From: Employee@MilVeh.com
Date: Sun May 25 2003 - 09:41:45 PDT
Re: Fuel Density Compensator v. fuel injector pump.
As a follow up to our previous thread when my truck
was not running properly and I couldn't make it past
40 mph on flat ground, I wanted to ask a couple of
"dumb" questions to help improve my learning curve:
Facts as I know them: 1. The fuel density compensator
(aka D.C.) adjusts the flow rate to the fuel pump in a
way that maintains a constant vicosity, thereby
keeping the relationship between "viscosity" and
resulting "heat" effect in cly. in check to a safe
level.... Correct so far?
Next: 2. The "fuel flow rate" at the "fuel
distribution pump" is critical and increasing the fuel
flow rate can cause overfueling and overheating,
right?
So we have two different things going on here. A
"density" compensator that ads oil to thinner than
dielsel fuels, before allowing said fuel to pass on to
the pump and a pump that is tuned to a specific
pressure. It does not compensate diesel and allow
diesel to pass at the maximum rate. (Feel free to
disagree or jump in anytime if you disagree.)
Ok....here's the question part:
When using diesel only....how can adjusting the flow
rate on the fuel compensation pump alter the law of
physics pertaining to the fuel distribution pump? You
can only squeeze so much diesel through the dist. pump
to the injectors, right? These two items peform two
different functions on a multi-fuel engine. As I
understand it, passing along kerosene or gasoline
without properly "compensating" the density would
cause overfueling and thus overheating, but how does
passing diesel along to a "diesel tuned" injector pump
cause over fueling? This is where the law of physics
comes in and if it can overheat an engine I guess I
must be missing some part of the equasion. A
pro-dielsel mechanic tells me I'm going to melt
pistons by messing with the D.C. and I want to know
how this is possible?
Let me back up a bit and say, in my case the truck was
obviously starved for fuel. It was underpowered to
the point of not being able to go over 40 mph on flat
ground! It made starting extremely difficult too.
By opening up the fuel compensation adjustment rod 1.2
turns, the engine took on a whole new sound and power
range. Starting is now instant. Response to throttle
was greatly improved. Conclusion: Ran poor before -
runs great now.
I noticed that someone had probably been adjusting the
D.C. before me, as the safety wire had been removed
from the outter nut on the adjustment rod. A new pump
was obviously added. So somewhere along the line of
the many hands working on this truck, the D.C. got out
of whack, least thats my theory and it seems proven
now.
Rather than bi-pass the D.C. as the military has done
in some cases for diesel fuel only engines, I
re-adjusted the D.C. only to the point where the
engine ran like it was orginally supposed to run.
Zero smoke...doesn't overfueling cause smoke?
I could find no other defect on the truck to account
for the low power and hard starting. It runs
beautifully now.
Would appreciate your thoughts on this so I can learn!
Jack (Chico-Ca)
M35A2
L3314N
PSI TUG
http://milveh.com
and
http://standupforamerica.us
PS Excellent post Jonathan, really enjoyed reading
it.
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