1985 Mercedes 300D. need help

[Burning oil]

I have a 300D. It started running bad and got to the point that it would not start. That was a couple months ago. Yesterday I went back out to see what I could do to get it running again. It actually started, but ran bad. It acts like its starving for fuel, but it is not. Just out of curiosity I took the fuel return hose off and blocked it off. The one ontop of the secondary filter that goes back to the tank. Well it perked right up and ran normal. If I hook the hose back up it go's to acting like its starving again.
There is a pressure relief valve on the IP that go's to a tee witch connects to the return hose that I removed.
Anyone have any ideas.
I do know the fuel system is primed up good and no air is in the system.
I think its strange that blocking the fuel return would make it run normal unless to much fuel is being bypassed and caping it keeps more fuel availible to the IP???

 

[DieselCash]

This site is good, maybe it can help you out;

http://www.dieselgiant.com/mercedes_diesel_maintenance_tips.htm

Wish you luck!

 

[Burning oil]

Thanks I will check it out next. If anyone here has an idea for me to try I'm still listening here to.

 

[db9938]

I am not particularly familiar with Mercedes diesels, but it sounds like injectors.

By pinching off the return line it forces the fuel through the injectors, instead of by passing them like it is without intervention.

Now the question is, what is restricting them, and what can be done to correct this.

 

[SfcJones]

Perhaps a clogged fuel filter.....even if you just changed it, there could be bad nasty fuel in the system that is messing up everything.....

 

[Burning oil]

I'm going to try and work on it tomorrow. I will post results later.
Thanks for helping.

 

[Burning oil]

Did not get a chance to work on it Sunday, but did a few minutes today. I replaced the pressure relief valve on the IP, No improvement.
I'm going to bypass the LP with a electric one and see what that does.
Thats all for now.

 

[Burning oil]

Perhaps a clogged fuel filter.....even if you just changed it, there could be bad nasty fuel in the system that is messing up everything.....

Update: You were right. I got her running good about a month ago. Turned out it was a filter. The filters were replaced less than 20 minutes on the new one. Must have had alot of junk in the tank. I boiled out the tank, put new filters on and it runs great again.