427 SBC Back to not starting. Changing PWs no effect..

[91blkvette]

Had it running last week, and in the mist of trying to figure out base timing, something has changed. Despite returning to a running restore point tune, it won't fire. Spark plugs are wet, and now I notice that my crank signal is inverted. Ignition is HEI 8 hooked up to MS3/3X.

Only changes since it was running was resetting the VR sensor to align at 0 BTDC. Would not start, realigned it back to 10 BTDC, and still no spark.

Logs attached.

[billr]

Does it spark in "Test Mode"? Where are you checking for spark while cranking, at a plug wire or at the coil? If you are testing at a plug wire, check also at the coil.

[Matt Cramer]

The "inverted" behavior is simply how TunerStudio visualizes a single ended signal.

Does it spark if you disconnect the "B" pin and crank it? If so, what timing do you see?

[91blkvette]

Spark is back, problem appears related to a bad dist to coil plug wire. Tested +12v and tach wires going into the coil and the voltage is as expected.

Matt, checked cranking timing, and it's reporting 12 degrees, which is what I expect as the dist is aligned at approx 10 degrees.

[91blkvette]

Still not firing. Plugs wet.. take them out to check spark..sparks on cranking.

Must be the cold weather messing things up. Well on to messing with pulse widths..

[91blkvette]

Still no start. Increasing and decreasing PWs not having any effect. Used a tune that at least resulted in a running engine 2 weeks ago.

Cranks, wont start despite adding throttle. Adjusting throttle body set screw ( and resetting TPS (v) has no effect.

First two logs are for increasing cranking PW. Started at base TS setting, worked down.

Suggestions appreciated.

[91blkvette]

Datalog attempt to decrese fuel...

[billr]

Have you checked ignition timing again recently, while cranking? Are you using a simple light, or a "dial-back" type? I would try disabling the fuel (pull fuses/relays for both pump and injectors, let the cylinders and plugs "air out" to dry, then try starting with a quick blast of starting fluid (fuel still disabled). That will easily tell you if the problem is fuel or something else; almost cuts your search in half.

[91blkvette]

Have you checked ignition timing again recently, while cranking? Are you using a simple light, or a "dial-back" type? I would try disabling the fuel (pull fuses/relays for both pump and injectors, let the cylinders and plugs "air out" to dry, then try starting with a quick blast of starting fluid (fuel still disabled). That will easily tell you if the problem is fuel or something else; almost cuts your search in half.

Yep...checked crank timing..coming in at 12..set the dist at 10. Using a dial back that's set at 0. Pretty sure it's fuel related. I have a fuel pressure gauge, and it's reading a steady 40psi at turn on and crank. Got spark at the plug..In fact I cleaned all the plugs last nite..and after 1hr of testing today..one of em is dark again. And that's just on cranking alone.