Note. Work on checking the working pressure in the fuel rail is shown on the VAZ 21124 engine (1,6i). Checking fuel pressure on a VAZ 2112 engine (1.5i) performed similarly. At the same time, it is difficult to connect a pressure gauge - you have to bend the hose strongly, as it rests on the back cover of the timing belt.
Warning. Before checking the fuel pressure in the fuel rail, read the safety rules for servicing and repairing the fuel system (see "Safety measures for the maintenance and repair of the power system").
To carry out repairs to check the fuel pressure in the fuel rail, you will need a special pressure gauge (see point 26 "Special tools and fixtures").
Check sequence
1. We prepare the car for work (see item 2a "Preparing the car for maintenance and repair").
2. Remove the engine trim (see "Decorative overlay of the engine - removal and installation")
3. Turn off the protective cap of the diagnostic fitting of the fuel rail.
4. We connect the tip of the pressure gauge hose to the fuel rail fitting.
5. With a 14 mm open-end wrench, wrap the hose tip.
Recommendation. If necessary, the pressure in the fuel rail can be measured with a home-made device, made from a pressure gauge from a foot pump. Before connecting such a pressure gauge, it is necessary to relieve the fuel pressure (see "Fuel Line - Pressure Relief"). After that, unscrew the spool from the fuel rail fitting. This can be done with a metal wheel valve cap. To connect the pressure gauge to the fuel rail fitting, use a piece of gasoline-resistant hose of a suitable diameter. The ends of the hoses must be securely fastened with clamps.
6. Turn on the ignition on the car. The fuel pump will then operate for a few seconds. After waiting for the pump to stop working, turn off the ignition.
7. To remove air from the pressure gauge, lowering the end of the drain tube into a small container, unscrew the pressure gauge bleed valve by 1/3-1/2 turn, and relieve excess gasoline pressure from the fuel rail. This will remove air from the pressure gauge hose.
8. We wrap the bleeder screw until it stops.
We start the engine on the car and measure the working pressure in the fuel rail at different crankshaft speeds. For a serviceable engine, it should be within: for a VAZ 2112 engine - 284-325 kPa (2.8-3.2 bar); for the VAZ 2112 engine - 378-390 kPa (3.8-3.9 bar).
9. Turn off the ignition.
10. Having lowered the end of the tube into the container, open the fitting and relieve pressure from the fuel line.
11. Disconnect the pressure gauge from the diagnostic fitting of the fuel rail.
12. We screw the protective cap onto the fuel rail fitting.
Recommendation. If the working pressure in the fuel rail is not stable or is higher than normal, then the fuel pressure regulator is faulty (see "Engine fuel module 21124 (1,6i) - replacement of the fuel pressure regulator" for engine 21124 or see "Fuel rail engine 2112 (1,5i) - removal, disassembly, assembly and installation", for engine 2112). Low pressure in the fuel rail (less than normal) can also be caused by a malfunctioning fuel pressure regulator. It is possible that the fuel pump strainer is clogged or the fuel pump does not develop the necessary pressure. To clean the fuel pump strainer, you need to remove the fuel module (see "Fuel pump engine fuel module 21124 (1,6i) - cleaning the strainer" for engine 21124 or see "2112 engine fuel pump fuel module (1,5i) - cleaning the strainer" for engine 2112).