Secondaries vacuum pump working??

[marteeni]

How loud or noticeable is the sound of the vacuum pump running when the key is on with the engine off?? I've tried to listen for it several times and don't seem to hear it ruuning.

 

[secondchance]

Diffrent but about as loud as rad. fan sound.
You might open the hood and turn the key to run position and walk up to the front passenger side. Pump is right in front of the rad overflow.

 

[Rob]

With the hood up and the window down, you should very easily here the pump prime the system.

 

[marteeni]

Well the pump has voltage but does not turn. Ordered a new one from gmpartsdirect.com. P/N 10098493. This certainly explains why I was never very impressed with the power of a ZR1, THE SECONDARIES WERE NEVER OPENING!!! It's funny that an error code didn't get set or the "full power" mode diidn't shut off?? Thanks for the replies guys!

 

[Rob]

Actually, that may not necessarily be true. The purpose of the pump is to help keep the secondaries open during long periods of wide open throttle. In most driving conditions, the engine produces enough vacuum on its own to work the secondaries so an ECM/PCM won't always register a code if the pump is not working.

Chances are the pump is shorted out. If that's the case, I guarantee, if you pry the top cover off the burned out pump, you'll see that the metal contacts inside are corroded.

 

[marteeni]

Actually, the inside looked really clean and the pump measured around 30 ohms (not shorted). The motor just wouldn't spin to operate the diaphram, like it was jammed up. Unfortunately, the diaphram linkage is encased in plastic, so I ordered a new one. I think it is interesting in what you said about the secondaries operating from the engine vacuum?? If that is the case, why bother with a seperate vacuum pump??

 

[Rob]

Actually, the inside looked really clean and the pump measured around 30 ohms (not shorted). The motor just wouldn't spin to operate the diaphram, like it was jammed up. Unfortunately, the diaphram linkage is encased in plastic, so I ordered a new one. I think it is interesting in what you said about the secondaries operating from the engine vacuum?? If that is the case, why bother with a seperate vacuum pump??

From: http://corvetteactioncenter.com/forums/showthread.php?s=&threadid=14272

So what does this pump do? There is a vacuum reservoir located under the plenum. If the vacuum level in the reservoir drops below 41 kPa (12" Hg) while the secondary port throttle valves are open, the pump is turned "on" by a vacuum switch to supplement engine vacuum.