GMC 1986 P-Truck Service Manual page 217

flow control valve and recheck. If the
pressures are still low, replace the rotating
group in the pump.
8. If the pump checks within specifications, leave
the valve open and turn (or have turned) the
steering wheel into both corners. Record the
h ig h e st p re ssures and com pare w ith the
maximum pump pressure recorded. If this
pressure cannot be built in either (or one) side of
the gear, the gear is leaking internally and must
be disassembled and repaired.
9. Shut the engine off, remove the testing gage,
reconnect the pressure hose, check the fluid level
and/or make the needed repairs.
10. If the problem still exists, the steering and front
suspension must be thoroughly examined. Refer
to " Diagnosis of Power Steering System."
Test With J-25323
1. Place a container under the steering gear or
pump to catch the fluid when disconnecting or
connecting the hoses.
2. With the engine NOT running, disconnect the
pressure hose at the steering gear or power
steering pump. Thread J-29525 female adapter
into the pressure hose and the male adapter into
the gear or pump. Connect J-25323 analyzer
hoses to the adapters.
3. If the analyzer has never been used, it will be
necessary to bleed the power steering system to
remove all the air. Refer to " Bleeding the Power
Steering System" in this section. The analyzer
gate must be open during this procedure.
4. Add power steering fluid to the pump if required.
5. Run the engine at idle speed w ith the gate valve
open and record flow (A) and pressure (B).
• If the flow is below 7.4 L/min. (2 gpm), the
pump appears to be in need of repair, but
continue the test.
• If the pressure is above 1035 kPa (150 psi),
check the hoses for restriction and check
the steering gear.
6. Partially close the gate valve to build 4278 kPa
(620 psi). Record the flow (C).
• If the flow (C) drops more than 3.7 L/min. (1
gpm) under flow (A), disassemble the pump
and replace the ring, rotor, and vanes. If the
pressure plates are worn or cracked,
replace them. Replace all O-ring seals when
reassembling the pump. Continue the test.
7. Completely close and partially open the gate
valve three times (do not allow the valve to
rem ain closed fo r more than 5 seconds).
Record the " gate closed" pressure (D).
8. Check the pressure specifications, at the end of
this section for the correct pump model, and if the
pump pressure recorded is 690 kPa (100 psi)
lower than the minimum specification listed,
POWER STEERING 3B3-11
replace the flow control valve in the pump. If the
pressure recorded is above the maximum
specification listed, the flow control valve in the
pump should be removed and cleaned or
replaced. If the system is exceptionally dirty, both
the steering gear and pump must be completely
disassembled and cleaned before reassembly.
9. Increase the engine speed from idle to about
1500 rpm. Record the flow (E).
• If flow (E) varies more than 1 gpm from flow
(A), then the flow control valve should be
removed and cleaned or replaced, the same
as in step 8.
10. Have the steering wheel turned into the left and
then right corner lightly against the wheel stops.
Record the pressure and flow (F).
• Pressures developed in both corners should
be nearly the same as the maximum pump
output (D). At the same time the flow should
drop below 1.85 L/min. (0.5 gpm).
• If the pressure does not reach maximum
output or the flow does not drop below the
specified value, excessive internal leakage
is occurring. Remove and disassemble the
steering gear and remove the control valve.
Repair the steering gear as outlined in the
Unit Repair Manual.
11. Have the steering wheel turned slightly in both
directions and release quickly while watching the
pressure gage. The needle should move from the
normal back pressure reading and snap back as
the wheel is released. If it comes back slowly, or
sticks, the rotary valve in the steering gear is
sticking. Remove, disassemble and clean the
rotary valve. If the system contains a lot of dirt
and foreign material, disassemble the pump the
gear, clean and reassemble.
12. If the problem still exists, the steering and front
suspension must be thoroughly examined. Refer
to " Diagnosis of Power Steering System" in this
section.