Hey all, I am trying to do an injector balance test on 99 silverado 4.3 when i hit test the pressure drops to 40 and vehicle cuts off. I remember this happening on previous vehicle to. Fuel system is the spider type csfi. Am i doing something wrong? Problem is hard miss on 3&4 under load at 55mph or powerbraking and always at 1850 rpm and up. Pressure holds steady at 60 under load. But ignition pattern shows upward slope spark line meaning lean on all cylinders but 3&4 are the worse. So i guess this is a two part question. Any input would be much appreciated.
Injector Balance Testing
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Here is an ignition wave form from a 4.3 with a bad distributor cap, had misfires mostly showing on cylinders 4 and 3Attached FilesComment
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as greasybob and benelli have said, don't do the injector balance with the engine running. that test is meant for static pressure drops.
when you mention upward spikes in secondary that usually means a lean density misfire, but be cautious with that assumption because iatn member scott hager has discussed this at long length and determined alternate issues.
if you have access to iatn, i recommend reading these threads regardless of rather they pertain to your current issue or not.
I am putting up my information here for all to see. It took a while to put all of this together. I hope I didn't make too many mistakes. I am admitting that I could not prove what was causing a dead miss on cylinder #2 on a 95 Chevy S-10 Blazer with a 4.3 lite
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Just wanted to say thanks for the info,it turned out to be clogged injectors and pinhole in #4spider tube. I am not a member of IATN so could not view that info.What was the just of it pertaining to upward slope? I would like to know so i dont tunnel vision on thinking lean next time i see this pattern.Comment
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Just wanted to say thanks for the info,it turned out to be clogged injectors and pinhole in #4spider tube. I am not a member of IATN so could not view that info.What was the just of it pertaining to upward slope? I would like to know so i dont tunnel vision on thinking lean next time i see this pattern.
With today's leaner burning engines, the plug firing line is usually around 2-kv and tends to last for 1.75ms to 2.25ms and will rise slightly, and I mean slightly as the plug fires and uses up the fuel, just a little leaner as it burns, thus increasing the voltage as it finishes firing by 0.1 or 0.2kv.
EG, if you plug firing line starts at 2.0-kv and runs across for 1.5ms and then finishes up at 2.2kv in the last 0.5ms then it's burning properly.
If the plug starts at 2.0kv and by the time it has burned for the full 2.0milliseconds it is up to 4 or 5 or 6 (or even more) KV then that cylinder is suffering from a lean condition (not enough fuel in the air/fuel mixture)
At least that's what I was taught 30 years ago and hasn't been proven wrong (yet LOL)Comment
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