Engine crank but no start

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Ksarge

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So today, (this morning) I went out to good ole Diasy. She’s a 99 Chevy Silverado 2500 with the L29 454 (Gen VI) rwd everything is all original.

When I put the key in the ignition and put it on acc, everything works fine when I go to start it, it cranks over a few times doesn’t start.
Try a second time it starts but the rpm’s jump up to 1k fires about 1 full cycle (all pistons firing) and just dies.
Try a third time, it doesn’t want to crank but tries to start held the key about 3-5 seconds. Doesn’t start
Try for a fourth try, put a little throttle into it ram rough when first started until it leveled out on the Rpm’s and it’s perfectly fine.

It’s like every day or every other day it will fire up on the first try other times it takes about 2-5 times for it to start and crank up.

I’ve replaced the oil pressure switch (whole truck died when it happened)
Replaced the rotor and cap
Replaced the oil after the pressure switch went out

I’m just stuck and not 100% sure of what’s the main issue for it not starting the first time

Any help would be greatly appreciated
 

HotWheelsBurban

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I'm thinking, Passlock is starting to get janky, or fuel pump is weak. Have you changed the fuel filter? A blocked or clogged one can definitely cause fuel delivery issues especially on startup.
 

someotherguy

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We may be missing what's really going on based on terminology used.

Cranking = starter turning the engine so we know starter and battery are good and engine isn't locked up. Some people misuse the term so we need to be clear.

It sounds vaguely to me like you may have the classic failed fuel pressure regulator and/or leaking injectors that the Vortec 7.4's are prone to. The last part you mentioned about giving it a little pedal and it runs rough and stumbles to an idle is what tells me that.

Richard
 

Schurkey

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Lotsa folks think that the engine "running" means it's cranking.

Think about ancient cars. They gave you a crank-handle that lived on the car somewhere, perhaps on the floorboard of the passenger compartment. You'd grab the handle, poke it though the grille so the handle engaged the front of the crankshaft. You'd turn on the ignition, retard the spark, and then spin the crankshaft with arm-power using the handle--cranking the engine before electric "starters" (cranking motors) were invented. In fact, electric starters were invented because a friend of the inventor was killed by cranking an engine by hand...and he forgot to retard the spark. The first cylinder to fire, fired early (advanced) which spun the crankshaft backwards, and the handle smacked the poor guy.

(Yes, I'm old...but not that old.)

As said, verify fuel pressure. Verify all the usual "tune-up" items: Cap, rotor, plug wires, spark plugs, fuel and air filters, PCV system.

Then connect a scan tool, verify all sensors, spark advance, etc.
 
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