Diagnostics and testing 2.7L (Discovery 3)

Review

On diesel engines there is an additional drive belt for the high pressure fuel pump. This section covers basic checks of both.

Information about the system and its operation can be found in the relevant section of the service station manual.

Inspection and verification

1. Ensure that the customer's complaint is justified.

2. Visually inspect for obvious mechanical problems.

Mechanical factors

Drive belt condition (cracking/damage/contamination) Intermediate pulley assembly Generator Engine cooling fan Tensioner assembly Engine coolant pump Power steering pump Air Conditioning (A/C) Compressor Torsional vibration damper Dynamic response pump Tensioner assembly Auxiliary drive belt Fastening/correct installation of the high pressure fuel pump cover Fuel injection pump belt condition (cracking/damage/contamination) High pressure fuel pump belt tensioner assembly High pressure fuel pump High pressure fuel pump belt

3. If an obvious cause for the problem you identified or the customer described is found, resolve it before moving on to further action. (if possible).

CAUTION: If the engine is run without the accessory drive belt in order to avoid activating certain components, diagnostic trouble codes (DTCs) may be generated that should be cleared before returning the vehicle to the owner. The engine should not be run for more than 2-3 minutes with the belts removed. Failure to follow this instruction may result in vehicle damage.

4. Use the approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the Symptom Chart and DTC Index.

[The article was taken from this resource: LRman.ru]

Clear all DTCs after troubleshooting.

Table of signs of malfunction (accessory drive belt)

Sign of malfunction	Possible reason	Actions
Noise	Belt condition Belt tension Skewed pulleys Elements driven by (including tensioners)	Check the condition of the belt (see visual inspection). Check the operation of the tensioner. Check the pulley alignment. Check the driven elements for increased resistance to rotation. Repair if necessary.
The drive belt does not hold tension	Belt condition Tensioner malfunction	Check the condition of the belt (see visual inspection). Check the operation of the tensioner. Repair if necessary.

Table of signs of malfunction (high pressure fuel pump belt)

Sign of malfunction	Possible reasons	Actions
Noise	Belt condition Belt cover contamination Tensioner bearing failure High pressure fuel pump malfunction	Check the condition of the belt (see visual inspection). Check the belt cover for signs of contamination. (this may indicate a misalignment of the pump.), see the relevant section of the workshop manual. If the belt is removed, replace the belt tensioner, checking the bearing for failure. Remove the belt, check the high-pressure fuel pump pulley fastening. Check the high-pressure fuel pump for increased resistance to rotation (increased resistance in the pump causes the pulley lock nut to loosen - this is a design feature). Check for diagnostic trouble codes (DTCs) indicating a pump problem.
The drive belt does not hold tension	Belt condition Tensioner malfunction	Check the condition of the belt (see visual inspection). Check the operation of the tensioner. Repair if necessary.
Loss of motion transmission (without transmission of power to the high pressure fuel pump, the engine will not operate.)	Broken belt/cut teeth Loosening of drive pulleys	Investigate the cause of the belt break/damage (a belt break at a 45 degree angle usually indicates a shear, a break straight across the belt usually indicates the belt has been pinched). Check the high pressure fuel pump for increased rotational resistance. (increased resistance in the pump causes the pulley lock nut to loosen - this is a design feature). Check for diagnostic trouble codes (DTCs) indicating a pump problem.

DTC Index

NOTE: Generic scan tools cannot read the codes listed or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7-digit code to identify the fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

NOTE: For a complete listing of ECM DTCs, refer to Section 303-14, Electronic Engine Control System, in the service manual.

DTC codes	Description	Possible reasons	Actions
P050600	Crankshaft speed with air supply management system in idle mode is lower than expected	Reducing the air intake capacity Auxiliary drive overload (defective/sticking element)	Check the air intake system. Check the accessory drive belt and components. Refer to the appropriate section in the workshop manual.