Load-Sensing Proportioning Valve Test

Before diagnosing Load-Sensing Proportioning Valve (LSPV), ensure all other brake components are operating properly. When all other brake system components are determined to be okay, perform LSPV test beginning with next step.
Ensure unladen vehicle is on level ground. Ensure lever is not contacting stopper bolt. See Fig 1.
When lever is pushed toward valve, distance from LSPV lever hole and support hole must be within specification. Refer to the LOAD-SENSING SPRING LENGTH table under ADJUSTMENTS. If measured distance is not within specification, loosen support bolt. Adjust support until measured distance is within specification.
After measured distance is within specification, connect pressure gauges to input and output ports of LSPV. See Fig 2. Bleed brake system. See BRAKE SYSTEM BLEEDING in this article.
Remove the LSPV load-sensing spring. Slowly depress the brake pedal while checking the readings on the pressure gauges. Refer to the LSPV PRESSURE SPECIFICATIONS table.
Install LSPV load-sensing spring. Load weight into rear of vehicle until measured distance is 6 55/64" (174 mm) with lever slightly pressed in. See Fig 1. Slowly depress brake pedal. Check readings on pressure gauges. See LSPV PRESSURE SPECIFICATIONS table.
If fluid pressure is not within specification, ensure all other brake system components are okay. If other components are okay, replace LSPV assembly.

LSPV PRESSURE SPECIFICATIONS (LOAD-SENSING SPRING)

Application/Condition

Inlet Pressure psi (kg/cm² )

Outlet Pressure psi (kg/cm² )

Removed

853 (60)

242-327 (17-23)

Installed

1991 (140)

⁽¹⁾ 299-583 (21-40)

⁽¹⁾	On vehicles with 2WD and heavy duty suspension, outlet pressure is 526-697 psi (37-49 kg/cm² ).

Fig 1: Testing LSPV (Colt Wagon, Colt Vista & Ram-50)

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Fig 2: Connecting Pressure Gauges to LSPV

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.