Now everyone knows that when the engine is running, the fuel system of the car inevitably gets dirty. The dirt is not only solid particles (dirt), but also tar and varnish deposits. This is due to the presence of some chemical elements and their compounds in gasoline – sulfur, olefin, etc. Injection nozzles of fuel dosing systems operating at high temperatures (up to 120°C) and injection pressure (1 to 6 atm) are most susceptible to this contamination. The use of low-quality gasoline further aggravates the situation. It also happens that you have to sell your car for scrap metal. Fortunately, sometimes you can get a lot of cash for cars newmarket.
Clogged injectors change the direction and shape of the spray pattern, reducing the performance, and possibly even stopping injection altogether. All this leads to uneven fuel supply to the cylinders, as well as to a lack of fuel in the transient and power modes of the engine. Nozzles pollution manifests itself by reduced engine power and injectivity, detonation knocking during acceleration, unstable engine idling, difficult engine start (especially at low temperatures), increased fuel consumption, increased toxicity of exhaust.
These signs may be a manifestation of other malfunctions of the engine and its control system, and to identify the real cause of poor engine performance, it is necessary to carry out diagnostics. Indirect signs of clogged injectors can be increased injection time, the difference of unburned fuel emission in the power balance test by cylinders with ignition cutoff on the engine tester, integrated with a gas analyzer. To test this hypothesis, you can either immediately apply the injectors wash, or, to determine their actual condition, dismantle the injectors from the engine and check the performance, quality of the spray pattern, tightness in the closed state.
Diagnosis led to the conclusion about the need to wash injectors. Nozzles can be washed either by dismantling them from the engine, if it is not already done, or without dismantling. Methods of washing without dismantling are less time-consuming, but the quality control of washing can only be carried out by indirect methods. Dismantling of the injector should be considered as a repair operation. It often requires replacing the seals of the injectors and the fuel rail, and sometimes the seals of the engine intake manifold. On some engine types, this is a time-consuming and expensive procedure. However, laboriousness of disassembly of injectors is compensated by the possibility of their qualitative diagnostics. Let’s consider the most used methods of injector flushing and their advantages and disadvantages.
1) The first method is the easiest way to flush the injectors and the entire gasoline line – adding a detergent additive to the fuel tank. Almost all manufacturers of automotive chemicals offer such preparations. Usually 200…500 ml bottle of additive is designed for 40…80 liters of petrol. This method has the advantage that washing includes practically all components of the fuel system, assembled on a gas line: gas tank, fuel pump, gas lines, fuel manifold, pressure regulator, injectors. Particularly, there have been cases in the service practice when the gasoline pump started to “stick” because of heavy tar sediments in the working chamber. However, you should take into consideration that there is a risk that deposits and dirt washed out of a gas tank, gas pipe and gas filter will block even more the injectors and pressure regulator valve. Another important thing is that washing with petrol additives is not very effective in case of heavy contamination. From the above it follows that washing the fuel system and injectors with gasoline additives should be considered more as a preventive measure when the parts of the gasoline line are clean to begin with. It is also confirmed by the recommendations of producers of washing additives, recommending to repeat the flushing procedure every 2…4 thousand km, and by our experience. If you dared to use fuel washing additives, choose a well-known and reliable producer of auto chemical goods.
2) The second method of flushing injectors without disassembling them from the engine is flushing with special units of washing solvent supply to the fuel rail. When working with such units the regular fuel system (gas tank, fuel pump, fuel lines) is disconnected. A distinction is made between one-circuit and two-circuit units. In case of one-circuit unit only solvent supply to the fuel ramp is carried out, whereas two-circuit units use return line from the ramp. The advantage of a two-circuit unit is the possibility of flushing the fuel ramp and pressure regulator. This is achieved by pumping the cleaning solvent through the fuel rail from the connector of the fuel supply line to the connector of the return line without opening the injectors until the injectors are washed. For heavily contaminated fuel systems, the use of single-circuit installation without pre-washing of the fuel rail can lead to severe clogging of injectors with the dirt that flakes off the walls of the fuel rail and then wash the injectors with their disassembly from the engine or even replace them. Actually washing of injectors at the washing installations of both types is carried out by starting the engine on the washing solvent and running it in different modes. Fuel pressure in single-circuit units is set by the unit itself, and in the two-circuit – the regular pressure regulator.
Flushing with the help of special units has a fairly high efficiency. In the literature there are estimates of a positive result from 60% to 90% of cases. In the remaining cases, either repeated similar flushing or flushing with nozzle removal helps. Quality control of flushing is again carried out by indirect signs. When flushing the injectors without dismantling, there is also a cleaning of the inlet valve stems and combustion chambers from carbon deposits. Such useful property may result in decreased compression due to burnt-out carbon deposits in the pistons’ grooves if the engine is strongly worn. There are cases when after flushing the injectors a worn out engine will not start at all. Another negative consequence is that washing with some solvents damages spark plugs. Therefore, it is advisable to wash the spark plugs at the same time as replacing them.
In both methods, the control of the state of the injectors is carried out on the stand, as a rule, which is a part of the washing unit. The bench provides the supply of solvent to the nozzles at the required pressure, the supply of controlling electrical pulses, allows a visual control of the spray pattern, control passed through each nozzle of solvent for a certain period of time. If the nozzles did not pass the control for compliance with the factory parameters or the difference in nozzle performance is more than 5% (in the absence of data on the required performance), then the decision to continue washing or culling of nozzles is made. Some benches provide solvent supply to the nozzle in the reverse direction. This allows you to wash more fully the inner cavity of the nozzle after the detachment of dirt and slag in an ultrasonic bath. Checking injector tightness is performed by injecting solvent to the injector at a pressure 10% higher than the nominal pressure and with no control pulses. Under these conditions, most nozzle manufacturers allow no more than one drop per minute. A leaky injector may be flushed again or discarded if repeated flushes are unsuccessful.
There are a couple of other comments to the methods of flushing injectors with disassembly. A great many types of injectors are equipped with replaceable fine filters. These filters, as well as removable caps in the working part of the injectors are recommended to be replaced with new ones after flushing the injectors. Also do not forget that when washing the injectors with disassembly we do not touch the whole other part of the gasoline line. If it is also very dirty, it is possible that in a short time the injectors will be clogged again. In these cases we have to recommend flushing the gas tank, gas pipes and fuel rail.