OK to test the 5th injector, first check the fuel supply is good, remove the fuel pipe from injector [ be carefull hear as there should be residule pressure left in the system as this line is on the main pressure line 85/90psi]...so some fuel will come out, place the pipe in a container..need 2 people really one to hold the pipe steady , then remove pump relay, bridge out 30 & 87..ie Red to Red/black tracer...you should see Fuel come out under very High pressure....if fine refit relay and fuel pipe, now to test the Electrical side, This test must be done on a stone cold engine...well we know yours is as does not run, but have to mention this.... unplug its blue plug, unplug the ignition coil by pulling off Black wire as we don't want any ignition to take place..... with a meter or Test lamp probe each wire..get someone to crank engine on starter...you should see cranking voltage , good battery 9 to 11 volt, for wire colure its Black/yellowtracer is the power + side...very unlikely this down as its on starter side [ known as circuit 50 ], the other wire Brown/white tracer comes from the Thermo timer..Brown plug...this is where it gets its negative...if the Timer is faulty then then unplug it and ground Brown/white wire re-test power should be there, this what ive wrote is for no power at injector plug....it seems to me there may not be...as if the metering unit..4 injectors all be blocked through Bad gunged petrol, yet the 5th injector sprays neat fuel into manifold...good spark...the engine must run, all be it for 2/3 seconds, I assume you have spark. once you know it runs can advise on the rest, but it may well be the metering head and 4 injectors blocked . Peter. just to add, never had a 5th injector faulty....so just apply 12volt poss & neg to terminals...you will hear it click.