E527 High Brake Pump Command [PDF]

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Troubleshooting 793F and 797F Off-Highway Trucks Braking System Media Number -KENR8395-09

Publication Date -01/11/2014

Date Updated -11/07/2017

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E527 High Brake Pump Command SMCS - 4014-035 View Image

Illustration 1 Tools to help diagnose issue: Cat® ET data log,

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Illustration 2 A Cat® ET data log file (E) Poor charge time (15) Poor stability

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Illustration 3

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A Cat® ET data log file (F) Good charge time (16) Good stability

Refer to Systems Operations, KENR8738, "Control Valve (Brake)" for the locations of the components in the table below. Table 1 Problem: EID 527 High Brake Pump Command is active if the engine is running, and the brake system is charging for more than 90 seconds without cutting out. Component

Possible Component Root Causes Seal Damaged causing leaking.

Valve improperly installed causing Solenoid Valve (Brake screen damage Pump Unloader)

NonComponent Root Causes

How to Diagnose

Corrective Action

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Open circuit/short to ground fault codes logged in ET. Measure coil resistance when cool 20° C (68° F). The resistance should be close to 32 +/- 2 ohms.

Replace Solenoid Valve (Brake Pump Unloader).

Harness connector not locked in place

Stuck Closed: Measure actual brake pump pressure. Install 35000 kPa (5000 psi) gauge on brake pump pressure tap. Brake pump pressure at 22408 ± 345 kPa (3250 ± 50 psi) relief pressure constantly. Remove the access plug for OR1. Install a 35000 kPa (5000 psi) gauge. Pressure at OR1 is the same as pump discharge pressure, replace solenoid valve.

Bent or damaged solenoid valve.

Make sure that oil is ISO 18/15 or better. If more than 18/15, kidney loop machine and change filter. If kidney loop not available, change oil.

Remove solenoid and visually inspect screen for damage.

Pumping over relief valve for an extended period > 90 seconds Valve(Brake Pump Unloader)

Stuck Open or Closed

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Stuck Closed: Measure actual brake pump pressure. Install 35000 kPa (5000 psi) gauge on brake pump pressure tap. Brake pump pressure at 22408 ± 345 kPa (3250 ± 50 psi) relief pressure constantly.

Replace Valve (Brake Pump Unloader).

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Remove the access plug for OR1. Install a 35000 kPa (5000 psi) gauge. Pressure at OR1 is less than brake pump pressure, replace Valve. Stuck Open: Measure actual brake pump pressure. Install 35000 kPa (5000 psi) gauge on brake pump pressure tap. Brake pump pressure at standby constantly.

Seal damage

Remove valve and visually inspect to determine if valve stuck open

Stuck Open: Measure actual brake pump pressure. Install 35000 kPa (5000 psi) gauge on brake pump pressure tap. Brake pump pressure at low pressure constantly.

Stuck Open

Relief Valve (Main) Pressure Setting Drifting Low causing a stalled charge

Brake Pump

Poor Volumetric Efficiency

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Drifting Low: Measure actual brake pump pressure. Install 35000 kPa (5000 psi) gauge on brake pump pressure tap. Brake pump pressure below Brake Accumulator cut out pressure ( 20684 kPa (3000 psi)). Low Idle Charging may stall or charge time be extended.

Make sure that oil is ISO 18/15 or better. If more than 18/15, kidney loop machine and change filter. If kidney loop not available, change oil.

Increase Relief Valve (Main) pressure setting. Replace Relief Valve (Main). Make sure that oil is ISO 18/15 or better. If more than 18/15, kidney loop machine and change filter. If kidney loop not available, change oil.

If you cannot reach cutout at Replace low idle, the pump efficiency Brake Pump. is possibly too low. To test, run Tank line into bucket and plug Tank port on tank. Disconnect charging solenoid and accumulator purge solenoid. Activate engine kill switch (Engine will not start) and Transmission lockout switch-on bumper. Turn over engine until air tank drains two times. If little oil drains out of tank line replace pump due to no large leakage in

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rest of system. If oil does discharge out of the tank port, measure and track the accumulator pressures. If pressure at service accumulators drops quickly, inspect the service brake valves. If the secondary accumulator pressures drop quickly, inspect the secondary brake valves. If accumulators do not drop quickly, inspect the system relief valve. After testing, insure that the charging solenoid and accumulator purge solenoid are reconnected. Reconnect all lines and dry crank engine again, allow accumulators to purge back to tank. After accumulators have been purged, work may begin on the truck. After the procedure is complete, the brakes must be purged.

Brake Accumulator Pressure Sensors

Solenoid Valve Gp (Brake Accumulator Purge)

Failed In Range /Stuck at one pressure

Short to Battery

Stuck Open

Harness connector not locked in place

With machine off, verify that the sensors are reading less than 517 kPa (75 psi).

Locking tab broken on mating connector.

Install 35000 kPa (5000 psi) gauge on the brake accumulator pressure taps to verify that the accumulator pressure matches the gauge pressure. With machine running at low idle check to see if the gauge matches the sensor in Cat® ET.

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Short To Battery Fault Code

If you cannot reach cutout at low idle and both accumulators cycle rapidly, then the valve could be stuck open.

Replace Brake Accumulator Pressure Sensors.

Replace Solenoid Valve Gp (Brake Accumulator Purge) Make sure that oil is ISO 18/15 or better. If more than 18/15, kidney loop

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machine and change filter. If kidney loop not available, change oil.

Check Valve (Hoist Pilot Check)

Incorrectly installed in place of tow motor check.

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Check Valve (Tow Motor Check)

Incorrectly installed in place of hoist pilot check.

Contamination: Brake system oil (significantly) dirtier than ISO 18/15

Verify arrow on hex of check Properly valve is flowing in the install check correct direction. valve.

System Overheating

Remove filter element and inspect for damage and loose pieces of yellow plastic. Remove and inspect Accumulator purge solenoid screens for debris.

Filter Element

Damaged on Installation

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Verify arrow on hex of check Properly valve is flowing in the install check correct direction. valve.

Contact product support through the DSN.

Tue Oct 23 2018 10:58:22 GMT-0300 (Hora verano Sudamérica Pacífico)

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