Case IH 329 – Engine Controller (ENG / ECM): CAPS Pump has an overpumping failure.

The CAPS (Cummins Accumulator Pump System) accumulator is failing to regulate fuel pressure properly, resulting in an over-pumping condition.

• MX Magnum
• STX Steiger
• MX215
• MX240
• MX245
• MX255
• MX270
• MX275
• MX285
• MX305
• STX275
• STX280
• STX330
• STX440
• 2377
• 2388
• 2577
• 2588
• Patriot 4420
• FLX3020
• FLX3510
• Titan 4020
• Titan 4520

1. 1

   Check the electric lift pump for leaks and air infiltration, which can cause erratic pressures and trigger CAPS failure codes.

2. 2

   Inspect inline fuel filters and lines for blockages or air leaks, as fuel starvation can trigger a cascade of CAPS codes.

3. 3

   Perform a bypass test by running the system from a remote reservoir with a separate pump and hose to isolate the issue to the CAPS pump itself.

4. 4

   Check for accompanying codes like 276 or 277; if present, replacing just the Injection Control Valve module may resolve the issue without a full pump replacement.

1. 1

   Clean engine area

   Disconnect the battery and thoroughly clean the engine area around the fuel pump to prevent debris from entering the fuel lines.

2. 2

   Remove fuel lines

   Remove the high-pressure fuel injection lines and the low-pressure supply lines.

3. 3

   Disconnect wiring

   Disconnect the wiring harnesses to the Injection Control Valve and the Engine Controller sensors.

4. 4

   Remove CAPS pump

   Remove the CAPS pump assembly from the engine gear housing.

5. 5

   Repair Option A (OEM Replacement)

   Install a remanufactured or new CAPS injection pump. Time the pump to the engine according to the Case IH/Cummins service manual, reattach all lines, and bleed the fuel system.

6. 6

   Repair Option B (P-Pump Conversion)

   Remove the CAPS system and install an aftermarket P-Pump Conversion Kit (an inline mechanical Bosch P7100 pump). This requires installing the new heavy-duty pump, new custom fuel injection lines, and conversion hardware.

7. 7

   Clear codes and verify

   Clear the permanent fault codes from the ECM using a diagnostic tool and perform multiple driving/operating cycles to verify the repair.