Katerina Swanson
Kubota is a popular tractor brand that offers diesel engine options. The fuel return line in a diesel Kubota is a critical component that needs periodic checks and maintenance. Issues with the fuel return line can lead to tractor malfunction and performance issues. This line transfers fuel from the injector to the fuel tank and can sometimes face problems due to fuel contamination, debris, or internal flaking. Regular inspections and timely replacements of the fuel return line are essential to ensure the tractor's optimal performance and longevity.
| Characteristics | Values |
|---|---|
| Fuel return line replacement | Remove the deteriorated hose from the hose barbs and replace with a new hose |
| Fuel return line assembly | 4 washer-like parts with 2 port holes each |
| Fuel return line maintenance | Check the vent on the tank to ensure it is open and clear of debris |
| Fuel line hose size | 1/8 inch, 3/16 inch, or 5/16 inch |
| Fuel line hose type | Clear poly, Hatz diesel injector return, or rubber |
| Fuel line hose clamps | Small spring clamps, fuel injector clamps, or hose clamps |
| Fuel line issues | Lack of fuel, fuel contamination, or collapsed fuel line |
| Fuel pump issues | Lift/primer pump malfunction or fuel pump malfunction |
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What You'll Learn
Check the fuel return line is clear
To check the fuel return line is clear on a Kubota diesel engine, you should first identify the return line. This is the line that runs from the injector pump to the fuel tank.
The return line shouldn't be under pressure like the other fuel lines, so if it is, it's likely that there is a blockage causing a build-up of pressure. Check the vent on the tank to ensure it is open and clear—the vent hole can be found in the fuel cap. Sometimes, the vent hole will get clogged with debris, which can prevent the tank from venting properly.
If the vent is clear, the next step is to check the return line itself. There are four washer-like parts with two port holes each that sit between the return line and the top of the injector. Remove the deteriorated hose from the hose barbs and replace it with a new hose. The injector closest to the firewall usually has only one barb, and it faces the next injector. The other injectors will have two barbs.
By ensuring the vent is clear and the return line is free of blockages, you can help maintain the proper functioning of the fuel system and prevent pressure build-up.
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Check the vent on the tank is open
To check the fuel return line on a diesel Kubota, it is important to check the vent on the tank to ensure it is open. This is because the tank needs to breathe, and this breathing mechanism relies on a vent that relieves both vacuum and pressure. Gasoline expands in volume as it warms up and shrinks as it cools down, and this movement of fuel in and out of the tank requires the release and intake of air.
The vent is usually located in the fuel cap, which is typically found at the top of the tank. The fuel cap will have a hole in it, which acts as the vent. This hole can sometimes get blocked, for example, by dirt or trash, and this blockage can cause a build-up of pressure in the tank. This pressure build-up can, in turn, cause the return line to pop off. Therefore, it is important to check that the vent is clear and open.
To check if the vent is open, locate the fuel cap and inspect the hole to ensure it is not blocked. If the hole appears clear, you can try covering and uncovering the hole to feel for a change in pressure, which will indicate that the vent is functioning. If the hole appears blocked, you can try cleaning it out.
It is also important to ensure that the vent is mounted vertically. If the vent is mounted at an angle, it may shut off, which can cause issues with the pressure in the tank.
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Check the fuel cap vent hole is clear
To check the fuel cap vent hole is clear, you must first locate the vent hole, which is usually found in the fuel cap. Sometimes, the vent hole can get clogged, leading to a build-up of pressure in the tank.
To check if the vent hole is clear, start by inspecting the hole for any debris or blockages. If the hole appears clear, you can try blowing compressed air through it to ensure it is functioning properly. If the vent hole is blocked, you can try cleaning it with a small tool, such as a nail or guitar string, being careful not to damage the surrounding components.
If the vent hole is severely clogged or damaged, it may be necessary to replace the fuel cap entirely. This is a relatively inexpensive solution, with replacement caps typically costing around $9.
Additionally, it is important to note that fuel filters can also contribute to vapor lock, especially if more than one filter is used per line. In such cases, it is recommended to stick to filters with metal screens or paper elements to avoid vapor lock.
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Check the fuel line for contamination
If your Kubota diesel engine does not start, begin by confirming that your electrical and fuel delivery systems are performing properly. Electrical issues are among the most common reasons for engines not starting. Check to make sure the actual return line is clear. The return fuel will pressure up if that line is plugged.
If your diesel-powered Kubota tractor or construction equipment sits idle for a few months without operating, water, sedatives, or other contaminants could appear in the fuel tank and clog up the fuel lines. You’ll most likely discover this situation shortly after you start up your Kubota. Not too long after you fire up the engine, it will most likely cut off – as if it’s out of fuel. When this happens, it’s important to drain the fuel and clean the tank and fuel lines on your Kubota.
To clean your tractor's diesel fuel tank, follow these steps:
- Remove the fuel cap.
- Place the fuel-catching container under the tank.
- Unscrew the fuel line nut or hose on the base of the fuel tank.
- Once the tank stops draining, use the extraction pump to remove any fuel and sediment settled at the base of the tank.
- Remove your fuel line just before your fuel rail or injection pump. Insert the air compressor nozzle into the hose and blow air back toward the tank to remove any debris in the fuel lines. After blowing out the lines, replace and secure them.
- Screw the diesel fuel line nut or hose back onto the base of the diesel fuel tank.
- If equipped, drain the water separator and replace the fuel filters.
- Fill up the tank with fresh diesel fuel.
- Pour the correct amount of diesel fuel tank cleaner into the tank.
- Replace the fuel cap and fire up your machine.
- Bleed your fuel system. On later model Kubota tractors, turn your key on and allow the electric fuel pump to flow fuel up to the filters. Crank the engine over until it self-bleeds and starts. On models with injection pumps, there is a bleeder screw where the fuel line meets the injection pump.
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Check the fuel line for internal flaking
To check the fuel line for internal flaking, start by disconnecting the battery to prevent stray sparks from igniting petrol or petrol vapour. Use a torch for inspection, rather than an inspection lamp, naked lights or cigarettes, as a broken bulb can cause a fire.
Next, look at the joint between the fuel line and the carburettor, and then check other joints, working your way back to the tank. Place the car on ramps or axle stands to inspect the section under the floor. Use a flashlight to follow the line, looking for areas of dust and road grime, as well as wet spots, which can indicate a fuel leak.
Feel around the joints to check for wetness, as petrol may run along a pipe before dripping. Bend flexible pipes between your fingers to expose splits or cracks. Push clips and metal joints to see if they are loose. If you suspect a blockage, free both ends of the pipe and blow through it. Kinks and dents in the line can cause blockages, as can dirt or rust in the fuel tank. Repeated blockages may be a sign of this.
If you find flaking inside the fuel line, it will need to be replaced.
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Frequently asked questions
Check the fuel lines to ensure that no pieces are stuck in the inlet of the primer pump. These fuel lines can sometimes break down and flake off internally.
Check the vent on the tank and make sure it is open. The tank should have a vent hole in the fuel cap. Clean out the cap to remove any trash that might be blocking the vent.
Open the decompression lever to make cranking easier on the battery. Loosen the fuel feed line for each cylinder, crank until all the air is gone and fuel comes out consistently, then close the decompression lever and heat the glow plugs.
You can use a 3/16 hose, which is rated for about 60 PSI and should be adequate for a return line. Alternatively, you can use the Hatz diesel injector return, which is immune to sunlight and doesn't harden or rub through easily.
