Diesel Timing and Bleeding

Diesel Bleeding

Engine that was bleed a Nissan TD27

This is done to remove air from the fuel lines in a diesel injection system. Because a diesel engine does not use spark plugs for combustion and instead uses compression to get a reaction air in the system will prevents the fuel from atomising correctly preventing the injectors from delivering enough fuel to the combustion chambers.

Bleeding was done by first clamping the fuel line of the diesel fuel filter and then removing it and emptying out the fuel from it into a container. 

Then replacing it and pumping the priming pump to remove excess air from the system. After this is complete the remaining air in the fuel lines can be removed by loosening each Injector one at a time to shut down one of the cylinders and allow the air to escape from the combustion chamber through the injectors to clear the lines.

Diesel pump and fuel filter

Electronic Shut off Valve

This is used to stop the engine from running when ignition key is turned off. Because a diesel engine does not use a ignition system that uses spark plugs turning off the key would not stop the engine from running under normal circumstances. So that is why a electronic shut off valve is used. It shuts off the engine using a solenoid controlled system that when the key is turned off the magnetic field of the solenoid collapses and plunger is forced to drop down and stop the flow of diesel from the pump. This in turn cause the engine to stop running.

Testing of this device is done using a ohmmeter to measure the resistance across the solenoid coil and a Voltmeter to check the supply voltage to solenoid.

The tested solenoid was in good order as the correct resistance of 7.5Ω  and a supply voltage of 12.95V was going to it. If the correct resistance was not shown this would mean that the solenoid was unable to work correctly and solenoid would not stop engine correctly and would need replacing.

Pump Timing

Diesel Pump

It is necessary to time the pump correctly because if it is not timed right it will be delivering the fuel at the wrong time during combustion, in turn causing the engine to run badly. 

this was tested using a DTI gauge.

Process:

1. First the gears needed to be aligned correctly using the indicator marks on them  



Picture showing pulleys and belt used to time engine

2. Once aligned correctly belt was reset and tensioned.
3. DTI (Dial Test Indicator) gauge was screwed into pump and zeroed at 1 degree.
4. Engine was then rotated 30 degrees to BTDC and reading was taken from gauge. The needle of gauge is supposed to go in a complete rotation and stop a 1mm if pump is set correctly.
5. Pump can be adjusted by turning it at bolts that till 1mm is read.  

DTI as it is set in pump

If pump is not aligned correctly it would be delivering fuel at the incorrect time during combustion causing it to run rough or not at all.