John wrote:
Many diesels are turbocharged. If those seals fail, the engine ingests
it's own lube oil and revs itself to destruction.
It sounds like these diesels were running on the well gas. The normal
engine governers would have shut off the fuel as soon as the speed
increased. There are only two ways to stop this overspeed. 1) increase
the mechainical load on the engine. This can be done in a car but not
on a generator like these. 2) shut the air intake to the engine.
That's also just about impossible on engines as big as these unless
there's a system in place to do it.

Many Diesels have one extra, last-chance emergency shutdown method, which is
a system that locks open a valve in each cylinder. On Detroit Diesel
engines
so equipped, there is a linkage on the valve cover that swings
spring-loaded catches
against the valve spring retainers. As each valve is opened, the catch
clicks into
place, holding the valve open. I have seen a similar mechanism on some
other
make of Diesel engines.

Jon