Start And Die!

[psymed]

Have a 96 c1500, 4.3, auto. Just rebuilt the engine at 178,000 because of coolant leak in intake manifold gasket. Contaminated oil was everywhere and a sweet chocolate brown at that! Had crank ground 10/10. Cylinders good at 3.997 to 4.00 and new standard size rings installed. Heads came back from machine shop with a valve job and a freshly milled surface.

 

 

 

Assembly was straightforward except for cam bearings - used two boxes to fit the journals and the cam bearing faces.

 

 

 

Engine turned over and fired up right away and ran roughly for about 3 minutes before I realized that I had reversed #3 and #5 wires! I started it again and it ran much smoother - but only for a minute before it died. Now it is down to about 5 - 6 seconds.

 

 

 

Here's the situation:

 

 

 

Engine starts and runs sweet for up to 5 seconds then dies.

 

Fuel pressure is 60 psi at start then drops to 50 psi and holds.

 

Disconnected Y pipe to eliminate potential catalytic converter pluggage.

 

Replaced fuel filter and fuel pressure regulator.

 

Distributor, module, cap, rotor, wires and plugs all new.

 

Timing spot on.

 

Oil pressure shows 50 psi and is a new sensor All controls connected and re-checked twice.

 

 

 

I guess it must be something in the engine control system or the emission control system. I am at a loss since these are part of what was a running engine. No harsh cleaners were used on sensors.

 

Is there a engine control system part that can kill the injectors or ignition system because of a factor I cannot find?

 

No check engine light or codes on scan tool.

 

 

 

 

Anybody got a good idea or two?

 

 

 

Thanks in advance

[rodram]

.. my guess is you need a new fuel pump... these Vortec engines (96-99) need 61+ psi at all times so that the poppet valve located at the tip of each injector can function properly... if the fuel pressure is low you can have difficulty starting the engine... like you describe

 

.. 50 psi is just not enough for the injectors to work properly... with the fuel pressure dropping like that it is your warning that the pump is on its way out...

 

.. get an ACDelco or Delphi brand and replace the in-tank filter sock and the external wiring harness at the same time.

[psymed]

.. my guess is you need a new fuel pump... these Vortec engines (96-99) need 61+ psi at all times so that the poppet valve located at the tip of each injector can function properly... if the fuel pressure is low you can have difficulty starting the engine... like you describe

 

.. 50 psi is just not enough for the injectors to work properly... with the fuel pressure dropping like that it is your warning that the pump is on its way out...

 

.. get an ACDelco or Delphi brand and replace the in-tank filter sock and the external wiring harness at the same time.

 

 

Thanks Rod - that is kinda what I was thinking - just didn't want to change yet another part and have the same issue.

[psymed]

.. my guess is you need a new fuel pump... these Vortec engines (96-99) need 61+ psi at all times so that the poppet valve located at the tip of each injector can function properly... if the fuel pressure is low you can have difficulty starting the engine... like you describe

 

.. 50 psi is just not enough for the injectors to work properly... with the fuel pressure dropping like that it is your warning that the pump is on its way out...

 

.. get an ACDelco or Delphi brand and replace the in-tank filter sock and the external wiring harness at the same time.

 

 

Thanks Rod - that is kinda what I was thinking - just didn't want to change yet another part and have the same issue.

 

 

Well - what I did was pinch off the fuel return hose to raise and sustain fuel pressure. Now the pressure test indicates that the pump starts at 60 psi and when the engine starts it goes to 68 psi. Still the engine only runs for 5 - 6 seconds and dies.

 

Check IAC action and EGR action - both performing normally.

 

Something is still shutting the engine down for some unknown reason.

[DaleJrRocks88]

Just because you don't have any codes doesn't mean anything. Have you checked the passlock sensor which is located with the ignition lock housing. Seems like the ECM isn't receiving the ok to enable the fuel injectors for a continued operation. May have to be relearned with a tech 2

.. my guess is you need a new fuel pump... these Vortec engines (96-99) need 61+ psi at all times so that the poppet valve located at the tip of each injector can function properly... if the fuel pressure is low you can have difficulty starting the engine... like you describe

 

.. 50 psi is just not enough for the injectors to work properly... with the fuel pressure dropping like that it is your warning that the pump is on its way out...

 

.. get an ACDelco or Delphi brand and replace the in-tank filter sock and the external wiring harness at the same time.

 

 

Thanks Rod - that is kinda what I was thinking - just didn't want to change yet another part and have the same issue.

 

 

Well - what I did was pinch off the fuel return hose to raise and sustain fuel pressure. Now the pressure test indicates that the pump starts at 60 psi and when the engine starts it goes to 68 psi. Still the engine only runs for 5 - 6 seconds and dies.

 

Check IAC action and EGR action - both performing normally.

 

Something is still shutting the engine down for some unknown reason.