fuel issue

Asked by Jul 15, 2017 at 12:05 PM about the 1993 Chevrolet C/K 1500 Cheyenne LB RWD

Question type: Maintenance & Repair

i have a 93 chevy 1500  2wd with a 5.7 i am getting good spark and no
vacumm leaks but it will not stay running for very long in park before it stalls
out i had  my uncle look at it with me and we noticed a good fuel spray in a
cone shape at low idle but as soon a i step on the gas or try to put it in gear
the cone shape goes away and truck stalls probley fuel pump but i have
heard there has been issues with this on this before with this moter andy
help please i dont want it to nickle and dime me

2 Answers

5

All computerised cars basically do the same thing at startup. With the key on, but engine off (i.e. not in the "start" position), the fuel pump should activate for about 2 seconds to prime and pressurize the fuel system. If you roll the key straight to the start position, it still performs this prime function while trying to start. It also does this to provide fuel pressure REGARDLESS of the oil pressure. Now, if during startup, the computer (ECM or PCM) detects an adverse condition that could cause damage to the drivetrain, it will inhibit the signal that activates the "fuel pump relay", and subsequently, the "fuel pump". Side note* Most people think the fuel pump is activated directly from the computer. Not the case! It can't handle the necessary current needed to drive the pump. With "that" said, several of the conditions that would cause the fuel pump signal to be inhibited are "low oil pressure" and "wide open throttle". The latter is vastly more important than the first, and so, the computer will not provide fuel to an engine it thinks is set to redline, and then grenade your engine. Now, the throttle position is just a sensation provided to the computer so that it can adjust various things like a/f ratio, ignition timing, shift points, etc... The TBI "mechanically" acts like a carburetor regardless of the status of the throttle position sensor (TPS), meaning that when you put fuel or spray ether into the throttle body, it will generally start if it gets a spark and the oil pressure rises. If it starts and runs at this point, your "Oil Pressure Sensor" is fine and your "TPS" is suspect. If it starts and runs for a few seconds, and then shuts off, your "Oil Pressure Sensor" is suspect. I hope this helps. Philip

905

My thoughts...Fuel pressure regulator.

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