Tech Tips: Adjusting Diesel Injection Timing

What Is Diesel Injection Timing?

Injection timing, much like other timing related to internal combustion engines, is the process of carefully controlling when said combustion is to take place.


Diesel Engine Timing Diagram

The diesel internal combustion diesel engine is a very complicated and precise piece of modern engineering. By being able to control the exact moment the fuel gets delivered into the combustion chamber, manufacturers can closely control the amount of power and emissions an engine makes. 

Similar to spark plug timing on a gasoline engine, injection timing allows you to make adjustments to get the optimal fuel amount, at the perfect time to make the biggest “explosion”, if you will.

No matter if you are an owner-operator or you have your very own shop, knowing what injection timing is and how to adjust it is critical. However, automakers have designed the engine to work within certain parameters, so adjusting the injection pump timing may end doing more harm than good if done incorrectly.

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Why Do You Need to Adjust Injection Timing?

There are several reasons why someone may need to adjust injection timing. Most often, timing needs to be adjusted to resolve a problem with excessive smoke or turbo lag. Why these issues came up in the first place is a whole other story, but adjusting the injection pump timing is more likely to resolve the issue.

Can Injection Timing Be Adjusted On Any Diesel Engine? 

Of course! No matter how old, or new your diesel engine is, an injection pump will always be there. Old school guys took pride in being able to adjust the timing by hand with a couple of common hand tools everyone had sitting around. 

Unfortunately nowadays, not much can be done on a vehicle without at least having basic computer skills. Technology is advancing at a rapid pace, and the once-simple diesel engine has been equipped with a series of computers that control everything from injection timing to the cab temperature. Injection timing can still be adjusted on a modern truck, but now it is done via the ECM. 

Advancing And Retarding Engine Timing

There are two main ways to adjust your injection pump timing. This can be done by advancing or retarding the actual point of when the fuel enters the combustion chamber.


Advancing the timing means that you are changing when the combustion process will take place in relation to the piston’s position. 

By advancing the injection timing, the combustion process will take place before the manufacturer initially intended it to. Doing this should increase horsepower. But like with anything, there are downsides to advancing the timing as well. 

Added smoke will be the main visual cue that someone has advanced the timing on a diesel engine. What you might not know is that emissions have a chance to be greatly increased as well by advancing injection timing. 

A delicate balancing act must be played by environmentalists and the engine manufacturers. Automakers and enthusiasts alike want to make as much power as possible from their diesel workhorses, while on the other end, strict pollution regulations must be followed. It is a subject that both sides butt heads on regularly.

Engine Timing Retarding

Retarding the timing, on the other hand, does the exact opposite of advancing. In other words, fuel will be delivered after the manufacturer intended it to.

You will rarely hear of people retarding their timing, mainly because this is one of the best ways to reduce horsepower output. However, if done right, it could help increase fuel efficiency. Since it isn’t a common procedure, we won’t go into further detail about retarding injection timing.

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How Can Diesel Engine Timing Be Adjusted?

Adjusting injection timing on a diesel engine can make a huge difference in terms of both performance and fuel consumption, if it’s done right that is. Depending on the make and model of your engine, timing can be adjusted in one of several ways. 

Reprogramming the ECM 

Remapping the ECM to squeeze more horsepower out of an engine has been done as long as the ECM itself. For those who know what they are doing(remember? we talked about being handy on a computer before), this means a few clicks of the mouse and poof! You have more power. Of course, this will only work if your engine came equipped with an electronic injection pump. and not a mechanical one.

Manually Adjusting The Injection Pump

Not so long ago, most diesel engines worked mechanically, and the injection pump was no different. A simple screwdriver and the right socket set would let you manually adjust the injection pump.

If you wanted to do it “by the book” so-to-say, a special probing meter would be required to accurately measure and adjust timing, but most did it by ear. Here is a good step-by-step guide for those who are willing to try their luck!

Upgrading The Camshaft

The camshaft plays an important role in the way an engine runs and performs. The lobes on a camshaft is the result of countless hour and dollars spent by engineers trying to make sure optimal performance is achieved without affecting the environment too much. 

Lucky for us, there are still some companies out there producing camshafts that have more aggressive lobes, giving the user more power. Replacing the camshaft is usually done only due to wear or in the pursuit of more power. A software tweak can only go so far, and sometimes actually hardware is needed to get additional ponies.

Replacing The Cam Followers And Gaskets

Similar to a new camshaft, replacing the cam followers and gaskets can be another way to adjust timing. The beauty of this is that new cam followers and gaskets are usually cost a fraction of what a new or aftermarket camshaft may be!

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Advantages And Disadvantages Of Diesel Timing Advancement 

Nothing in this world is free. There are pros and cons of advancing the timing on a diesel injection pump. Let’s have a look at some of the most common advantages and disadvantages of doing this.


Advancing the timing of an injection pump is nothing new. In most cases, it is done in an attempt to get more power from the engine. A lot of diesel tuners increase advance the timing to easily gain horsepower. On top of that, fuel mileage also gets a boost as the engine has to work less to carry the same amount of weight. 


If it were up to enthusiasts, the injection pump and engine would be tuned within an inch of its life and make maximum power. But we have to think about tomorrow. This is where emissions regulations come in and bring everyone back down to reality. There are some consequences when advancing injection timing that most don’t take into account. Exhaust emissions are real, and while the industry may overreact sometimes, it is a subject to take into consideration.

Adjusting the timing of an injection pump means helping your engine work at its peak. Manufacturers have a pre-set timing which is often directly affected by emissions regulations. Luckily, the diesel engine is getting so advanced that we can all benefit from increased horsepower as well as higher MPGs!

Highway and Heavy Parts staff have the technical knowledge and experience to help you with your internal engine needs. If you have any outstanding questions about fuel pump timing or diesel engines in general, please give our ASE Certified Techs a call at 844-304-7688 or simply request a quote online!


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