From the lr4x4 thread...
"Take a digital voltmeter (DVM) and check if the fuel solenoid (Tdi) or ignition coil/fuel pump (V8) has a 12 volt supply to it by connecting the meter to the relevant blade connector and earth and turning the key to position 1 (on). If there is a 12 volt supply to the circuit, then the fault probably lies elsewhere. (Note that a dry joint may not always provide a perfect break in the circuit; on my own vehicle, it caused a voltage drop at the coil which was only apparent once you started cranking. As a result all appeared OK at rest, but when you tried to crank there was no spark. As I "knew" there was power to the coil, I didn't look at this any further, so it took rather a long time to find out that the power consumption when cranking was causing a voltage drop at the coil, which in turn caused the ignition amplifier module to cut out). "