The FPR establishes a fixed base pressure that everything else is modified from.

The CPR is primarily for cold running via control of the pressure on top of the metering pin that is positioned (lifted) proportional to air flow passing and displacing the air metering disc in contoured airflow housing.

The fuel distributor feeds base fuel pressure through an orifice to the top of the metering pin bore. The CPR is controlling the outflow from this pin bore to decrease pressure to allow more lift of pin/airflow or increase pressure (less outflow) to apply more pressure to top of pin bore to give less pin lift/airflow. The thermostatic spring counteracts a regulator spring to give lower control pressure, once the CPR warms up, the thermostatic spring lifts away from the regulator spring(s) and the CPR goes to a 'fixed' pressure. The aneroid and/or the enrichment devices are under the spring seat for the regulator spring.

I should mention that the CPR had some added features over the years like acceleration enrichment via a single vaccum hose supplied all the time, or altitude compensation by use of aneroid chamber below one of the CPR regulator springs, or cold acceleration enrichment via two vacuum hoses (one of the hoses with a delay vac valve in it) with altitude comp also.

One model has the altitude comp, cold enrichment, and two stage heater.

This is actually the superceded version for many late applications and sometimes requires the wires be reversed in electrical plug. The single stage heater models are not polarity sensitive but the two stage heater versions are.

The FPR on 78 and later models incorporates a CPR non-return valve that blocks fuel loss on shut-off through the CPR bleed hose.

The check valve is a separate part on all OE Bosch pumps but may not be detachable if some aftermarket pump has been substituted.

Residual pressure is a really important thing on this system and the accumulator is an additional source of pressurized fuel volume to assure retention of at least some pressure if there is a wee bit of leakage.

The accumulator on early models (up to approx 1980) had a vented plug on end (looks like a screw) and will leak externallly if diaphragm is ruptured. The newer versions have a hose that runs to fuel tank and allows any leakage to be contained. These late ones give no tell-tale sign when faulty (no fuel running onto ground).