Fast355

iTrader: (2)

So I have had long and even multiple cranking times on my cammed 305 TBI and even my cammed 3.4 MPFI in my GMC Jimmy. The problem would become much worse in weather cooler than 45*F. I would turn the key, the engine would crank, crank, crank, for about 10 seconds while attempting to fire and run, then it would start up to a rough idle and a puff of grey smoke. Several seconds later, the engine would leap to life so to speak from the rough idle to a normal idle.

I adjusted the cranking and choke air/fuel mixture endlessly trying to make it start quicker, to no benifit.

Enter the solution! I was reading a book that covered electronic ignitions, namely the GM EST HEI. Turns out that I assumed that the ECM commanded timing from the second you started cranking the engine over. It does not! Roughly 5 seconds after the engine starts the ECM commands the module with the programmed timing advance. I also noticed that when I set my timing, with the timing wire disconnected, the engine barely keeps turning over. That means that my cammed engine only had NO timing advance when I was trying to start it. I bumped the initial timing to 18*and then corrected the initial timing in the chip to 18*. I then attempted to HOT start the heat soaked engine, the starter dragged lightly as the engine roared instantly to life. I then let it cool down over night. The next morning, blipped the key, the engine cranked over for about 2 seconds, and came instantly to life, and settled down to a smooth 1,000 RPM idle.

Did that to the Van 2 days ago, starts right up now. Will do it to the GMC on Saturday.

junkcltr

iTrader: (1)

Did you tune the chip for the (18-6)=12 extra degrees of spark?
If you had 30 degrees at cruise then you now have 30+12 = 42 degrees.

Fast355

iTrader: (2)

I did tune the chip.

You give the distributer +18*, then the chip is programmed at -18*, which nets 0*. From there when you enter 48* @ cruise you get 48*. When you enter 36* you get 36*.