Hydraulic system troubleshooting - check
the easy things first
Secrets To Hydraulics
In Part II of Insider Secrets to Hydraulics, I outline a logical
approach to hydraulic system troubleshooting that begins
with checking and eliminating the easy things first. The
benefits of this approach are clearly illustrated by a troubleshooting
situation I was involved in recently.
The machine in question had a complex hydraulic system, the
heart of which comprised two engines driving ten pumps. Six
of the pumps were variable displacement units and four of these
had electronic horsepower control.
The symptoms of the problem were slow cycle times in combination
with lug-down of the engines (loss of engine rpm). The machine
had just been fitted with a new set of pumps.
The diagnosis of the mechanic in charge was that the hydraulic
system was tuned above the power curve of the engines i.e.
the hydraulics were demanding more power than the engines could
produce, resulting in lug-down of the engines and therefore
slow cycle times. The other possible explanation of course,
was that the engines were not producing their rated horsepower.
Due to the complexity of the hydraulic system, I knew that
it would take around four hours to run a complete system check
and tune-up. So in order to eliminate the easy things first,
when I arrived on site I inquired about the condition of the
engines and their service history. The mechanic in charge not
only assured me that the engines were in top shape, he was
adamant that this was a "hydraulic" problem.
Four hours later, after running a complete check of the hydraulic
system without finding anything significant, I was not surprised
that the problem remained unchanged. After a lengthy discussion,
I managed to convince the mechanic in charge to change the
fuel filters and air cleaner elements on both engines.
This fixed the problem. It turned out that a bad batch of
fuel had caused premature clogging of the engine fuel filters,
which were preventing the engines from developing their rated
If the relatively simple task of changing the engine fuel
filters had been carried out when the problem was first noticed,
an expensive service call and four hours of downtime could
have been avoided.