If you haven't changed anything from when it ran before, ie.. plug wire orientation etc, then I think you will see a whole bunch of nothing when you do Tom's double spark plug trick... That being said, if you find that it is spark related, it shouldn't be a big deal to find the problem. We all wait for the results. Good luck..

 

I was able to test spark via Tom's method. It check out fine. I attempted to continue to check compression on my cylinders, but it seems my compression gauge is broken. I am in Florida for a week. When I get home, I'll borrow a gauge from a friend and continue the search.

I also called Aeromotive about the fuel pressure dropping off. They said their regulators are not necessarily made to hold pressure after priming. He said I could try to rebuild it to improve the issue. The issue is with the aluminum seat. This sounds silly to me. I'm not sure why someone would build a regulator to not hold pressure.

 

Just throwing this out: try advancing the timing (turning the distributor counterclockwise). If the spark it late, the motor won't necessarily backfire, but will not fire.

 

I am planning to try this when I get home, however the LT1s spark is directed by the computer, so I will have to tune it. How many degrees you think I should pull it back?

 

383 was suggesting that you advance the timing...not retard it. "Pull it back" typically means that you retard the timing.

Before getting into the tune, I'd suggest marking the damper, and checking the ignition timing w/a gun. You can do this by yourself and it should only take about 15 minutes.

 

Double check the plug wires going into the opti and make sure theyre on the correct plugs.

 

Ok, I've had some time to work on it, and I have found an interesting twist. It seems that the #2 intake valve spring is broken. It snapped 1 coil up from the bottom. These are lunati springs rated at 400 lb. I spoke to Lloyd Elliot about it, and he said he's never seen these snap, but my builder insists they were installed correctly.... Looks like I'll be checking the installed height to make sure it's within spec. I also ordered a new opti, since I know the sensor in mine is old if not original. I'm going to take off the front cover to make sure the gears are aligned correctly, and I just wanted to replace the opti while I'm already in there. So now I'm waiting on parts...

I know a broken valve spring won't cause a car to not start usually, but I have a theory of maybe how it can happen. So mine is an intake spring. The cylinder will not keep good compression while cranking, so air is escaping back into the intake. That would create a high pressure scenario in the intake, which the MAP would essentially tell the computer to retard the timing. Does this even sound like a possibility?

I did try advancing the timing at crank, but it did not help the situation. I think the valve itself is good, because if I blow compressed air through the spark plug hole, the valve seals. I guess normal compression just isn't enough to make the seal with the broken spring.

I was also able to fix my fuel pressure problem. There was a leak in the pump that was feeding back through the feed line.

 

No.

 

You're making stuff up.

 

Come again.

 

Many have asked this before but i didnt see any answer, are your plugs wet or dry right after those starting attempts?

 

The plugs do seem a little damp. But it is getting plenty of spark. It seems like the spark timing is off. Like it will backfire sometimes and puff while cranking. But no start. The fuel pressure is good and steady, and the plugs are not leaking. I just don't know how spark timing could have changed after already driving 50 miles fine. Hence, my theory above (that I'm apparently "making up").

 

You're making it up. You stated quite clearly that was the case;You ASKED...two people told you...and now you're upset about the response? What answer would you like us to provide?

The ECM doesn't change spark timing based on MAP during cranking. I don't believe that the ECM adjusts timing at all, during cranking. In fact, during cranking, most of the outputs from the ECM are fairly fixed. I'd say that the most influential inputs during cranking are CTS and TPS, and those influence fueling, not spark timing. And in addition to allof that, the one spring isn't going to change your cranking vacuum much anyway. Vacuum during cranking is very low...you cam would have at least as much effect of MAP, as your valve spring.

If you think that your spark timing is off, why don't you put a timing light on it, and see what the timing is...during cranking?

Why are you trying to start it w/a broken valve spring anyway?

 

Aren't all theories made up? That's the definition of a theory. Every suggestion made on corvette forum is a theory until proven. Last I checked the whole purpose of the tech section of corvette forum was to exchange ideas to help solve problems.

Why do you think I'm upset? Baffled at your comment maybe. But not upset.

Why do you think that? I'm not arguing your point here. I just want to know why you have that opinion. I can't find anything in the FSM to say one way or the other.

Coolant temp does affect spark timing. Look at the FSM. 6E3-C4-1.

I am planning to do that as soon as I complete the tasks I already said I was going to do. Obviously I can't do that with a broken spring.

Why do you think I have tried starting it since I found the broken spring? I wouldn't do that.

 

CT influences spark timing when running. As I said, I believe that spark timing is "fixed" during cranking, w/the exception of knock sensor check. I think that b/c that is what I have been taught and read over years of automotive school, and refreshers. I wouldn't expect to find something like that in the FSM.

Glad to hear that you're addressing the spring. I hadn't understood that from your posts, and I also misunderstood your "tone" which is why I thought you were upset.

You could disconnect the one rocker, and then check timing I would think, if you were curious about that.