My car has had a hard cold start for a while. Searching through the forum hasn't yielded any meaningful info, so any ideas are welcome. The current behavior is when fully cold, the car has excessive cranking and does not want to catch. It usually will catch for a short time but then immediately die out before revving up, then afterwards it will usually crank and catch fine. After that it has a much easier time starting. Starter was replaced with 4th gen gear reduction, cranks great. Fuel pressure holds fine during cranking and primes properly. Replaced spark plugs with another set of Delco R45TS, same behavior (old ones looked fine). New coil to see if it helped with a slight rough idle, no change. Datalogging reveals that CTS and MAT seem to be working properly. Distributor/ICM have not been replaced, but timing was last set at 6* with EST disconnected. Fuel pump/sender/filter/regulator were all replaced recently, but did not help with cold hard start. Interestingly enough, on the old 305 that was in there with the original starter it would actually start right away when it was very cold outside, better than when it was warm. Not sure if the new engine would show similar behavior since it's not been very cold recently.

In summary:

Fuel pump - new Walbro 340
Fuel sender - new ACDelco
Injectors - recently replaced with SouthBay Bosch III remans.

Coil - new BWD
Plugs - ACDelco R45TS all gapped to 0.035"
Wires/Cap/Rotor - replaced a few months ago.
Distributor/ICM - original, may be worn

IAC Valve - replaced a few months ago, passage is clean.

 

Test the CTS. If it reads incorrectly it may not be enriching the cold start. When you swapped to a 350 did you change PROMs?

 

 

I swapped over to a AUJP 350 memcal when I did the swap. Didn't get a chance to measure the resistance but in datalogs of cold-starts, the CTS reading matches up reasonably well with the outside temperature.

 

Well if those check out... is the 350 stock? Cam? Heads? You may need to enrich the cold start in the programming if the new 350 is hotter than stock.