The detent valve in a log splitter is the central assembly where the unpressurized hydraulic fluid interacts with the pressurized hydraulic fluid, creating the necessary reactions that make the log splitter work in the first place. However, if something goes wrong and the device lacks pressure or the detent valve isn't opening, you need to check through the assembly step-by-step to determine where the problem is before replacing the valve.
Find the diagram of the detent valve set up. There will be input valves for the pressurized and un-pressurized hose connections, and the diagram will show you which ones go on which side of the detent valve and in what order. If the hydraulic hoses are hooked up incorrectly, then the valve won't be able to function properly.
Check for leaks. If the hoses aren't connected completely in the detent valve, or if there's a leak in one of the hoses, then the pressure won't be enough for the mechanism to work properly.
Check the position of the lever. A detent valve lever can be pushed up or down to put the valve into operation. If you're used to the lever going one way on one log splitter, you might have overlooked the valve position on a different log splitter that works differently. Check the manual to be sure you have proper lever position.
Check the pressure going into the detent valve. Detent valves can be set for 1,000 to 2,000 pounds per square inch. If you have the wrong pressure going into the wrong setting, you're going to have poor results, if any at all. Be sure that the pressure and the hoses all measure up.