MU non return valves

[ijonsson]

Would malfunctioning non return valves in the MU cause an effect similar to misfiring when accelerating? Real suspect is actually the distributor, but still would like to know. I know that faulty NRV can be the reason for cranking a lot at start before injectors are filled up, but not if they have any impact while running at load.

Regards

Inge

[Mike C]

I don't think so- once the MU is pumping a solid column of petrol to the injector leaking backwards is a non event. In my experience the most common cause of misfiring during hard WOT acceleration is    defective spark  plugs .

Edited June 3, 2023 by Mike C

[astontr6]

1 hour ago, Mike C said:

I don't think so- once the MU is pumping a solid column of petrol to the injector leaking backwards is a non event. In my experience the most common cause of misfiring during hard WOT acceleration is    defective spark  plugs .

Or even air trapped in the injector fuel lines?

Bruce.

[stuart]

At what RPM does the missfire occur?

Stuart.

[ijonsson]

1 hour ago, stuart said:

At what RPM does the missfire occur?

Stuart.

It's noticeable at idle and revving the engine standing still, but really bad while accelerating under real load. MU was overhauled 2 years ago. Injectors some are new, some are overhauled, spray OK, pump pressure is stable (pressure gauge installed). Checked with various timings, a bit better at really retarded timing. Plugs, leads and cap are good, red rotor, DD condenser. The suspect is the springs and weights in the distributor, so we will try to find another distributor just to check.