LT1 Optispark/timing issues

[paul67]

Could you post a picture of the engine and opti as someone might spot something.

[gEtyOpAPiOn]

well when doing mechanic diagnostic work u always go from easy to hard ,so is there any spark,fuel?then go to firing order ,leakdown after that ,but if you are all over the place then it makes it harder

[barno68]

I am back in town now and am trying to find time to get back out to the garage. I just order a cable for AKM to check the codes and downloaded Freescan, so... that will be a few more days. To answer a few questions:
Grounding- I am using braided steel ground straps (1" wide) from the engine block to the frame and from the frame to the body. The battery negative is 2ga to the block. To be sure it is good I ran a jumper cable to the PCM/wiring harness (EZwiring) to check and also did and ohm check.
Spark- I am using a spark tester set at the electronic ignition gap and have good spark. However, as I plan to start the troubleshooting over again I will check all plugs in conjunction with a noid light for the injectors.
Air- looks good to me, but I am unsure where the idle screw should be set initially.
Fuel- as stated before I have good pressue, but have not yet checked flow. That is my next step after rechecking spark and injector signal.

As for a photo of the opti- it is back together so a pic will not show much.

[gEtyOpAPiOn]

oh u r in the bay area ,me too well hopefully you get it all sorted out ,if not i could help you but not this weekend haha

[barno68]

Ok- pulled the fuel rails and turned over the engine. All the injectors passed fuel so are getting signal and working. Tomorrow I will test the plugs for spark.

[paul67]

Keep posting

[barno68]

Using a spark tester- all plugs have spark when turning over.
Using a noid light- all injectors are firing. Only odd thing was that as I was going through them the first two I did were 2 & 4, which were fine. After them none of the others were working. I was using a remote starter to turn the engine over and decided to cycle the ignition and then they all worked fine. Not sure it that is an issue or a design feature. I checked the grounds and everything looks good.
Pulled four of the plugs and they smell a bit of fuel (not wet), not sure what to make of that. The plugs are autolite platinums gapped at .045. Also verified the firing order again.

I am still not sure where the throttle (idle screw) should be set. It is currently in the position (about 1/8" of threads protruding from throttle body) that it was when I got the engine before rebuilding. The butterfly valves look completely closed.

Any other thoughts?

[Derek69SS]

Be sure to let us know what solves it... my brother is going through what sounds like the exact same problem with his '95 Caprice right now. Had a local mechanic spend 8 hours on it, only to give up saying he has no idea what the problem is.

[WS6]

well, the intake valves don't need to be open if the IAC is working. What I would try though is cracking the throttle body open just a hair and see what happens. You can use your hand or use your foot from the driver's seat. At this point, you need to do something that causes a change even if it doesn't start. If it's a repeatable change that's even better.

[02WS6SSZ71]

I'm no LT1 expert, so I'll just hit on a couple of the basics again, most of which others have mentioned already:

-Do you have a ground from the battery to frame? You mentioned battery to block and block to frame, but didn't see battery to frame.
-Do you have compression? Know you said it was a fresh rebuild, but mistakes happen.
-Is it still cranking over slow? I know some people above ruled out starter, but it may be a bad solenoid. Test voltage going in and coming out of the solenoid...should see 12.6-12.8 from the battery and not more than a tenth or 2 drop coming out from the solenoid. I had this occur on a friend's car last month...turning over slow so I jumped the solenoid and the starter motor sounded good, so then I tested voltage at the solenoid...12.7 going in, 8.5 coming out. Had the starter tested at 2 different parts stores to verify my diagnosis, passed at both places. Bought a starter anyway, problem solved.

[barno68]

I'm no LT1 expert, so I'll just hit on a couple of the basics again, most of which others have mentioned already:

-Do you have a ground from the battery to frame? You mentioned battery to block and block to frame, but didn't see battery to frame.
-Do you have compression? Know you said it was a fresh rebuild, but mistakes happen.
-Is it still cranking over slow? I know some people above ruled out starter, but it may be a bad solenoid. Test voltage going in and coming out of the solenoid...should see 12.6-12.8 from the battery and not more than a tenth or 2 drop coming out from the solenoid. I had this occur on a friend's car last month...turning over slow so I jumped the solenoid and the starter motor sounded good, so then I tested voltage at the solenoid...12.7 going in, 8.5 coming out. Had the starter tested at 2 different parts stores to verify my diagnosis, passed at both places. Bought a starter anyway, problem solved.

The block is an extension of the ground from the battery, I have never seen two ground cables ran off a battery itself. In this case, even if the frame or body had a ground issue (which I have already tested for) the ECM grounds are connected to the block. Earlier I ran a jumper from battery to harness ground and saw no difference and had the same ohm reading.

While I have not put a gauge on it, the compression is good as it is a pain to turn over by hand.

I don't disagree about the starter, although I would question the solenoid being a problem as the battery cable connects to the starter so there would be no voltage drop across the solenoid. I am thinking about ordering a new one, but don't believe it is the reason the car will not fire. It is turning over fairly decently now, but it is still loud while cranking.

[paul67]

I hate to say this but were did you get the opti from, this is now sounding like it's the opti,open it up and see if the tips are alloy or copper,my were alloy and were corroded due to lack use.I'm on my third but we have damp weather being uk.

[barno68]

The opti contacts are clean and the rotor looks good- might say they look brand new :-) The contacts are copper and I bought it from an ebay seller that a forum member recommended who had been running one for some time. I know the opti's are always blamed, but I don't see how that could be it as I get good spark. I suppose the optical wheel could be off but that would be odd.

[paul67]

You posted earlier that 2and 4 sparked then the rest did not when testing then they did,you then say it sometimes catches which might be 2 and 4 trying to fire.I think I was the 1 that recommended the opti,bought the third 1 off him,as it was corroded my fault for not running the engine,as posted.Have you an alram fitted or an aftermarket wiring.

[barno68]

You posted earlier that 2and 4 sparked then the rest did not when testing then they did,you then say it sometimes catches which might be 2 and 4 trying to fire.I think I was the 1 that recommended the opti,bought the third 1 off him,as it was corroded my fault for not running the engine,as posted.Have you an alram fitted or an aftermarket wiring.

It has not fired since I put it back together this time. Later today I am going to increase the idle setpoint and give it another try. If nothing happens I will through the noid light on again and see if the injector issue pops up again. The reason I have doubts about the opti is that the cylinders were firing even when the injectors were not... Although, you never know with these things.

[MrQuick]

you might be getting spark but it might not be at the right time or proper saturation. Once under a load that might change.

[gEtyOpAPiOn]

it almost looks like vats ...well at first crank when cold all injectors spray 3 times at once then it goes sequential...but the spark should be consistent if your opti works then with the key on engine off if you plug and unplug the cam sensor on the opti distributor your should hear the fuel pump go on again ,,if it was wired with the pcm , if the opti dist had any moisture on it ,it may fog up the lens and then it wont spark ,you could kinda open the distributor cap and use a hair drier or just blow air while cranking the engine through the lil vent hoses ,but like i said make sure you have power while cranking and not only with key on

[barno68]

well, the intake valves don't need to be open if the IAC is working. What I would try though is cracking the throttle body open just a hair and see what happens. You can use your hand or use your foot from the driver's seat. At this point, you need to do something that causes a change even if it doesn't start. If it's a repeatable change that's even better.

I opened the throttle body a bit and cranked it over, no change that I could note in anything.

[barno68]

you might be getting spark but it might not be at the right time or proper saturation. Once under a load that might change.

Is there a way to check this without throwing more money at a new Opti-spark that may not have an issue?

[barno68]

This morning I hooked up the new ALDL cable and tried to check for codes. Freescan did not detect the correct COM port (maybe a Vista issue?) so I downloaded DataMaster which did communicate with the ECM. There were no codes present, but then again the vehicle has not run.

I am at a total loss on what to check next.