wheeljo2

iTrader: (2)

Ok just got my LT1 rebuilt and back in ready to fire, oil pressure primed to 60 psi, fuel pressure at 42 lbs, and NO FIRE !!

1) Getting fire to ignition module harness
2) Getting fire to opti spark harness
3) Getting fire to coil harness

4) NO FIRE to the plugs

What is the best way to try to diagnose this. Opti spark is GM Brand new and ran when I took it apart this last time.

borninatransam

iTrader: (4)

hmmm. did you hook all the grounds back up? i was having similar problems with my 383 not firing and i had forgotten to hook the ground back up that beside the power steering reservoir. if that ones hooked make sure you have a good grounds everywhere else. and i know this seems obvious but make sure the plug wire from the opti to the coil is plugged up good.

wheeljo2

iTrader: (2)

Thanks for the advice, I forgot to mention my LT1 is in a 94 Vette and yes my ground by the coil (ps reservoir) is hooked up and my plug wire for the coil is snug. Any other ideas?

94 F-body

iTrader: (1)

make shure that all fuses are good in both fuse boxes, all plugs are plugged in, charged battery, other than that I am at a loss.

borninatransam

iTrader: (4)

we're talking about two completely different grounds. the one im talking about come off the battery to either a post on the boy of the frame. just check all the grounds that come off the battery. i know i sound like a broken record here but the smaller wire that comes off the battery can very easily get tucked under the battery or to the side.

SincalT/A

iTrader: (16)

check icm and iac connections.it is possible on a vette to get them mixed up.seen it happen before.

Halok97

if i understand you correctly, you took a voltage reading at the main wiring harness connector at the 3 mentioned locations, did you check if the coil is firing?(before the opti)

transam5.7lt1

iTrader: (18)

Sounds like the optispark....

wheeljo2

iTrader: (2)

My understanding is that the opti triggers the ignition module and then the coil back to the opti which distributes the voltage to each cylinder. i check the main harness that enters the ignition module with the key on and leads A and D were fully lit, Leads B is fully lit went grounded and C is partially lit when grounded, nothing changed with any of the leads when the starter was engaged.

wheeljo2

iTrader: (2)

I agree this is the likely culprit it has less than 500 miles on it after a cam swap but it gets coolant spilled over it everytime you pull the water pump off and I'm afraid when I pulled the motor apart this last time it got moisture inside, plan to take apart tonight to inspect.

wheeljo2

iTrader: (2)

Are you referring to the 4 wire harness that connects either the ignition module or throttle body iac motor? I noticed that as well tried it both ways to no avail.

wheeljo2

iTrader: (2)

I checked all my grounds last night with a test light and they all lit up.

wheeljo2

iTrader: (2)

All fuses are good and battery was fully charged

SincalT/A

iTrader: (16)

2nd guess bad coil wire? 3rd guess optispark?if you have a buddy with a lt1 swap some parts to eliminate spending to much money.