Engine users face some challenges, one of which is gas bubbling out of the tank. It is a problem and usually gives the mechanics a lot of issues to sort.
I remember the first time I faced such a situation a few years ago; it took me about three days to figure it out.
That singular incident prompts me to write this article, so others to benefit from my experience.
The air bubbles in a fuel tank must be ventilated properly; if not, some trapped air may cause an airlock to the fuel pumps, cause the engine to run erratically, and even stop the engine.
Also, the fuel pumps can become overheated due to friction.
The most common misdiagnosed problem related to this issue was “air leaks” in the fuel line between the fuel tank and the fuel pump.
Pumps have a unique inherent quality. It will move the easiest substance available.
If the fuel line leaks air caused by deteriorated hoses, loose connections, or rusted-out fuel lines, the pump will move lots of air but no fuel.
Vapour lock” is a condition where the fuel pump has no liquid fuel. A fuel pump is designed to move fluid (specifically fuel).
When no fluid is present, the vacuum on the inlet side of the pump is low and, under certain conditions will not produce enough vacuum to lift the liquid fuel from the fuel tank to the pump.
High fuel pump temperatures can exaggerate this problem as it can cause the fuel to vaporize.
This problem was most prevalent in Carburetted engines where the fuel pump is attached directly to the engine, and the fuel lines are very close to the exhaust.
Until the 90s, this was a common problem for the mechanic
For the next ten years, mechanics have dealt with this problem less and less. Find an old machine with this issue today if you have a Carburetted vehicle.
SYMPTOMS OF CLOGGED FUEL FILTER
When you’re on the road, your car’s engine sucks fuel, and your fuel pump sends fuel from the fuel tank to the engine fuel system.
Before the fuel gets to the final destination, it gets to the fuel filter that filters the dirt from the fuel.
Cars use filters to filter air, fuel, and oil, among other things, but in this article, I will focus on the filter that filters the fuel.
Just like air filters, oil filter fuel filters can be clogged because they successfully perform their duties for an extended period.
The longer the filter runs, the more particles it can catch until it can’t catch any more. When that happens, it can interrupt fuel delivery, and your engine can starve and die.
To prevent your car from dying on the highway, it’s important to recognize early onset symptoms that could be a problem.
I want to help you with this article so your car will not disappoint you on the road. What is a fuel filter, and what can it do?
WHAT IS A FUEL FILTER AND WHAT ITS FUNCTION
A fuel filter is a device in a car’s fuel system that traps excess debris as the fuel passes through it.
It is usually made of a metal or plastic casing and contains different materials designed to trap harmful pollutants floating in the diesel.
So the fuel filter plays a significant role in cleansing the fuel from dirt and other debris.
Location; The fuel filter will be somewhere between the fuel tank and the engine; here are some helpful tips for finding it.
Inline: On some vehicles, usually those with a return fuel system, the filter is between the two fuel hose connections, so it’s in line with the fuel system.
Some are found on the fuel tank, usually those with a no-return system, where the fuel filter is either on or in the tank.
SYMPTOMS OF A CLOGGED FUEL FILTER
A clogged fuel filter prevents the engine from getting sufficient fuel, leading to engine malfunction.
If you observe any below-listed symptoms, it can be caused by a dirty, clogged, and old fuel filter.
These symptoms could also be a bad fuel pump or something else.
1. Difficult start; your engine needs fuel to start. If the filter is clogged and fuel cannot be delivered, it may not start.
Because the filter is clogged, it does not allow fuel to pass through to the necessary components that will make the engine start. Those components like carburettor, injection, or injector will be starving of diesel.
2. Sputtering; if you start your car and it sounds like an asthmatic howler monkey idling, it probably isn’t getting the proper fuel to idle at a consistent RPM. In this case, the engine is getting fuel, but it is not enough to run smoothly.
3. Inconsistent acceleration: fuel rushes into the engine every time you accelerate. If the amount reaching the blockage is insufficient, a clogged fuel filter may result.
4. Engine temperature is abnormally high; if the normal combustion cycle is out of balance due to a lack of fuel, the engine can overwork or be overstressed, leading to unhealthy high temperatures. And overheating will cause a lot of damage to the engine by affecting some engine components.
5. Fuel efficiency drops; if your engine isn’t getting enough fuel, the pressure can lead to lower fuel efficiency.
How Long Does the Fuel Filter Last?
It is recommended to replace or at least check your filter about every 30,000 miles. Some manufacturers recommend longer, others shorter, so it’s best to check your owner’s manual.
How Much is Labor Charge to fix a Clogged Fuel Filter?
In most cases, the price of a fuel filter depends on the size or quality. For the part itself, fuel filters range in price from $10 to $150.
Additional professional labour costs can add up to $100 or $200, depending on the location of the filter.
Why is There Air in the Diesel Circuit, and How to Get Rid of it?
Suppose the air in the fuel circuit is not exhausted. In that case, after the diesel engine runs for some time, the exhaust pipe exhaust will change the sound and intermittently emit white smoke, the speed will drop, the work will be weak, and in serious cases, it will turn off by itself.
The air in the fuel circuit mainly comes from two sources.
Of course, if there is air in the diesel fuel circuit, the air must be discharged; otherwise, the diesel engine will not be able to start.
A diesel fuel engine seems to be simple, but it is very technical.
A diesel engine fuel supply system can be divided into a low-pressure fuel circuit and a high-pressure fuel circuit.
Generally, after the diesel engine is repaired, the fuel supply system accidentally burns the diesel fuel in the fuel tank or the oil pipe leaks, and the outside air enters the fuel supply system.
Since the air is compressible, the pressure in the system cannot reach the opening pressure of the fuel injector, so the fuel cannot be injected into the engine, and the engine cannot be started naturally.
Generally, we only need to discharge the air in the low-pressure fuel circuit when exhausting, and the air in the high-pressure oil circuit will be automatically discharged.
1. Low pressure in the fuel circuit: The reasons for the inhalation of air in the low-pressure fuel circuit; first, the diesel fuel is safely used up, the vent hole of the fuel tank cap is blocked, and a vacuum is formed in the tank, and the air is inhaled.
The second is that the hand fuel pump’s sealing gasket and the pump body’s sound on the fuel transfer pump are broken or uneven, and the air enters from it.
The third is that the hand fuel pump piston or leather cup is seriously worn, and the air enters the low-pressure fuel circuit from the upper part of the hand fuel pump through the gap between the piston or the leather cup and the sound of the pump barrel.
Fourth, the sealing gasket of the fuel pipe joint in the low-pressure pipeline is uneven or damaged, or the hollow screw is not tightened, and air enters.
Fifth, the low-pressure fuel pipe of the fuel supply system is broken, causing air to enter.
The inspection method is to remove the low-pressure fuel pipe, clean the joint, block one end of the fuel pipe with fingers, and use the mouth to pressurize the pipe at the opposite side.
There will be a vacuum in between the pipe; if the pipe is good and if you suck it with your tongue to test the pipe, and the tongue sucks it, it proves that the tubing is broken.
Sixth, mechanical impurities make the fuel return valve not close tightly, and the diesel fuel is discharged through the fuel return valve, causing the pressure in the oil passage of the fuel injection pump to be replaced, the fuel injection volume is reduced, and there is endless air in the oil passage.
2. The high-pressure gas is flushed back from the fuel injector into the fuel supply circuit
Suppose the injector needle valve is stuck in the opening position. In that case, the oil outlet valve of the same cylinder is not tightly sealed, the needle valve and the needle valve body are seriously worn, and the high-pressure spring in the injector is broken.
The injector tappet and the needle. If the matching hole of the valve is worn out, the high-pressure air will flow back into the fuel supply circuit after each cylinder cycle.
The reason why the high-pressure air flows into the fuel supply system is that after the end of the compression stroke of the diesel engine,
the injector injects diesel fuel into the cylinder at a certain angle before the top dead centre of the piston.
When the injector is opened, the gas in the cylinder and the fuel circuit form a passage (the gas in the passage has a pressure difference that changes with time).
When the quality of the injector is poor, the high-pressure gas in the cylinder will pass through the sealing cone from the injection hole.
On the surface, through the gap at the needle valve of the nozzle coupler, the tappet hole in the injector body, and the fuel return pipe of the injector, it flows back into the diesel filter until it reaches the fuel circuit.
How to Remove the air in the Diesel Fuel Circuit
The fuel circuit of the diesel engine fuel supply system is roughly divided into several sections, the fuel tank – the fuel-water separator – the fuel transfer pump – the fuel filter – the high-pressure fuel pump; we need to operate in sections when exhausting.
The specific fuel circuit exhaust operation process is as follows:
1. Loosen the fuel outlet pipe joint screw of the fuel-water separator, and then press the hand pump on the fuel-water separator until the diesel fuel flowing out of the fuel-water separator has no air bubbles, and then tighten the screw;
2. Loosen the screw of the fuel inlet pipe joint of the fuel pump, and then press the hand fuel pump on the fuel-water separator until the diesel oil flowing out of the fuel pipe joint has no air bubbles, and then tighten the screw;
3. Loosen the screw of the fuel pump outlet pipe joint, and then press the hand fuel pump on the fuel transfer pump until the diesel fuel flowing out of the fuel pipe joint has no air bubbles, and then tighten the screw;
You will notice that when you press the mechanical fuel lifter, it will not respond, and it feels as if it is empty. In this case, the diaphragm of the fuel pump may be in the pumping position, and the hand pump will not work. At this point, turn the engine around once.
4. Loosen the fuel outlet joint screw or air bleed screw of the fine fuel filter, and then press the hand pump on the fuel transfer pump until there are no air bubbles in the diesel oil flowing out of the fuel pipe joint, and then tighten the screw; due to the large size of the fuel filter.
This process takes a long time;
5. Loosen the exhaust (fuel return) screw on the high-pressure fuel pump, continue to press the hand pump on the fuel delivery pump until there are no air bubbles in the output diesel fuel flowing out of the exhaust screw, then tighten the exhaust screw; continue to press on the fuel delivery pump the hand fuel pump until the fuel return valve on the high-pressure fuel pump makes a “squeak” fuel return sound.
After such an operation, the air in the low-pressure fuel circuit is eliminated.
The hand oil pump has a lot of resistance when pressed, and every time it is pressed requires a lot of force.
Then we press the hand oil pump a few times, start the engine, and generally, it can be started smoothly.
What Should I do if I Add Diesel to a Petrol Car?
It can be divided into two cases:
Situation 1: After finding that the wrong fuel is added (a full tank of diesel fuel is added by mistake), remember not to ignite the car to prevent the diesel from entering the fuel circuit.
Then toll the car to a repair shop, drain the diesel fuel, and add gasoline. If the diesel is only added a little (no more than 5-10% of the fuel tank volume), there is no big problem if it is discovered in time. Just add more gasoline, and it will not have any effect.
Situation 2: In fact, most of the friends who add the wrong fuel will not find out in time but find that the vehicle is abnormal after driving for some time before observing severe vibration, and poor acceleration are the most obvious symptoms of the engine has been turned off before they could realize their mistake.
In such a case, the first thing is to drain the diesel/fuel from the tank, then take it to a repair shop to clean the fuel circuit, replace the gasoline filter element, and perform a comprehensive inspection.
In most cases, before the knock is severe enough to destroy the engine, the engine has been turned off, and generally, there is no such tragic situation.
You have learned a lot from this article on how your fuel system can be free from air lock.