April 27, 2021

How to Check the Injector Pump on 5.9 Cummins

Written By: ProSource Diesel

How can you tell when a 5.9 Cummins injector pump replacement is imminent? Some symptoms of 5.9 Cummins injector pump problems include lack of power, not starting, or hard starting. Bad injectors can also cause a knock in the engine.

There are two fuel pumps on the 5.9 Cummins. One is a lift pump that lifts fuel from the fuel tank. The fuel is siphoned to the main 5.9 Cummins injection pump, which then sprays it into the engine. In order to check the performance of fuel system parts, you’ll need a scanner.

Signs of a Broken Lift Pump

You might not initially realize that the lift pump is broken. The Cummins 5.9 injection pump will continue drawing fuel out from the lift pump. However, since the lift pump no longer has enough force to do its job, it will eventually wear down the injector pump. The injector pump can’t handle the loss of pressure forever, which means you will eventually start noticing a lack of power in the engine. At some point, the engine may also be hard to start or not start at all.

5.9 Cummins Lift Pumps

How Long Do Injectors Last?

The fuel injectors on the Cummins 5.9 engine should last between 120,000 and 150,000 miles depending on the fuel quality and regular filter maintenance. These fuel injectors fail due to mechanical wear and not dirt, so there’s generally no point in trying to clean them if they show signs of failure. Like many long-lasting diesel parts, replacing fuel injectors can be a pretty expensive job.

5.9 Cummins Injectors


Diagnosing the 5.9 Cummins Injector Pump

In order to diagnose whether your injector pump is failing, you will need a scan tool. Do not attempt to find leaks manually as the fuel system contains pressurized fuel up to 25,000 PSI. This amount of pressure can slice into your skin and cause fuel to enter your bloodstream, which could result in death.

Start by recording and repairing any active DTC as they might be related to the problem. Secondly, make sure that you have clean fuel and good supply pressure.

If your engine doesn’t start or is hard to start, it could be due to low or no fuel supply to the high-pressure injection pump. Check the rail pressure and make sure you have at least 4,000 PSI when cranking. If it’s less than that, it could be due to bad injectors.

If you crank the engine for 10 seconds and don’t see any smoke coming from the tailpipe, it means that the cylinders are not receiving any fuel. Most cranking and starting issues are caused by low rail pressure. Injector wear can also cause slow deceleration when driving and blue-white smoke when cold at idle.

5.9 Cummins Injection Pumps


Diagnostic Trouble Codes (DTC) and What To Check

  • DTC P0148 indicates checking the high-pressure common rail. It indicates a difference between the actual fuel pressure and the set point. This could be due to the fuel pressure sensor as well as lift pump issues or problems with fuel supply. Check the fuel supply pressure and the condition of the fuel filter.
  • DTC P0201 – P0206 is the injector control circuit. Check resistance in the injectors to make sure it’s higher than zero ohms but less than one ohm.
  • DTC P0300 – P0306 is an injector misfire. Check fuel supply pressure, and use the scan tool to isolate each cylinder. Check each injector for contribution rates.
  • DTC P1223 is leak detection based on quantity balance. When this fault happens, the “wait to start” light will illuminate and you’ll hear a chime 10 times. This code occurs when the calculated fuel flow exceeds a certain expected value. If you get this code, you should first check for other codes related to the fuel system. If there are other codes, address them first. If there are no other codes, then do the checks related to the P0148 DTC.
  • DTC P2146 and DTC P2149 are cylinders 1-3 and cylinders 4-6 respectively shorted high or low. If this code happens, you should check the injector wire harness as well as the valve cover gasket and the injectors themselves. Test with a zero ohm meter and you should see resistance less than one and greater than zero.

Rely on ProSource Diesel for all your Cummins parts needs, including the 5.9 Cummins injector pump, fuel injectors, and other Cummins fuel system parts. We have a big selection of hard-to-find diesel truck parts as well as kits and accessories. ProSource Diesel is where diesel repair shops shop for diesel parts.

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