Welcome to JA, I hope I can offer you some assistance.
There are no timing marks on this engine all the engine timing is done with locking pins.
The timing pin required for setting the crankshaft is a special pin that screws in to the engine block and locates against the crankshaft, you can buy this
quite cheaply from a local motor factors, the fuel pump can be timed using a 6mm drill bit and the camshaft uses a flat plate that fits in a slot in the rear
You need to find the position of cylinder 1 piston you may need to remove an injector for this, you need the piston coming up to top dead center, remove
the blanking plug from the cylinder block just below the fuel injection pump and screw in the crank locating pin, below is a diagram to assist.
Once this is in turn the crankshaft until it stops against the pin, as the belt has snapped make sure the crank is against the pin and it isn't a piston
contacting a valve that has stopped the crank from turning.
To fit the camshaft locking plate remove the valve cover, you'll see the slot in the rear of the camshaft for the plate, this will only fit in when the camshaft
is in the correct position as shown below
The fuel injection pump has a hole in the pulley and in the body for the 6mm drill to go in to time the pump as shown below.
You can also see the crank locating pin again in this diagram.
The camshaft pulley doesn't have any key to locate it when you fit the belt the pulley needs to be loose to spin on the camshaft, the camshaft is locked by the
plate in the correct position. Also the three bolts for the fuel pump pulley need to be loose when the pump belt is fitted, again the pump is locked by the drill bit.
The reason the camshaft and pump pulleys are like this is so when the belts are tensioned all the slack is taken up, once the belts are correctly tensioned tighten
the camshaft and pump pulleys.
When you've replaced the belts turn the engine over using a socket on the crank pulley bolt, turn the engine 2 complete turns to ensure that it turns over, if it is
correctly timed but won't turn over then there may be a bent valve or valves.
I hope this is of help but if I can assist further or if you have more questions regarding this let me know and I'll reply as soon as I can.
Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer. Bonuses and Feedback are Appreciated, Thank you. Best wishes with your repairs.
Leon Davidian, Sr. ( Master Tech Leon ).