5.7 LITER DIESEL ENGINE UPDATE MULTIPLE SUBJECTS

5.7 LITER DIESEL ENGINE UPDATE

1. HEAD BOLTS

When removing head bolts on the 5.7 liter diesel engine for any reason, it is recommended that the new design head bolt, which is identified by a (-) on the bolt head, be reinstalled. The new style bolt is of sufficient hardness that stretching of the bolt will not occur. The new style bolt does not require replacement when removed for service unless it is broken.

2. VALVE COVER REMOVAL

When removing valve covers on a 5.7 liter diesel engine, it is not necessary to remove the injection pump and lines as stated in the 1978 through 1982 Cadillac Service Manuals. It is necessary to remove ONLY the injection pump lines from either the left or right side as required. When performing any service on a 5.7 liter diesel that requires valve cover removal, always remove the pump lines completely. NEVER disconnect the lines from the injector nozzles and try to position out of the way. This will cause damage to the lines and result in poor engine performance.

3. DIESEL ENGINE TIMING

The Service Manual points out that the timing marks on the injection pump and the injection pump adaptor should be close to being lined up after dynamic timing the engine. If they are not, and the engine still exhibits a poor performance condition, the dynamic timing still could be incorrect. It is possible that a misfiring cylinder will result in the incorrect timing. Whenever this occurs, it is essential that timing be checked in the alternate cylinder. Timing can be checked in cylinders 2 and 3. If a difference in timing exists between cylinders, try timing the engine in both positions to determine which timing gives the best engine performance.

4. DIESEL TIMING METER

Snap-On Corporation advises that luminosity probes are being damaged by being overtorqued in the cylinder head, which cracks the quartz and allows soot to get behind the lens where it cannot be cleaned. In some cases, meters have been returned for repair when only the probe was at fault. Before the probe is used, hold it up to the light to make sure it is clear. When installing the probe in the cylinder, do not exceed the torque specifications of 11 N.m.

5. EXCESSIVE EXHAUST SMOKE

Some 5.7L diesel engines may experience an excessive exhaust smoke and a rough running condition. This condition can usually be corrected by dynamic timing the engine. If timing does not correct this condition, check the housing pressure cold advance for proper operation (1981 through 1983 models); refer to 1983 Cadillac Service Information Manual, page 6B3-9. Also check for a sticking advance piston in the injection pump (1980 through 1983 models) by pushing in on the bottom of the face cam lever on the right side of the injection pump. This will retard the timing and cause the engine to run rough if the advance piston is free. If there is no change, the piston is sticking and must be repaired.

6. STUCK PISTON RINGS

Some 5.7 liter diesel engines may experience an excessive oil consumption and low compression and/or excessive blowby condition. This condition may be caused by stuck piston rings. To correct this condition, proceed as follows:

a. With the engine warm, remove glow plugs from all cylinders.

b. Equally divide the contents of one can of top engine cleaner (P/N 1050002) into each cylinder. Allow the engine to soak for 24 hours with glow plugs removed.

c. Crank the engine with the glow plugs removed to expel the top engine cleaner.

d. Reinstall the glow plugs and start the engine.

For warranty purposes, use Operation No. T6068 at 0.7 hour.

7. HARD STARTING

Some 5.7 liter diesels may experience a hard starting condition, either hot or cold. This condition may be caused by insufficient cranking speed. This condition may be difficult to diagnose due to the inaccuracy of many tachometers at cranking speed. To determine cranking speed and the accuracy of the tachometer, proceed as follows:

a. Install J-26999 compression gage into any cylinder.

b. Disconnect the injection pump fuel shut off solenoid lead at the injection pump.

c. Install a tachometer.

d. Depress the pressure release valve on the compression gage.

e. With the aid of an assistant, crank the engine for two or three seconds to get the starter up to speed; then, without stopping, count the number of "puffs" at the compression gage that occur in the next ten seconds. Multiply the number of "puffs" in the ten-second period by 12 and that will be the cranking RPM.

Tests conducted show that diesel engines will start hot at approximately 200 RPM and cold at 100 RPM.

8. DIESEL INJECTION PUMP REPAIR PARTS

Diesel engine injection pump repair parts are now available through GMWDD. Repair parts available are listed in the current Parts Catalog, Groups 3.300 through 3.340.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.