Im not a GM tech, but Im pretty sure all VATS does on these cars is disable the starter circuit. The pcm wont send spark or an injector pulse simply because it doesnt see the opti sending a signal(because the engine isnt moving), not because its disabled.

Yeah on a 95 you can essentially only put the opti on one way, I was thinking of earlier LT1's like mine where its possible to force the dowel pin in the wrong position.


I noticed your comment on the cranking voltage. With a charged battery, your cranking voltage should be in the low 11V/high 10V range. You might check voltage at the pcm during cranking. If its dropping below 10V, you have issues.

Other than that Id start double checking the basics. Inspect fuses, wires(burned/frayed), do resistance checks on key wires(remember to disconnect the battery first), and check the contact on connections. It could very well be something simple your overlooking. I've learned thats generally what it is when the issue seems overly complex.

If everything checks out, it very well may be a bad opti.

 

hook up altnater and waterpump i had no injector pulse and some how that worked

 

I'm getting to the point now where I'd like to see a video of said problem.

 

I was wrong on this, I looked it up. The Passkey module is in direct control of the starter circuit, but also must send a signal to the PCM to allow activation of the fuel pump circuit. So it is possible to have a crank, no start issue with a bad passkey module/wiring issue, although that possibility is pretty much eliminated by your "rolling start" occurence.

 

I really wish I had a digital video camera, I`d love to show you, it`s wack.




For what it`s worth, I`ve had three Opti`s in the car so far. The original GM one, a used GM one, and a rebuilt unit from NAPA, all acted the exact same way.

 

I've been following this post for some time now and just sorta had a quick thing... Napa here where I live will do a swap out on parts no questions. They can also test parts such as distributors. Is it possible to see if perhaps you've been very very unlucky with opti's? Perhaps your first opti did go out, you replaced it with a used one which also went out (perhaps due to a part you have since replaced?), and the third one is simply incorrectly reman'd? I understand it's a long shot but it wouldn't be the first time I've replaced a few of the same parts trying to alter parts that were fine.

In short if Napa will allow an exchange of your current opti for another maybe go that route? Call them and let them know you just put it in and are having the same problem. And check if perhaps they can bench test that opti for correct degree on the gear?

I don't mean to take steps backwards however I do think it's at least a place to start since this all sounds like incorrect spark advance at start. Could not be releasing at low RPM's which would allow you to push start? Again simply throwing an idea on the table as a potential fix.

 

Does the opti use/send diffrent signals for start and run?? If the opti works push starting it and it runs fine, does it use diffrent wires or something for starting? If not I don`t see how another opti would do anything. Or am I missing something?

 

I have been working on my car sense May with a very simular problem except for the running backwards. I replaced the opti spark twice, coil, control module, spark plugs. I tested fuel pressure, fire in the spark plug wires, fire from the coil to the opti, fuses, scanned the computer, swapped the computer with my stock computer. My car sat sense February of this year and I worked on it for 2 months. I had at least 5 different mechanical friends come by and do some testing. I did all this and wasted my time, blood, and money on parts I didn't need. Finally, I hauled the car to a mechanic that knows electronics and he fixed the car in less than 2 days for $238.00 with no parts. I feel your pain. I almost hate my car now. I suggest you do as I did. I could have saved a lot of money.

Mark

PS Part of my problem was the new aftermarket parts I purchased fit, but the pin connections were loose. So you might try wiggling the wiring harness connections around the control module and coil.

 

It would seem since most everything has been picked apart in this thread that it may be mechanical... say... a piston too far down in its bore?
hellifiknow...

 

Well if you're getting a seemingly weaker then normal spark then yes the opti can cause problems. I have seen a car pushstart but not crank due to simply not cranking fast enough... I'm not saying this is your case but I'm trying to add some info to your table. Any possibility of it being something like a bad battery simply reading well but not performing correctly? I saw earlier in the posts that you had problems with voltage readings at the battery? Could also explain the ability to push start and not crank? (I really don't think this 2nd one is the problem but perhaps something easy to check again)


What about a bad key?
After you get it push started and let it idle will it set there running? I would suggest letting it idle until it reaches operating temp. At that point perhaps go over some of the diag steps you have done? Maybe try starting at that point just to check? You seem to have a problem that is not an easy fix without hearing/seeing the problem and we're simply going off someone typing it out.

 

It`s not the spark that appears weak durring crank, it`s the injector pulse that`s weak to non-existant.

I added a second battery to only turn over the starter ~ that should have duplicated the push start to the cars battery. But I have a new battery here I can throw in just to check.


After push starting it`ll run as long as you want. As soon as you turn it off, it won`t restart with the starter.

 

Does it feel rough, or shaky when idling normally? Anything to indicate a mechanical problem?

And you tried the fuel in the intake correct? To rule out the injectors as the cause.

 

Just another idea something cheap/easy to check... perhaps the fuel filter is nearly plugged up? I've seen some pretty amazing things from that being a cause. I imagine it was changed when the tuneup was done though? Just a thought I had after finding mine nearly plugged up and rough starting but would also run great once running.

 

It runs fine when push started, no shaking, no missing, plenty of power.


Yes I did, adding fuel into the intake does nothing. The injectors work fine, there`s just no signal from the computer during crank. And it appears the spark is at the wrong time during crank, however, it has stopped trying to run backwards for now.

Adding a new battery did nothing.

 

Check voltage at the pcm during cranking. Your PCM could be dropping off If you have an excessive voltage drop at the pcm during cranking.