Chevy Express van problem starting at various temps.

Code reader does not indicate replacing ECT sensor, but it seems that may be the problem. Van starts (cold first start) on single try only at certain temp. Otherwise, depending on the temp that moment, it requires anywhere from 2 to 10 turnovers to start. Once started, runs well (but sometimes has raw gas odor). The number of required turnovers seems very consistant with engine temps.

If it is the ECT sensor, I can't seem to locate where it goes so I can replace it.

Thanks, John