Rob;

Very good info from 142g, as usual!

I would like to add a bit to clarify about the Injector power which can be tricky to understand for non electronics guys...one side of ALL Injectors is in fact tied to chassis so you should ALWAYS read 0V there (Ref: https://www.sw-em.com/bosch_d-jetronic_injection.htm#Bosch_D-Jetronic_Circuit ), and yes, the other side of all will measure at 12V, but this is deceiving in that it measures this only when the associated transistor switch in the ECU is OPEN, and NO current is flowing through Injector (and its Pintle and fuelflow are CLOSED!)...when the transistor switch (momentarily) closes during operation, does current flow through the Injector, Pintle opens allowing fuelflow, and at that time, voltage on the side previously measured at 12V will drop to 3V as supplied voltage is divided by 6Ohm series resistor within ECU and Injector, but as this is strictly a transient condition, this can ONLY be seen on a DVM with a catch-and-hold function, or oscilloscope.

Injectors are NOT designed or intended for a full 12V...in fact, applying this voltage directly would overheat and kill an Injector short order (and guys who have applied a full 12V, even if only for test purposes, have lunched Lord knows how many like that)...DON'T DO IT!...Injector CAN be safely tested by (momentarily) applying 12V, but by way of a 6Ohm 5W limiting resistor.

One of the TPS functions can be checked with Ign ON, open Throttle and listen for 20 clicks all the way to Wide Open Throttle. Ref: https://www.brickboard.com/RWD/volvo/758191/1800/throttle_position_switch_test.html (Note: this test does NOT check adjustment!) More on TPS here (there's a lot happening in this little box!): https://www.sw-em.com/bosch_d-jetronic_injection.htm#TPS

Cheers