Modern Cummins engines are capable of more than 20,000 psi in the fuel injection system. Unlike past injection systems like the VP44 and P7100 injection pumps, these injectors fire multiple times for every engine cycle.

With more and more firing sequences and more operating pressure, there is potential for injector failure. We’ll look into when you should look at replacing your injectors and preventive maintenance that will prolong the life of your injectors

An injection pump for the late model Cummins engines like the one above.  This item is called a CP3 and it gets the fuel from the tank and feeds your fuel rail and fuel injectors at very high pressures!

Our friends over at Scheid Diesel offer different options for you and your common rail truck when fuel injector replacement is inevitable. Standard remanufactured, premium red top series, and HP are options to choose from no matter the application or horsepower range.

Behind The Nozzle

As you can see, at Scheid Diesel they do a thorough tear down to inspect all vital items inside of the fuel injector.

Their remanufactured injectors are rebuilt back to spec using new OEM parts and new nozzles. However, if parts of your injectors are still within spec, they will reuse your part in the rebuild. They offer a one-year unlimited mileage warranty on all remanufactured injectors.

Your other options from Scheid are the red top series and HP injectors. We met up with Debbie from Scheid, to discuss the difference in a red top unit and remanufactured injectors. “All of the internal pieces will be replaced inside the injector no matter the shape of the originals unlike the remanufactured,” said Debbie. “The HP level of their injector are for different applications, from wanting more power to tow the trailer at the farm to a purpose-built sled pulling or drag racing truck.”

Scheid Diesel’s very own Red Top Series Injector line are spec’d, balanced, and ready for any build.

Scheid injectors are designed to flow more fuel than a factory injector which in turn creates more horsepower. “Our HP upgrade injectors start at 50 horsepower and we can build them to suit from there,” explained Debbie.

Some end users prefer to go the alternate route and replace just the nozzles of the injectors, better known as the tips. After speaking with Debbie, she explained, “We prefer not to sell nozzles only.”

The reason that it’s looked down on is that these common rail injectors are extremely sensitive to dirt, dust, and debris. When these injectors come in contact with any sort of debris it will cause major issues after installation. “After the nozzles are installed we run the set of injectors through what we call the equalization process,” said Debbie.

The equalization process is where the entire set of injectors are dialed in so to speak, to guarantee the flow rates on each injector are firing to specifications before you, the end user, are nothing but satisfied. Scheid injectors are just as high quality as the new units without the price tag.

Knowing When To Replace

There are plenty of symptoms that could lead you to think you may need new injectors. If you are firing the truck up in the morning before work and notice a regular hard start or longer than normal cranking time, this could be a sign leading towards an injector failure.

Debbie also stated that if you are experiencing excessive smoke at idle or an engine miss that you could also be witnessing injector failure. With the help of a scanner from a local automotive shop, you can also look for TDC (trouble data codes) that could point in the direction of injector failure codes.

If you aren't comfortable installing your new injectors, utilize the full service department that Scheid Diesel offers! Shown is a Red Top Install on a customers common rail cummins!

If you aren’t comfortable installing your new injectors, utilize the full-service department that Scheid Diesel offers. Shown is a Red Top Install on a customer’s common rail, Cummins.

The cost is the same to rebuild injectors versus exchanging them for new injectors. Trying to make ends meet and you can’t have the truck down for very long time Scheid Diesel Service is here to help. “Here at Scheid, we offer an exchange program,” Debbie explained. “This gives you the opportunity during crunch time to send in your injectors and exchange them for their new ones.”

Here is a live photo of actual fuel injector nozzle testing. As you can see, these are a five-hole injector. Scheid offers many different configurations

Preventing injector failure on these trucks is doable. The biggest issue that causes these high-pressure system injectors to fail are the internal mechanical parts inside and the lack of quality fuel run through them.

From personal experience, we can say that fueling up at not so reliable fueling stations can create serious problems. You’re going to want to fuel up at fuel stations that are known to be a reliable source.

If you fill up with debris and water-filled diesel fuel, the contaminants that you are pumping in is eventually going to run through your injectors. Keeping your fuel system clean and changing your fuel filters religiously are key to continuing the life of your fuel system.

Do you want to drink this? Neither does your fuel system. Be smart and fuel up at sufficient places, your injectors life depend on it!

Points Of Failure

Shown are the parts explained. High-pressure connector, ball, needle, actuator, and nozzle.

The high-pressure system forces fuel into the injector. Once the pressure is equalized in the entire injector the electric solenoids on top are energized which pulls the control plunger upwards. Once the control plunger releases it releases a bit of fuel which creates a different pressure in the injector allowing the pintel to come off of its seat.

Once the pintel has moved upward it has now allowed fuel to inject in to the cylinder. After this combination of steps the electric solenoids are cut off of current and the pintel ball will reseat. Once it reseats, the pressure above increases and will push the nozzle closed.

If you take your fuel filtration serious, you’ll be in good shape. Unlike this guy, who will never live this picture down.

The ball that reseats during the injection process becomes eroded, causing high return flow. This could be what is occurring if you are experiencing hard starts or not starting at all.

Erosion of the nozzle is another issue, with the nozzle eroding it will have what’s called seepage. This allows fuel to drain in to the cylinder. This will cause poor fuel mileage and/or even that blue white smoke at idle that we previously talked about.

On the other side of things, the electrical solenoids on top of the injectors are what controls the injection. These studs coming off the injector are what the harness threads on too. The harness or solenoids coil can short out which will commonly cause a misfire.

Shown here the solenoids that top off all common rail cummins injectors. This is how the injectors get electricity from the harness and signal to fire.

In extreme cases, debris can build up in the injector which causes an injector to stick wide open. That can cause a washout of the cylinder which will damage the cylinder walls, pistons, and rings.

First thing is first, when purchasing one of these late model trucks, ask around and find out a reputable fuel station. You’ll save yourself a lot of money in the long run. If you were unfortunate and purchased a neglected Cummins, go see our friends at Scheid. They can help you in every way needed. Do you have water in your fuel? What will you do about it?  Do you need new injectors?  Let us know in the comments below!