Section 5.8 Low Compression

Section 5.8
Low Compression

To determine if low compression is causing starting difficulty, perform the following steps:‪

1. Perform a cylinder compression test. Refer to "2.2 Compression Pressure Test" .
2. Compare cylinder compression test results to specifications as listed in Table "Compression Testing Specifications" .

   Description‪	Pressure in kPa (psi)‪
   Compression Pressure at Starter Speed‪	2800 (406)‪
   Permissible Difference between Individual Cylinders‪	400 (58)‪

   Table 1. Compression Testing Specifications
   1. If cylinder compression pressure is below specifications, refer to .
   2. If cylinder compression pressure is within specifications, call Detroit Diesel Customer Support Center at 313-592-5800.

Section 5.8.1
Low Compression Repair

Perform the following steps for low compression repair:‪

1. Remove cylinder head. Refer to the MBE 4000 Service Manual (6SE420), Chapter 1, “Engine”.
2. Inspect the cylinder head for worn or damaged valves. Refer to the MBE 4000 Service Manual (6SE420), Chapter 1, “Engine”.
3. Replace damaged valves. Refer to the MBE 4000 Service Manual (6SE420), Chapter 1, “Engine”.
4. Inspect the cylinder kit components for worn or damaged liners; pistons or piston rings. Refer to the MBE 4000 Service Manual (6SE420), Chapter 1, “Engine”.
5. Attempt to start and run the engine, if the engine starts and runs, no further troubleshooting is required. Shut down the engine.
6. If the engine fails to start and run, call the Detroit Diesel Customer Support Center at 313-592-5800.

Section 5.8.2
Verify Repairs

Perform the following steps for low compression repair:‪

1. Start and run the engine.
2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range, 88-96°C (190-210°F).
   1. Perform compressions test using DDDL 7.x or later.
   2. If the engine is not running rough or stalling, no further troubleshooting is required. Shut down the engine.
   3. If the engine is running rough or stalling, shut down the engine. Call Detroit Diesel Customer Support Center (313-592-5800).