300D turbo low on power

[funola]

My 300D turbo feels anemic. The banjo bolt and line at the inlet manifold is clean. I applied power to the overboost protection solenoid (next to the brake booster) and heard it click and was able to blow through it with power applied. However, there is no voltage going to it (from the harness connector). Where and what is the sensor that supplies power to the overboost protection solenoid?

[jt20]

I beleive its on the intake manifold. Its called the pressure switch and is hexagonal with a one pin connector

[Brian Carlton]

Voltage always goes to the solenoid via the harness connector.

If an overboost condition is present, and the pressure switch isn't clogged, it provides a ground path for the solenoid and it diverts the ALDA to atmospheric.

Under normal conditions, the overboost solenoid does nothing and allows the pressure signal from the manifold to pass directly to the ALDA.

[funola]

I think I found the pressure switch on the IM hidden behind the air cleaner housing. With a flashlight and ohmeter I found the pressure switch is open. Shoudn't it be normally closed to keep the overboost protection solenoid open until a certain presssure in the IM is reached?

[jt20]

BC is saying that when a pressure is reached, the pressure switch closes the circuit.

Open is the default setting.

[bigfredb]

When was the last time you did a valve adjustment?

[funola]

jt20, if the pressure switch is normally open, then there must be a relay in the circuit. Where is the relay located? Can someone post a link to a wiring diagram?

[funola]

Originally Posted by bigfredb

When was the last time you did a valve adjustment?

They were adjusted approx 5k miles ago.

[funola]

Did some tracing with an ohmmeter. The single wire from the pressure switch goes to one of the terminals of the overboost protection solenoid connector. If the other terminal of the connector gets switched +12V, then it makes sense that the pressure switch should be normally closed, which then makes a working circuit. But I did not find switched +12V on the other terminal of the overboost protection solenoid, and the pressure switch is open, a double fault. How likely is that? I can really use a wiring diagram. Can someone buzz out their pressure sensor and the overboost protection solenoid connector? Which fuse is this circuit on?

[funola]

Originally Posted by Brian Carlton

Voltage always goes to the solenoid via the harness connector.

If an overboost condition is present, and the pressure switch isn't clogged, it provides a ground path for the solenoid and it diverts the ALDA to atmospheric.

Under normal conditions, the overboost solenoid does nothing and allows the pressure signal from the manifold to pass directly to the ALDA.

Brian, I read this a few times and still scratching my head.
With no power going to the overboost protection solenoid, should it be open or closed? Mine is closed.

[Brian Carlton]

Originally Posted by funola

Brian, I read this a few times and still scratching my head.
With no power going to the overboost protection solenoid, should it be open or closed? Mine is closed.

If no power is going to the overboost protection solenoid, you've got a failure somewhere. The device gets power all the time and the pressure switch grounds the circuit.

[funola]

Originally Posted by Brian Carlton

If no power is going to the overboost protection solenoid, you've got a failure somewhere. The device gets power all the time and the pressure switch grounds the circuit.

Then the pressure switch has to be normally closed if the overboost protection solenoid is normally closed?

[Brian Carlton]

Originally Posted by funola

Then the pressure switch has to be normally closed if the overboost protection solenoid is normally closed?

The pressure switch is normally open (electrically).

The overboost protection solenoid is normally open (electrically).

When the pressure switch closes, the solenoid closes and opens the ALDA to atmospheric pressure.

[funola]

Brian, what did you mean by "Voltage always goes to the solenoid via the harness connector"?

[Brian Carlton]

The solenoid has voltage all the time.

It operates (closes) when the pressure switch grounds at the intake manifold.