1994 Chevy Blazer cuts off

I'm just double checking, is 94 s10 blazer, four cylinder?
If it cranks good, but won't start, have a helper crank it, while you visually check for spark at the plugs. To check for spark, use a known good spark plug or spark tester, pull spark plug wire, stick tester in the boot, ground metal part of tester to metal part of engine, watch for spark. If you have spark everywhere, use a gage and check fuel pressure. Even if the parts are new, I'd still want to check pressure. Some of the national brand autostores used to loan out a fuel pressure gage, if you don't have one.

Any applicable trouble codes? You should be able to check for mil codes yourself. To check for codes, you use a jumper wire between the A & B terminals of the datalink connector. Turn the key, just till the dash lites come on, no further, the mil starts flashing, you count the flashes to get the codes, your looking for two digit codes. Each codes will flash three times before moving to next code, if there is one. It should flash a code 12 anyway, that is one flash, a slight pause, then 2 quick flashes, the code will flash three times.

Hi Deb, thanks for the donation. The 4.3 is a 6 cylinder, The code 34 is map sensor, low voltage. I can't say that the sensor is faulty, that might be an old code. I'd have to check the sensor circuits at the sensor wiring connector, check vacuum, also.