James -

To ensure that you have electrical power to your system ---

1)  Place the landing gear switch in the DOWN position and turn the master switch ON.

2)  Check the voltage level at the center terminal of the landing gear switch.  It should read 12 V.  If so, your problem is hydraulic, not electric.  If it reads 0 V, then you don't have control power to your relays, probably from a blown fuse or tripped breaker.

When you put the switch to DOWN then you are applying power to the LO PRESSURE limit switch which, if the pressure is not above 500 psi, will then send power to a relay which will turn the pump on in the proper direction.  When you put the switch to UP then you are applying power to the HI PRESSURE limit switch which, if the pressure below 1200 psi, will then send power to a relay which will turn the pump on in the opposite direction.  If you don't have power to the landing gear switch, the motor will not run at all.  You can also test this at the LO PRESSURE limit switch.  One lead should have 12 V and the other will have zero volts if the pressure is above 500 psi and 12 V if the pressre is below 500 psi.

3)  If you DON'T have power to the landing gear switch, you probably have a blown fuse.  The gear pump circuit breaker is 50 amps but the power to the control relay only needs about 1 amp.  The builder should have a second circuit breaker (or fuse) allowing lighter weight wire to the relays.  This fuse may be blown.

4)  Check the voltage on the output side of the 50 amp breaker.  If it reads 0 V, you have a tripped breaker (even if the beake looks untripped).  Breakers can fail, but it doesn't happen very often. 

5)  If you DO have power to the landing gear switch and you DO have power on the output side of the 50 amp breaker, then your hydraulic system pressure is above 1200 psi.  The dump valve only equalizes the pressure between the low and high side, but if the whole system is above 1200 psi then nothing will happen.  TURN OFF THE MASTER SWITCH, then pick any fitting and crack it open.  The pressure will be relieved with a tiny gush of fluid.  Have a rag handy.  Tighten the fitting.  Your system should now work.

Please be careful if putting the gear switch in the UP position on the ground.  Like, have the airplane on jackstands or something.

Hope this helps.

- Rob Wolf