How to Check If Your Fuel Pump is Bad on a Bobcat with a D24 D34 Engine

Bobcat machines powered by Doosan engines, especially the D24 (2.4L) and D34 (3.4L) are known for their power and reliability. But when fuel delivery issues arise, diagnosing the problem correctly becomes critical. In past articles, we’ve covered diesel fuel injectors, common failures, and the warning signs operators should watch for. Now, we’re turning our focus to one of the most essential components in your fuel system: the high-pressure fuel pump.

Both the D24 and D34 high-pressure pumps are similar in design, widely used across Bobcat excavators, skid steers, and track loaders. While the D24 pump includes an internal pressure relief valve that activates around 36,000 psi, the D34 pump uses a rail-mounted pressure relief instead. Understanding these distinctions helps you pinpoint where failures may occur, especially when your machine throws alerts such as “low fuel pressure” or “check fuel filter.”

When an issue arises with our high pressure fuel pump, we want to properly diagnose it. This guide walks you through the complete process of diagnosing a failing fuel pump on Bobcat machines equipped with D24 and D34 engines. With step-by-step instructions, you’ll gain clarity on how the pump functions, what components affect pressure, and how to determine whether contamination, electrical faults, or internal wear are to blame.

Understanding the Fuel Pump

Let's start with a quick deep dive to understand a key section of the pump: the lift pump. This portion pulls fuel from the tank through the fuel filter, and into the cavity of the pump. The lift pump is what charges and pressurizes the cavity to 86-87 psi. This pressure is maintained by the rotary vane pump and regulated by a low-pressure relief valve. Since the vane pump lives inside the lift pump assembly, any contamination or mechanical wear in this area can impact pressure at the IMV Valve, the rail, and ultimately the injectors. 

(the vane pump can be found inside of the lift pump) 

Step 1: Remove the IMV Valve (Inlet Metering Valve)

Begin your diagnostics by removing the IMV Valve, which regulates how much fuel is metered into the high-pressure piston. You’ll need a T25 Torx screwdriver to remove the two retaining bolts.

This electrically controlled valve is responsible for supplying the correct amount of low-pressure fuel (86–87 psi) to the high-pressure side, which includes one piston on the top and another on the bottom of the D24 pump.

IMV Valve: “The Inlet Metering Valve in the common rail fuel system regulates the amount of fuel in a fuel pump, conserving energy used by the pump in allowing only the required volume of fuel to be pumped through the system.” (Source)

Step 2: Check IMV Valve Screen for Contaminants

Once removed, you’ll see a fine mesh screen wrapped around the IMV Valve. This screen acts as a final protective filter before fuel reaches the rail and injectors. You can reference the photo included below.

Carefully inspect the screen for metal flakes, dirt or sludge, rust particles or any discoloration or debris buildup. If contamination is present, move to Step 3. 

Step 3: Test the IMV Valve With Voltage

If you find any kind of debris in the screen of the IMV Valve, we want to further test the IMV Valve by driving 12V through the wire connector and seeing if the solenoid will slam shut.

To determine whether the IMV Valve is sticking or malfunctioning, apply 12 volts directly through its connector. The solenoid should slam shut when energized and reopen when voltage is removed.

If your engine is experiencing no rail pressure, this simple test may free a stuck IMV Valve and restore temporary operation. This is one of the quickest ways to confirm whether your IMV is functioning properly.

Step 4: Remove the Lift Pump Cover

If debris was found on the IMV Valve screen, it likely came from the vane pump which pulls fuel from the tank through the filter and into the pump. To check the vane pump you will want to remove the outer cover around the lift pump to inspect internal components.

Step 5: Inspect the Vane Pump Area for Debris or Wear

Once the cover is removed, inside the vane pump, you’ll find four vanes responsible for drawing fuel into the system. Even a small amount of debris can become lodged between the vanes which can cause fuel starvation, inconsistent pressure or progressive system contamination. Debris from this area often travels to the IMV Valve first, then to the fuel rail, and ultimately into the injectors, leading to premature injector failure. Before replacing injectors, always understand why they failed. Otherwise, you risk repeating the same issue.

Step 6: Check for Rust, Water or Internal Contamination

Let’s go ahead and move over to the engine side of the pump. Remove the three bolts located on the back side of the pump to access the gear housing. Once the gear and head are removed, you’ll see the pump’s internal cavity including four corner channels and a center opening. You may find rust contamination, water intrusion, mud-like residue or corrosion around the piston area. Any of these conditions point to a deeper system contamination issue that must be addressed before installing a new pump.

Step 7: Inspect the Fuel Rail Pressure Sensor for Contamination

If you're finding that the pump is contaminated, the rest of the fuel system may also be contaminated. In order to check the fuel rail, find the pressure sensor and remove it. Insert a long clean swab into the opening, and rotate it gently. Examine the swab for dust, dirt, or metal particles. If contamination is found here, you can assume that the fuel injectors are contaminated, the rail requires a complete cleaning and the entire fuel system may need to be replaced. Skipping this step is one of the most common mistakes owners make, often resulting in repeat fuel system failure.

Step 8: Use a Fuel Pump Diagnostic Scanner

As an alternative, you can also purchase a Fuel Pump Diagnostic Scanner online for $100-$200. These tools help you determine whether the pump is maintaining proper rail pressure under load.

This is especially helpful for intermittent failures that are difficult to diagnose manually.

Step 9: Check for Air Leaks in the System

To check for a fuel injection pump leak, open the filler cap and start the machine. After running briefly, shut off the ignition and reopen the cap. 

If the engine continues to run, air is being drawn into the fuel system, indicating a leak that must be addressed immediately.

Diagnose Before Replacing

We hope this guide was helpful in giving you the basics on how to troubleshoot your pump and/or fuel system. Please reach out for additional questions or feedback. At the end of the day, we want to assist you in accurately diagnosing your parts in order to ensure that you’re attending to the correct issue in your fuel system. 

If you do find that you need to replace your high pressure pump or fuel system, we offer a complete range of D24 and D34 fuel system parts and can help you find the correct components for your machine.

The information provided in this article is for general guidance only. Always refer to your machine’s manual or consult a qualified mechanic before performing any maintenance or repairs.