Got injector pump out today. As I need to sort thermostat as well, I drained coolant & remove the various hoses at the front of the engine.

Cleaned the pump exterior of the years of oil, dirt & grime, and then took the regulator off. Both rubber & plastic o-ring not looking their best. Wondering what impact these have on the fuel regulation ?

Should there be an o-ring in the slot next to the regulator body ?

Pump seals will also be done this week.