ZR-1 Net Registry Forums - View Single Post

tccrab · 11-17-2009

First things first, find the vacuum leak.
You've got a big one.
The vacuum pump only assists the secondary system when the engine is at high rpms for an extended time.
Don't worry about him right now, but know that you'll have to come back to him later.
First thing is to check the MAP sensor hose.
It's behind the plenum on the drivers side.
Use a flashlight and look for a pipe that is disconnected.
It's a common thing, this hose pops off when the engine backfires during a startup when the key is not held in the start position until the engine is running.
The LT5 takes longer to start than a regular Chevy engine for a couple of reasons, but primarily it's because there's no distributor. All the sensors have to polled by the ECM before the actual signal to fire the coils is sent.

Here's all you need to know about your secondary system:
http://www.corvetteactioncenter.com/...diagnosis.html

After you get your leak fixed, then it's time to work on the vacuum pump.
Let us know when you get there. There are a few options.

TomC
"Crabs"

11-17-2009	#4
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,663	Re: Vacuum pump not coming on? First things first, find the vacuum leak. You've got a big one. The vacuum pump only assists the secondary system when the engine is at high rpms for an extended time. Don't worry about him right now, but know that you'll have to come back to him later. First thing is to check the MAP sensor hose. It's behind the plenum on the drivers side. Use a flashlight and look for a pipe that is disconnected. It's a common thing, this hose pops off when the engine backfires during a startup when the key is not held in the start position until the engine is running. The LT5 takes longer to start than a regular Chevy engine for a couple of reasons, but primarily it's because there's no distributor. All the sensors have to polled by the ECM before the actual signal to fire the coils is sent. Here's all you need to know about your secondary system: http://www.corvetteactioncenter.com/...diagnosis.html After you get your leak fixed, then it's time to work on the vacuum pump. Let us know when you get there. There are a few options. TomC "Crabs"