chevzuki

i have an 04 stock lm7 with a msd 6014 , performer rpm and a holley 650 cylinder #1 and #4 are not firing (on time?) anyway.... ive swapped coils,plugs,wires carbs they have 160 psi compression and passed a leak down test. the coils are firing but you pull the wires off while running and it doest change the headers are warm to the touch .... im running out of ideas

Pop N Wood

iTrader: (1)

Maybe the wires are swapped in the harness. Sort of like swapping two plug wires.

They have wiring diagrams on line, carefully trace out the wires and make sure the connectors are pinned correctly.

BTW, how do you know they aren't firing? Usually an IR temp gauge on each header is a sanity check, but you say the headers are warm (hot?)?

chevzuki

i did trace the wires they are good, ir guns does not work that great on shiny headers but the rest are turning gold color and #1 is not, its cool enough to touch.... i have also swapped the coil pack assy. today i tried anther brand new msd 6010 box and harness from a friend same thing. could a bad crank sensor or reluctor wheel throw the timing off on that cylinder ?

i am out of ideas.....
the engine has 160psi compression
pulls a steady 18" of vacuum at idle
has ~10% leakdown
ir header temp is ~240-280 on the good cylinders
temp is ~ 130 on #1 &#4

TTur1996

You positive you don't have both coil harnesses flipped over backwards?

chevzuki

yes, the 6014 box uses the factory temp sender and it comes off the driver side bank coil pack connector, so it really only goes one way and i also checked the wiring diagram

TTur1996

I'm not talking about the harness from your MSD box. But the two harnesses that are plugged directly into the coils. They both have the same colored wires in them. Just make sure the plug with the purple wire goes to number 1 coil and the plug with the red wire goes to number 2 on the other side. Then the rest will lay out accordingly. If not, they are both flipped over backwards. If it was just one side it would run backfiring and such. But it will run with them both flipped but not right. You wouldn't think it would run at all. But it will. You should be hearing a faint popping in the exhaust from the plugs not firing at the right time at idle.

Pop N Wood

iTrader: (1)

Man that is a weird one. 1&4 are on opposite sides of the motor. You completely swapped out the harness and it still did it.

Guess I would try rigging up some sort of crank degree wheel and use an old fashioned timing light to check each cylinder individually.

Could you have a dead valve? If an exhaust valve wasn't opening than that would pass a compression and leak down test. Not likely but just thinking out loud.

Evdawg42

try a niode light between the coil and plug and be sure its strong like the firing cylinders.. could be a failing coil on both, also can't have enough grounds on these swaps. I learned that on my first couple LS swaps. Check the tune dial on the msd box also to whatever motor your using. I had someone turn the dial on my current g body swap to ls1 and it was a cammed truck 5.3 I knew would fire up before I set a tune.

G Atsma

Chevzuki hasn't been here for over 4 years. Check post dates....