Poor fuel economy - PeachParts Mercedes-Benz Forum

t walgamuth · #1 11-05-2006, 06:18 AM

Quote:

Originally Posted by cavaliers16

I've searched around a bit about this problem, but each case is slightly different. As I've heard, the 300D gets around 25 mpg city and 30+ mpg highway. Mine gets 15-17 mpg city, 21 highway.

So, things I've checked:
-Filters, screens
-ALDA
What's next? Should I check the timing chain stretch (it has never been replaced)? Should I have the injectors pop tested? I can live with low mileage but it has been getting progressively worse. The PO two owners ago (owned the car for 8 years) kept a log of mileage that I found in the glovebox. He was averaging 29 mpg at the beginning of his ownership. At the end it was averaging just 25. I'm inclined to think timing chain but that will be expensive to fix- one of the many problems with the low income high school job

.

BTW- it burns no oil

i never saw how fast you are driving. if you drive very fast, this might be about right.

brian is getting 29 but he drives very slow. for me driving 75 on the highway i usually would get 22 or 23. if you are driving faster 21 may not be too bad. also what tires are you running? if you have very large ones and arent correcting mathematically you may actually be getting 24.

so speed is a question and as noted above checking your odo against the mile markers. i always also check my speedo against the mile markers too. sixty mph will take you one minute to go one mile.

tom w

cavaliers16 · #2 11-05-2006, 08:00 AM

Around town: 25-40 mph
Highway: 55-65 mph

I'm going to try building a pop tester for the injectors- we'll see what happens.

t walgamuth · #3 11-05-2006, 08:56 AM

if it is running really well, then i would suspect the odo.

what about your tire sizes?

tom w

cavaliers16 · #4 11-05-2006, 09:26 AM

Tires are stock size: 195-70/R14
It has good low end power and great high end power. I usually don't drive on the highway but when I do it is very smooth at 65 mph. I'll have to check the odometer against the Volvo's odometer.

cavaliers16 · #5 11-05-2006, 08:15 PM

Ok, rechecked the ALDA- it is fine. I took the valve cover off- the valves need adjusting bad. There is tons of room on the exhaust valve on #1, and the rest are incredibly tight. I don't know how to test the timing chain stretch though.
For the odometer, I checked the trip meter (what I've been using to calculate mileage) against my dad's Jetta. My odometer marked out exactly 4.0 miles, his marked out 3.8. This is not helping my cause- it means that I am getting fewer miles/ gallon than I originally thought. His is a "new" car (a 97). I'm going to build an injector pop tester this week and do a valve adjustment next weekend.

I have one quick question on the valve adjustment: When I tried to do it today with flat wrenches (it didn't work) I couldn't rotate the engine. I know it has to be turned clockwise, but it wouldn't turn. If I turned the power steering pump bolt or the engine bolt it met heavy resistance. If I put a lot of leverage in it the whole engine moved. I needed to turn the timing chain sprocket bolt about 1/8 in. to get the engine to turn again. Every time I turned the timing chain sprocket 1/8 in, it would stop (same resistance). Then I would turn the power steering pump bolt and the camshaft turned maybe 1/10 turn until it stopped, when I would turn the sprocket again. Repeat several (hundred) times. Why is this happening? The car is in neutral.

BenzDieselTuner · #6 11-05-2006, 08:18 PM

be sure and loosen the injector pipes before u turn the engine with the power steering bolt, because if u dont, the engine could fire, injuring you severely....

BenzDieselTuner · #7 11-05-2006, 08:20 PM

Quote:

Originally Posted by cavaliers16

Ok, rechecked the ALDA- it is fine. I took the valve cover off- the valves need adjusting bad. There is tons of room on the exhaust valve on #1, and the rest are incredibly tight. I don't know how to test the timing chain stretch though.
For the odometer, I checked the trip meter (what I've been using to calculate mileage) against my dad's Jetta. My odometer marked out exactly 4.0 miles, his marked out 3.8. This is not helping my cause- it means that I am getting fewer miles/ gallon than I originally thought. His is a "new" car (a 97). I'm going to build an injector pop tester this week and do a valve adjustment next weekend.

I have one quick question on the valve adjustment: When I tried to do it today with flat wrenches (it didn't work) I couldn't rotate the engine. I know it has to be turned clockwise, but it wouldn't turn. If I turned the power steering pump bolt or the engine bolt it met heavy resistance. If I put a lot of leverage in it the whole engine moved. I needed to turn the timing chain sprocket bolt about 1/8 in. to get the engine to turn again. Every time I turned the timing chain sprocket 1/8 in, it would stop (same resistance). Then I would turn the power steering pump bolt and the camshaft turned maybe 1/10 turn until it stopped, when I would turn the sprocket again. Repeat several (hundred) times. Why is this happening? The car is in neutral.

u know that you have to turn it until each of the camshaft lobes is "straight up and down", and then adjust each valve while it is in this position.....in other words, you have to have each valve at "top dead center" when u adjust it......

cavaliers16 · #8 11-05-2006, 08:21 PM

Right, I got that part. It was really tight. I just can't figure out how to turn the engine easily.