I - SYSTEM/COMPONENT TESTS
Article Text (p. 10)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
FUEL CONTROL
COLD START VALVE (ALL MODELS EXCEPT VANAGON)
1) Engine temperature must be below 85øF (30øC). Disconnect
cold start valve attaching screws and remove valve with harness
connector and fuel line attached.
2) Remove ignition coil secondary wire and jumper to ground.
Attach metal housing of cold start valve to ground. Direct cold start
valve nozzle into a clean container. See Fig. 8. Have assistant turn
ignition switch to START position, while observing cold start valve
spray pattern.
3) The valve should deliver a consistent cone-shaped pattern
until the thermo time switch interrupts fuel flow. Ensure valve does
not leak after fuel flow stops. If spray pattern is uneven or
inconsistent, check for plugged or defective cold start valve. If
valve does not function, proceed to THERMO TIME SWITCH.Fig. 8: Testing Typical Cold Start Valve
Courtesy of Volkswagen United States, Inc.
NOTE: On AFC-Digifant II System, cold start valve is not used.
Cold starts are controlled by ECU.
THERMO TIME SWITCH
1) Engine temperature must be below 86
øF (30øC). Disconnect
cold start valve wiring harness connector and attach LED test light to
terminals. Have assistant hold ignition switch in START position while
observing test light.
2) Light should stay on for 3-8 seconds depending on coolant
temperature. If light does not come on, check voltage supply to cold
start valve and repair as necessary. If voltage to cold start valve is
WAVEFORMS - INJECTOR PATTERN TUTORIAL
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:52PM
Let's move to the other situation where a noid light flashes
normally when it should be dim. This could occur if a more sensitive
noid light is used on a higher voltage/amperage circuit that was
weakened enough to cause problems (but not outright broken). A circuit
with an actual problem would thus appear normal.
Let's look at why. A noid light does not come close to
consuming as much amperage as an injector solenoid. If there is a
partial driver failure or a minor voltage drop in the injector
circuit, there can be adequate amperage to fully operate the noid
light BUT NOT ENOUGH TO OPERATE THE INJECTOR.
If this is not clear, picture a battery with a lot of
corrosion on the terminals. Say there is enough corrosion that the
starter motor will not operate; it only clicks. Now imagine turning on
the headlights (with the ignition in the RUN position). You find they
light normally and are fully bright. This is the same idea as noid
light: There is a problem, but enough amp flow exists to operate the
headlights ("noid light"), but not the starter motor ("injector").
How do you identify and avoid all these situations? By using
the correct type of noid light. This requires that you understanding
the types of injector circuits that your noid lights are designed for.
There are three. They are:
* Systems with a voltage controlled injector driver. Another
way to say it: The noid light is designed for a circuit with
a "high" resistance injector (generally 12 ohms or above).
* Systems with a current controlled injector driver. Another
way to say it: The noid light is designed for a circuit with
a low resistance injector (generally less than 12 ohms)
without an external injector resistor.
* Systems with a voltage controlled injector driver and an
external injector resistor. Another way of saying it: The
noid light is designed for a circuit with a low resistance
injector (generally less than 12 ohms) and an external
injector resistor.
NOTE: Some noid lights can meet both the second and third
categories simultaneously.
If you are not sure which type of circuit your noid light is
designed for, plug it into a known good car and check out the results.
If it flashes normally during cranking, determine the circuit type by
finding out injector resistance and if an external injector resistor
is used. You now know enough to identify the type of injector circuit.
Label the noid light appropriately.
Next time you need to use a noid light for diagnosis,
determine what type of injector circuit you are dealing with and
select the appropriate noid light.
Of course, if you suspect a no-pulse condition you could plug
in any one whose connector fit without fear of misdiagnosis. This is
because it is unimportant if the flashing light is dim or bright. It
is only important that it flashes.
