Shuvl82

First off I feel I should give a little backround history on this project. Please bear with me:

I recently bought a 96 camao Z28 that had been sitting for a year with a bad engine. When I got the car home I was able to get it started although it ran really rough. The previous owner had run it out of oil and it was knocking really bad. I replaced the engine with one I've had out of a 95 caprice cop car. The engine has been sitting on the engine stand for about 6 years in my shop. I swapped everything over from the 96 engine to make it work (timing cover, crank position sensor, crank hub, various other sensors etc.). I also deleted the EGR, EVAP, air pump and catalyc convertors then sent the pcm to pcmforless to be re programmed. VATS deleted as well. Here in Oklahoma we don't have to worry about emissiions checks. I also drained the fuel tank, filled with new gas and some injector cleaner, flushed the fuel line and replaced the fuel filter.

Now for the problem. When I try to start the car it turns over and acts like it wants to start every couple of revolutions but doesn't start. I can squirt gas in the intake and it will fire up for a couple of seconds then die. I checked the fuel pressure and it is 78 psi when I turn the key to run but don't crank. When i crank it the fuel pressure stays around 70 psi. I checked the pressure on another LT1 car of mine just to make sure the guage wasn't faulty and it checked out fine (42 with key on, 38 when cranking).

I'm thinking there's possibly an obstruction in the fuel rail or maybe the injectors are stuck shut from sitting for so long. I just want to make sure I haven't missed something before I pull the fuel rails and injectors. Any input is greatly appreciated.

Fatdog2

I've heard this before somewhere here that maybe the fuel pump is wrong for this model year car (98 and up).I heard on the radio from some talk show that when you spray the carb,and it starts,then the car isn't getting any fuel.I hope you get this resolved.My02.

Injuneer

Definitely a problem with the fuel pressure. As you noted, should prime to about 40psi before the fuel pump stops priming. Then hold near there while the engine cranks. Highly unlikely the problem would be caused by the wrong fuel pump being installed. The pressure is controlled by the fuel pressure regulator. Verify it is not stuck closed.

Pull the fuel rails up with injectors intact, and OUTDOORS with a COLD ENGINE and a FIRE EXTINGUISHER NEARBY, put jars under each injector, and crank the engine briefly to determine whether the injectors are flowing fuel when they pulse. In any case, after sitting that long, they probably need a professional cleaning to restore the spray pattern.

Next, disconnect the fuel return line at the hard line from the fuel pressure regulator. Connect a rubber hose to the hardline, and run it into a gallon jug. Turn key to "run" (not "start") briefly, and verify flow out of the pressure regulator.

If fuel flows, apply air pressure to the return line and see if that flows to the tank freely.

Shuvl82

Ok I pulled the fuel rails up and cranked the engine and only #1, #2, #3 and #4 flowed fuel. I don't have anyone helping me at the moment so I wasn't able to physically watch them as the engine was cranked. When I disconnected the return line and turned the key to run only a small trickle of fuel flowed out. I applied air pressure to the return line and was not able to blow fuel freely back to the tank.

Shuvl82

Well since it appeared to be a stuck regulator and I was only getting fuel out of for injectors I decided to swap it out with the fuel rails, injectors and regulator from the motor I pulled out. Fires right up and the fuel pressure is as it should be. The only problem now is that it doesn't want to idle now. When it does it idle it's only about 500 rpm. Any ideas on why it's idling so low or not at all? I've looked for vacuum leaks and haven't found any as of yet.

Injuneer

Possible problem with the idle air control (IAC) valve, plugged IAC passages, dirty throttle body.

Fatdog2

Just for kicks I would put my thumbs on the inlets (2) where the coolant used to flow on the throttle body while the engine is running and see if that raises the rpm's .I was watching on u-tube on how to rebuild a corvette c4 throttle body part 1 0f 4 and the gasket from the coolant area(idle control valve) seems to be brittle and my guess is it can leak causing unwanted air to go into the engine.(idle control valve readings could be off).If you corked these inlets off then disregard my post.Sure hope you keep us posted.Hope this helps.