Testing of the secondary system - ZR-1 Net Registry Forums

c4koh · 03-15-2007

All,

Further to my previous mail, my secondary system is not functioning... at all, or not very well I can't tell.

I have no codes, the vacuum holds etc.

I've been travelling of late, with not much time spent investigating the issue, but this weekend I'm planning to look into it.

I will check the resistance of the primary+secondary injectors.

No apparent vacuum leaks: pump runs at start, vacuum holds.

Can I check the operation of the secondary actuators without removing the plenum [a Marc Haibeck article in a KOTH magazine appears to say 'yes' to this... but I couldn't find the article!]

tccrab · 03-15-2007

Absolutely everything you need to know (and MORE) about the Secondary System:
http://www.corvetteactioncenter.com/...ad.php?t=14272

TomC
'90ZR1 #792
Honorary Pirate

Quote:

Originally Posted by c4koh

All,

Further to my previous mail, my secondary system is not functioning... at all, or not very well I can't tell.

I have no codes, the vacuum holds etc.

I've been travelling of late, with not much time spent investigating the issue, but this weekend I'm planning to look into it.

I will check the resistance of the primary+secondary injectors.

No apparent vacuum leaks: pump runs at start, vacuum holds.

Can I check the operation of the secondary actuators without removing the plenum [a Marc Haibeck article in a KOTH magazine appears to say 'yes' to this... but I couldn't find the article!]

tomtom72 · 03-16-2007

I remember that write up.....but can't remember if I saw it at Marc's site or in our newsletter, sorry.

If you can trigger the secondary solenoid to allow vacuum to pass to the actuators you can see them thru the plenum tubes with a flash light. I believe if you look near the rear most runners on both side you can see them.

Usually if the ohms are off on the injectors you'll get a miss. Check the plugs & see what story they tell...rich or lean. If you have a scan tool look at the O2 cross counts and the Block Learn #'s and the Integrator #'s. There is a page in the Helm manual, in section 6E(?) "Driveability and Emissions" that has a data snap shot in closed loop of a normal LT5.

Also did you check your fuel pump output, both pumps 55 psi. Also how is your fuel filter? You also may want to check that the accordian duct from the air filter to the T/Body is not sucking shut at high engine loads...yes if it is old & soft the motor draws enough air to suck it shut when the rpms get up past about 4K. You'll never notice this unless you put your foot in it. At the netregistry site there are a coupla of home cures for the duct, in the maintenance section under "How to" & "common issues".

Do you have a miss? Does the exhaust smell rich or lean? You said there were no DTC's, right? Does it "feel" the same with the power key on vs off? If all those answers are "no", "no", and "yes", and "can't tell for sure"; I'd check the duct, JMHO.

Tom

03-15-2007	#1
c4koh Join Date: Aug 2006 Location: Fishkill, NY Posts: 87	Testing of the secondary system All, Further to my previous mail, my secondary system is not functioning... at all, or not very well I can't tell. I have no codes, the vacuum holds etc. I've been travelling of late, with not much time spent investigating the issue, but this weekend I'm planning to look into it. I will check the resistance of the primary+secondary injectors. No apparent vacuum leaks: pump runs at start, vacuum holds. Can I check the operation of the secondary actuators without removing the plenum [a Marc Haibeck article in a KOTH magazine appears to say 'yes' to this... but I couldn't find the article!]

03-16-2007	#3
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: Testing of the secondary system I remember that write up.....but can't remember if I saw it at Marc's site or in our newsletter, sorry. If you can trigger the secondary solenoid to allow vacuum to pass to the actuators you can see them thru the plenum tubes with a flash light. I believe if you look near the rear most runners on both side you can see them. Usually if the ohms are off on the injectors you'll get a miss. Check the plugs & see what story they tell...rich or lean. If you have a scan tool look at the O2 cross counts and the Block Learn #'s and the Integrator #'s. There is a page in the Helm manual, in section 6E(?) "Driveability and Emissions" that has a data snap shot in closed loop of a normal LT5. Also did you check your fuel pump output, both pumps 55 psi. Also how is your fuel filter? You also may want to check that the accordian duct from the air filter to the T/Body is not sucking shut at high engine loads...yes if it is old & soft the motor draws enough air to suck it shut when the rpms get up past about 4K. You'll never notice this unless you put your foot in it. At the netregistry site there are a coupla of home cures for the duct, in the maintenance section under "How to" & "common issues". Do you have a miss? Does the exhaust smell rich or lean? You said there were no DTC's, right? Does it "feel" the same with the power key on vs off? If all those answers are "no", "no", and "yes", and "can't tell for sure"; I'd check the duct, JMHO. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member Last edited by tomtom72; 03-16-2007 at 08:47 AM.