y2kfirefly

Hi
Just got a 92 zr1 one and was hoping someone could answer a question. Upon checking the vacuum pump I found the motor in it rusted and not working. I have another one ordered but was wanting some clarification. Does this pump keep full power from operating or does it just hinder it from working to its full potential? Ive googled it but can't find any thing directly stating this.

Scrrem

The vacuum pump applies vacuum so that when the secondary circuit is energized, the vacuum pulls open the secondary throttle plates. if the pump is non-functional, the secondaries will never open and you will never have FULL POWER.
Rich

y2kfirefly

Thanks for the answer. So I am basically running in normal mode until I get the pump installed correct.

ZR-71

Yes and keep the valet key in normal mode until the pump is replaced and working

stevdug

What's the easiest way to check to see if the pump is functioning correctly

y2kfirefly

When you turn ignition on you should hear it run for 5 to 10 seconds.

Z51JEFF

Unplug the line at the union by the plenum,the pump will run until it's plugged. Just curious,what did you pay for a new pump?

Dynomite

Yes.....there are two sources of vacuum for secondaries (vacuum pump and Plenum vacuum). There is a check valve under the plenum that closes when the vacuum pump takes over with wide open throttle (Plenum vacuum drops at wide open throttle). Without that check valve the vacuum pump (if you have some vacuum leaks) would be running all the time while cruising with relatively high Plenum vacuum. With that check valve operational, the vacuum pump is not required when cruising to maintain sufficient vacuum should you step on the gas. But once you step on the gas the vacuum pump takes over as Plenum vacuum drops

One of the first checks for a vacuum pump that continues to run at all times is the functioning of that check valve. Just pull the Plenum vacuum hose between the two runners on the Drivers side and hold finger over pulled vacuum connector (the vacuum pump should stop running immediately.

Failed Vacuum Check Valve TIPS

A26B

Agree! Engine vacuum charges the Secondary Port Throttle System during normal operation, just as Dynomite said. Even without the Secondary PT Vacuum Pump running, there is enough vacuum to open the Secondaries, SO LONG AS THE SYSTEM IS 100% LEAK FREE. How long the Actuators will hold the Secondaries open, depends entirely on how bad the leaks are & how good the check valve is holding. The bigger the leaks, the faster the Secondarys will close or even fail to open completely.

The Secondary PT Pump is there to supply vacuum under WOT & will keep up with small leaks, but not major leaks.