Zr1 secondary pump
 

My pump runs constantly with key on engine off on my 93,pump and vacuum line to plenum looks good,what's the next step?

Re: Zr1 secondary pump
 

You probably need to check the whole system for leasks as it it not holding a vacuum. The pump runs until vacuum is acheived then intermittantly to maintain. A constant running leads me to belive that you have a leak some where. Ylou may have to get under the plenum.

I'd first disconnect the line at the fitting on the outside of the engine and run the pump, with your thumb over the hose. If the vacuum increases on your thumb and the motor shuts down, then you have a leak under your plenum. If conversely, the pump continues to run, you have a leak "out side" your motor and probably around the secondary vacuum pump. There are rubber hoses on the pump that could be cracked and leaky.

Re: Zr1 secondary pump
 

Thankyou

Re: Zr1 secondary pump
 

If you have access to a smoke machine, I prefer to hook it up and confirm that there will be smoke coming from under the plenum.
One time I found the leak was in the pump itself.
Once you see smoke coming from under the plenum, you will now prepare for your first plenum pull.
Likely a hose has fallen off.
Marc's plenum pull Instructional or just look in the stickies on this forum and you will find any questions answered.
Order your plenum gaskets from Jerry's first.
Keep us posted, nothing really complex about it.
:cheers:
Marty

Re: Zr1 secondary pump
 

Thanks!

Re: Zr1 secondary pump
 

After all the above, if pump stops running by plugging hose near it & you don’t have a smoke machine just yet—pull & put your finger over the vacuum line going into driver’s side of the plenum (with key on and pump assumably running). Does the pump stop/intermittent?

Yes: [at a minimum] failed check valve under plenum. Temp solution: buy $7 check valve & hose to adapt at local auto parts & put inline at plenum hose connection until you can get under plenum.

No: see above comments—leak under plenum.

Ted

Re: Zr1 secondary pump
 

Agreed. While leaks can be in many places. More often than not I’ve found the check valve to be bad. But do check the main line from the pump into the engine first. If the pump runs continuously you run the risk of burning it out. I’ve seen a bunch of those too.

Just to finish Demps train of thought above, if you put your finger over the vacuum line noted above and the pump does not stop you have a vacuum leak in one of the lines or components under the plenum (other than or even in addition to the check valve) Hope that makes sense.
H
:cheers:

Re: Zr1 secondary pump
 

Thx guys

Re: Zr1 secondary pump
 

My experience is that the under plenum electrically activated vacuum valve gets old and leaks. Thus the pump does not cycle on and off normally. I go throughly through all connections and clamp, zip tie or glue all connections. Personally message me and I will forward you the part number. I have done this on 2 different cars. Last valve I ordered was 25 bucks on Amazon.

Re: Zr1 secondary pump
 

And...(at the risk of offending the NCRS or other "purists";), it is possible to have the "chip" re-programmed & eliminate the secondary port throttle plates, all the vacuum lines, check valves, pump, etc., etc. and run on the secondaries FULL TIME.

PROS: Parts that don't exist NEVER FAIL, & they don't cost much!

CONS: The need for the FULL POWER switch is vacated. NCRS points lost.