Hi Nick, yes it is most likely the element is worn. Could be just regular wear caused by it`s age, much more likely fuel contamination, dirt or water. Clean out the fuel tank and fuel lines, replace the fuel filter before connecting your refurbished injector pump.
The AV1 has an externally mounted injector pump but it would still be possible for fuel to leak down into the sump, check the oil level, if it has risen you have diesel in the sump and you should probably do an oil change.
Bob