PeachParts Mercedes-Benz Forum - View Single Post - Reconstructing Fuel Feed System: 1983 300TD

Zacharias · #2 04-25-2016, 03:15 PM

Welcome to the group. I can provide some limited answers. Some of this may already have been obvious to you, with your background.

The cigar hose is not critical to the function of the fuel system (or for starting), but it's helpful on the turbodiesels. It's designed to dampen pulses from the fuel return.

Many people say their car runs fine without the cigar-style hose installed in that particular position, but in the past I have read posts from others who say that minor idle issues were cured by its installation, where they acquired the car without it. They are not expensive if you shop around, I vote to keep it original.

After any work on the fuel system, it is not unusual for the turbodiesels to have stubborn air locks. My '85 300d is the worst of the six or so I have owned. Generally I have to enlist a helper to pump like their life depends on it while I crank the car over. It's even difficult after just changing the spin-on filter. My earlier Mercedes diesels were far less prone to this.

Another problem is the manual primer pump. You did not mention having used it. There are two styles. If yours is white/creamish in colour and has to be unscrewed to operate, it's very old and more than likely leaking air into the fuel system.

If yours is the "new" black style that is pump-and-go, when you pump it, do you feel like you are pumping anything? If it feels like you are pushing air, then the seal is gone inside. It is also possible for these to not leak fuel out, but to suck air in.

I don't believe that the banjo bolt valve you mention is critical to starting, but some people have said their on-the-road performance improved from installing a fresh or upgraded one (available from Greazzer on this forum).

Since you say someone had messed around with the hoses, was the car run on any form of alternative fuel? If this was the case there could be other issues with the lift pump, injectors....

I am assuming that you have checked that you have voltage at the glowplugs, etc.

Bottom line is, if you are not getting a serious smell of diesel out the tailpipe as you crank, then you probably have an airlock.