crank no start issue

[nickhinton]

I need some help guys, I just built my 355 over the winter, got the car fired up and it sounded like it was running great. Long story short I got code 36 High res failure from my new msd optispark.. Well I ordered a new one from autozone, got it installed today and same issue. The car cranks and cranks but acts as if there is no spark. The ICM tested good, as well as the coil. I have spark if i hold the coil wire to a ground and the same with the individual plug wires. When I watch data on my scan tool it is not displaying rpm on the scanner, every once in a great great while (every 5th round of cranking or so) the car will cough once like its trying to roll over and it will display rpm for that split second and go right back away. The only things that have changed since the car ran was two new 02 sensors.. Any ideas fellas? at this point I may have to consider taking it in, im out of ideas on where to look. thanks guys

[1BADAIR]

Did you get pcm back tuned? Did you chAnge plugs after

[nickhinton]

yeah i've got the tuned pcm back and in, I have not changed the plugs yet, I was going to pull them tomorrow and see what they look like

[zeeman]

Nick you may need to try a known good opti. I had issues with my msd opti also, it was the deciding factor in my decision to the ls swap for me. On one of the other forums a gent by the handle usmc has had numerous msd opti's fail. even the redesigned units are having problems. I would swap in a unit you know is good and see if it runs, then work from there.

[69LS1]

Were the o2 sensors you replaced before or after the cat?

I believe that if the pcm is getting a bad reading from on of the pre-cat sensors, it cuts off fuel or spark to the engine so it will not start. It will crank but won't do anything.

So if it is a pre cat sensor, I would double check there. But after the cat I am not sure...

[nickhinton]

I'm 94 so I've only got the pre cat sensors, I messed around with it a little bit today going over all my grounds, connections, and wiring. Nothing seems out of the ordinary. I guess it's time to bite the bullet and take it in to someone that knows lt1s and see if they can get it going. It's just mind boggling how it ran good and all of a sudden there's nothing anymore. When I unplug and plug on opti harness fuel pump primes and sounds like injectors click but nothing when cranking still. I'm stumped

[zeeman]

Did you test for spark? Throw an old plug into a spark plug wire ang ground it where you can see it. Have someone crank it over while you watch the plug. Or get one of those fancy lights that goes between the plug and the wire.
Fuel, air, and ignition, @ the propper time and it has to run.

[zeeman]

also. On a cold start the 94 puter doesn't look @ sensor data. It will be in speed density mode so o2s wont effect anything. My moneys on the opti. How old is your msd unit? I know they did a redesign last year. AndbI heard rumors about another change over the summer.

[nickhinton]

I have spark out of both the coil wire into the opti, and at the end of the wires (only checked a couple since they're a pita to get to) but did have blue spark at the wires. However it seemed intermittent. I know that's hard to tell since there's no way to tell when it should fire that cylinder by just looking at the motor visually, but it didn't seem to spark as often as I would think. I will have autozone order me another replacement and try it a third round.

[nickhinton]

Just went through my tests from the FSM, I have all specified values at the opti harness on the car side, nothing coming from the opti while cranking as far as voltage. I have 45 lbs of fuel pressure on prime at the rail. I can manually operate my injectors as well with a test light and they click and fuel pressure drops. Only thing left according to FSM and my thoughts has to be the OPTI. This controls fuel as well as spark right?

[zeeman]

I cant remember if the opti controls fuel pump or not. So shoot some starting fluid into it and see if it fires.
Fuel, air and ignition. If you put fuel and air intotit and nothing happens. Most likely there is a problem with ignition.
Pull the cap and look inside the opti. You have ti pull it anyway. make sure its dry etc.