What is the Automatic Timing Advance Unit all about?
Gasoline and diesel engines may seem similar, and they do work on the same basic principle of combustion, but they’re very different. They require significantly different steps taken to control fuel flow throughout engine operation. Diesel fuel takes longer to combust than gasoline, and in an operating engine, combustion can take place well after the timing hits top dead center (TDC). If this occurs, then it creates lag, which has a negative impact on engine performance. To combat lag, diesel must be injected before the timing reaches TDC to provide enough time for combustion to take place. This job is handled by the automatic timing advance unit. Essentially, the unit ensures that no matter what speed the engine is operating, fuel is injected with ample time for combustion to occur before TDC is reached.
The automatic timing advance unit should be located on the fuel pump itself, and is operated by the engine's primary drive gear.
Keep in mind:
- The automatic timing advance unit is not inspected during maintenance, and will only be checked if there is a problem with the fuel delivery.
- The automatic timing advance unit is subject to a lot of wear and tear, particularly if you accelerate harshly, or drive frequently.
How it's done:
- The automatic timing advance unit is verified that it needs to be replaced. The battery is then disconnected.
- The injection pump front cover is removed and gear location aligned and marked.
- The center bolt is removed and then the defective automatic timing advance unit is taken out.
- The new advance unit is installed and the gears are aligned. The center bolt and cover are reinstalled. The battery is reconnected.
- The engine is started and the automatic timing advance unit is tested to ensure proper operation.
Without an operational automatic timing advance unit, your diesel engine will not have a reliable fuel supply at all speeds, which causes serious problems. If you suspect a problem with your automatic timing advance unit or have similar symptoms, have one of our expert mechanics inspect and diagnose the problem.
What common symptoms indicate you may need to replace the Automatic Timing Advance Unit?
- Severe engine knock
- Sluggish engine operation
- White smoke from exhaust
- Significant amounts of black smoke from exhaust (more smoke is normal for a diesel)
How important is this service?
The automatic timing advance unit is crucial for safe and reliable engine operation. If the unit begins to fail, or fails completely, serious engine damage can result. If you have noticed any abnormal operations in term of sluggish performance or smoking, have the problem diagnosed immediately by one of our expert mechanics.