Lost Power in the Mountains Going Uphill - PeachParts Mercedes-Benz Forum

dave_zook@hyper · #1 03-26-2010, 11:39 AM

Hello,

Yesterday, I was driving my 85 300SD up I-70 into the mountains in Colorado. I was driving along doing okay when the car started to buck just a little like a clogged fuel filter. I stopped, put in some new diesel and some injector cleaner and things seemed to improve. However, on my way back down, there is a huge hill (Floyd Hill) that you go up heading east. The car kept slowing down until I was doing about 25 mph. I got to the top of the hill and going down the other side, things worked again and I got back up to 65 or 70. There was one more hill by El Rancho and the car did the same thing again. I drove it home and when there were no hills, the car seemed to run fine.

That's my story. Any suggestions about what the problem is and how to fix it?

Sorry if I started a new thread but I couldn't find any answers when I searched the forum.

Thanks,

Dave -- 85 300SD, 150k.

Brian Carlton · #2 03-26-2010, 11:50 AM

Quote:

Originally Posted by dave_zook@hyper

the car started to buck just a little like a clogged fuel filter.

..........ahem.........

#3 03-26-2010, 12:45 PM

After changing the fuel filter, also consider air leaks. In my experience a clogged filter does not result in "bucking," just a steady loss of power. How much fuel did you have in the tank? Is it possible that you were drawing some air into the system when the car was pointing uphill for an extended amount of time?

Diesel911 · #4 03-26-2010, 12:45 PM

x2 on the Clogged Filter and/or a clogged Fuel Tank Screen.

Look in the Plastic Pre/Primary Filter. If it has blackish gray green slimy stuff in it you have something growing inside of your Fuel tank.

dave_zook@hyper · #5 03-26-2010, 02:16 PM

I will check for the green slime. If I see it what do I do? Also the tank was close to empty when the problem started but I filled it before I had the trouble on the hill.

I was also wondering if there was some kind of Turbo problem.

dave_zook@hyper · #6 03-26-2010, 02:18 PM

Yes, Brian. It also seems obvious to me in retrospect. I just can't seem to be objective when it comes to a problem with my beloved 300SD.

dave_zook@hyper · #7 03-26-2010, 02:25 PM

I checked the fuel filter and there is a slight greenish cast to it but the filter doesn't look bad. (though I don't really know what a bad filter looks like). There are no obvious clogs and the screen looks clean.

okyoureabeast · #8 03-26-2010, 02:38 PM

Diesel fuel has many colors but typically has a blue, greenish color. It varies, but the color you're seeing is normal.

Did you see any black bits in the filter? That is the crud you should be watching for.

I think you just ran very low on fuel however and the line was pulling air.

dave_zook@hyper · #9 03-26-2010, 03:02 PM

I did see a few little black bits.

Diesel911 · #10 03-26-2010, 03:04 PM

The on the Road Diesel Fuel is I believe dyed green.

okyoureabeast · #11 03-26-2010, 03:12 PM

A little or a lot of black dots?

If it's completely covered then you're in trouble, but if it is nearly clean then you're ok.

dave_zook@hyper · #12 03-26-2010, 04:32 PM

No, its nearly clean. Just four or five if that. And they are tiny tiny. So you guys think it is just that I had some air in the system? Will that work itself out?

vstech · #13 03-26-2010, 05:01 PM

... there are two fuel filters.
the one you are looking at is for stopping big chunks from getting to the main filter.
next to the power steering pump is an oil filter looking item with a bolt on top. go to the store and get a new fuel filter. fill it with fresh diesel fuel, and then remove the old filter, and put on the full of diesel fuel new filter. tighten that large nut, REALLY GOOD and pump the primer pump until you feel it gurgling past the IP...
start the car and go climb some mountains.

Heh, post 6969... I need to stop posting now. that's just too good a number...

#14 03-26-2010, 05:27 PM

Quote:

Originally Posted by dave_zook@hyper

No, its nearly clean. Just four or five if that. And they are tiny tiny. So you guys think it is just that I had some air in the system? Will that work itself out?

I was suspecting that a leak in one of the fuel lines could draw in air when the tank level was low and the front of the car was elevated. It's just a guess but I would clean up the area and look for any leaks in the fuel lines or connections. I would also change the filters just to make sure.

dave_zook@hyper · #15 03-26-2010, 06:16 PM

Thanks everyone. I will let you know how it turns out.