testing isv off car

[mattkh 0]

Hi

Supplied 12v to the ISV in isolation. All I hear is a click when it opens.

What makes it buzz when on the car ?

Should it buzz when tested in isolation ?

[ProdigalSon 1]

Hi

Supplied 12v to the ISV in isolation. All I hear is a click when it opens.

What makes it buzz when on the car ?

The ECU pulses the 12V line to the ISV, which is why it buzzes when ignition is switched on.

Should it buzz when tested in isolation ?

No, unless it is really bizarrely broken :lol:

 

As long as it opens and closes quickly when you apply/remove the 12V, then it is probably fine (look in the side when you do it to see the movement)... Proper broken ISVs don't move much/at all when the 12V is pulsed.

 

HTH :wink:

[mattkh 0]

The ECU pulses the 12V line to the ISV, which is why it buzzes when ignition is switched on.

Hi

Most grateful to you. What frequency are the pulses ?

Are the pulses matching the chatter of the injectors ?

[ProdigalSon 1]

The ECU pulses the 12V line to the ISV, which is why it buzzes when ignition is switched on.

Hi

Most grateful to you. What frequency are the pulses ?

No idea, sorry, didn't do a frequency reading on it... Would guess it to be several hundred Hertz/times per second, but that's judging by feel alone :cuckoo:

Are the pulses matching the chatter of the injectors ?

If they do match it is probably entirely coincidental - the pulsing of the fuel injectors is linked to the rpm I think (they fire twice every revolution IIRC), but the ISV frequency is pretty steady... Both ISV and injectors vary their 'open' duration to allow a carefully measured amount of air or fuel (respectively) to be delivered to the inlet, so there is a relationship there it just isn't necessarily one of pulse frequency/regularity.

[Supercharged 2]

Sounds like it working electrically but they fail due to dirt etc mixing with oil and causing a 'cutting paste' that wears the shaft... very difficult thing to test really.