1996 K1500 Everything is new fuel/ignition wise, besides injectors. Will start and idle for a few seconds then dies. Pouring fuel straight into the throttle body it will stay running. No codes.

 

Sounds like a fuel problem. Did you do a fuel pressure test? You said everything fuel/ignition is new, does that include a new fuel pump? If so, did you install a Delco or Delphi fuel pump?

 

That motor has the older Fuel injection system as my 1998 does. Use cheap gas and the poppets will start to cause issues. Put some Techron or Seafoam down the tank, let it mix, find a straight unused road, and use the Italian clean-out method.

 

I have done a pressure test and with the key on its 60-65 once it start it's around 50-55. Fuel pump is new. Fuel lines is new. Fuel filter is new. Fuel tank is new.

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Can you pump the throttle to keep it going? Don't know if applies to your motor, but I recall something about an oil pressure switch/sensor will shut off fuel pump after a few seconds if it doesn't see pressure after start. Common inboard boat problem for the 5.7's. Your description fits that perfectly.

 

Will not stay running if I pump the pedal. But if I pour fuel straight into the TB it will stay running until I stop pouring. Thinking of checking that and the fuel relay?

 

You posted you had 55 psi from the pump. Are you checking this at the rail?

 

Yes at the fuel pressure test spot. Right after it starts it's around 50-55. Key on its 65-60.

 

Just tested fuel pump relay and it clicks on like it's supposed to.

 

If anyone is following my POS 😂 just tested fuel pressure again. Spikes up to 60-65 then it starts jumps down to around 50. Then with key off fuel pressure instantly drops to 0. I'm thinking my new fuel pump is ****.