What is the pressure switch on top of the intake for?
 

I can't find where this sends the "signal". Mine was not connected when I bought the engine.

Any input?

Roy

Should we guess which car and year you are asking about?

Geez, I'm sorry. It's been a long weekend.

It's a 1983 300TD

I'm guessing your refferring to a turbo charged 5 cylinder. If it's the switch on the rear of the intake manifold, it's the over boost switch. It cuts out the pressure signal to the injector pump when manifold pressure exceeds approx 20psi. If you look, you'll find a small solenoid on the fire wall just behind the pump. The switch activates that solenoid to "dump" the pressure, which in turns reduces the fuel delivered.

Dieselnut got it, it is a switch for the overboost "switchover" valve. It does not dump pressure though, just blocks the pressure signal to the ALDA, thus limiting the fuel available.

In theory you could add to the setup to dump pressure, by installing some sort of solenoid valve on the waste gate hose's path, then it'd open and dump the pressure, thus no boost....

I suppose you could also add a valve with a similar device to the intake itself....either location would work I suppose....so long as it eliminated boost/pressure.

I removed my switchover valves.



inb4 "your gonna hurt your engine"

I meant it dumps the pressure going to the ALDA unit, not the pressure from the turbo, my bad. lol. Mine's been disconnected for the last 75K along with my EGR valve. Runs better!!!

Pressure regulated BOV?

Its not made to be switched that often or quickly. If an intake switch sees contact once every 20 years, its probably above the average count.

On most of the 617's I've owned, it has been bypassed.

Its still active on all of ours.....not on the one we got with a blown engine though, I wonder why. :rolleyes:

The switchover vavle does, in fact, "dump" (vent) the pressure between the valve and the ALDA. In simple terms, pressure is blocked on the upstream side and vented on the downstream side of the switchover valve. Otherwise, residual pressure would prevent the overboost protection system from functioning as intended.

Naturally.

fail safe
 

the pressure swtich is a failsafe if the dump gate fails to open properly