carbed ls3 problem,.help
12-11-2011, 03:50 PM
#1
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carbed ls3 problem,.help hello, i bought a ls3 cammed and built with a t56.i got it all wired up and hit the key,and it pops out the carb and exhaust. wait a little bit crank and it runs. sounds great!. after a while crank and crank and crank and...POP! backfire through exhaust and intake. crank again and it fires up and runs smooth and fine. i know its not flooding out,and i know the block is grounded properly and has full switched 12V to box... so i dunno what im overlooking....i bought the engine already dyno tuned with the 6ls box.so the box should be insync with the motor....?/ im lost. and now it will just only crank and crank and not fire
12-11-2011, 05:06 PM
#2
I have the same problem with mine. The MSD is showing a cam sensor fail on my laptop display every time I try start it. Sometimes it guesses right and runs perfect, other times it backfires .
For some reason my msd 6012 will NOT read my cam sensor, I have not figured it out yet, I am certain I have good 12v supply, and good grounds, but I am going to start doubling up grounds from msd to battery, and block to battery/frame/body.
do you have the short cam sensor extension harness on the front cover?
For some reason my msd 6012 will NOT read my cam sensor, I have not figured it out yet, I am certain I have good 12v supply, and good grounds, but I am going to start doubling up grounds from msd to battery, and block to battery/frame/body.
do you have the short cam sensor extension harness on the front cover?
12-11-2011, 05:33 PM
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ls3 issue thanks for the insight and reply, yea i do have the short harness on the cover from the sensor down to the crank. i havent hooked mine up to the computer yet. but i figure maybe for some reason my cam sensor is bad/?. it sucks cause im ready to drive it but i got a damn gremlin lol. how do you like your carbed set up?.
12-11-2011, 06:46 PM
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Nice nice, have your tried a new camshaft sensor? I wish I still had my 66'week I sold it a few months back. I got a 72 nova with a stage 2 t56 and a ls3 that im trying to put on the road. I like the Camaro alot that car looks sweet. Im hoping to be in the low 11's high tens on motor.
12-11-2011, 06:55 PM
#6
MSD says on their tech line that there is a 50-50 chance of the box coming up right with no cam sensor. I had a loose connector which caused exactly what you saw.
FWIW once it comes upright you can drive.
FWIW once it comes upright you can drive.
12-11-2011, 07:10 PM
#7
Concerning these 'LS3' problems, I can't help but wonder if the front covers are the 'long' (VVT) style instead of the regular short covers. Would the added depth put the sensor far enough away from the cam gear to reduce the signal strength to where it would have problems synching up?
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12-11-2011, 11:12 PM
#8
Concerning these 'LS3' problems, I can't help but wonder if the front covers are the 'long' (VVT) style instead of the regular short covers. Would the added depth put the sensor far enough away from the cam gear to reduce the signal strength to where it would have problems synching up?
12-12-2011, 06:41 AM
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I changed to an ls2 type cover, no vvt. For me. Im thinking my grounds aren't great. I have an aluminum block that's grounded to the frame and the msd box ground is on the valley cover. Maybe its not making a good ground connection
01-05-2012, 06:02 PM
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figured it out my cam sensor wiring harness was original and i did not have to modify it.What happened was, when installing the engine the cam sensor plug(msd wiring harness side) must have bumped the frame rail. when looking at it it looked plugged in,i pushed on it and it locked,but still same issue. message "cam sensor fail".i unplugged the connector and the bottom of the extension harness and looked into the female end of the socket and 1 of the 3 pins were mis alighned.and wasnt making a connection. bent the pins straight and.....voiiila ls3 fired up and ready to roll!
01-05-2012, 08:37 PM
#15
Well that's great news, I remember my issues with my gen IV in my 86 TA, because my gm extention harness was not there for the cam sensor, so I sPliced and swapped them per MSDs direction over the phone, when I did the gen IV 4.8 in my 94 gmc, I used the gm extension that time and it was flawless.
