[Alberg30] RE: Bukh 10 Startup

[Bob Chambers]

I found your dissertation quite interesting, but I believe a little flawed.
With regard to my diesel, in particular, and I believe most others I have
seen, there is a single injection pump for the engine, mine having four
separate pistons inside it.  The lines from it to the injectors are not that
short, mine are some 12 to 18 inches, though they are made of high strength
steel as the pressure in them is in the 2500 psi range.  The returned fuel
is not from the injector pump manifold as you state, but from the injectors
themselves.  While a measured amount of fuel is delivered by the pump to the
injector, each injector has its own 'personality' and does not necessarily
inject all the fuel sent to it.  What is not injected is returned to the
tank.  The return fuel line on my Ford Lehman is actually inside the valve
cover and has a take off from each injector.

The fuel lift pump is sized to deliver sufficient fuel for full speed
operation, but if not all that is required, bypass springs on the valves in
the fuel lift pump open so that it only pumps what is required.  With the
engine off, I can manually pump the lift pump and once it builds up a
predetermined pressure, no more fuel is pumped, rather the valves open
causing a bypass effect.

Having just had my injector pump rebuilt, I asked the mechanic to show me
what the insides look like and found it quite interesting.  The pistons are
each on a spiral shaft or rod and the throttle lever turns these spiral
shafts so that the effective piston stroke is changed.  More of a stroke for
high speed so that more fuel is sucked into the chamber and pumped to the
injector and a much smaller stroke for slow and or idle speed.  Seeing the
insides of the pump and having the hundreds of small parts explained quickly
showed why an expert ONLY should re-build it and why the cost is so high.
($600 for mine).

For those interested, hope this helps.

Bob Chambers

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