You need to get some proper diagnostics on it.
Is it a YD22DDT or YD22DDTi? One is Denso Commonrail, one is a Bosch VP44 system - if it's branded dCi it should be a DDTi which is the Denso CR system which is old and a bit batshit crazy.
If it's the CR one, ignore the pump - it'll be purely electrical as to why it's not running - again diagnostics required. If it's a VP44, the pumps die for no apparent reason.
Is it a YD22DDT or YD22DDTi? One is Denso Commonrail, one is a Bosch VP44 system - if it's branded dCi it should be a DDTi which is the Denso CR system which is old and a bit batshit crazy.
If it's the CR one, ignore the pump - it'll be purely electrical as to why it's not running - again diagnostics required. If it's a VP44, the pumps die for no apparent reason.