Take-7

so many of you may have seen my other post involving my nikki carb on my 80's LS. well, today i got a phone call from a guy out here who races them, he told me that BOTH trailing AND lead plugs should be firing on start up, despite what one member on here told me... so he told me to run a jumper wire from the positive on the battery to the trailing coil wire. i did, and zoom-zoom-zoom! my engine actually took off! briefly... it kinda stays running, but then dies after about fifteen seconds. (tons of smoke, ATF) i happened to notice a drip after a few start ups like this, under the engine near where the exhaust amnifold connects the rotor housing. it's an oily fuel mix. you guys think there could be an exhaust leak?

DivinDriver

iTrader: (15)

More likely a leak on the carb is running down the side of the block.

Shouldn't be anything liquid in your exhaust that could drip out, at all.

On an 80, both leading and trailing should run 'on startup.' Trailing gets shut down under some engine conditions, for emissions purposes involving the way the thermal reactor works.

You can just barely hear the difference in exhaust note when trailing is firing, if you have a 'trained' ear.

Controlled by the "Ignition Control System," discussed on page 1A:8 - 1A:9 in the FSM

Take-7

interesting. i swapped out trailing ignitors today because that same guy (let's call him "Racer X" since he's mysterious) left a message saying the trailing ignitor also controls the fuel pump. so i found this strange looking thing in place of my trailing ignitor, it plugged in the same way, but was shorter than the other leading ignitor and the ignitors from the spare i had. in fact it only had one bolt holding to the box thing. so whatevers right? i stuff in another ignitor thingy (this time it looked identical to the leading iggy) it ran at about 4k for about 15 secs again. what the hell now? this is the first time i actually had a decent tachmoeter reading too, normally it's all jumpy when i try starting it. this time it took off on it's own with barely any starter power, and registered about 4k.

that fuel leak you speak of. i notice there is no hose, nor vacuum plug on the part of the carb where the sub-zero box thing used to hook to. does that need a plug?

DivinDriver

iTrader: (15)

Trailing ignitor controls the fuel pump on some of the FB designs; not true for SAs. On an SA, the fuel pump runs whenever the ignition is on. Sounds like "Racer X" may know FB's, but not SA's. Many differences in their ignition and electrical.

The "shorter ignitor" is probably a J109... SA's need J105's. They are not interchangeable.

I'm guessing your problem is with the front ignitor; they often get intermittent before they fail. your tach (if wired properly) is triggered from the lead ignitor. On FB's it's triggered from the trail.

Try swapping your new "longer thingy" to the lead position, & see if it helps. & make sure you're using heat sink compound on the back of the ignitors, where they bolt to the amplifier box. Keeps them from overheating.

I'd definitely cap off that subzero nipple.

Take-7

excellent info. that you so much, i'm going home today to swap ignitors. and yes it was a j-109, i put in a j-105. that got me to where i am now. i'll report back with findings after i get home tonight.

Take-7

Plugged subzero box into carb nipple. Switched leading ignitors. Didn't really make difference. The pool of fuel on the ground is scaring the daylights out of me though. Ill crawl under the 7 soon and see whats up

DivinDriver

iTrader: (15)

By all means, you want to deal with a fuel leak before you do anything else. Fires are destructive.

If swapping the ignitors made no difference, the next thing I would check would be to go over the wiring for the coils and the exterior plugs for the ignitors, and make sure the PO didn't get anything mixed between leading and trailing, which is actually quite easy to do on an 80, especially when the wiring gets old and colors aren't so obvious. You'll want the wiring diagram for this, and it downloadable from the stickied thread atop the forum.

If that wiring is verified, things get a little trickier.

Take-7

will do. probably get to that a few days from now as i am a little busy in life... thanks again for so much help divindriver