I have a 1991 Volvo 740 Turbo. AFter eliminating a bad plug and wire I have ordered a new bosh injector to replace #4 which seems to have failed.
I have not replaced one before, what procedure do I use to avoid causing more problems for myself? Do I need any special tools?

 

It is very easy remove the 2 10mm screws and pull the rail off. Sometimes you need to remove the fuel line. Other times you can move it out enough to change them out.

 

One watchpoint when removing the fuel rail (aside from the hazard of spilled gasoline) is that the two ground wires on the fuel rail fixing bolts are critical for proper injector operation. Make sure the there is no dirt on the mating surfaces.

It's also good practice to replace the injector o-rings on all the injectors after you remove them. You don't want any vacuum leaks! The o-rings are the same for Bosch and Regina injectors. Coat the o-rings with either ATF or synthetic grease before pushing the injectors into the manifold...it's easier that way, and you are less likely to tear them.