2000 chevy,5.3 starting issue

[metallica21156]

i have a 2000 chevy silverado z71 with the 5.3. 160,000 miles on it. the issue is that sometimes it has problems starting. other times its fine. when it does start on first crank it starts and then almost dies but then recovers and runs fine. other times it wont start even after 3 cranks. hold the pedal to the floor and it starts right up. any ideas? replaced crank sensor,engine coolant sensor and fuel pump. fuel pump does run while trying to start. no codes in computer.

[Airjer_]

Pull the vacuum line of of the fuel pressure regulator. Its on the drivers side of the fuel rail about in the middle. If gas comes out replace it.

[j cAT]

Originally Posted by metallica21156

i have a 2000 chevy silverado z71 with the 5.3. 160,000 miles on it. the issue is that sometimes it has problems starting. other times its fine. when it does start on first crank it starts and then almost dies but then recovers and runs fine. other times it wont start even after 3 cranks. hold the pedal to the floor and it starts right up. any ideas? replaced crank sensor,engine coolant sensor and fuel pump. fuel pump does run while trying to start. no codes in computer.

if there are no codes this could be the fuel pressure being low..spec is 53to 62 psi key on engine off..if the fuel pressure drops off quickly then the fuel pump is most likely bad..

since this is only on cold start ,,, you could also have a bad ECT..did you replace the driverside coolant sensor next to #1 spark plug ?


your engine has a PCV ..this needs replacing..the hoses need to be checked with this as well..

[brianelton]

I just dealt with this on my 2003 5.3

Everyone will says FPR is bad if it leaks gas out the nipple, or its good if pressure goes up by +5 psi when vacuum is removed.

This isnt always the case.

My pressure would rise when I turned key on, then immediately drop to 0. I pinched off return line, and pressure would hold. I released the pinch and pressure fell - that meant bad FPR. I replaced the FPR - got a bad one right off the shelf, went back and got another one, and been fine since.

You can get a fuel test gauge at harbor frieght for $30. Or get the master fuel injection kit for like $100. The products suck, but can do what you need. If you get the master kit, the o-rings are too big, the schrader wont catch, gauge will stick, play with it - remove the schraders, and cut the o-ring down that is on the hose that connects to your truck.

[j cAT]

[quote=brianelton;6967256]I just dealt with this on my 2003 5.3

My pressure would rise when I turned key on, then immediately drop to 0. I pinched off return line, and pressure would hold. I released the pinch and pressure fell - that meant bad FPR. I replaced the FPR - got a bad one right off the shelf, went back and got another one, and been fine since.
[quote]


with the test you did as described, the fuel pump check valve has failed.

rapid pressure loss on fuel pump shutdown , then pinching return line and no pressure loss this is always whats the problem.

the regulator just regulates the pressure a small amount by a vac signal controlling the diaphram. the diaphram leaks this then can cause , if real bad flood engine and create a hard start.the injectors leaking will also cause these issues.

pinching the return line and no pressure drop point to the pump.

could be the pump had contaiminated fuel that effected its check valve.

[brianelton]

No. The FPR was bad. I replaced it, and it fixed the problem.

I put the test gauge directly on the fuel pump - pressure held.

If return line is pinched, and pressure holds, the injectors definitely are not leaking. By pinching it, you are artificially forcing the FPR not to allow the fuel to return to the tank.

The pressure was rising and immediately falling because the FPR was holding the fuel pressure against the injectors - it was collapsing and letting the fuel run back to the tank.

Also, if the injectors had been leaking, with each on/off of the key switch, it would have been dumping fuel into manifold. I did about 15 on/offs, this would have dumped an extraordinary amount of fuel into manifold causing it to run like hell and smoke - it never did that.

Your description of what the FPR does is accurate, but it regulates the fuel pressure by preventing all the fuel from running back to the tank through the return line.