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How to Check the Fuel Pump Injection Timing

Posted by Scott Goldfarb on

The injection system is a complex set of components that delivers fuel into the engine’s combustion chamber. The combustion must occur on time, and there’s a special system to delegate the precise timing of the pump. Knowing how to check the fuel pump injection timing is key to diagnosing performance issues.

Hence, we will explain how to notice if anything is wrong with the injection’s timing by describing the common symptoms.

How to Check the Fuel Pump Injection Timing

Source: shutterstock.com/ Photo Contributor: Roman Zaiets

How to Check the Fuel Pump Injection Timing

The most common problems associated with improper injection timing are related to poor engine performance. Problems like difficulty with starting the car, misfiring, or noticeable performance drops often indicate that something is wrong with the injection timing and that intervention may be necessary.

A prompt reaction can not only fix the problem but also prevent more damage from happening. That's why diesel injection pump rebuilders recommend regular maintenance checks and timing adjustments, as it will prolong the engine’s lifespan and fulfill its potential.

Knowing the symptoms of a faulty injection timing is crucial to early diagnosis, but going for regular checkups is still the best and most proactive way of properly caring for your engine.

These are the most common symptoms related to fuel pump injection timing issues:

Hard starting

You know there’s something wrong when your engine has trouble getting going. While it can also be a symptom of other defects, like a weak battery or problems with the ignition system, hard starting is a common sign that the timing might be wrong.

If the injection timing is not synchronized with the engine’s cycles, the fuel will reach the cylinders at the wrong time. This will cause an incomplete combustion or one that will occur at the wrong phase of the cycle, making it problematic for the engine to start.

If the engine has difficulty starting due to poor timing, it’s imperative to fix the issue promptly.

Reduced power

If the fuel doesn’t combust at just the right time, then the engine won’t be able to produce the necessary amount of power. With untimely injection, the fuel will burn only partially, with a lot of it going to waste.

When the gas pedal gets pressed, the engine must respond quickly by providing the car with acceleration. This happens by increasing the fuel delivery to the engine cylinders and igniting the fuel-air mixture at the right moment to create a mini explosion that generates power.

Problems with the timing can severely impact the engine capacity, but it can also reduce it only slightly, causing a minor and less detectable decrease. 

Improper combustion over a prolonged period will eventually lead to other problems like bad fuel economy, higher emissions, and even damage to the engine.

Bad fuel economy

Incorrect timing will cause a lot of fuel to go to waste, which will lead to a higher demand for fuel by the engine. 

Fundamentally, it means using more fuel to travel the same distance. Increased fuel consumption is easily detectable if you need to go for a refuel more frequently for the same amount of driving.

It is one of the biggest indicators of an off-timing, and it’s how many drivers get alerted about this specific problem. When you notice a sudden change in the fuel-to-miles ratio, then it’s time to go for a checkup.


Misfiring is a common indicator of bad fuel pump injection timing. It is a noticeable issue, and it happens when the fuel-air mixture doesn’t ignite properly in some cylinders. It is manifested through shaking, rough idling, and, in some cases, even flames.

It often results in excess of unburned fuel entering the exhaust system and igniting there because of the high heat of the gases. This creates a distinct popping sound, sometimes accompanied by flames. 

Needless to say, a misfiring engine requires urgent intervention to prevent further complications and improve performance.

Misfiring engine

Source:  shutterstock.com/ Photo Contributor: DedMityay

Checking the Fuel Pump Injection Timing

Sometimes, the signs of a fuel pump defect aren’t as noticeable, and some drivers like to stay vigilant for any problems by performing inspections by themselves. If you want to perform this task, you will need a solid understanding of diesel engine systems and the patience to adhere to instructions. 

The basic tools required typically include:

  • Wrench
  • Timing light
  • Dial indicator
  • Basic hand tools

You should embrace a meticulous approach and adhere to the instructions from the engine’s manual. Additional prerequisites for performing this task successfully would be using the proper tools, double-checking the measurements, and taking the necessary precautionary measures to ensure the environment is safe for work.

Here are the steps to performing a timing inspection for the injection pump:

1. Locate the timing marks

Once you turn off the engine and disconnect the battery, the first step to performing a pump timing checkup is locating the timing marks. 

The timing marks are indicators that help mechanics synchronize various parts or components. Various types of timing marks can commonly be found on engine components, providing data for different phases of the engine’s work.

When it comes to the injection system, specifically the injection pump, the timing mark is usually located on the housing. This mark aligns with a pointer on the engine block to indicate the correct timing position.

Engines with a mechanical injection have a mark on the crankshaft pulley, which aligns with the fixed mark on the engine block, ensuring the pump is in sync with the crankshaft.

All manufacturers provide information about where to find the timing marks and how they need to align with other components. You simply have to find the manual of the specific engine you possess or acquire it if you don’t have it.

2. Find the TDC

The Top Dead Center references the highest position of the piston during its compression stroke. The position indicates when to set the ignition timing and how to adjust the valve clearances and align other engine components.

Finding the TDC is easy if you follow the appropriate steps:

  • Locate cylinder number one.
  • Remove the glow plug.
  • Place your finger over the glow plug hole and feel the pressure as you turn the crankshaft. Set it to the point where the pressure reaches its highest point.
  • Learn the timing marks from the manual and align the marks of the crankshaft pulley and the timing cover.

3. Use timing light

Plug the timing light into the glow plug of the first cylinder to allow it to detect the electrical pulses. Point the timing light at the marks on the crankshaft pulley, start the engine, and let it idle. 

The timing light will flash each time to signal the glow plug firing into the first cylinder. It will freeze the movement of the timing marks and make them seem stationary, allowing you to check the alignment of the marks.

Using this method, you can ensure that the engine's timing is correct. If there’s something off, you can adjust the timing by carefully loosening the bolts on the injection pump. Then, turn the pump to align it to the position specified in the manufacturer's specifications.

4. Testing injection pump timing

If you had to adjust the timing, you will need to double-check your adjustments to see if everything is in order. Finally, take the vehicle for a test run to confirm the improved performance and the correct function of the timing.

You should be mindful of the engine’s performance during acceleration, cruising, and idling. Look for abnormal sounds and vibrations as you press the gas pedal, and make sure the engine runs smoothly. Monitor the temperature and exhaust smoke for signs of incomplete combustion.

Testing injection pump timing

Source: shutterstock.com/ Photo Contributor: Aleksandr178


The injection pump delivers fuel to the cylinders at the right moment in order to achieve efficient combustion. Correct injection timing is vital for an engine that performs to its capacity, while even a slight misalignment can cause serious problems.

The usual signs of incorrect injection timing include difficulty starting, reduced power, and worsened fuel economy. Often, they are difficult to detect, and knowing how to check the fuel pump injection timing enables drivers to diagnose the problems early before they cause further damage.

Checking the timing is a demanding task that requires a meticulous approach and a fair amount of knowledge and skill. 

Once you ensure you have a safe working environment, you should start by locating the timing marks on the relevant engine components and move on to finding the TDC in the engine’s first cylinder. Using a timing light, you can check the alignment between the components and learn if adjustment will be necessary.


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