Of course, you need a computer to diagnose the engine. Renault VDIAG or Clip service computers are best, but you can use the ddt2000 program. Both in Laguna idE (CAN) and Megane, it is possible to record the operating parameters of the regulator and the pressure on the injection rail as a function of time using the Clip interface, which allows for precise determination of damage. In the case of Megane, however, there is no detailed error data (DEF) because this function is very limited. Most universal diagnostic programs connect to the F5R engine computer (Sirius 31H, Sirius 35), but often the reading of errors or parameters is not accurate or even confusing, so it's best to use the Clip interface.
Nevertheless, some damage can be located on the basis of symptoms and an ordinary voltmeter.

Emergency engine shutdown

When the engine temperature light comes on and the stop light comes on and the engine goes out after 5 seconds, this is an emergency engine shutdown procedure. The most common cause is damage to the fuel regulator, but it can also be caused by excessive engine temperature or a blocked EGR valve (Megane IDE only). In the event of damage to the regulator, the phenomenon begins to appear mostly on the hot engine when parked in a traffic jam. Over time, this phenomenon begins to intensify, making it practically impossible to drive. The controller temperature then exceeds 80 ° C. This can be temporarily remedied by turning on the air conditioning. Then the fan is turned on and the temperature of the regulator is slightly lowered. This is when the computer tries to open the regulator valve to relieve pressure, but the valve cannot open and the pressure does not drop. The computer treats it as a loss of control over the pressure in the rail and, for safety reasons, it turns off the engine in an emergency by switching off the electric forepump. In this case, the controller is suitable for regeneration.

Limp mode

When the injection system warning light comes on at idle speed or during acceleration, the cause is insufficient pressure in the injection rail. The engine speed is then limited to 2000 rpm. There may be several reasons for this: low efficiency of the preliminary fuel pump. It can be checked by measuring the pressure (4.5-5 bar). In the absence of a pressure gauge, the performance can be measured roughly by disconnecting the fuel line and letting it into a separate container. Then we close the fuel pump relay for 1 min. The pump should fill at least 2.75 liters of gasoline.
fuel filter clogging (Megane). The filter should be replaced every 60,000 km. It is located under the floor near the fuel tank. In Laguna, the filter (mesh) is located in the fuel tank in the pump assembly. This filter only requires cleaning. Due to the somewhat strange structure in the Lagoon, it is recommended to use an additional fuel filter on the engine supply line.
wear or damage to the high pressure pump. The pump runs "dry" as gasoline does not have lubricating properties. In addition, impurities in the fuel (mainly sulfur compounds) cause the precipitation of sediments which turn into sandpaper and destroy the pumping sections of the pump. It is best to check the efficiency with a diagnostic computer after eliminating the first two points. The pressure should be between 60-100 bar. The pressure can also be measured with an ordinary voltmeter. We connect it to wires 2 and 3 of the pressure sensor. The voltage of about 0.5V should appear with the ignition on. When the engine is started, the voltage increases with the pressure. It should vary between 2.2V and 3V with 2.2V corresponding to a pressure of 60bar and 3V 90bar. When the voltage rises above 3.2V, the pressure of 125bar is exceeded and the engine is shut down in an emergency. Pump wear is also visible in the black deposit in the filter at the entrance to the injector rail. It can be assumed that the service life of the pump is 180-250 thousand km and depends largely on the quality of the fuel
Leak in the high pressure system. The connections between the pump and the rail should be carefully checked, as well as the tightness of the pressure sensor and pressure regulator. Often the cause of leakage is the lower O-ring on the regulator which separates the high pressure section from the low pressure section. Often the cause is also damage to the surface of the strip in the area of the lower O-ring, which occurs when the regulator is not pulled out skillfully. The original rubber o-ring size 7x1.5 is best replaced with a fluorine ring size 7.1x1.6. Fluorine O-rings are more mechanically and chemically resistant and can withstand temperatures up to 200 ° C.
defective pressure regulator. The leakage of the ball valve in the regulator is caused by wear (mileage over 200-250 thousand km) or mechanical damage that prevents the regulator from closing. This may be due to larger contamination that may have fallen into the open fuel system. It can also be caused by seizing the regulator spool. When dismantling, pay attention to the cleanliness of the fuel system. While cleaning the valve is not a problem, the leakage of the valve basically completely disqualifies it, although in some cases, after replacing the needle with the ball and the seat, the valve regains its tightness.

Check Engine

Check Engine. Determining the cause of the light switching on requires connecting the diagnostic computer and reading the errors. Most often it results from damage to the engine computer circuits or readings outside the acceptable range.

Unevenly engine idling


Uneven work, especially when idling, is a very common problem with IDE engines. The causes can be divided into three groups: the ignition system, the injection system, and the engine itself. However, before doing anything, it is best to connect the Clip and check that the computer does not see any errors, in particular the camshaft sensor and the flywheel.

First, check the most common cause, i.e. the ignition system. It is best to replace the coil with wires and install new candles. Damage to the coil until it breaks is not visible, similarly with wires, if the wire burns at the connection with the terminal, the spark arises inside the wire, which cannot be seen from the outside.

If the ignition system is operational, check the pressure in the cylinders. Nominally, it should be above 16 bar, a tolerance of up to 10% between the highest and lowest result is possible. In the event of a reduction in compression pressure, it is most often caused by leakage in the exhaust valve seats.

If the compression pressure is correct, the next step is to check the injector, damage is rare but it does happen and you need to take a fuel pressure reading at idle. It happens, for example, when the filter under the pressure regulator is clogged or the regulator itself is damaged, the pressure can fluctuate and within very wide limits (below the Megane mileage of 29-100 bar) and in places of the highest drop of drop, ignitions can fall out. If the problem is still not resolved, check the timing. Very often there is a misalignment of the exhaust valve shaft pulley. Delayed injection can reduce the flexibility of the engine and cause uneven operation.

If the problem persists, also check the condition of the intake pipes. In engines, an early wear of the intake valve seals is a fairly common case, which in turn leads to valve sticking. The degree of sizing is uneven and where it is greatest it can cause a bad mixture composition in a given cylinder.

Difficult start


Direct injection engines should ignite within 2 seconds, even in the coldest frost. The main problem here is the time it takes for the injection system to reach the appropriate pressure. During start-up, the pressure regulator is practically closed and the high pressure pump increases the pressure in the system with each revolution. When it reaches the required 20 bar or more, the fuel is atomized sufficiently and the engine starts immediately.

The time to reach the required pressure depends mainly on the efficiency of the high pressure pump, the pressure regulator and the tightness of the system. With an efficient system, this time is less than 2 seconds. The rate of pressure build-up in the system can be measured by including pressure recording before starting the engine.

If the problem is only related to the hot engine, pay attention to the pressure from the forepump and the possibility of gasoline vapors in the high pressure pump when the engine temperature exceeds 70C

CAN-Clip diagnostics

 Laguna idE diagnostics

Starting page

Fuel system page

Recording of the work of an efficient system

Typical damage to a jamming regulator

Typical leak in the high pressure system, most often caused by worn regulator valve
When the RCO of 54% is exceeded, the emergency mode is activated.

Starting a fully functional engine
Megane idE diagnstics

Fuel injection page

Fuel injection page

Recording working parametry 

Electrical connection Laguna idE
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