Gomog, I think you have somewhat misunderstood what I have been saying.

Firstly I fully agree with Bunny, Red Three and Planenut that the published fuel system diagram is wrong. The fuel flow is from the pump to the injectors and returns via the fuel filter.

When the fuel pump fails it can sometimes initially provide the required 58psi and so the engine can start but the pressure rapidly falls away leading to the engine spluttering and stopping.

So, back to the original post, if they have access to a Schrader valved fuel pressure gauge check the pressure is 58psi and holds whilst trying to start the engine and for a minute or so afterwards. Somthing like Fuel Pressure Gauge


Alternatively replace the fuel pump again.

Red Leader drive