Replacing The Fuel Pump On A 742 Bobcat: Step-By-Step Guide

If you're looking to replace the fuel pump on your Bobcat 742, there are a few things you should keep in mind. Firstly, it's important to identify whether the fuel pump is the source of the issue. One way to do this is by checking the fuel flow rate by placing the fuel line in a can and examining the flow for at least 30 seconds. If there is inadequate flow, the issue could be with the fuel pump or a restriction in the fuel system, such as a clogged screen in the tank. Additionally, ensure that the old mechanical pump's fuel lines are disconnected when installing a new electric fuel pump.

Troubleshooting a faulty fuel pump

Identifying the Issue:

• Clicking Noise: If you hear a clicking noise when you turn the key to the "run" position, it could be coming from the fuel pump relay located in the dash panel. This may or may not cause operational issues but understanding the source of the noise is important.
• Fuel Pump Not Priming: Ensure the fuel pump is priming properly. If it's not, check the fuel filter and fuel lines for any obstructions or leaks.
• Fuel Starvation: If your Bobcat keeps losing power and then regaining it, you may have an issue with fuel starvation. This could be due to a faulty fuel pump or a restriction in the fuel system.

Troubleshooting Steps:

• Voltage and Relay: Check the voltage at the fuel pump using a voltmeter. If the voltage is low, there may be an issue with the wiring or the relay. Consider rewiring the accessory power or installing a relay in the engine bay to provide direct power to the fuel pump.
• Fuel Filter and Pickup Tube: Check the fuel filter and replace it if necessary. Also, inspect the pickup tube for any damage or blockages. Ensure that the pickup tube screen is clean and properly attached.
• Fuel Lines: Inspect the fuel lines for any leaks or damage. Ensure that the lines are not pinched or restricted, especially if the tank is close to empty.
• Fuel Pump: If the above steps do not resolve the issue, the fuel pump itself may be faulty. Consider replacing the fuel pump with a new one.
• Diode Installation: In some cases, installing a diode across the power wires to the fuel pump can help prevent power spikes and voltage fluctuations. This can be done to smooth out the voltage and reduce pulsing lights.
• Electric Lift Pump: If the issue persists, consider installing an aftermarket electric lift pump to increase fuel pressure and volume.

When troubleshooting a faulty fuel pump, it is important to cover all bases, from checking voltage and relays to inspecting fuel filters, lines, and the pump itself. If you are unsure about any steps or the problem persists, it is recommended to consult a qualified mechanic or seek advice from Bobcat experts on online forums.

Installing a new electric fuel pump

To install a new electric fuel pump on your Bobcat 742, follow these steps:

Firstly, ensure that you have a brand new electric fuel pump, a new fuel filter, and a Pertronix electronic ignition. If your old mechanical pump is still connected, you will need to remove it. The fuel lines from the tank should now go to the new electric fuel pump and then to the carb.

Next, turn the key to start the engine. If the engine fires up but then shuts down after 20-30 seconds, you may have a restriction in the old pump that is only allowing a small amount of fuel into the carb bowl. This will need to be addressed before proceeding.

If your machine has an electric fuel solenoid on the carb bowl, check that the float valve is not sticky and is allowing fuel in freely. You can also try removing the solenoid and plugging the hole – if the machine continues to run without it, you will know the solenoid was faulty and will need to be replaced.

Now, check the timing of your engine. If it is off, adjust it and see if this solves the problem.

If your machine continues to shut down, try the following: remove the fuel line at the carb and place it into a can. Have a friend turn on the ignition and check the fuel flow rate for at least 30 seconds. If the flow rate is inadequate, there may be a restriction somewhere in the fuel line. Check the screen in the tank, the electric safety shutoff near the firewall passthrough, and the fuel petcock on the passenger side of the firewall. Ensure that the fuel petcock is in the full open position, which may be several turns out.

Finally, if all else fails, try replacing the fuel pump. This was the solution for one user whose Bobcat 742 was shutting down after 30 seconds, even after addressing potential issues with the float valve and timing.

Note: When working on a Bobcat 742, it is recommended to refer to the machine's manual or seek assistance from a qualified mechanic to ensure the correct and safe installation of the electric fuel pump.

Fuel pick-up tube repairs

A common repair task for Bobcat skid machines is problems with the fuel pick-up tube inside the fuel tank. This repair guide will focus on the Bobcat 742 model.

First, you need to identify the location of the fuel pick-up tube. On the Bobcat 742, the fuel tank is located behind the seat when the cab is raised.

Once you have located the fuel tank, the next step is to remove the old fuel pick-up tube assembly. This process can vary depending on the model of the Bobcat machine. For the Bobcat 742, you will need to raise the cab and access the pick-up tube through a side panel.

When removing the old fuel pick-up tube assembly, it is important to note that Bobcat has used different types of tubing on early and later models. Early machines used a flexible tubing with a strainer screen and check ball at the end of the pick-up tube, while later models use a more rigid plastic tubing without a strainer or check ball. If your machine uses flexible tubing, do not attempt to replace it with clear vinyl tubing as it is not an acceptable replacement. Always use a length of tubing from Bobcat, as it is specifically designed for their machines.

To remove the old fuel pick-up tube assembly, follow these steps:

• Use a pair of snap ring pliers to gently spread the compression clamp and work it onto the pick-up tubing.
• Use a small screwdriver to work the compression clamp onto the tubing, leaving approximately 1/16" of tubing outside of the clamp.
• Lightly coat the inside of the tubing and the hose barb on the strainer screen with petroleum jelly.
• Gently press the hose barb into the tubing until it is fully seated.
• Prepare the opposite end of the pick-up tube by lightly coating the inside of the seal grommet and about 2-3 inches of tubing with petroleum jelly.
• Slip the seal grommet onto the tubing.
• Fit a compression clamp onto the tubing, similar to the opposite end of the tube.
• Lubricate the inside of the tube and the barb of the elbow with petroleum jelly.
• Gently push the hose barb into the tubing.

At this point, you should have the pick-up tube assembled and ready to install. Now, you can remove the old assembly from the fuel tank. Cut the fuel hose where it connects to the elbow with a razor knife. Turn the elbow fitting so that you can grip it with a long-nose pair of vice grips and gently work the elbow and grommet out of the tank. Be careful, as the elbow is made of plastic on some models.

If the tube and elbow are in good shape, simply remove the old grommet, remaining piece of hose, and compression clamp. If they are damaged, replace them with a new assembly from Bobcat.

To install the new fuel pick-up tube assembly, follow these steps:

• Lubricate the inside of the new grommet with petroleum jelly and press it into the hole in the top of the fuel tank.
• Lubricate the pick-up tube and elbow barb with petroleum jelly.
• Fit the tube into the grommet in the fuel tank and gently push it in until the barb on the elbow meets the grommet.
• Gently push the elbow into the grommet using the end of a pry bar.
• Do not attempt to fit a compression clamp. Instead, fit a worm gear clamp onto the fuel hose, push the fuel hose onto the elbow, and tighten the clamp.

Your Bobcat 742's fuel pick-up tube repair is now complete!

Checking for fuel flow issues

If you're experiencing issues with fuel flow to the carburettor, there are a few things you can check.

Firstly, ensure that the fuel lines are connected correctly. On the Bobcat 742, fuel travels from the tank to the electric fuel pump and then to the carburettor. If the fuel lines are not connected correctly, this could be the source of your issue.

Next, check the fuel filter and the electric fuel pump. If the filter is clogged or the pump is faulty, this could restrict fuel flow to the carburettor.

Another potential issue could be a restriction in the old mechanical fuel pump. Even if the lines are connected to the new electric pump, a restriction in the old pump could be allowing only a small amount of fuel into the carburettor, causing the engine to shut down after a short period of time.

Additionally, you should check the fuel pick-up tube inside the fuel tank. This is a common repair issue on Bobcat skid machines. The pick-up tube can become clogged or restricted, preventing adequate fuel flow to the engine.

Finally, you can perform a fuel flow test by disconnecting the fuel line at the carburettor and placing it into a container. Have an assistant turn on the ignition and observe the fuel flow for at least 30 seconds. If the flow is inconsistent or inadequate, there may be a restriction in the fuel system, such as a clogged screen in the tank or a wiring issue with the electric fuel pump.

Replacing the fuel filter

To replace the fuel filter on your Bobcat 742, follow these steps:

Firstly, locate the fuel filter. On the Bobcat 742, the fuel filter is typically found near the fuel tank, which is located either behind the seat or in the belly of the machine under the engine. Once you have located the fuel filter, you can begin the replacement process.

Before starting, ensure you have the necessary tools and safety equipment, such as gloves and eye protection, and a suitable replacement fuel filter.

Next, carefully disconnect the fuel lines from the old fuel filter. This may require some force, but be gentle to avoid damaging any nearby components. Once the fuel lines are disconnected, set the old fuel filter aside.

Take your new fuel filter and inspect it for any damage. Ensure that the new fuel filter is the correct type and size for your Bobcat 742.

Now, carefully connect the fuel lines to the new fuel filter. Ensure that the connections are secure and tight to prevent any fuel leaks.

Finally, check for any fuel leaks around the new fuel filter and the fuel lines. If no leaks are detected, lower the cab and close any access panels. Your Bobcat 742's fuel filter replacement is now complete.

It is important to note that working on fuel systems can be dangerous, and you should always take the necessary precautions to ensure your safety. Always refer to the official Bobcat 742 manual or seek the assistance of a qualified technician if you are unsure about any part of the process.

Frequently asked questions