Hello,
I have a 2001 Chevy S-10 Blazer LT 4X4 with a 4.3 V-6 that will not start unless it is jump started... After the Blazer is jumped it will idle all day but when I try to drive it down a small hill in our driveway with the tranny in neutral & at around 2500 RPM's the Blazer will stall and can not be started again unless it is jumped... Bought and installed a new battery and still it will not start unless jumped... Before I replaced the battery I scanned the Blazer for trouble codes and P1638 was all that showed up... Would a bad alternator keep the Blazer from starting???
God bless and thanks a LOT!!!!

 

Could be a failing fuel pump, and the jump gives it more amperage/voltage to produce ample pressure and volume. Follow the steps in this link, and post all 4 readings: https://blazerforum.com/forum/2nd-ge...eakdown-88305/