My 99 turbodiesel rather suddenly developed a problem of losing fuel prime after setting for a day. It will start again after much cranking. It acts just as if there is air getting into the fuel system somehow. Any common cause for this problem?

 

If you are using only Diesel Fuel and not an anternative Fuel.

You pretty much diagnosed the problem yourself as Air getting into the system (the most common cause). PLease note that bad seals and tiny cracks in rubber hoses often do not leak Fuel out but allow Air to come into the system due to Atmospheric pressure outside of them.

The next source would be the Fuel Suppl/Lift Pump.

I have never even seen the System on the newer models but I believe they have some sort of seals on the Fuel Lines and/or Fue Inlet Hoses; and some of the newer models have a Feul Heater that also has seals that can go bad.
I would replace the seals before messing with the Fuel Supply/Lift Pump (there is a rebuild kit for the pump).

Also take a look at the top of your Fuel Injction Pump for leaks. If it is leaking at the top where the Fuel Injection Lines/Tubings that go to your Injectors; the seals on your Fuel Injection Pump Delivery Valve need replacing.

This site shows some of the stuff that might be on your car.
http://www.detali.ru/cat/oem_mb2.asp...SGR=120&SGN=04

 

This is a Russian parts site. However, 95% of it is in English.
You can look up your Car and see the parts arrangements.
http://www.detali.ru/cat/oem_mb0.asp?TP=1

This is an online Service Manual. It only goes up to 1995 but some of the Engine stuff is similar.
http://www.ps2cho.net/downloads/MB%20CD/W124/Main.html

 

I have parked the car for the winter and am using the trusty old 1983 300D for now.

After replacing o-rings and hoses, what is the best way to get the system primed again for starting? I hate cranking the starter a lot because I am thinking the starter is very expensive to replace. On my other diesels I have opened the injector lines a bit to let the air move out faster. Is that something that needs to done on this engine as well?

Thanks

 

I am not sure how easy it is to access but if you loosend the Hose/Connector where it comes out of the Spin On Fuel Filter or down where it First goes into the Fuel Injection Pump that will allow any Air up to that point to come out fast. When resonable amout of Fuel comes out hook up or tighten the fittings and hope it does not take too much more Cranking to get it started.

The other place you could bleed the Air in addition to the above woul be to loosen the Fuel Injection Line Nuts at the Injectors.
If your Engine was going when you parked in the Garage you will not have to do that but for instance if you ran out of Fuel to the point that the Car stopped; after putting fuel in the tank I would loosen those Injector Line Nuts because Air trapped between the Fuel Injection Pump and the Injectors is very difficult to get out only by Cranking the Engine. And, on the newer Engines the Fuel Injection Lines are almost 3 times as long as on the older ones.
Because the Injectors are spring loaded valves the Air in the Fuel Injection Lines tends to compress a lot and move out very little.

Any way for your initial craking use you best judgement if you want to loosen the Injector Line Nuts at the Injectors also.