i have an 84 300d td in need of a tuneup (starts, runs, drives etc) but has been sitting for awhile needs a tuneup (hoses/wires connected, fluids flushed, etc). talked to my neighbor who owns a diesel shop and he said he don't know much about those motors and one needs special tools to do anything with it. can anyone tell me if hes tellin the truth or if he just dont wanna f with it?

i can understand the special tools, but i find it hard to believe he needs a whole set of special tools to do a basic tuneup. any help is appreciated

 

The only special tools needed for a typical tune up would be the wrenches for adjusting the valves and feeler gagues. Other than that regular metric wrenches combination wrenches,socket set and screwdriver for changing fluids and filters. Not falling under a typical tune up you need a allen type socket for differential plug removal to change gear lube.

 

Well Mercedes wanted or expected the Car to be returned to them for Service.

Valve adjustment every 15,000 miles. There is a special 3 Wrench set to do that. The Wrenches are Bent so that the clear the Fuel Injection Lines and there is a 3rd Wrench to hold the Valve Spring Retainer incase an ajutment Nut is stuck.
You can do the job with regular 14mm Wrenches if the Heads on the Wrenches are about 1/4" thick and you are willing to remove the Fuel Injection Lines (this means you need to know how to bleed the Air out of those Lines when the are re-installed). If one of the adjustment Nuts is stuck you need to find something to hold the Valve Spring Retainer to keep it from rotating so you can loosen the Nut.

Fuel Injection Pump Timing- You need somthing called a Drip Tube (about $30 or you can make one). However, people doing Drip Timing for the first time seem to have a lot of trouble Drip Timing for the first time. You need to develop a skill to do it.
It does not sound like Your Mechanic is up to that.
There is an Electrical Timing device called an A&B Light that makes the Timing easy but it is a $350+ item.

If your Fuel Injectors are the originals and they have over 100,000 Miles on them they are likely close to the end of their life and at the very least should be removed and tested.
The Injectors are sort of a Spring loaded Valve and over time the Spring tension decreases and that effects the atomization of the Fuel and that is called the Pop Pressure or Opening Pressure.
The stock Injectors also have some tiny Passages drilled into them that if the Prior owner did not do Diesel Purges are likely plugged solid with Carbon. (This is how mine were and most of the Injectors I have removed at the Junk Yard were similarly plugged.)

Of the above stuff the Valve Adjustment can have the most helpful effect on starting and running.

 

thanks dude that helps more than you know as far as what to look for. also you confirmed my suspicion about his motives. like i said i understand there's gonna be special tools but homeboy didn't even look at just said no. even after i said i just needed the basicest of tuneups (**** i could do myself if i knew what to look for)

i do have a shop where i live now that does a lot of beemers and such. i talked with him last week and he's at least willing look at it (and do what he can) but he also said hes lookin to hire a master mercedes tech so as soon i can get the car down here he'll look it. (hopefully with a shiny new mb master tech. he also has a shiny new lift in his shop yay)

subsequent question: my shutoff valve and/or vacuum line to shutoff valve needs replaced. is it hard on the motor in any way to shut it off with the stop lever?

 

For the pump drip timing I just took an injector line off of a junkyard motor and made the bend and cut it. Depending on mileage you could have chain stretch. A good indication of this would be if you cannot turn your pump enough to regain factory timing. Offset keys for the cam are available to compensate for this, although once you get your cam in time you may well have to restab the pump. I would personally rather just pull in a new chain as chain stretch will also wear sprockets. As ForcedInduction said, pump timing is an easy adjustment. Valve lash is not that hard either. As for a purge, it is easy enough to fill a bottle with injector cleaner, put your fuel feed and return lines in it, and run it through your pump. Not too much in the way of tune up to do. Basically fuel filters, pump timing, air filter, valve lash. You should also check the banjo bolt on the back of the intake manifold that provides boost reference to the alda. There are many write ups on how to do this.

 

They don't mark the Pump Flage to Block so they can return the Pump back to where it was if they screw up.

From what I have read that people do is they do not keep the Pressure up and get and uneven amount of drips; more pressure more drips; less pressure less drips.

The other think is the Rotate the Pump to much and go past the area where they would get the drips they want.
Along with the above they leave the other Fuel Injection Hard Lines attached and have trouble rotating the Fuel Injection Pump and/or getting the Pump to stay in place.

Other than that you are correct. Once someone knows how to do it is not hard.