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Old 06-13-2009, 02:55 PM   #1 (permalink)
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Finding a vacuum leak

I'm having a problem with a lean condition with my EFI setup. I've hosed it down with carb cleaner and used a MAPP gas torch trying to find a leak and did not. I also did a compression test, which came back good, and leads me to believe the HG is not blown. The bad new is that I should not start and run the vehicle because the tcase had to go back to AA for repair (auto trans). Anything else I can check or tests that I can do? Chevy SBC, if it matters.
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Old 06-15-2009, 12:34 AM   #2 (permalink)
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Check your brake booster. They go bad and cause vac leaks that you'll never find by spraying.
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Old 06-15-2009, 05:51 PM   #3 (permalink)
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No booster, twin willwood manuals. Would it be possible to ahve a leak on the inside of the galley and have it scavenge air from within the engine? About the only place I can think of at this point, but hate to tear it down again on a hunch.
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Old 06-15-2009, 06:00 PM   #4 (permalink)
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yes you could have a vacuum leak in the valley and be sucking air through the pvc valve or breather.

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Old 06-16-2009, 08:57 AM   #5 (permalink)
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I've read that you can test for vacuum leaks under the intake manifold by injecting propane into the valve cover.
Personally, I find that approach a little "scary".
Give it try, and report back--if you are able!!
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Old 06-19-2009, 12:50 AM   #6 (permalink)
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What symtoms are you getting? I assume you checked fuel preasure and volume, but would it be possible to just simply have a bad IAC solinoid or fuel preasure regulator?
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Old 06-21-2009, 05:30 AM   #7 (permalink)
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Quote:
Originally Posted by Wilson View Post
I'm having a problem with a lean condition with my EFI setup. I've hosed it down with carb cleaner and used a MAPP gas torch trying to find a leak and did not. I also did a compression test, which came back good, and leads me to believe the HG is not blown. The bad new is that I should not start and run the vehicle because the tcase had to go back to AA for repair (auto trans). Anything else I can check or tests that I can do? Chevy SBC, if it matters.
Is it TBI or something else? Check and make sure everything is tight and the gasklets are sealed well, check hoses for cracks, check all you unused vacuum ports are plugged, etc. I don't think this is your problem since you've been using carb cleaner and mapp gas.

I wouldn't worry about the PCV, it is supposed to pass air from the engine into the intake.

Do check that your injectors are working, with TBI you can use a timing light. Otherwise, you can use a meter to make sure you have power to all your injectors. (GM TBI supplies power to the injefctors, and the ECM grounds them.) Check your fuses, too.

I worked on a motor with a lean condition, turned out to be bad wiring to the injectors.
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Old 06-22-2009, 08:13 PM   #8 (permalink)
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he is running a massflow setup now - i think its the same one ?



wilson ? lean when? at idle, off idle - cruz, WOT ?
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