Issued July 2024
Pumps
Copyright 2024, The Heil Co.
Printed in the U.S.A.
Pumps
39
TANDEM VANE PUMP O.I.G.A.I. HYDRAULIC SYSTEM TROUBLESHOOTING
The Operate-in-Gear-at-Idle (OIGAI) system is designed to perform the side loading operations at standard idle speed. It is
comprised of two major components, the monoblock tandem vane pump and attached unloader valve assembly.
On Rapid Rail systems the P1 or front section (closest to the pump input shaft) operates the loader section of the truck while
the P2 or rear section (farthest from the input shaft) operates the body section, which includes the packer. On F7000 series
units the flows from both pump sections are combined to run the lift (loader) then exit the lift valve to operate the body valve.
On the Python, P1 goes to the lift and P2 combines after the lift valve to run the body.
The unloader valve assemblies consist of a manifold (pressure) block, a normally open (N.O. or NO) cartridge valve and a
12VDC-solenoid coil. In operation mode, the current is supplied to the valve coil causing the valve to close, forcing pump flow
to the respective hydraulic circuit. In bypass mode, the coil is de-energized causing the valve to open, allowing the oil to re-
circulate either back to tank or to the pump inlet.
A. Troubleshooting
The symptoms of a problem in the pump circuit are no operation or slow operation of the loader or packer system. Since
the F7000 series uses combined flows, a possible symptom of system malfunction is the packer operating at half the
normal speed. On a Rapid Rail body with a Rapid Rail lift, each pump section controls one aspect of the system
independent of the other. A malfunction of one pump’s section will normally only affect one function of the truck. For
example the packer will work correctly but not the loader or vice versa.
There are three primary causes for the pump circuit not to operate properly:
Low or no voltage to the unloader valve coil.
Malfunction in the unloader valve assembly.
Internal problem with the pump.
Perform the following test after finding that there is insufficient or no flow to the loader and/or body valves.
1. Check the Electrical Supply to the Unloader Valve Coils
a. With the system turned on and the engine operating at idle, test the voltage at the coil. It should read a minimum of
10 VDC. If proper voltage is present and the problem persists, proceed to step 2. If the voltage is below 10 VDC,
check the electrical system for problems that can cause a drop or loss of voltage to the unloader valve solenoid coil.
Some examples are a broken or shorted wire, blown fuse, fault in the side door switch (if equipped), no alternator
input or a failed PLC calibration.
b. Use an ohm meter to check resistance in the coil. If the measurement is less than 5 ohms or more than 20 then the
circuit coil is damaged. If the coil is damaged, replace the coil.
2. Eliminate the Unloader Valve from the Circuit
a. With the engine off, remove the bypass line from the pressure block port marked bypass . Disconnect the pressure
hose or hoses sending oil to the lift and body functions. On the Rapid Rail and Pythons, there are two pressure
hoses to be capped; on the F7000 and F4000 there is one hose to be capped. Cap and plug the tube connection for
the bypass to the pump inlet. This forces all oil to the hydraulic circuits as if the pump is on. (NOTE: Pump control
switches in the cab are no longer effective.)
b. Restart the truck and test the functions. If the lift and packer functions return to normal operation (speed and
pressure within specifications), replace or repair the unloader assembly.
If flow is present and the lift or packer operate only with no load, check the main relief valves for proper adjustment and
operation.
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