Vacuum leak? Marc has me confused now!
 

Hey guys,

My vacuum pump (under the pass. headlight) cycles on for a moment every 4 to 5 seconds, when the ignition is on with the car not running. I've come to understand that this indicates a vacuum leak somewhere under the plenum. A no-brainer, right?

BUT, on page 19 of the latest HOTB, Marc says in his troubleshooting tips:

"If the pump cycles on and off the vacuum connections up to the secondary port solenoid are tight. As long as the pump will turn off for one second, the secondary port throttles will operate normally. If the pump shuts off for longer than five seconds it indicates that the vacuum system connections are tighter than average."

So, according to Marc, my vacuum system connections are tight? Am I misunderstanding what I've just read? Anybody willing to help confuse me further?

Thanks!
Chris

Re: Vacuum leak? Marc has me confused now!
 

Also, forgot to mention that my car idles normally...no high idle.

Re: Vacuum leak? Marc has me confused now!
 

Mine cycles like yours. Runs for 2-3 seconds, off for 4-5 seconds. I took my car to Marc last fall for injectors, coils, radiator clean, and tuning - he said mine was perfectly normal. He drove it with his laptop hooked up to it as well - and all was good....

Re: Vacuum leak? Marc has me confused now!
 

Mine does the same. I also thought I had a leak. Glad to know otherwise.

Re: Vacuum leak? Marc has me confused now!
 

WOW, I'm kinda shocked...lots of views but not many replies. Anybody have any thoughts on this?

Re: Vacuum leak? Marc has me confused now!
 

Thanks Racinfan, good to know Marc gave yours his seal of approval!

Re: Vacuum leak? Marc has me confused now!
 

A good working secondary system is a good setup. My 95 works fine...for now. My 91 has no secondary hardware and will never have a leak from that area.

Re: Vacuum leak? Marc has me confused now!
 

Thanks for getting back, Brett! But my question for you and the rest of our brothers is this:

The conventional wisdom (or my rookie understanding of it) is that a cycling pump means an under-the-plenum vacuum leak. Is that correct? Does my cycling pump mean that I have a vacuum leak? Or do I understand what I read from Marc correctly? If so, John and Racinfan and I don't have leaks. What are your thoughts?

Everybody?

Re: Vacuum leak? Marc has me confused now!
 

Honestly, I'm not the person with that specific knowledge. I trust in Marc and Pete. I truly wish I was the expert to give you the answer.

Sincerely
Brett

Re: Vacuum leak? Marc has me confused now!
 

Thanks Brett. I'm with you on trusting Marc. I woke up today thinking I had a leak. Now I don't and I didn't have to pull the plenum...I'd call that a good day! LOL

Great night all!
Chris