My Audi A4 2.5 tdi 1998 MY broke down last week (was low on fuel)

The RAC had the engine run on easy start (so cam belt OK)
Topped up diesel
And there was fuel coming out of the injectors, but it would not start on Diesel only?

The Garage said the Fuel Injector Pump is showing as a fault but they dont have the full Audi diagnostics?
They mention and ECU being part of the pump and that it wil be an expensive job.


Any advise on what to do next?