1997 Z28 starting problems
10-04-2018, 03:36 PM
#1
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1997 Z28 starting problems
Hi everyone. I have a 1997 Z28 6-speed which after a complete top end engine rebuild was running fine for a while, however after having the clutch changed recently, the car now generally wont start on the first crank. I have checked over the engine bay visually and the car is not throwing any codes. Usually takes three to four cranking sessions for the car to start, and it starts sluggishly. When driving, the car actually runs well and pulls strong on the highway. After getting gas today, I pulled the stock intake elbow to replace it with a NOS part and noticed fuel pooled inside of the elbow. No noticable fuel leaks on the ground or anywhere inside the engine bay. Could I have accidentally over filled the fuel tank? Car has a new fuel pump and filter. Also the car has a brand new battery.
Last edited by CayenneRed97Z; 10-04-2018 at 03:38 PM. Reason: More info provided
10-04-2018, 04:54 PM
#2
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Re: 1997 Z28 starting problems
I would double check the injectors. Pull the rail off with the lines still attached. Put clear bags over the injectors then turn the key to start to allow the pump to prime. Check the bags for fuel.
Have you tested fuel pressure?
Have you tested fuel pressure?
10-04-2018, 05:37 PM
#3
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Re: 1997 Z28 starting problems
Haven't had time to test the fuel pressure but I will soon. The car started immediately with the new elbow, idled smoother and felt faster by the seat of the pants. Could a heavily damaged intake elbow for a TPI LT1 cause fuel to pool up inside of it?(my original was held together by tape and was quite loose) I'll pull the new elbow tomorrow to see if any new fuel has accumulated there and test the pressure. If fuel has accumulated in the elbow I'll just replace the rails and injectors I think.
10-04-2018, 09:34 PM
#4
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Re: 1997 Z28 starting problems
It is very difficult for fuel to get in the 90-degree inlet elbow.
The injectors spray in on top of the intake valves in the heads. Virtually impossible to fill up the intake manifold. The rails and injectors can't leak into the intake elbow.
The vacuum compensation line for the fuel pressure regulator can dump fuel into the intake manifold if the diaphragm in the fuel pressure manifold is leaking, Again, the vacuum connection is toward the rear of the manifold, and hard to fill up the intake manifold, since some of the valves are always open. Check for wet fuel in the vacuum line.
EVAP system, which can be flooded with fuel if you habitually overfill the tank, can vent fuel into the into the throttle body, which would empty into the intake manifold from the back of the throttle body. But the fuel would only flow when there is vacuum in the line, due to air flowing inwards as the engine is cranking with the throttle blades closed. It could also only flow fuel if the EVAP purge solenoid is open. Check the EVAP vacuum line connected to the throttle body for wet fuel.
Courtesy of Shoebox
http://shbox.com/1/evap_sol.jpg
Are you sure it was fuel in the elbow? It is remotely possible for coolant to flow out of the idle air passage in the throttle body, into the elbow, but that would require failure of the gasket where the bottom plate with the coolant lines attaches to the bottom of the throttle body. Very unusual for that to fail, and when I have traced it down to a leaking gasket, it’s just drops that spill into the intake air flow passage, which is also in the bottom plate. In those cases it would have interfered with idle air flow and made the engine difficult to start.
The injectors spray in on top of the intake valves in the heads. Virtually impossible to fill up the intake manifold. The rails and injectors can't leak into the intake elbow.
The vacuum compensation line for the fuel pressure regulator can dump fuel into the intake manifold if the diaphragm in the fuel pressure manifold is leaking, Again, the vacuum connection is toward the rear of the manifold, and hard to fill up the intake manifold, since some of the valves are always open. Check for wet fuel in the vacuum line.
EVAP system, which can be flooded with fuel if you habitually overfill the tank, can vent fuel into the into the throttle body, which would empty into the intake manifold from the back of the throttle body. But the fuel would only flow when there is vacuum in the line, due to air flowing inwards as the engine is cranking with the throttle blades closed. It could also only flow fuel if the EVAP purge solenoid is open. Check the EVAP vacuum line connected to the throttle body for wet fuel.
Courtesy of Shoebox
http://shbox.com/1/evap_sol.jpg
Are you sure it was fuel in the elbow? It is remotely possible for coolant to flow out of the idle air passage in the throttle body, into the elbow, but that would require failure of the gasket where the bottom plate with the coolant lines attaches to the bottom of the throttle body. Very unusual for that to fail, and when I have traced it down to a leaking gasket, it’s just drops that spill into the intake air flow passage, which is also in the bottom plate. In those cases it would have interfered with idle air flow and made the engine difficult to start.
Last edited by Injuneer; 10-04-2018 at 09:39 PM.
10-05-2018, 03:14 PM
#6
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Re: 1997 Z28 starting problems
OP
Injuneer pretty much covers it. A leaking FPR can cause prolonged starts. start car and let run for a minute. Shut off. Pull vacuum elbow from FPR...is there any sign of fuel in that elbow?
If yes FPR is bad
Torn or damaged TB elbow will cause engine to run pig rich as the un metered air is getting in motor. PCM (02's) see more air and PCM commands more fuel. More fuel really should never be in intake elbow so if it is confirm and fix the "why". Keep a fire extinguisher handy in the mean time....
Injuneer pretty much covers it. A leaking FPR can cause prolonged starts. start car and let run for a minute. Shut off. Pull vacuum elbow from FPR...is there any sign of fuel in that elbow?
If yes FPR is bad
Torn or damaged TB elbow will cause engine to run pig rich as the un metered air is getting in motor. PCM (02's) see more air and PCM commands more fuel. More fuel really should never be in intake elbow so if it is confirm and fix the "why". Keep a fire extinguisher handy in the mean time....
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