rebuilt lq4 wont start
10-15-2012, 10:45 PM
#24
Does it have the right cam sprocket? Some were 1x, 4x and so on. Could be reading cam position all wrong or sumething. Also isnt the crank rotation vs cam rotation like 2:1 or sumething. U can set the timing 180 degrees off. Make sure piston #1 up top when the cranks dot is lined with the cams. I did it once on my old v8 s10.
Last edited by RS/SS 4.8; 10-15-2012 at 10:50 PM.
10-16-2012, 09:05 PM
#25
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The tune is the same os as the original tune in the truck. By original I mean when it was a v6 5 speed. It wont start on the old 4.8 tune either. So I think its time to pull the intake and canker it and see if it is sucking and blowing in the right holes.
10-16-2012, 09:38 PM
#27
Does it have the right cam sprocket? Some were 1x, 4x and so on. Could be reading cam position all wrong or sumething. Also isnt the crank rotation vs cam rotation like 2:1 or sumething. U can set the timing 180 degrees off. Make sure piston #1 up top when the cranks dot is lined with the cams. I did it once on my old v8 s10.
On an LQ4 generation 3 LS motor the cam sensor reads off the back of the cam. This is something that can not be changed. It is manufactured into the camshaft.
On the crank they had 24x teeth wheel on the Gen 3 and 58X teeth wheel on the Gen 4 motors.
The crank spins 2 full revolutions to every 1 full rotation of the camshaft. If you lined the cam sprocket up at dot to dot. Or in other words Cam dot at 6 o'clock and crank at 12 o'clock At 1 revolution of the crank the cam and crank would both be facing up at the 12 o'clock position.
Unless you spin the crank trigger wheel on the crank, It is physically impossible to have the timing out 180* on one of these motors. This is not a Distributor engine.
Hope that helps clear things up.
11-02-2012, 07:53 PM
#30
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Ok so its torn down again. Its firing 180 out. When the exhaust closes and the intake just open and the exhaust isn't quite closed it fires...or its firing in overlap instead of compression.
I just want it to run so I can sell it.
Also recap, the cam is installed right. Sensors work. I have fuel spark and compression its just not firing in the fight time. Tune is the old turbo 4.8 tune.
I just want it to run so I can sell it.
Also recap, the cam is installed right. Sensors work. I have fuel spark and compression its just not firing in the fight time. Tune is the old turbo 4.8 tune.