Chery S11 / Chery QQ. Manual — part 229

Chery QQ Maintenance Manual 465 EFI System

12． Fuel pressure regulator
Usage: This regulator is not electric component, but it is used to regulate the fuel pressure in
fuel distribution pipe for gasoline engine electronic control system to keep constant value
with the differential of manifold. It controls fuel rate and makes easy for ECU to control fuel
inject pulse width.
Constitute and principle: As shown in the figure, a film made of rubber-fiber separates the
regulator to up and down chambers. The up chamber connects manifold through connector
with hose. There is a spring in the up chamber. The down chamber is filled with the fuel that
flows from the regulator through fuel inlet. The lower part of film gets the fuel pressure in
fuel distribution pipe and the upper part of film gets the pressure of manifold and spring force.
Film deforms to open or close the valve. Since the degree of deforming is very small, the
action force of the spring could be taken as constant. So the open and close of valve is
decided by the difference between the fuel pressure both in the lower chamber and the upper
chamber. If the valve is closed at first, the differential of pressure will increase because of
engine load reducing or fuel pressure increasing, which results lifting the film by fuel pressure
to open the valve. In this way, even the engine working condition is changed, the pressure
differential between fuel distribution pipe and manifold keeps constant. This is the basic
precondition for control fuel fixing quantity. In fact, when fuel flow increases, the differential
increases a little with linearity. When MAP pressure changing, the differential will change
little too.
Fuel request: The regulator can use the fuel according to the standard of “ Non-lead fuel for
vehicle” in GB 17930-1999 and “ The standard for controlling injurant in fuel” in GWKB
1-1999.

Fuel pressure regulator

The section of fuel pressure regulator

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Chery QQ Maintenance Manual 465 EFI System

Mounting position: The regulator is mounted on fuel supplying pipe with one end
connecting with the pipe, one with return fuel pipe to fuel tank, and the other end connecting
with intake air pipe to supply vacuum for the regulator.

13. Steel fuel distribution pipe assembly
Usage: To store and distribute fuel and return superfluous fuel into fuel tank. Injector and fuel
pressure regulator are mounted on the tank to offer stable pressure circumstance to balance
the fuel pressure and amount of fuel for smooth running of engine.
Constitute: The fuel distribution pipe assembly consists of injector(EV) , regulating valve
(DR) and fuel supply pipe assembly( KVS-S).
Install request: Clamp in/out fuel pipe and rubber hose with clip. The type of clip should be
matched with rubber hose to insure the seal between in/out fuel pipe and the hose.
Diagnosis: Usually, fuel supply pipe assembly is seldom to be fault. Mostly bad installing
causes the fuel leakage. Pay more attention during installation. Don’t install the seal that are
used.

Chapter 2 Basic principle for EFI diagnosis

(1) Fault information record
ECU continually detect the sensors, actuator, related circuit, MIL and battery voltage as well
as ECU itself, and carry on reliability test for sensor output signal, actuator drive signal and
internal signal such as oxygen close loop control, knock control, idle control and battery
voltage control. Once the malfunction in one point is found, or one signal is not true, ECU
will set the malfunction information record on RAM memory. The record exists as DTC form
and displays as the order of DTC appearing. 12 malfunction information records at most can
be stored in memory.
Malfunction can de divided as stable malfunction or temporary malfunction such as the fault
caused by short-lived, harness open or bad contact for inserters according to the frequency

(2) Malfunction

statues

If the lasting time for one malfunction detected exceeds stable time settled, ECU will consider
it as a stable fault and stores it as “stable malfunction”. If it disappears, ECU will store it as
“temporary malfunction” or “not existing”. If it is detected again, it will be “temporary
malfunction”, but the existing history malfunction does not influence the normal use of
engine.

(3) Malfunction

types

Short to positive pole of battery
Short to ground
Open (In the case of up or down resistors, ECU will identify the open fault in input terminal
as short between input terminal and battery positive pole or short to ground).

(4) Malfunction frequency counter

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Chery QQ Maintenance Manual 465 EFI System

Foe each malfunction detected, one independent frequency counter value (Hz) will be set.
The frequency counter value (Hz) will decide the storing time for store the malfunction
information to the stores when this malfunction disappears or eliminates.
When malfunction is detected first time, Hz is set to initial value 40. If fault statues do not
change, the value will keep on.
Once the malfunction detected disappears and keeps for a while, HZ will be deducted 1 when
starting engine or engine speed exceeds the speed after starting. ECU will consider the
malfunction disappears, but the record still exists.
If the fault such as bad contact frequently appears and disappears, Hz will increase 1 but does
not exceeds up limit 100.
If Hz is deducted to zero, the fault information records in the store will be cleared completely.

(5) Limp drive home
For some important faults detected, if their lasting time exceeds the setting stable time, ECU
will apply some software methods, for example, to close some control function of oxygen
sensor close loop control and set substitute value for some unbelievable value. At the moment,
through the working condition of engine is not so good, but the vehicle can be drive home. In
this way, vehicle can drive home or service station for repairing to void stop on road. Once
the fault detected disappears and Hz deducted to 40, the normal values will be used again.

(6) Warning
Some M1.5.4 system vehicles equip MIL. When some important parts such as ECU, MAP,
TPS, ECT, KS, O2, phase sensor, injector, idle actuator, 2 drive poles of step motor, canister
control valve, fan repay are fault, ECU will turn MIL on and warning until the faults
disappear.

(7) Fault read out
The malfunction information records can be read out from ECU by tester, or be read by
flashing DTC codes. If the faults relate the function of fuel/air mix ratio regulator, engine will
read malfunction information records after running at least 5 minutes.

Fig. 3 ISO 9141-2 Standard diagnosis connector

Read DTC by flashing light
The flashing DTC is the DTC which could be read out by flashing light in MIL. In the vehicle

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Chery QQ Maintenance Manual 465 EFI System

equipped MIL, MIL will be flashing light. The other end of K terminal connects pin 55 of
ECU.
Method: Turn on ignition switch, but not run engine. Use K terminal to ground pin 55 of
ECU for 2.5s or more. The light will flash. Flashing DTC is 2 digits with hexadecimal, and
each digit consists with o or 1-9. Every light on will last 0.3s, and is on again after 0.3s. The
flashing times mean one digit. If flashing 10 times, it means 0. First flashing means high
position number and later flashing means low position number. There 1 second between 2
digits. After 2 numbers displayed, it will flash again after stopping 3s and display some
number. One number will flash 2 times (totally flash 3 times). Then the next one. The process
circles until engine start again or ignition switch turns off, or ground pin 55 with K line for
more than 2.5s. According to DTC, the malfunction, position, condition, solving or reset
condition can be found in “malfunction information record set condition” in this manual can
be found.

(8) Clear

DTC

When eliminate the faults, DTC should be cleared. There are 5 methods:
For DTC appears on igniting but not keeps on to stable time, it will not be recorded.
When Hz reach to zero, DTC in store will be cleared automatically.
Clear DTC by using tester with the order of “clear DTC”.
Remove ECU terminals or battery terminals to clear DTC outside of RAM.
Ground pin 55 of ECU 2 times for more than 2.5s.

(9) Finding

faults

Getting above DTC means only to know the faults position, but not the real fault because the
reason for one fault may be the electric or mechanical one such as sensor, ECU or actuator
damage, or open circuit or short circuit or even mechanical damage.
Fault is internal, but the appearances are various. Firstly use tester or flashing light to check if
existing any DTC, and troubleshoot the faults accord to DTC, then find the reason of fault
according to engine symptom.

4． The condition for malfunction information record

No.

Malfunction
information
name

The condition for
marking malfunction
position

Software method during
malfunction happens

Flash
- ing
code

The resume
position
condition

1

Knock
control ， test
pulse, zero
test
malfunction(
Condition:

In continues test pulse
measuring, the
frequency that pulse
integral value is equal or
below gate value of
voltage exceeds the set
value.

Setting KS, harness or
hardware malf-
unction:
Ignition advanced angle
reduced to a safety value:
If load signal( mass flow for

1

Fault frequency
does not exceed
set value

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