fuel starved 300CD??? - PeachParts Mercedes-Benz Forum

freesprung · #1 05-09-2004, 06:43 PM

So on my trip to my mom's to day car begins loosing power at 60 mph. Car is only a few months old and I have just begun to use the AC and I thought that could be it. Did better with the AC off but on log acceleration began loosing power to the point I pulled off the highway. Then it recovered and I made it to my destination on side streets. Well, to make a short story long when I looked under the hood and raced the engine I could see the small see through fuel filter get depleated of fule and then refill. Supposedly all fuel filters have about 2000 miles on them. Clear filter looks clean to me.
1. Fuel pump problem?
2. Crud in gas tank cloggin line (down to less that 1/4 tank for first time for me).
3. Hot day vapour lock?

Thanks for any help.
Chad

"Experience is somthing you get just after you need it"

freesprung · #2 05-09-2004, 06:47 PM

Sorry. Meant to say car is new to me. Its an 83 and I have only had it a few months. Beer does not improve my composition skills (or spelling).

Chad

FrankM · #3 05-09-2004, 07:49 PM

i pick choice #2

coachgeo · #4 05-09-2004, 10:07 PM

I would say number two also, but you say the prefilter is not dirty soooooo..... I think that would eleminate #2. Lift pump maybe? Air leak maybe?

dmorrison · #5 05-09-2004, 10:46 PM

#2 in a way. Your fuel tank screen is clogged with debris or algae. You will have to remove the screen and clean it. My daughters new 240D would do the same. Screen was coated with algae.
Do a search on fuel tank screen. Lots discussed on this.

Dave

BoostnBenz · #6 05-09-2004, 11:00 PM

Most people seem to feel a power gain on the bottom 1/4 of the tank (additives?!), but when you get the power loss on the bottom of the tank it is most likely a clogged fuel tank screen.

There is no lift pump.

The IP sucks the fuel in as wanted.

freesprung · #7 05-10-2004, 07:48 AM

Thanks for giving me a place to start.

SoyDriver Matt · #8 05-10-2004, 09:51 AM

I could be wrong but I think there is a fuel pump in addition to the I.P. but much, much more likely to be something easier to check. Here's a pic of my tank filter in case someone tries to tell you it's not worth checking...the crud was clogging up the whole inside too.

P.E.Haiges · #9 05-10-2004, 11:57 AM

Boost.... ,

You are incorrect: there is a fuel pump. It is mounted on the side of the IP. The fuel goes from this fuel pump into the secondary (can) filter and then into the IP reservoir. The overflow valve in the IP regulates the fuel pressure and releases overpressure fuel back thru the return libes to the fuel tank.

The IP has to be pressurized for the fuel to be pushed into the barrels. No fuel pressure in the IP, no fuel injected into the engine and the engine will not run.

Power gain for fuel tank 1/4 full. There is a German word for this: Sheizen. Look it up.

P E H

BoostnBenz · #10 05-11-2004, 12:02 AM

I completely agree there is a pump but I don't believe it is coined a "lift pump." Lift pumps are normally seperate of the IP, in the fuel line somewhere between the tank and IP. I thought the pump was inside the IP, requiring partial disassembly to replace it. Learn something new everyday.

Lol, not a word in the translator but I know what it is. After finishing up all those words in english while working on cars I revert to other languages.

P.E.Haiges · #11 05-11-2004, 01:09 AM

Boost... ,

My Chevy Diesel PU truck has a lift pump. Its mounted on the side of the engine exactly like the ones on the gasoline engines, and driven by the same internal camshaft that works the valves. However the MB fuel pump serves the same purpose, to pressurize the IP pump.

The fuel pump on MB Diesel engines is held on the IP with two nuts if I remember correctly. It is integral with the primer pump.

The newer engines like the 603 don't have a primer pump. I wonder what they changed that allows the newer engines to prime themselves. I ran my 603 out of fuel and just cranked the engine with the starter until it started. I found out you need to add more than one gallon of fuel to get it started, though. My 617 engine will start with a gallon added to an empty tank.

P E H

TonyFromWestOz · #12 05-11-2004, 08:37 AM

Quote:

Originally posted by freesprung
So on my trip to my mom's to day car begins loosing power at 60 mph. Car is only a few months old and I have just begun to use the AC and I thought that could be it. Did better with the AC off but on log acceleration began loosing power to the point I pulled off the highway. Then it recovered and I made it to my destination on side streets. Well, to make a short story long when I looked under the hood and raced the engine I could see the small see through fuel filter get depleated of fule and then refill. Supposedly all fuel filters have about 2000 miles on them. Clear filter looks clean to me.
1. Fuel pump problem?
2. Crud in gas tank cloggin line (down to less that 1/4 tank for first time for me).
3. Hot day vapour lock?

Thanks for any help.
Chad

"Experience is somthing you get just after you need it"

My wife's 300D has a similar problem. It runs normally for 10 minutes, and then starves of fuel. I removed the fuel line from the prefilter and heard a sucking noise from the pipe. I have a parts car, (a gasser) so I removed it's clean gas tank (internals are shiny metal) and replaced my wife's tank.
The problem still occurs. The only components common the before/after, are the metal fuel line, and the flexible pipe from the strainer to that metal fuel line.
I suspect that the flexible fuel line has delaminated internally and is blocking itself when conditions are conducive, releasing when the suction is released.

I have reversed the fuel and return lines, as they both go to the bottom of the fuel tank.

The car no longer has fuel starvation problems.

I will buy a replacement flexible fuel hose to hold as a spare.