F355 no vaccum to by pass valve (5:2)

So either the ECU is not sending a signal to open the solenoid valve at high engine rpms or the solenoid valve is faulty. In theory, with the engine off, you could take off the electrical plug of the solenoid valve and apply a voltage to the pins to open it, but I don't know if the solenoid valve makes an audible sound. If you tried it with the engine running, the ECU may sense the plug is not connected and illuminate the Check Engine light. It may depend on the type of valve.

How were you sensing the vacuum at the bypass valve (or were you simply listening for an increase in noise when you were driving the car?)

Experts: Is the solenoid a frequency valve? Does it modulate the vacuum by rapidly opening and closing of solenoid valve or is it just an open and hold kind of valve?

 

Klas, can you confirm that the correct electrical connector has been fitted to the solenoid valve? On my car, the connector is black. The connector for the Secondary Air Solenoid Valve is blue. I confirmed this by checking the wiring from the ECU to the valves.

 

Wiring...

Exhaust Bypass Solenoid Wiring

 

Its open or closed depending on computer

 

Thanks, Grant.

I was thinking of the kind of valves which control turbo wastegates which provide a varying pressure. These report back to the engine ECU if the solenoid is faulty. I'm not sure if the open/closed type does this.

Cheers
Ian

 

Ian do you have a WSM for your car it explains it quite well.

Talks about all the variables.

 

I have, Grant, but it says (in the 2.7 section), that the solenoid "adjusts" the exhaust back pressure, so, to me, this suggests something more than fully open or fully closed. In the 5.2 section, it says less. It could be either type of control.

Cheers

 

I'm not really sure I understand your test results, Klas.
I'm wondering why you only got 6V to the connector. There should have been 11~12 (that is, battery power). Putting the ignition on alone should not activate the valve unless there is also a signal from the ECU to open the valve. Does the ECU open the valve with the ignition switch in RUN/ON (before start) and START, to assist with the engine starting process? My old Lotus Esprit used to do this in the START position with the Exhaust Back Pressure Valve.

Anyway, thanks for the update. It's good to know it makes an audible click.

Cheers

 

Ian the amount of vacume determines open, closed partway open all way, etc.

If i am in 4 gear with light throttle and start to accelarate when I hear the valve start to open if I back off a bit it will maintain partial opening, if I floor it it opens and if i backout of it it closes.

The way I read it the computer decides whether the solenoid is allowing vacume or not then the vacume has to overcome the spring on the valve which can be manipulated by throttle possition.

 

Thanks, Grant, but that may take me a while to digest I'm trying to factor in rpm, throttle position, reservoir vacuum storage ... then introducing the effect of the US/Australian bypass temperature sensor and Italian translations (It took me a while to figure out that a "remote controlled switch" in the wiring diagrams was just a common "relay")

Cheers

 

The solenoid valve is just a simple electromagnetically activated device powered by the ignition key (in RUN). There are no resistors/transformers in the line, so the reading should be 11~12 volts. If you're getting 6 volts, your battery is flat. With the car running, the voltage at the connector plug should go up slightly (the alternator is providing power).

My coil was 55 ohms. To me, this seems good. The coil on the electromagnet is not open circuit or completely short circuited. If the coil is ok, all that can stop the valve is a blocked airway or the plunger is jammed... or the valve is not getting an earth signal from the ECU

There is no easy way to check the voltage with the connector fitted to the valve and the car running. I wasn't expecting you to do this. I wasn't expecting you to check the signal from the ECU, either (I was just curious about the operation).

Cheers,