Pump cycling with key on???

[rudolph schenker]

I'm a newbie, so this is probably a dumb question.

With the key in the on position (engine is off) a pump cycles on and off every few seconds. Is this normal? Is it the vacuum pump? Should it only cycle once before starting? Any info appreciated. Thank you.

[flyin ryan]

Should cycle, but not every few seconds...must have a small vacuum leak. Would be the 'Secondary' vacuum pump. Not 100% sure what normal would be/is... , 30-45 seconds anyways. Lots of info on this subject around.

[flyin ryan]

I should mention..., the secondaries will still work fine. The pump is really an 'Auxiliary' pump, when it cycles it's more annoying than anything else

[rudolph schenker]

Originally Posted by flyin ryan

I should mention..., the secondaries will still work fine. The pump is really an 'Auxiliary' pump, when it cycles it's more annoying than anything else

Yes, car runs fine, it is annoying though. Where are common leaks found? I'll start checking, where is a good place to start?

[WB9MCW]

If the pump cycles on and off every few seconds or it runs continuously, chances are, you have a vacuum leak somewhere in the system.

All you need should be covered here

http://www.corvetteactioncenter.com/...cuum+Diagnosis

[jonszr1]

ball ck valves are a common thing that goes wrong . but ypu need to pull the plenum. its an easy job .just ask most of us we all havew done it a few times .do you have a fsm?

[Sgreg]

Originally Posted by rudolph schenker

Yes, car runs fine, it is annoying though. Where are common leaks found? I'll start checking, where is a good place to start?

Ck the long lead hose that goes from the pump to the plenum. Particularly the fitting at the plenum. If no leaks at the pump or at the plenum you will become the umpteenth member of the pull the plenum club !! Lots of things to check under there.

[Ccmano]

Originally Posted by rudolph schenker

Yes, car runs fine, it is annoying though. Where are common leaks found? I'll start checking, where is a good place to start?

I wouldn't get too excited about it. The only time it is even noticable is when the key is on and the engine is off. Unless it runs almost continuosly or the secondaries aren't coming on there is really no need to go to the trouble of pulling the plenum to fix it.

If you do, you might as well change out the coils, wires and injectors as preventative maintainance. Otherwise it's not worth the hassle.

H

Start with the easy section first. The line between vacuum pump and the connection to the vacuum spider (It's by the oil filter). After that, it can be a number of small things. But it's best to pull the plenum and assess everything underneath.

What is your interval of the pump running?

[rudolph schenker]

Originally Posted by Jeffvette

Start with the easy section first. The line between vacuum pump and the connection to the vacuum spider (It's by the oil filter). After that, it can be a number of small things. But it's best to pull the plenum and assess everything underneath.

What is your interval of the pump running?

Cycles only for a second then turns off for 5 sec. The line to the plenum is fine. I figure there is a small leak under the plenum and I will have to pull it. The secondaries work fine. Could somebody give me a list of things to do with the plenum off and cost of repacing some items?