How to check the injector on a diesel power tiller
The main reasons why the diesel engine won’t start (by the example of a power tiller)
When a diesel engine won’t start, there may not actually be that many reasons. The basic and most frequently encountered only 7. The more problems these causes, the more complicated the engine. The simplest example. a single-cylinder diesel single-axle tractor, there may be only one and a half times more problems than causes. Knowing them, you are 90% able to find and fix the problem, and successfully start the engine. The remaining 10% are attributed to the specifics of a particular engine, and therefore the probability of encountering them is not very high.
Even if you consider yourself not a beginner, and have a good understanding of diesel engines, do not be lazy to periodically return to the basics. Very often when there is a problem your brain flatly refuses to recognize basic things, so you can overlook the simplest fault. So if you can not start the diesel engine, recall the basics. This often helps.
How to start a single axle tractor with a water cooled diesel engine?
When carrying out a brief test run of the engine of the power tiller it is essential to check the oil level in the engine crankcase, but you may not check the gearbox and the air filter, as well as the presence of water in the cooling system.
For information on starting the engine normally during operation refer to your power tool operator’s manual.
- Completely free the single axle tractor from packing materials and place it on a level and hard surface.
- Unscrew the dipstick (9) and check the oil level in the engine crankcase. If necessary. add 10W30 or 15W40 oil.
- After unscrewing the fuel cap (6) check that there is no diesel fuel. If it is absent or very little, refill with diesel fuel. Screw on fuel cap.
ATTENTION! Diesel fuel is toxic and flammable. When filling fuel tank observe safety precautions and fire safety measures.
In sub-zero temperatures, starting the engine can be difficult. Before the first start-up it is advisable to keep the single axle tractor in a warm room for 2-3 hours or pour warm water into radiator.
Test run engine
- Push the clutch lever (3) to the “off” position.”. Put the gear lever (2) in neutral position.
- Check that the wing nut (4) is not tightened. Turn the hand throttle lever (1) to maximum (upwards). Open the fuel cock (7) to make sure there is no fuel leakage.
- Take out the starting handle (11) from the tool box and insert it into the special socket (10) on the engine crankcase cover. Hand lever must engage in the ratchet catch on the starter shaft.
- To create the right pressure at the nozzle with your left hand turn the decompressor lever (12) to extreme position until it stops and with your right hand turn the handle (11) smoothly clockwise. make a couple of revolutions.
- Hold the decompressor (12) in the turned position and rock the flywheel (8) with acceleration, increasing the rpm as much as possible. After 5-7 crank revolutions maximal speed of the flywheel, give strong pull of the lever and at the same time release the decompressor.
- As soon as the engine starts, return the handle (11) to the toolbox.
- After 5-10 seconds after starting the engine, set the hand throttle lever (1) to medium rpm. let the engine run for 1 to 2 minutes to check if it is operational.
- If the engine fails to start, repeat p. 6 a few more times until the engine fails to start.
- To turn the engine off, set the hand throttle lever (1) to the minimum position and immediately close the fuel cock (7).
To make the first start easier, you may remove the V-belts (15). It is easier to start the engine without a load. After successfully starting and stopping the engine. put the belts in place.
Eliminating starting problems
Often the repair of the engine of a motorblock is needed because this motor does not start.If such a problem occurs after winter storage, you may suspect:
- clogging of fuel or oil with water;
- oxidation of electrical contacts;
- Damage to the insulation;
- debris in the carburetor.
To prevent these violations, you need to carefully inspect any connections before each start-up. If you notice the slightest clamping of the cable, especially if it is twisted, do not start the engine.
Before the first start, check that the oil in the crankcase is sufficient. If it is insufficient, the piston group is likely to be rapidly destroyed. In less than a second, the cylinders will be covered with burrs.
In this case a very serious repair is needed, and sometimes even the replacement of the damaged parts. Sometimes instability in the functioning of the machine is provoked by leaving the lubricant for the winter. If that’s the reason, a puff of white smoke may billow from the exhaust pipe in the first few moments after starting. Immediately afterwards, the power unit will stop.
Diesel motor blocks may also fail to start due to a lack of oil. Only few models are equipped with a system that prevents the lubricant level from dropping. Most people have to service their power tillers by themselves. Also note that failures occur due to the systematic use of unsuitable fuel. If the usual recommendations do not give much effect, it is necessary to remove the plug and see if there are oil spots.
The oil, especially the soot, should be carefully cleaned out. Then the spark plug must be dried. The cylinder also needs to be dried out. A very simple method of “drying” is used: repeated abrupt pulling of the starter rope. The question often arises: what to do if a single-axle tractor won’t start, and smokes black smoke.
Usually such a manifestation indicates that the engine has overfilled with gasoline. You should also be wary of damage to the piston group. If both assumptions are wrong, call the service center. Further attempts to fix the problem yourself can lead to an aggravation of the failure.
- Pour out the previous fuel;
- thoroughly clean the gasoline or diesel tank;
- Clean the air filter;
- clean the fuel hose and nozzles with a jet of compressed air;
- add fresh fuel;
- After opening the fuel line, blow out the channel in the fuel tank lid.
Проверка дизельной форсунки R-175
In some cases the failure is due to gasoline getting into the oil sump. Check if there is no this problem, you must after any adjustment, adjustment of the carburetor.
Adjusting the valve clearance of the engine of a power harvester
If clogging of the lubricant with fuel occurs constantly, you need to look at the carburetor needle. It is likely that this was the weak point of the engine. It is worth noting that sometimes also the motor of the motorblock shoots into the muffler, and maybe even with a flame.
READ STIHL 250 carburetor adjustment
The most probable reason. incomplete combustion.It is provoked:
When the single-axle tractor is also unwilling to act, a breakdown in the ignition system should be looked for thoughtfully and consistently. Inspect magnetos, caps, spark plugs, and high-voltage wires.
Of primary importance is the search for even minor dirt. If all is clear, it is required to inspect the contacts of ignition wires. Next, check the stability of the electrodes, measure the distance between them with a special probe.
Bench for checking injectors of diesel engines
Homemade stand for checking diesel injectors with their own hands: photo and description of making a homemade.
Needed to check the injectors on the diesel engine of the minivan. The engine starts well, the traction is there, but it began misfiring. It is necessary to check the state of injectors, at what pressure they open, what is the spray pattern.
Of course there are craftsmen who can check, but I do not trust our mechanics, so I decided to do everything myself.
How to find a knocking injector
To check which injectors knock, you need to do the following. Starting from the first cylinder it is necessary to unscrew the fuel pipe going to the nozzle and screw a plug instead of the nozzle (if the diesel is Common Rail) or if you have a spare nozzle and drop it into a plastic bottle. Then start the diesel: it will run on the remaining cylinders with unnecessary vibrations. And if the knocking from the nozzle is gone, it means that we managed to find the knocking nozzle. In the same way you can check even a couple of injectors at once, as the diesel will be able to start even on two cylinders.
Nozzle is designed to supply a strictly dosed amount of fuel into the combustion chamber. Closed-type nozzles with hydraulic needle lift and calibrated spray channel are used. Injection start pressure is determined by the nozzle type, so when replacing the nozzle install a new nozzle of the same type. The nozzle arrangement is shown in Fig.235. Fuel flows to the nozzle from the high-pressure pump through the high-pressure line and the passage in the nozzle body to the fuel tank. When the fuel pressure exceeds the resistance of the spring, the needle will move up and open the fuel to the nozzle that injects fuel into the combustion chamber. When fuel pressure is lowered by the spring, the needle lowers and cuts off the fuel supply.
Nozzle performance can be checked while the engine is running. To do so, loosen the nut on the high pressure line to the nozzle (Fig. 8.2).236). If the nozzle is defective, disconnecting it will change the engine sound and the smoke of the exhaust. If the nozzle is defective, disconnecting it will not change anything.To remove injectors, disconnect high pressure fuel lines (see Fig. Figure.236) and fuel dump tube (Fig.237), then unscrew the injectors (Fig.238). When installing the injector, position the shims according to Fig.239. Tighten with 6-7 kgfm torque.
To check injection start pressure, connect injector to a tester, create pressure by pumping, loosen injector fastening nut and bleed air (Fig.240), then tighten the nut, raise the pressure until the start of injection and read the pressure on the tester pressure gauge at the moment of the start of reduction. For the RD28 engine, the injection start pressure of the new injector is 135-145 kg/cm2. Pressure of working injector is usually lower than indicated by about 10 kg/cm2 (not more). The initial injection pressure is adjusted by placing a shim (1) under the spring (Fig.241). Increasing the thickness of the gasket increases the injection start pressure, decreasing the. Decrease. Changing the gasket thickness by 0.04 mm changes the injection start pressure by 4.8 kg/cm2 (injectors for the RD28 engine). Check quality of spraying: spray pattern e.б. evenly spaced across the entire cross section of the spraying cone, and atomization e.б.foggy (Fig.242). Start and end of injection e.б. clear. In new injectors, there is a sharp squeal. If the nozzle is working, the absence of this sharp sound is not an indication that the nozzle should be discarded. The following table summarizes the spray pressure information for nozzles on different engines. To check injector tightness, connect injector to a tester, deflate, raise pressure to a value 20 kg/cm2 below the start of injection. No fuel is allowed to leak out of the injector at the specified pressure (Fig.243). Nozzles that do not meet the requirements should be replaced.
The nozzles may be used if they can be disassembled, cleaned and reassembled again to make sure they are fully functional and can stand the tests described above. Wash the elements only in kerosene or a solvent that does not attack the element material (e.g. white spirit). When cleaning do not touch the surfaces of nozzle working elements with your hands.
Only use tools made of wood or soft metal (brass brushes) for cleaning. After cleaning, rinse elements in clean diesel fuel and dry them. When disassembling do not mix up the parts from different nozzles, before reassembling check that the needle and the body are the same, as they are not interchangeable. Remove the needle from the housing by about half its length and lower it (Fig.244). It should come down smoothly without jamming. Check several times with a different needle rotation. After assembly check pressure at the beginning of injection and tightness of injector.
|Engine||Pressure (kg/cm2)||Engine||Pressure (kg/cm2)|
Injector repair technology (nozzle replacement)
Everyone sooner or later has to deal with high fuel consumption, a drop in power, and sometimes the complete refusal of your car to move. One way or another you end up with the problem of having to replace the nozzles. The easiest way is to take the injectors to the nearest diesel service and leave some money there. This is by far the right method. But what to do, if the nearest service is in 200 km or the owner of a car thinks that he will cope with this problem himself as well as servicemen and will save money? These are the cases for which this text is intended. Either it will help the person not to make mistakes, or will help to give up in time.
First of all, it is necessary to say that simple replacement of nozzle in an injector on the level: unscrew nut, replace the nozzle, screw up the nut carries in itself a great danger to receive as a result an injector of much worse quality than it was before replacement. And this is under the condition of the highest quality of atomizers. We will not discuss cases of low-quality or defective sprayers here. And the main conclusion from the above. without checking the result on a special stand or the simplest device amateur replacement of atomizers is at least doubtful thing.
To begin with you need to understand the structure of a diesel injector and what happens there and what can affect it. The cross-section of the injector is presented on Fig. 1.а). All nozzles (with the exception of super modern ones) are fundamentally similar and the processes taking place in one type of nozzles are similar in others.
So, the high pressure fuel pump (HPF) transmits fuel under pressure to the nozzle choke from where it goes to the cavity “A” of the atomizer through the duct system. There is nowhere else for the fuel to go.к. the path to it is blocked by the needle of atomizer 1, compressed by spring 9. The HPV, continuing to deliver fuel, raises its pressure to a level sufficient to overcome spring force and raise the nozzle tip above the seat (Fig. 1.б). Fuel injection into the cylinder takes place, the system pressure drops, and the needle sits on the seat, locking the system. If fuel injection pump continues to supply fuel, the process repeats. The main condition is that after the end of injection the system is closed. Otherwise in the next measure the fuel feed is not going to be performed when the pressure in the system is up to the set pressure but at any moment (namely as soon as the pump starts feeding fuel). As a consequence, hard and shocking work of engine up to refusal to accept load Combustion products can also get into an unlocked system and cause the atomizer to malfunction.
What can prevent normal operation and seemingly serviceable parts from locking the system?? This is mainly due to the lateral force pushing the needle against the atomizer body. To combat this force, there is an intermediate tappet 10, which relieves the needle from the possible effects of a distorted spring. The pusher is placed in the lantern piece 3. But the intermediate tappet itself can also give rise to lateral forces if it has a certain amount of wear. That is, when replacing nozzles, you should always be prepared for the fact that the new nozzle can “pour” and then require repeated overhaul with the flip of the spring or with the replacement of the spring or tappet. In the rarest of cases, even the nozzle body has to be replaced.
The rest of the nozzle is very simple. As the needle in the atomizer is not sealed by anything, some amount of fuel leaks into the gap between the needle and the atomizer body and gets into the cavity “B” where the spring 9 is located. If the fuel is not removed from there, then after filling the cavity the atomizer needle will lose the ability to move and the nozzle will be “banned”. To remove leaked fuel serve the “return” channel 7. It remains to add that for regulation of size of pressure of opening of an atomizer needle serve adjusting washers 8. The entire nozzle structure is tightened with a cap nut 4. No gaskets are provided inside the nozzle and tightness of joints is secured by nothing but accuracy and cleanliness of machining and mating surfaces. So, we came close to the process of replacing the nozzles. In all presentation we will stick to the idea that you have something to check the injectors after the job is done. There are only three rules to follow in all work on fuel equipment.
It’s cleanliness, cleanliness and cleanliness again!
And cleanliness is not only at the stage of direct disassembly of injectors, but also at all the stages, starting with the removal of injectors from the engine. So, first of all, thoroughly wash the upcoming operating field, especially the nozzle bodies and the head in the area of the nozzle channels. It is important because dirt and sand when removing a nozzle can get into the channel and then damage the thread or break the seal of the nozzle. Alas, it happens quite often and the hapless owner does not even compare the cause with the consequence. After putting the debris in the thread and putting the nozzle in place, then perhaps a year later, with horror discovers that when you try to unscrew the nozzle from him a piece of the head of the block breaks out. The second point which is extremely important for achieving a good result is to close the nozzle connection with clean and tight cap immediately after unscrewing the high pressure hose from the nozzle.
In doing so, do not torture yourself with the idea that the nozzles should be replaced anyway and you can not worry too much about cleanliness. Here it is, then. there will be no aftertreatment if there was no aftertreatment at once. The slightest debris that gets inside the nozzle fitting during bench testing will be trapped by the fuel and could jam the nozzle needle. Then there are only two possible developments: either, if you have not yet replaced the nozzle, you deprive yourself of the opportunity to see what was bad with your old nozzles, or condemn yourself to the not always successful cleaning of new nozzles.
Hence the conclusion. the nozzle cavity should always be absolutely protected from any dust, not to mention debris, even before checking and adjusting, even afterwards. By the way, tobacco chips in your are also garbage and have a destructive effect on the nozzle. By the way, it is reasonable to remove high pressure tubes with bag together with connectors (if motor construction allows it), so there is less reason to puzzle over how it was all standing. For all the outward simplicity of the problem, thousands of people have suffered because of their own negligence. If it is impossible to remove the tubes with a batch, it is necessary to mark on the pump the connection of the first cylinder and mark the tubes themselves in what order they were standing. Life shows that it saves a lot of time and nerves.
Removing the “returns” is usually not difficult. The only thing on Japanese models, where it is necessary to remove the return flow ramp, you must loosen return flow nuts with protective caps on the connectors. Of course, to remove the ramp itself you have to remove the caps, but then you have to put them back on immediately. In the vast majority of cases the nozzles are directly screwed into the cylinder head housing. To unscrew them you should not even try to use wrenches. Even if you can do it without damaging injectors, screwing them back in is doomed to failure. You cannot tighten the nozzle to the specified torque. Vast majority of injectors have hex socket 24 or 27 and standard socket heads are quite suitable for their unscrewing. Twelve-sided heads are more convenient for such works, because they are a bit more convenient in cramped conditions of the under-hood space.
If you cannot buy long heads you can get out of the situation by cutting off the hex part of the usual head and welding it to a piece of pipe at one end and the other end with a mating part for a screwdriver. That is the whole problem. To unscrew nozzles not at once, but at first gently wiggle in the thread after stripping. It is necessary to do it in order not to damage the threads in the head or the head itself, if during the previous incursions into the channel dirt was brought in.
So, nozzles are safely removed.
Now immediately (before you forget what and how, and while the stock lasts) it is necessary to remove from nozzle channels sealing washers or their remnants and all kinds of debris in general. Removing washers often turns out to be a painful dental operation. As a rule, normal washers are simply removed with a hook, but sometimes you have to invent all sorts of individual “pullers” for this (for example, to screw in a tap and pull on it).
I would like to categorically warn against one thing. these are attempts to undercut the washer in the channel with a chisel. Damage to the end part of the channel is inevitable and its repair will require removing the head of the block. The attempt to solve the problem of a damaged end with installation of cunning washers can be safely called a gamble. After cleaning the channels for complete removal of debris from them always crank the engine with the starter for 10-20 seconds. The motor will completely clean itself. By the way, at the same time it is very convenient to check the condition of the spark plugs and their control system. With the nozzles removed, the work of the plugs is perfectly visible. Now (if the car is not in a garage and you are not going to put nozzles in place today) we plug nozzle channels with oily rags and cover the motor with polyethylene from above so that water could not get into channels under any circumstances (for example, from rain). In Nissan Patrol, for example, flooding of cylinders with rain water flowing down the hood through nozzle channels. The phenomenon is the most common.
Having removed nozzles, first of all, we check their operability and make sure that the earlier verdict was fair. What are the criteria for assessing the performance of nozzles? Although the issue in the literature is described in detail, in order to maintain the integrity of the presentation, I bring these criteria here: when supplying fuel injector should open at a given pressure; before the opening of the nozzle leakage or jets of fuel from the nozzle is not allowed; at the time of spraying fuel drops and jets are not allowed; spray pattern should be smooth without deviation and match the direction of the hole (or holes) in the nozzle ; after stopping the fuel supply at the nozzle should maintain pressure for some time (strictly speaking, the rate of drop.
It is still customary to talk about the characteristic sound of the nozzles, but the sound is not an objective parameter for evaluating the nozzles. You can not ignore this parameter, but you should not put it at the head of the column, either. If it turns out that you really need to change the nozzles, put on the nozzle protective caps and prepare the workplace. The preparation consists of thorough cleaning and washing of the table, vice and preparation of at least two tubs of pure diesel fuel, necessary keys (usually two pieces) and possibly a knife. everything unnecessary will prevent the work. Assume that you do not have in your garage a special device for fixing nozzles during disassembly. So we will disassemble in a vise. We must say at once that Japanese nozzles, in which the “return” is taken away through the ramp, categorically cannot be clamped in a vice. At clamping in a vice the edges of sealing surface for “return” are crumpled Such injectors are disassembled by putting them in the ring spanner clamped in the vice. German injectors (not from the most advanced models) can be disassembled in a vice without any damage. But for disassembling nozzles can not use wrenches. To begin with, it is simply inconvenient, but the most important thing is that the wing nuts of injector bodies of some engines (for example, Mercedes OM601,602,603) crack at the attempt to disassemble or assemble them with a socket wrench. But this part is very expensive and hard to buy. So, to disassemble nozzles we use the same extended head that is used for removing from the motor. After loosening the captive nut, we unscrew it by hand. It often screws together with the atomizer, which sticks to it. No problem. Sprayer, after removing the nut, should be pounded out with any suitable tool, and the cavity of the nut should be cleaned from all nastiness with a dustpan for cleaning battery terminals. Of course, for this work we move a couple of meters away from the clean area. Let’s wash the nut in the first tub. it will be for the dirty works. and set it aside on a piece of paper. Then we remove the intermediate casing and rinse it in a clean bath, drain the nozzle body, clamped in a vice, with fuel and put the intermediate casing in place without touching anything else. Open the package of a new nozzle and, without disassembling it, rinse in clean fuel. Nozzle or intermediate casing (as well as any part of fuel injection equipment) should be taken out of the tray after rinsing so that flowing down fuel could remove possible dust from the mating surfaces (Fig. 5 и 6).
Install the atomizer and tighten the cap nut. Now check on the stand what we got. Quite often, when before replacement the nozzle had a worthy manufacturer’s nozzle, and we install no less worthy one. If other parts of the nozzle are not very worn out, it may well happen that after changing the nozzle the nozzle will work properly and no adjustments will be required. If this is the case, immediately close the nozzle connection with the cap and finally check the tightening of the cap nut. The matter is that when you do this procedure many times a day, you involuntarily do not pull the coupling nut very strongly. in fact you will have to disassemble it again in a minute. Unfortunately it doesn’t always work at once: either the pressure doesn’t match or the atomizer pours. Don’t get your hopes up that it’s pouring because we didn’t take it apart and wash it from the preservative the first time.
Such hopes can have ground only in case of conservation of atomizers by dipping them into gelatin-like mass, and even that seldom. Usually, modern atomizers are preserved by the manufacturer either in a special oil, or in an inert environment. And we won’t do any cleaner than Bosch or Delphi cleaned their parts before packing. So the cause of poor spraying will be in the wear of the intermediate tappet (item 2, see “Tappet”). rice. 1,a) or a deformed spring. Sometimes turning over the spring in the housing helps, but usually the cardinal solution is in replacing the worn parts. And this way the atomizer replacement procedure becomes a series of assembly-disassembly-testing until the desired result is achieved. But, at last, the result is achieved, we like the work of injectors, it is possible to put them on the engine. Let’s not be in a hurry! Remember that injectors are sealed with special washers which not only seal the injector channel, but also take away heat from atomizers, preventing them from overheating and getting corked. Without putting new washers we can easily ruin brand-new sprayers in the first half an hour of engine operation. At Japanese injectors are one-time washers sealing the return line ramp also.
About the Japanese injectors I want to especially note that on the engines of various designs the washers of sealing “return” are very similar (almost indistinguishable) to each other and, nevertheless, putting a foreign washer or a washer from a strange manufacturer very often leads to leakage of return flow. Therefore, when selecting sealing washers of return nozzles, it is necessary to find out the possibility of lateral displacement of the washer on the nozzle when tightening and the possibility of overlapping or on the contrary not sealing of fuel take-off channels. Before screwing in nozzles make sure by turning crankshaft starter, as well as by the oil dipstick that the enemy forces have not harmed you, and the cylinders did not get water or something else. Now you can screw in the injectors in place, pre-lubricate the threads on the housing with copper or graphite grease, and tighten the required torque (usually 6-7 kg).м.). But here is a nice detail: always screw in the nozzle into the channel by finger pressure only (if it does not work). clean the threads), on some cars (e.g. Mercedes) it is very easy to screw in a nozzle that is not threaded and ruin the pre-camera by screwing in a tight nozzle with a wrench.
I can’t count the number of such cases. Reassembly is no problem if you did not overdo it and marked all the pipes and fittings when removing. Just a few tips. Before setting, the high-pressure tubes should be flushed from the outside and must be flushed with fuel from the inside. And you should not neglect to put in place the clips that collect the tubes in the package. These clamps don’t exist for aesthetics. They keep the tubes from vibrating. Tubes without clamps break quickly (like a knife cuts them off). So that’s it, you can blow the air out of the machine and try to start it up.
On what to check the performance of injectors. Undoubtedly, the best tool for this is the stand to check the injectors, which can be the most complex electronic one for thousands of dollars and very simple, even primitive in the spirit of the fifties, or even homemade
Any one of them can be used for more or less comfortably. There are a lot of diesel garages in the country and they have test benches, even the simplest ones. And we know how to negotiate. But what if your diesel is the only one around? Not very terrible effort should be made to make a homemade stand from the written-off tractor-KAMAZovskogo or marine pump or adapt the fuel injection valve of your motor to check the injectors. Of course, it’s not the most beautiful way, but it’s a good way.
It is necessary to produce a pipe. tee which will be connected by one end to one of the connectors of high pressure of your fuel injection pump, on the other end we will fix the nozzle and on the third one you will attach the pressure gauge of about 200-300 atmospheres (it is possible and more). First of all we crank the engine with the starter until the nozzle starts to fire, and then, without forgetting to leave the ignition on, by hand. Excruciating, of course, but if there is no other way out. quite realistic.
About the nozzle opening pressure. At the compression stroke, the air charge from the cylinder flows into the combustion chamber at a very high speed. In this case, in the combustion chamber, due to its shape, there is a directional vortex in which the fuel is injected. Depending on the combustion chamber design and degree of compression, swirl speed and shape are different, so there are different types of atomizers and different values of fuel injection pressure. Engine designers define the recommended, as well as allowable values of injection pressure for each engine. As a rule these values should be observed with an accuracy of 5-10.cm2 within a set of injectors. When reassembling injectors it makes sense to adjust injection pressure by 10-15 kg.cm2 more than required, in the expectation that in the first minutes of operation of the injector there will be some shrinkage of the moving parts and, accordingly, a decrease in the set pressure.
Especially it is necessary to note the specific property of fuel distribution pumps of rotary type from LUCAS. very strict requirements to the accuracy of adjustment of the injection pressure within the set of injectors. For reference, in engines with these fuel pumps it is often impossible to find a faulty injector by disconnecting. The engine will immediately shut down because the fuel supply to the remaining injectors is.
How to adjust nozzle opening pressure at home. In the great majority of modern injectors the opening pressure is regulated by selection of thickness of spacer washer between spring and casing. In decent workshops there are sets of these washers to solve any problems with the adjustment. For amateurs you should keep in mind that washers are of different diameters (for different nozzle bodies), and can be in the version with a hole and without it. Washers with a hole can always be used instead of washers without a hole, but the reverse is not allowed. It is also inadmissible to use washers of “non-native” diameter.
As a rule, injectors are designed in a way that increasing washer thickness by 0.1 mm leads to injection pressure increase by 10 kG.cm2. Very often you see during the repair of injectors that during the previous interventions the injection pressure was adjusted with the pieces of razor blades put under the spring. This way of adjustment is completely unacceptable. Firstly, having a shim of uncontrolled shape, you create an uncertainty of the spring support and thereby non-uniformity of its development and provoke the emergence of lateral force. And secondly, there is a risk of chipping a bit of blade and no one knows what it will do inside the nozzle. Therefore, the only quality solution to the problem should be to make new shims of the calculated thickness. And only in those cases where turning lathe, heat treatment and grinding is absolutely inaccessible, it is acceptable to regulate pressure with steel foil washers, putting them only between the body and standard washer. If you have a spring resting on a non-hardened pad, after a short time there will be not much left of it.
A typical problem with Japanese injectors. A distinctive feature of Japanese engines injectors is the “return” through the end of the injector into a special ramp. If disassembled carelessly, the sealing face of the nozzle is very often deformed, so that the hermetic sealing of the “return” can not be achieved. Beginning “experiments” with tightening ramp nuts, putting sealing washers under the nuts, etc.д. However, the only way to solve this problem is to undercut the sealing face of the nozzle on a lathe. However it must be taken into account that facing corrects only one nozzle surface and groove shape at the end can become so deformed that sealing washer cannot cover it anymore. This injector must be replaced. Irrepressible attempts to tighten leaky or flowing returns often lead to deformation of return ramp flanges. With these flanges the sealing cannot be achieved and it is necessary to rebuild them. This is not difficult to do by hand on a small sanded tile by putting sandpaper on it.
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Nozzle operation and spray pattern
The key performance indicator of a fuel nozzle is its spray pattern. This is the shape the portion of fluid that comes out of the nozzle. Ideally, it is a water mist forming a cloud of a given shape: fuel mixes well with air, does not settle on the walls of the combustion chamber, does not spray. Depending on where the nozzle is routed (into the intake manifold or combustion chamber), fuel can be atomized in different ways. Quantity of liquid, dispersity and the shape of the torch are defined at the engine design stage and any deviation from the normal parameters will affect the operation, performance and service life of the engine.
One of their technical characteristics is the injector performance. Constituted as volume (cubic centimeters) filled per minute at 3 bar. The most common indicators are from 180 to 240.
Units of performance in catalogs may be referred to differently:
The translation of one value into another is done by the following formula:
Diesel engine compression has dropped: timing and piston wear
Diesel engine by the principle of its operation is only partially similar to a gasoline engine. The main feature of this type of internal combustion engine is the realization of fuel autoignition by strong compression of a mixture of fuel and air in the diesel engine cylinders. Compression causes the mixture to heat up, resulting in a flash.
The most important condition for the proper operation of a diesel engine is the cylinder compression. Cylinder compression with the ignition switch off for gasoline engines and without fuel injection for diesel engines. During the operation of any engine is subject to wear, but for a diesel engine even a slight loss of compression is a serious problem, especially in the cold season.
We also recommend reading the article about what to do if the diesel engine starts badly or does not start in the cold. From this article you will learn about the main causes of difficulty starting a diesel engine after a long idle time.
The compression of a gasoline or diesel engine often decreases in different cylinders with a noticeable scatter of readings. Decreased compression can be caused by wear of the cylinder mirror or compression rings of a diesel engine, but such wear is not uniform from cylinder to cylinder. Different compression in the diesel engine cylinders leads to its extremely unstable operation after start-up. Loss of compression and irregularity in the cylinders can identify one of the possible causes and answer the question of why a diesel engine does not start well or trots.