually went down because the carburetor didn't compensate and ran rich. Today's SI fuel controls would maintain the correct O/F ratio.

No manufacturer has pre-heating because power decreases, and in fact they cool the air as much as possible, especially w/ inter-coolers for turbo cars. But, I expect it is used in certain cases like large stationary engines. An experimental engine pre-heats using a rotating porous wheel to transfer heat between exhaust and intake air flows (type of Stirling cycle, I recall). Diesel fuel management is much simpler. An OM617 runs "wide open throttle" and simply squirts more fuel for more power. No adjustment is needed for warmer inlet air, but seems you run more risk of melting pistons at high power and boost.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Understood ! .

Most 240D's I see, when I look under the hood are covered in fresh oil and when I hear them go by the driver's (your Mn, always) over rev. the engine until the valves float before up shifting .

I drive my 240D on road rallies, it's pokey in the hills but I get it up to speed quickly and don't let off the throttle unless I absolutely have to .

I saw a 240CD graymarket in Korea town once, I tried like mad to catch it but the traffic was bad and I got stuck behind it .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Reading thru this thread I can add some generic info as I've experienced both the 30's and 20's mpg's on my 240D's.

Both my previous one and my current one are 81 manuals. I'd love to know how close they were on the production line to each other. Identical vehicles in fact except for the paint.

My previous one consistently achieved 30 to 33 mpg's. My current one consistently around 25 to 27. I used to average around 460 miles on a tank with my previous one. 360 per tank now. I check and record mileage with every tank. I will say though that my previous one had had the motor rebuilt at some stage and was smooth as silk. In fact when idling you couldn't tell that the motor was running other than by sound.

My current one has never had the engine opened and rattles, buzzes and vibrates so badly it's almost like it had a brutal massage function built into the car.

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

Thanx Peter ;

The recently rebuilt engine in this one vibrates at idle .

I keep being told they're normal like this, I disagree .

Maybe I should double check the IP timing .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Is it really that bad?? I'm trying to get some baseline of how much idle shake is reasonable. In my case, it's definitely shaking, vibrating all of the components/pumps/hoses under the hood but not terribly. When I'm sitting in the car, I feel the slightest vibration on the back rest. The hood/bonnet doesn't shake, nor do the mirrors.

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1981 240D 4sp manual. Ivory White.

Yep. I have to keep the idle control adjusted to max to try and smooth it out somewhat. The vibration never goes away and is felt variously thru the seat itself, the back rest, the steering wheel and the whole body of the vehicle depending on where in the acceleration band I am, what gear, and wether or not I'm cruising. At some revs the buzz is so bad from the seat belt recepticals that I had to wedge some foam rubber between the drivers seat and the mounting point to try and stop it.

Could be any number of things. Bad compression, shot injectors, IP timing, engine mounts etc, timing chain stretch etc.

Just too many things for me to try and tear into. I cannot afford to have the vehicle out of service for an extended period of time in case my truck breaks again. The 240D despite it's old and beat up condition is simply the most reliable vehicle I have ever owned and it has to serve it's role as backup until I can get a new vehicle and chance working on the 240 for extended periods of time.

Of course having the idle speed adjusted to max undoubtedly contributes some to the poor fuel economy as I do a lot of stop start city driving with much idling at stop lights. But I'm sure it's not the principal culprit.

And yes, my previous one was genuinely so smooth I once absent mindedly grated the starter horribly trying to start it at a light when it was already running as I thought it had stopped.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

What a dream!

I'm not that far off. Biggest issue is air in the system which I've consistently failed to pinpoint. Means the first start of the day is a little bucky for about 30 seconds until the air has cleared. One of these days though.

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1981 240D 4sp manual. Ivory White.