77 300d turn but wont start
 

hello, I bought the car from an auction. it turns over but doesnt even sound like it wants to start. the glow plugs have the common rail system and i can see that the rails have power to them because they are hot when i touch them. I am not very familiar with the common rail relay system. if the rails are hot that means the glow plugs are working right? the car has been sitting for over a year and it turns over but doesnt act like it wants to start and the glow plugs seem to be working...what do you think it could be? thanks

There's a limited number of things that could be wrong with it:
No air.
No fuel.
No compression
No heat
All there but not happening at the right time

Looks like you have heat so chase down the others.

Many forum members have discovered in the case of Mercedes diesels that have sat for a long time, that pull starting is the most effective means of reanimating them.

Air in the fuel feed system would be my guess. Crack open/loose an injector line at couple of injectors, then crank it untill they bleed says me. Naturally yer working with fresh fuel filters and fabric coated fuel return lines aint leakin, and priming pump aint leaking either.

In addition to the above, setting up a temp tank in the engine compartment rules out bad fuel and immediately shows if the lift pump is cycling fuel from the tank through the IP and out the return line.

A good strong battery to spin the engine is also a must.

Glow plugs are working by your description. You don't say where you are located or what the outside temps are. You might need to glow more than oce before you start. The engine needs to turn at least 100 RPM so if the battery or starter is weak you might have problems. The series glow plugs that you have weren't very good for me so I bought the conversion kit to pencil type from diesel giant.

Add to this list that the starter/battery must be able to spin the engine fast enough. A gas engine will start even if your starter can just barely get a cylinder to the top and the spark plug to fire, a diesel engine needs to be spinning at a fairly good clip to get started. If the compression is low it'll need to spin faster.

I haven't had to resurrect a sitting engine.. isn't there something about adding a small amount of oil to each cylinder to lube the rings and get higher compression for that first start? Or am I confused?