Hesitating to Start

Still seeking answers on this with my 03 Tahoe with the 5.3 engine. I noticed at about 1/4 a tank if it’s sitting all day/nignt you go to start it and it takes a little longer for it to fire up. There’s been times the gas light was on and I was parked at an include downhill and it would not start and I had to put it neutral and let it roll to a flat surface for it to start. I’ve noticed now when it’s down to 1/4th a tank on level surface after sitting all night it does the same thing.
I do believe if I turned the key to the on position and let the fuel pump run for a few seconds before starting, it will fire up. The fuel pressure was below specs that I outlined in a previous post. I’ve already placed the fuel pump with an OEM. Still trying to figure out what’s causing this. Perhaps fuel filter or fuel pressure regulator?
Below is a link to a video of what it’s doing.

I cannot view the video, says private. Anyway, I think the pump is losing it's prime because of a leak, the system isn't sealed anymore.

My first look would be the pump but you said that that has been replaced. Did you replace the entire unit with the sensors and sender and such or just the pump? Did you triple check the lines for leakage?

swathdiver said:

I cannot view the video, says private. Anyway, I think the pump is losing it's prime because of a leak, the system isn't sealed anymore.

My first look would be the pump but you said that that has been replaced. Did you replace the entire unit with the sensors and sender and such or just the pump? Did you triple check the lines for leakage?

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I replaced the entire unit. As far as I could see there were no leaks.

diezelraccoon said:

I replaced the entire unit. As far as I could see there were no leaks.

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Did you use aftermarket or OEM pump module? If your pressure is out of spec then its either the regulator, pump or less likely filter. You should replace sock and inline filter always when installing a new pump. I would put a new regulator on at this time also.

diezelraccoon said:

I replaced the entire unit. As far as I could see there were no leaks.

Click to expand...

I had a similar issue with my '02 Z71. I had replaced the internal tank fuel pump as well. You state your replacement was OEM, where was it purchased? I had to replace my "new" OEM to correct the problem. As @swathdiver stated, it sounds like you are loosing prime. Replacing the fuel filter is always a good idea when servicing the fuel system. I would put a pressure gauge on the fuel rail, and monitor initial pressure when key is "on", and watch the leakdown over time. Check the pressure spec for your rig, as gas and flex are different.

I was able to view the video. It took "a little" longer to crank, but not that bad honestly.

Your next step would be to check fuel pressure with a gauge. It could be the pump, but could also be the FPR.

rockola1971 said:

Did you use aftermarket or OEM pump module? If your pressure is out of spec then its either the regulator, pump or less likely filter. You should replace sock and inline filter always when installing a new pump. I would put a new regulator on at this time also.

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It was an OEM/ACdelco fuel pump sending unit, the entire thing. This problem is occurring with the old fuel pump so it can’t be the fuel pump.

diezelraccoon said:

It was an OEM/ACdelco fuel pump sending unit, the entire thing. This problem is occurring with the old fuel pump so it can’t be the fuel pump.

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Unless your new fuel pump is bad too.

justirv said:

I had a similar issue with my '02 Z71. I had replaced the internal tank fuel pump as well. You state your replacement was OEM, where was it purchased? I had to replace my "new" OEM to correct the problem. As @swathdiver stated, it sounds like you are loosing prime. Replacing the fuel filter is always a good idea when servicing the fuel system. I would put a pressure gauge on the fuel rail, and monitor initial pressure when key is "on", and watch the leakdown over time. Check the pressure spec for your rig, as gas and flex are different.

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At the time I bought it off Amazon, but I stopped buying OEM parts from Amazon. I’m confident it’s not the fuel pump because this issue was occurring before I replaced it. The fuel pressure specs are as follows before I replaced the fuel pump.

46 psi when key was on but engine off.
42 psi with engine running
42 psi after engine was ofF

strutaeng said:

I was able to view the video. It took "a little" longer to crank, but not that bad honestly.

Your next step would be to check fuel pressure with a gauge. It could be the pump, but could also be the FPR.

Click to expand...

These were the fuel pressure readings before I replace the fuel pump.

46 psi when key was on but engine off.
42 psi with engine running
42 psi after engine was off