Enerpac P-391, 1004, P-392, 1005 Service Instructions Manual

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L1743 02/04 Rev. B Refer to Repair Parts Sheet L-1771

Service Instructions

P-391, 1004 & P-392, 1005 Hand Pumps

SERVICE INSTRUCTIONS: These Service Instructions are intended to be used by qualified personnel at
Authorized Enerpac Service Centers. Users of Enerpac equipment should see the pump Instruction Sheet
for installation, operation, and maintenance information.

Before repairing the pump, see trouble-shooting guide on page 3 to isolate possible pump malfunctions.

YOU MAY NEED:

✔ Repair Parts Sheet L-1771
✔ Repair Kit P-391K2
✔ 10 ton single-acting cylinder

rated to 10,000 psi

✔ 0-15,000 psi pressure gauge
✔ high pressure hose (10,000 psi rating)

✔ torque wrench
✔ Allen wrenches
✔ box and wrenches
✔ o-ring pick
✔ roller bearing grease
✔ Enerpac hydraulic oil

1. Remove reservoir:

a. Remove acorn nut, gasket, end cap, and

reservoir gasket from reservoir.

b. Remove the reservoir, round reservoir gasket,

and tie rod from the pump base.

2. Remove handle and plunger assembly:

a. Remove plunger cross pin and plunger clip.

Remove handle assembly from the base.

Note: Older solid plungers have a plunger clip
and cross pin. The new two-piece flex design
has a cylindrical cross pin only.

b. Remove the plunger assembly from the

pump base.

3. Remove release valve assembly:

Unscrew the machine screw underneath the
spindle with a 5/32" Allen wrench. Remove the
spindle and the 7/32" check ball.

4. Remove check assemblies:

Unscrew the large pipe plugs from the pump
base. Remove the spring cap, spring, 5/16"
check ball, and 7/32" check ball from the
respective high and low pressure check
assemblies.

Note: The P-392, 1005 has two check
assemblies and the P-391, 1004 has one check
assembly.

5. Inspect oil filter to determine if it is clogged
with debris or needs replacement.

6. If relief valves need to be reset or removed, do
so at this point.

Pump is now disassembled. Clean all parts
and flush out the base to remove contaminants
from pump.

■ Disassembly

Before disassembly, remove oil from pump. (DISPOSE OF USED OIL PROPERLY)

®

2

■ Assembly

Refer to Repair Parts Sheet L-1771 and use Repair Kit number P-391K2.

Important: Set relief valves before assembling pump. Use new parts from the pump repair kit when
assembling pump.

FLEX PLUNGER STYLE: The old, solid style plunger has been replaced by the flex plunger. With the flex plunger
style, the P-391, 1004 and P-392, 1005 use the same type of base. When servicing the P-392, 1005, you will install a
bypass valve in the base and put a 7/32" check ball in the low-pressure check assembly. When servicing the P-391,
1004, the 7/32" inlet check ball is not used and a pipe plug is installed in place of the bypass valve. Refer to NOTE
in Repair Parts Sheet L-1771.

1. Replace relief valve(s) inside the pump base.

a. Older, solid plunger pumps require

replacement gasket(s) from kit. Torque to
60 to 70 in-lbs.

b. Newer, two-piece flex plunger pumps have

relief valves with 1/8" NPT threads. Gaskets
are not required. Torque to 10 to 12 ft-lbs.

2. Replace oil filter screen if necessary.

3. To install check assemblies, replace the 7/32"
and 5/16" check balls, spring, and spring cap
from the repair kit. Reseat check balls if
necessary. Torque the pipe plugs to
28 to 34 ft-lbs.

4. Before installing the release valve assembly,
remove and replace the spindle o-ring and the
7/32" check ball. Reseat ball if necessary. Put
roller bearing grease on the o-ring before
installing. Tighten the machine screw with a
5/32" Allen wrench.

5. When you re-assemble the reservoir, install a
new round reservoir o-ring when you position
reservoir onto the pump base. Be sure reservoir
is properly placed on the location pin.

a. Drop cap assembly chain through reservoir fill

port. Loop chain around the tie rod and
thread tie rod into pump base.

b. Replace end cap gasket and put end cap

onto end of reservoir.

c. Using new copper gasket, tighten the acorn

nut to 15 ft-lbs.

6. Install plunger assembly. For two stage
plungers (P-392, 1005), replace the o-ring and
back-up rings on both small and large pistons.
For single stage plungers (P-391, 1004), replace
the oil seal back-up ring and the o-ring.

Note: Put roller bearing grease on the plunger
before replacing oil seal and installing the piston
into the bore.

7. Install handle by inserting the new beam pin
into the beam pin hole on the pump base and
through the beam and handle assembly. Secure
the beam pin with new retaining ring.

a. For older solid plunger pumps, install plunger

clip and cross pin, with the flat of the cross
pin against the top of the plunger. Apply
bearing grease at this location.

b. For newer two-piece flex plunger pumps,

apply roller bearing grease to the cylindrical
shaped cross pin. Insert the cross pin into
the beam pin hole of the pump base, and
through the plunger and handle.

8. Refill the reservoir with the appropriate volume
of Enerpac hydraulic oil.

Pump is now assembled. Follow Testing Procedure
below to verify operation.

■ Testing Procedure

Test setup: connect (1) high-pressure hose, (1) 0­15,000 psi gauge, and (1) 10-ton single-acting
cylinder to the hand pump.

1. Single stage pump: (P-391, 1004) set high­pressure relief valve to 10,000-10,500 psi.

2. Two stage pump: (P-392, 1005) set the low­pressure relief valve to 200-275 psi; set high­pressure relief valve to 10,000-10,500 psi.

3. Test for loss of pressure. Operate the pump to
build pressure to 9,000-9,500 psi and watch
pressure gauge to see if pump maintains
pressure. The maximum drift or pressure drop
allowable is 250 psi in 10 seconds.

3

■ Troubleshooting Guide

IMPORTANT: To remove system variables and isolate pump for testing, connect test circuit of a known

good hose, a 0-15,000 psi gauge, and a 10 ton single-acting cylinder to the pump.

To protect warranties, use only Enerpac Hydraulic Oil.

Problem

Pump does not hold pressure

Pump loses pressure and the
handle rises.

Pump does not build pressure.

Pump does not create flow.

Probable Cause

Leak in the release check.

Leaking at hose and/or coupler
connection.

Outlet check seat leaking.

Inlet check balls leaking.

Damaged seals on the pump
plunger.

Oil filter screen clogged with
debris.

Relief setting too low or leaking
valve gasket.

Low or no oil in reservoir.

Debris in pump.

Pump not vented.

Coupler checked.

Low or no oil in reservoir.

Remedy

Inspect and clean ball and
seat. Reseat check ball.

Check for leak. Reseal with
appropriate sealant.

Inspect and clean ball and
check seat. Reseat check ball.

Inspect spring ball and seat.
Reseat check ball.

Inspect and replace seals if
necessary.

Flush pump, replace oil and
screen.

Inspect valve, check pressure
setting, and replace gasket.

Fill reservoir with Enerpac oil.

Inspect all components for
contamination, then flush.

Open vent cap.

Correctly couple together.

Fill reservoir with Enerpac oil.