Fuel pump belt

[riverhead]

Hi all
I'm a newbie here
I've had a few volvos and this is my second 940 tdi
I have a problem I'd like to share and see if anyone can help.
My engine conked out and became very hard to start and misses and smokes like hell.
I'd say running on 3 cylinders if lucky.
After a lot of head scratching and removal if rocker cover I deduced it must be the fuel pump drive belt.
It's very loose and I've never changed it.
So I'm going to check the timing of it but I'm not 100% sure if what I'm doing.
If I get TDC and put the locating pin I the fuel pump will that give me the timing set up so I can put a new belt on in the right position?
It will also tell me if the engine has slipped a couple of teeth on the pump drive belt.
Any feedback would be welcome.
I'm pretty handy with a spanner and ratchet, but not great at the technical end of things.