Plant & Works Engineering
Why is my excavator so slow?
Published:  21 October, 2020

Tim Bone, cylinder parts manager at FPE Seals explains some of the reasons why an excavator can be operating slowly.

Modern day excavators come in many shapes and sizes, with most now fitted with more than one hydraulic pump, along with various system relief valves, service relief valves and priority valves to make the excavator run more smoothly.

Generally, there are two main hydraulic pumps, one for each of the track motors and possibly a smaller displacement pump for the pilot circuit. Reasons as to why an excavator is running slowly, can be down to the two main hydraulic pumps, as it is these that are primarily designed to power the main function of the excavator. 

An excavator’s load is spread equally across both pumps. On its return, flow it is diverted through a loading valve or regeneration valve, combining both flows and giving the extra power needed to the required cylinder, resulting in a better tear out force.

An excavator’s two power supplies, the engine and the hydraulic pumps, are driven through a flexible drive coupling. The first signs of a problem will show when an excavator tracks to one side or some of the functions are slow, while others are working normally. If all the functions are slow then this might be a sign that the power unit has a fault, or the drive coupling is worn and slipping.

First check the power unit. Is the engine struggling? Basically, if the engine is not running correctly or in need of a service, then it cannot provide the necessary power for the hydraulic pumps to supply the flow to run the system.

Secondly, check the flexible drive coupling. This could be worn, shattered or even slipping on the drive shaft. Drive couplings wear out as the rubber segment that gives it the flexibility take a lot of stress. Also check the hydraulic fluid levels, if the suction strainer is blocked this can cause cavitation and starvation to the pumps.

Finding a fault on any machine is time consuming, but by using a process of elimination component by component as this will make a diagnosis easier. Try not to think that the problem is a major component, in the majority of cases it is often something very simple like an O-ring or a damaged seat of a valve.