FAILED SMOG - AGAIN part 2
Thread Starter
Burning Brakes
Joined: Jul 2003
Posts: 873
Likes: 2
From: Whittier ca
FAILED SMOG - AGAIN part 2
The previous post http://forums.corvetteforum.com/show....php?t=1733864 lead to checking for a leaking injector. I took the following steps:
Pulled plugs to check for damp/gas soaked - 6 & 8 looked slightly different than the other 6, but none soaked Checked ohms on al injectors - 14.8 - 14.9 on all injectors
Hooked up F/P gauge - 40# to 30# in 3 minutes - down to 18# in 14 minutes ; 40# - pinch return line at tank - jumped up 4# and dropped to 36# in 5 minutes, removed clamp dropped the 4# ; 40# - pinch fuel line at tank - 40# dropped to 30# in 15 minutes
pulled injectors, left them in the rail, placed a sheet of white paper under the injectors, pressureized - injector #1 leaked from the top seal , reseated and restarted test - no leaking injector. Not even a drop. Reinstalled the F/P gauge and pulled the leak down again with injectors outside the holes - 40# to 30# in 3 minutes - down to 18# in 14 minutes ; 40# - pinch return line at tank - jumped up 4# and no drop in pressure for 3 minutes, removed clamp dropped the 4# ; 40# - pinch fuel line at tank - 40# dropped to 32# in 10 minutes
If I read it all correctly, the second set of tests indicated a faulty F/P regulator (it's about 6 months old)
I pulled all the injectors and replaced all the seals, pulled the right runner and pulled the entire fuel rail, checked for leaking seals and found none, pulled apart the FPR and found no holes, rips or tears in the diaphragm.
At 3:00 AM, I called it a night but still wondering, WTF is going on with my 91?
Any suggestions from the forum as to "what next"?
Thanks in advance
Subman
Pulled plugs to check for damp/gas soaked - 6 & 8 looked slightly different than the other 6, but none soaked Checked ohms on al injectors - 14.8 - 14.9 on all injectors
Hooked up F/P gauge - 40# to 30# in 3 minutes - down to 18# in 14 minutes ; 40# - pinch return line at tank - jumped up 4# and dropped to 36# in 5 minutes, removed clamp dropped the 4# ; 40# - pinch fuel line at tank - 40# dropped to 30# in 15 minutes
pulled injectors, left them in the rail, placed a sheet of white paper under the injectors, pressureized - injector #1 leaked from the top seal , reseated and restarted test - no leaking injector. Not even a drop. Reinstalled the F/P gauge and pulled the leak down again with injectors outside the holes - 40# to 30# in 3 minutes - down to 18# in 14 minutes ; 40# - pinch return line at tank - jumped up 4# and no drop in pressure for 3 minutes, removed clamp dropped the 4# ; 40# - pinch fuel line at tank - 40# dropped to 32# in 10 minutes
If I read it all correctly, the second set of tests indicated a faulty F/P regulator (it's about 6 months old)
I pulled all the injectors and replaced all the seals, pulled the right runner and pulled the entire fuel rail, checked for leaking seals and found none, pulled apart the FPR and found no holes, rips or tears in the diaphragm.
At 3:00 AM, I called it a night but still wondering, WTF is going on with my 91?
Any suggestions from the forum as to "what next"?
Thanks in advance
Subman
Last edited by subman; Jun 18, 2007 at 11:32 AM. Reason: added test results
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Leaking injectors usually cause driveability issues - none of which you seem to have. Far easier to figure this out by checking fuel delivery with a scanner. Given the high NOX at cruise, I'd guess that you have a vacuum leak or some sort of extra air - probably in the EGR vacuum hoses or gasket. A vacuum/air leak will cause extra air to flow by the O2 and when it senses a lean condition, the ECM fattens up the mixture. The ECM is simply responding to what the O2 relays to it and with the wrong info, the motor has less than an ideal burn. The scan will show whether or not that's the case and narrow down the troubleshooting. EGR is used to keep combustion temps down (NOX doesn't form until about 2300 degrees), so if that leak exists, that valve isn't functioning correctly. Get some data and post it - either buy a scanner or talk to the guys in Scan and Tune about a cable and some free software to run on a laptop.
Thread Starter
Burning Brakes
Joined: Jul 2003
Posts: 873
Likes: 2
From: Whittier ca
Checked the EGR for vacuum loss, sticking, etc as soon as I got home.
Pulled about 15" direct to the EGR valve. Diaphragm opened fully, vacuum dropped steadily until it reached 6" or so then stayed there for about 30 minutes. Diaphragm stayed full open until I released the vacuum. Used the vacuum again to open and close about 5 times full open to full close (I am assuming it is full close) I have not checked the solinoid yet, but will later tonight.
When I pulled the plenium yesterday, I checked to make sure all vacuum lines were connected. Will check for broken/cracked lines tonight as well. I did notice that the brake booster line was not real tight, but I still needed the wrench to loosen it. The breather hose between the right valve cover and the trottle body was a little sloppy at the TB, but again, it wasn't falling off.
I'll keep on checking for anything out of the ordinary. Going to tune forum for additional info and some "freeware" for a laptop, if available.
Thanks for the help.
Subman
Pulled about 15" direct to the EGR valve. Diaphragm opened fully, vacuum dropped steadily until it reached 6" or so then stayed there for about 30 minutes. Diaphragm stayed full open until I released the vacuum. Used the vacuum again to open and close about 5 times full open to full close (I am assuming it is full close) I have not checked the solinoid yet, but will later tonight.
When I pulled the plenium yesterday, I checked to make sure all vacuum lines were connected. Will check for broken/cracked lines tonight as well. I did notice that the brake booster line was not real tight, but I still needed the wrench to loosen it. The breather hose between the right valve cover and the trottle body was a little sloppy at the TB, but again, it wasn't falling off.
I'll keep on checking for anything out of the ordinary. Going to tune forum for additional info and some "freeware" for a laptop, if available.
Thanks for the help.
Subman
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
My 87 failed for the first time this yr. HC, but I didn't do what I normally do prior to the test.Sooooooo, went home, ran a can of SeaFoam through it, changed the oil and filter, through in a new air filter and drove it hard to the test site, temps were at 180-185. Passed with flying colors. That's what I usually do before a smog test.
When I SeaFoam it I skip adding it to the crankcase, put 1/2 through the brake booster vac. line, the other 1/2 in the fuel tank.
When I SeaFoam it I skip adding it to the crankcase, put 1/2 through the brake booster vac. line, the other 1/2 in the fuel tank.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Rick - Interesting. I'm assuming Sea Foam cleans the carbon off the plugs and pistons, so my first thought would be that you need a hotter plug or the Coolant Temp Signal isn't accurate and/or you're getting too much fuel vapor which ends up in the oil (Canister - PCV maybe). I remember you hooking up a laptop, but I can't remember the results. Assuming it's some of the above, a scan would usually show up as Rich, meaning the ECM is attempting to lean out the injectors. I think for this car, the ECM is sensing Lean and adding fuel and with high NOX, suspect a vacuum air/leak on the EGR side. Speaking of which, applying vacuum with a pump to the EGR valve doesn't duplicate the vacuum supply from the engine. An old trick that use to work would be to ground the ECM side of the solenoid and then crack the throttle while observing the EGR valve. Not easy to do on a TPI and if it's at idle most stall the minute you do this because some vacuum is directed to the valve and it lifts off it's seat. Much easier with a helping hand. Spraying some TB cleaner around the EGR mount and seeing if it speeds up is another method, but of course you need to be cautious with anything that's flammable and it's still damn hard to get to with the Runners and everything else in the way.
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