[ngoma]

What a shame!

There is a failure mode that causes a runaway, stoppable only by blocking the intake.

Ball actuator at the bottom of the fulcrum lever breaks off, leaving the fuel collar uncontrollable. If the fuel collar slides into WOT or near-WOT position the engine will rev uncontrollably.

Member v8volvo had this happen; his main theory is that running w/ clogged fuel filter caused the internal vane pump to self-destruct somewhat, sending shavings into the rest of the IP, some of which lodged between the fuel collar and shaft, causing the fuel collar to seize on the shaft, breaking the ball actuator off the end of the fulcrum lever, the weak point.

De-energizing the fuel shutoff solenoid may not be able to overcome this. Actuating the manual fuel shutoff (auto trans IP) has no effect (linkage is effectively disconnected at the fuel collar in this scenario). Dumping the clutch (manual trans car) may not slow engine in time to avoid damage.

Now that this failure mode has been identified, for future bench testing, we should all make sure to have a suitably-sized wood (or similar) plate positioned ready to slap over the intake.

What are you going to do with it now?