Ⅰ. Function

   It is necessary to test fuel pressure during trouble shooting of fuel injection system. When an engine is working, high fuel pressure will make the gas mixture of engine too heavy to cause malfunction of engine, incomplete combustion, increase of carbon deposition, and over-standard emission of tail gas, etc. On the other hand, low fuel pressure will make the gas mixture of engine too thin to cause burning of injector and detonation of engine, this will further damage piston, piston ring, connecting rod and crankshaft, and as a result, the automobile won’t work. Therefore, the automobile engine fuel pressure test kit is a necessary tool to maintain the injection system of an engine.

 

Ⅱ, Safety rules for testing and cleaning of system beforehand

1. Wear protective glasses;

2. Choose a well-ventilated working area, and never inhale waste gas;

3. Prepare a fire extinguisher used for gasoline / electronics / chemicals to prevent fire;

4. Never touch revolvable or over-heated parts of engine during operation;

5. Be sure to put the transmission shift lever on “P”(automatic speed change box) or neutral position, pull tight the parking brake, and lock up the driving wheel;

6. Never put tools on the storage battery, otherwise it would cause short circuit, body injury or damage of the tools and storage battery.

7. Never smoking or making open fire near the automobile, since fuel vapor or gas emitted from the storage battery easily burns and explodes;

8. Ask a person to keep a close watch on what is going on during test run;

9. When the fuel pipe is being taken down or connected, put cloth at the adaptor of the fuel pipe to prevent fuel spill and then properly treat all the cloth that has absorbed fuel;

10. If there’s any fuel spill, clean off the spilled fuel immediately;

11. Keep away from the cooling fan of engine, and the cooling fan may suddenly rotate in some automobile;

12. Relieve the fuel pressure before taking down the fuel pipe;

13. As for automobiles equipped with air bags, strictly observe relevant rules listed in the maintenance manual; otherwise the air bags would suddenly unfold and cause body injury. Please remember that the air bags will unfold several minutes after turning off of ignition switch (even the storage battery isn’t connected) due to a special storage equipment of the engine;

14. After testing, discharge all the fuel in the connection pipe of the pressure gauge into a proper container, and then take down the pressure gauge and connection pipe.

 

Ⅲ Check before testing

   Before testing, please carefully read the points for attention on test and the maintenance manual offered by the manufacturer, and ask whether the automobile has been repaired recently, if it has been repaired, the repaired part shall be especially checked, the engine and fuel system shall be thoroughly examined by eyes, and the fuel pipe and vacuum pipe shall also be checked to find out whether there’s any loosening or breakage, and whether the fuel pipe, vacuum pipe and pipeline is properly connected.

1. Check of fuel system

(1). Check whether there’s fuel leakage, and if there’s leaked fuel, clean off it immediately, and remedy the trouble;

(2). Check whether the cover of fuel tank is broken, whether the ventilation system of the fuel tank is stuffed, and whether there’s enough fuel in the fuel tank( never depending on the fuel gauge in the automobile only);  

(3). Check whether there’s any water, coagulative crystal or other impurities in the fuel tank, and whether the filter screen at the fuel filler is stuffed;

(4). Be sure to keep the fuse of the fuel system in good conditions;

(5). Check whether the degree of vacuum of the air inlet pipe is within the standard set by the manufacturer.

 

2. Check of the electrical system

(1) Be sure that there shall be enough power in the storage battery, and the voltage of the storage battery can’t be below 12 V;

(2) Check the function of battery charging system;

(3) Check whether the wire or connector of the storage battery is loosened or erosive;

(4)Check whether the electrical components and circuit are properly connected, and whether there’s short circuit, open circuit or imperfect contact at the connection point;

(5)Check whether the fault indicating lamp of the engine functions properly.

 

3. Other checks

(1) Check whether the vacuum pipeline is loosened or disconnected;

(2) Check whether there’s any water leakage from the water tank, and whether there’s any gas leakage or abnormal noises from the engine.

(3). Check whether the sound of engine is abnormal, and whether the noises from the fuel pump is too loud;

(4) Check the opening and closing time of the inlet/outlet valve, and adjust it.

 

Ⅳ Test methods of fuel pressure

1. Connect the fuel pressure test kit to the fuel pipeline, and there’s a Schrader valve on the fuel guide rail of most automobiles to facilitate such connection. As for an automobile without a Schrader valve, its fuel guide rail can be unblocked and fuel pressure gauge can be installed as follows:

Be sure to keep in mind: Read carefully and follow what are listed in this instruction and automobile service manual concerning all advance checks, safety warning, and fuel pressure test procedure.

Attention: Be careful when working around the fuel system, and the fuel in the fuel guide rail will be pressurized even if the engine doesn’t run, thus the Schrader valve shall always be wrapped with a piece of cloth whenever a adapter shall be connected to the fuel system, and the leaked fuel shall be cleaned off immediately.

 

2. As for an automobile without a Schrader valve on the fuel guide rail:

(1) The fuel system shall be depressurized according to the automobile service manual, electronic fuel pump shall be taken down or stagnated for most automobiles, and the engine shall run until the fuel pump stops. Note: since most automobiles have more than one fuel pump, all the fuel pumps shall be stagnated. Otherwise, there would be body damage, automobile damage, fuel leakage, fire or other dangerous cases.

(2) According to what is described in the automobile service manual, a proper adapter shall be connected tight to a fuel gauge and disconnect fuel pipeline, and then connect the adapter to the fuel pipeline. Different adapters shall be used for specific types of automobiles as the following chart:

 

Note:  The procedures listed in this instruction can’t replace the maintenance description in the automobile service manual.

(3) Put the end of discharging hose into the fuel storage unit and keep it there until the test finishes.

(4) Hang the head of fuel pressure gauge onto the engine cover.

(5) Switch off all accessories.(Such as radio, air conditioner, electric fan, head lamp and rain brusher, etc.)

(6) Turn on ignition switch.

 

Tests shall be carried out as follows:

a. Pressurize the fuel system through each cycle of turning on/off the ignition switch every ten seconds until the fuel pressure reaches the standard set by the manufacturer (Please see the automobile service manual).

b. Check whether there’s leakage at the fuel system, if there’s leakage, turn off the ignition switch and immediately clean off the leaked fuel;

c. If the fuel pressure fails to reach the standard set by the manufacturer, turn the ignition switch by 2-3 times, if the fuel pressure still fails to reach the standard, repair and maintain the automobile according to the automobile maintenance manual.

d. Idle the engine and read the fuel pressure indicated on the pressure gauge, if the fuel pressure fails to reach the standard, repair and maintain the automobile according to the automobile maintenance manual.

e. Turn off the ignition switch and stop the engine;

f. Take down the fuel pressure gauge and reinstall the fuel pipe.

Note: Pay attention to the following points when taking down the fuel pressure gauge:

① Be sure to keep the fuel discharging hose of the fuel pressure gauge in the fuel storage.

② Press the pressure relief button until the reading of fuel pressure gauge becomes 0. (Note: The pressurized fuel will inject from the discharging hose into the storage during pressurization).

③ Shake the discharging hose until all the fuel flows into the storage.

④ Take down the hose of the fuel pressure gauge from the fuel test port or fuel pipe.

² Cover the adapter of fuel guide rail test port or fuel pipe with a piece of cloth to prevent leakage of a small amount of fuel when the adapter of the test port is loosened.

² Take down the fuel pressure gauge from the adapter connecting with the fuel guide rail test port or the fuel pipe.

² Wrap tight the end of fuel pressure gauge hose with cloth to absorb the fuel dropping from the absorption hose.

⑤ Take down the adapter on the fuel pipe(If the adapter shall be used, reconnect it to the fuel pipe according to the automobile service manual, and immediately clean off all leaked fuel)

⑥ Properly treat all used cloth to prevent fire.

⑦ Keep the fuel pressure gauge in a ventilated place to prevent body injury or other damage.

 

 

Ⅴ. Basic causes of abnormal fuel pressure

If the fuel pressure is higher than the standard set by the manufacturer, there may be trouble in the fuel return pipe; on the other hand, if the fuel pressure is lower than the standard, there may be trouble in components of the fuel system.

There are may be following causes of high fuel pressure:

(1)  There’s a breakdown in fuel pressure regulator;

(2)  The fuel return pipe is stuffed.

(3)  There’s trouble in the connection of fuel pipe at the fuel tank or fuel induction line.

(4)  The injection nozzle gets stuck or reacts slowly.

 

There may be following causes of low fuel pressure:

(1)  The fuel filtrator is stuffed.

(2)  The fuel pipe is stuffed.

(3)  There’s trouble in the fuel pump.

(4)  There’s trouble in the relay of fuel pump.

(5)  The fuse of the fuel pump burns out.

(6)  There’s trouble in the connection line of fuel pump.

(7)  There’s breakdown in the fuel pressure regulator.

(8)  There’s leakage in the injection nozzle.

 

VI Maintenance

1. There shall be no corrosive substances in the working and storage environment.

2. We guarantee to keep our products in good repair within half a year since they are sold.( If a product is damaged due to improper use by our customer, we won’t be responsible for such damage).

 

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