Wont start! Truck has 4.3L Vortec. Engine Code W and is 4x4 New Alternator, new fuel pump relay, new fuses, Starter is new, Fuel pump just changed, new cap and rotor, new plugs, new fuel regulator!! i had just changed the fuel pump a couple weeks ago and ran fine for the first 40km then it started to run hard and then sputter and turn off! i waited a few hours to try and restart it started fine but the next day i came back to it it was very hesitant to start and once i got it started it didnt even make it to the end of the block and died out again! what could my issue be this time?

There could be several reasons why your truck is acting like it has a dead battery when you try to start it. Here are a few common possibilities:

1. Dead battery: The most common cause of a vehicle not starting is a dead battery. If your battery is old or has been drained of its charge, it may not have enough power to start the engine. You can try jump-starting the vehicle or replacing the battery if it is too old.

2. Bad starter: A bad starter is another common reason why a vehicle may not start. The starter is responsible for turning the engine over when you turn the key. If the starter is failing, it may not be able to turn the engine over, causing the vehicle not to start.

3. Faulty alternator: The alternator is responsible for charging the battery while the engine is running. If the alternator is failing, it may not be able to charge the battery properly, causing the battery to drain and the vehicle not to start.

4. Ignition switch problem: The ignition switch is responsible for sending power to the starter when you turn the key. If the ignition switch is faulty, it may not send power to the starter, causing the vehicle not to start.

5. Fuel system issues: If the fuel pump or fuel injectors are not working properly, the engine may not be getting the fuel it needs to start.

It's best to have a professional mechanic diagnose the issue to determine the exact cause of the problem and provide an appropriate solution.

If this truck has the 4.3L vortec motor it will not start with 40-45 PSI fuel Pressure.Thius engine requires approx. 56 PSI fuel pressure or it will not start. The fuel pump more than likely needs to be replaced this is a common problem with the 4.3L vortec engine.Change the fuel pump and your problems will be solved.

Check the primary and secondary resistance on your coil, also check the resistance of the plug wires and verify the spark plug gap.

Fuel pump may be getting weak. If pressure is not high enough the injectors wont open.

mcdevito75 here, You"ll have to trace the fuel lines from the gas tank to the carb. look for kinks, breaks, beds in the fuel lines. Also change the gas filter.

fuel pump relay

sounds as if the wires on the fuel pump are unplugged or broken,or maybe a bad fuse,fuel pump relay.

Had the same problem with my '96 Silverado with 350 Vortec. The truck would only crank. It would start if fuel was poured down the throttle body. Could not hear the fuel pump hum. Fuse was good, but could not hear relay click. Relay was good, Did some electrical wiring trouble shooting. Turned out that one of the connectors that clasp onto one of the pins of the fuel pump relay wasn't making a good connection, too loose. I just stuck a peice of wire into the connector and pushed the relay back in. Relay clicked, Truck Started. It's been more than 4 yrs. since I made that McGuyver fix. Still firing.