Why do diesels have return lines?
OK, The real reason for the fuel return line is that the extra fuel pulls heat off of the injector and makes it last a long time. Remember that the injector is in direct contact with the very hot cylinder head and combustion chamber.
It's primary purpose is to return excess fuel from the carburetor to the fuel pump, however it serves other important functions as well. Aside from providing a path for excess fuel to return to the tank, the fuel return hose also prevents vapor lock and over pressurization from occurring within the carburetor.
Setting up fuel lines for fuel injection.
That's because almost all fuel injection systems require higher fuel pressures than a carbureted system, and most also require a fuel return line, not often found on a carbureted vehicle.
Any fuel going through the return line is simply fuel your engine did not need/could not use. Blocking or restricting the line only increases fuel pressure at the injectors. Blocking the line results in the fuel pressure just being the maximum the pump can push.
New member. Some in-line pumps models (Bosch P7100) return at least 40/50% of fuel to the tank, and Cummins PT returns over 80%. Rotary pumps return around 20/30%.
With a return system, the base pressure is set with the engine off, but the pump running. For a GM, this pressure is usually set to 58psi (factory fuel pressure in the rail).
There are some key benefits to a return-style setup. Vapor lock is mitigated because the constant cycle of fuel back into the tank cools the gasoline. Engine tuning is easier because the fuel temperatures in a return-style system are typically more consistent.
FAST: Return vs Returnless Fuel Systems - YouTube
The Fuel Return Line should be at least the same size, or one size larger than the supply. Make sure there are no sharp bends or kinks. The return line should direct fuel close to the bottom of the tank and away from the pickup.
A returnless-type fuel system is one that is designed to use the powertrain control module (PCM) to regulate fuel delivery. A fuel pressure sensor mounted to the supply rail of the fuel injectors allows the powertrain control module to keep an eye on the fuel pressure.
How does a non return fuel system work?
On returnless systems, fuel is picked up via the fuel screen sock at the bottom of the tank, then routed to the fuel pump. The pump supplies the needed fuel pressure and volume to the engine and the excess is directed back into the tank after passing through a pressure regulator.
There are only two hoses running from the pump. One is the high pressure line, which sends fuel to the injectors. The other is the return line, which dumps fuel that the injectors don't use back into the tank.
When unwanted air finds its way into your fuel system, your car becomes at risk of reduced performance, and even engine failure. The best way to prevent this from happening is to take your vehicle in for regular maintenance.
The only things that are likely to cause fuel not to return are either a failed fuel pressure regulator, or an obstruction in the fuel rail.
- Check engine light.
- The exhaust gives off fuel smell.
- Low fuel economy and constant refuelling.
- Poor engine performance.
- Blackened spark plugs.
- Spark plugs that are wet with fuel.
- Restrictions in return line.
Diesel Injector Installation and Leak Off Test Tutorial - YouTube
Good injectors should not leak more than 25ml in this test.
It should be noted that fuel lines which feed pressure gauges experience the least amount of loss, as the flow rate through the gauge line plummets to near zero flow levels. This is why gauges typically use 3/16-inch or 1/4-inch line size, as they will not affect performance due to pressure loss.
Fuel is fed to the injector at a relatively low pressure (50-70 psi) and a solenoid controls the high-pressure oil going into the plunging mechanism to ramp injection pressure up to 21,000 psi.
Fast-forward to the present day, and those diesel fuel injector pumps are operating in the 30,000 to 40,000 psi range. Top-end engine performance is in many ways dictated by how much fuel can be processed by the engine.
How does a fuel filter with return line work?
But in situations where the engine doesn't require that much fuel, the fuel filter will gradually fill up. Once the excess fuel reaches the secondary return line, it's simply sent back to the gas tank to be cycled through again. That prevents the carburetor from getting too much fuel pressure.
The term "dead head" simply means that the fuel in the system does not recirculate back to the gas tank from the front of the car. A return system recycles fuel back to the tank using either a bypass at the fuel pump or at the regulator.
When the pressure inside the bottom chamber of the FPR exerts a high enough force on the valve. It overcomes the spring force and lift's the valve off its seat. This allows fuel to flow through the outlet port effectively controlling the fuel pressure in the fuel rail.
Return style fuel system LS engine
In what has been termed a return style fuel system the fuel pressure regulator is integrated into the fuel rail on the LS engine itself. In this type of system you will have a fuel line running up to the fuel rail and return line also coming back from the fuel rail.
Fuel pressure checks on returnless systems can be done in the usual way by attaching a gauge to the service valve fitting on the fuel supply rail, or you can hook up a scan tool and read the pressure value via the pressure sensor.
A deadhead regulator controls fuel pressure by restricting fuel flow between the pump and the regulator. This not only places additional load on the fuel system, but the amount of strain increases as pump volume and flow increases.
Return line means that portion of the recirculating system piping which carries clean water from the filter back to the swimming pool.
How to replace Diesel Injector fuel return lines - YouTube
Water removal is performed by a fuel-water separation filter mounted in the engine fuel system. The most typical filtration media found in such separators is hydrophobic barrier media, such as silicone treated cellulose. This media separates water on its water repellent surface.
FAST: Return vs Returnless Fuel Systems - YouTube
Which fuel line is the return line?
The vapor-return line normally runs from the fuel pump or the fuel filter to the fuel tank. This vapor-return line is connected to a special outlet in the fuel pump. Any vapor that forms in the fuel pump returns to the fuel tank through this line.
The only things that are likely to cause fuel not to return are either a failed fuel pressure regulator, or an obstruction in the fuel rail.
Think of a traditional return-style fuel system as an endless cycle. Your fuel pump (electrical or mechanical) constantly pumps gas from the tank, through a regulator, to either the injectors or carburetor. The fuel pressure regulator is charged with sending the excess fuel back to the tank.
A returnless-type fuel system is one that is designed to use the powertrain control module (PCM) to regulate fuel delivery. A fuel pressure sensor mounted to the supply rail of the fuel injectors allows the powertrain control module to keep an eye on the fuel pressure.
On returnless systems, fuel is picked up via the fuel screen sock at the bottom of the tank, then routed to the fuel pump. The pump supplies the needed fuel pressure and volume to the engine and the excess is directed back into the tank after passing through a pressure regulator.
The term "dead head" simply means that the fuel in the system does not recirculate back to the gas tank from the front of the car. A return system recycles fuel back to the tank using either a bypass at the fuel pump or at the regulator.
The American Boat & Yacht Council (ABYC) recommends the Type B1 fuel hose for diesel-based applications. The Type A1 hose is the best option for gasoline supply. This hose is less permeable, highly durable, heat resistant and does not collapse under high pressure or vacuum.
Some fuel return hoses will run along the frame of the vehicle and go straight to the fuel tank with little as possible bends. Other fuel return lines have many bends and may be longer than normal. This helps the fuel cool down prior to entering the fuel tank.
It appears that the route of the fuel lines and fuel flow goes: From the tank to the fuel pump on the engine in the upper hose to the pump that appears to come from under the firewall, then. To the fuel filter in the lower hose from the pump to the right hand side of the fuel filter, then.
The most common causes of low fuel pressure are a clogged oil filter or a bad fuel pump. It can also be caused by a bad fuel pressure regulator, a stuck fuel injector, a fuel pressure sensor, or a smashed fuel pressure line.
What causes diesel injector pump failure?
A major cause for fuel injection pump problems is the use of dirty fuel. Over time, residue builds up throughout your system. Using poor-quality fuel exacerbates this issue. Bring your vehicle in for auto repair if you notice sputtering or your vehicle hesitates when accelerating.
If fuel pressure is too high, your vehicle's engine could be over fueled, leading to many of the symptoms listed below. Some of these symptoms include your engine running rough, poor fuel economy and black smoke from the exhaust.
There are only two hoses running from the pump. One is the high pressure line, which sends fuel to the injectors. The other is the return line, which dumps fuel that the injectors don't use back into the tank.
But in situations where the engine doesn't require that much fuel, the fuel filter will gradually fill up. Once the excess fuel reaches the secondary return line, it's simply sent back to the gas tank to be cycled through again. That prevents the carburetor from getting too much fuel pressure.
When unwanted air finds its way into your fuel system, your car becomes at risk of reduced performance, and even engine failure. The best way to prevent this from happening is to take your vehicle in for regular maintenance.