Good Evening All,
I have been reading the forum for awhile but this is my first time posting. I have a 98 k1500 Z71 ext cab short bed with the 5.7 Vortec that won't start. A few weeks ago, it started, ran rough for a minute, died, and has not started since. I have checked and/or replaced a lot in an attempt to get it fixed. A similar issue happened a few months ago and I replaced the fuel pressure regulator with a Delphi unit and that fixed it until now. At first I checked fuel pressure and it was not holding after the pump shut off so I figured there must be a leak inside the upper intake manifold. When I pulled the upper intake manifold, it looked like fuel had been pooling under the cylinder number 6 and 8 injectors so I figured viola there is the problem. I replaced the injector assembly with a re-manufactured unit from Rock Auto but still no joy.
After replacing the injector assembly, I have checked fuel pressure (55 psi at the service port with key on and now holds for awhile after the pump kicks off), I have good spark, I have compression, I used a noid light to verify that the ECU was pulsing the injectors, the spark plugs are wet with gasoline, and when I spray a little carb cleaner in the throttle body, she runs until she burns up the carb cleaner and seemingly floods out since the plugs are wet. The only code I get is P1351 but that can happen from just a long crank time (from what I have read). I have also tested a re-manufactured ECU that was pre-programmed with my VIN, a new ignition control module, a new TPS sensor, and a new idle air control valve. Additionally, in the past 6 months I have replaced the mass air flow (MAF) sensor and the manifold absolute pressure (MAP) sensor. Lastly, I have a pretty good scanner and can see that the values for the sensors are showing values that make sense.
So with all that, my only real question is what should the vacuum pressure be when cranking over the engine? When cranking the engine, my MAP sensor shows like 97 kPa which is basically atmospheric pressure (ie no vacuum). I also checked it during the few seconds I can get it to run on carb cleaner and it goes down to about 40 kPa pretty quickly, once she fires, and from what I have read it should run at that vacuum pressure so I do not think it is a large vacuum leak.
Unless you all have any better ideas, my last thought is that the re-manufactured injector assembly was just bad from the get go. Any other ideas? I am taking it to the mechanic this weekend unless you guys come up with a really good idea.
