Bs diesel

E7 454 Random/ intermediate shutdown

hey guys ive got a 1998 CHR Vmac 2 with a E7 454 engine, truck is a salt field truck that has come into the workshop for a suspected electrical fault, engine will start to stall and then grab revs last minute before shutting off, then idle fine with no faults, or will stall all together and then when u try to start it again it will crank with no start. when it first came in  battery's where dead, alternator belts where extremely loose and main battery earth cable was split. replaced battery's fixed earth cable, tightened up belt then checked DTC's only found three fault in system, ( fuel rack position sensor/ current below normal or open circuit, Fuel actuator/ current below normal or open circuit and Timing sensor/ data erratic, intermittent or incorrect). 

with these faults i checked over the wiring to the inline pump and found the connector had bear wires showing, replaced and re-pined a new plug, and repaired a few other rubbed wire's in the engine harness by the alternator. once done cleared codes in the truck, truck started up fine and would run fine for a while drove around yard no problem for two days but then when i went to park up on the fence for customer truck faulted again tried checking for any DTC's nothing was logged both active or inactive. if anyone's come across a fault that sounds the same and has a idea what to check out that would be great as this is the first time in dealing with this old of a truck.  

UPDATE...

found out what was wrong. the customer has had this truck at another shop for the same faults and didnt say anything about it, but what they did was cut all the wires at the ECU and ran 7 core trailer wiring out the LHS of the Cab firewall all the way to the pump, Bypassing the cab loom and engine harness, but what they did was they wired it up wrong at the pump side and ECU plug, finally found a wiring diagram and yeah found what they had done, so re-wired it all and put a new RPM/TDC sensor on and now she runs like a dream.