Hesitating to Start

diezelraccoon said:

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

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I agree with you on re: AMZ "oem" parts, I quit ordering those from them several years ago. Your fuel pressure sounds low to me, I do not recall actual spec (maybe 58psi?), with a bit of difference between gas and flex. Check the fuel pressure regulator on the rail? That bleeding off pressure could also affect your hard starts.

It would be helpful if there was some vehicle and drivetrain info in your signature. Not all are the same.

For fuel pressure, according to Haynes:
KOEO
Flex Fuel: 48-54 psi
Non-Flex: 55-62 psi

Either way the KOEO pressure is below the minimum. If it's a FF system has the inline fuel filter been changed?

diezelraccoon said:

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

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Isn't that a little low? Should be between 55-62 PSI, so you should swap the fuel pressure regulator and fuel filter, if your Tahoe has one. Some of the cars have the fuel filter inside the fuel pump.

nonickatall said:

Isn't that a little low? Should be between 55-62 PSI, so you should swap the fuel pressure regulator and fuel filter, if your Tahoe has one. Some of the cars have the fuel filter inside the fuel pump.

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Well since I relaxed the entire fuel pump assembly that takes care of fuel filter if it was on it, but I believe mine is elsewhere.
I will try replacing that and fuel pressure regulator.

Fless said:

It would be helpful if there was some vehicle and drivetrain info in your signature. Not all are the same.

For fuel pressure, according to Haynes:
KOEO
Flex Fuel: 48-54 psi
Non-Flex: 55-62 psi

Either way the KOEO pressure is below the minimum. If it's a FF system has the inline fuel filter been changed?

Click to expand...

Not to my knowledge but I will replace it along with fuel pressure regulator

FYI the FPR has no effect on the fuel pressure when running KOEO tests. On your system it works using supplied manifold vacuum, which is nonexistent when the engine isn't running.

Fless said:

FYI the FPR has no effect on the fuel pressure when running KOEO tests. On your system it works using supplied manifold vacuum, which is nonexistent when the engine isn't running.

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Where do you suggest I go from here since I’ve already replaced the fuel pump?

Fless said:

FYI the FPR has no effect on the fuel pressure when running KOEO tests. On your system it works using supplied manifold vacuum, which is nonexistent when the engine isn't running.

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I didn't know this. I thought it was possible for a faulty FPR to send excess fuel back to the tank, causing a low fuel system pressure. Something about the spring inside the FPR diaphragm getting weak or something like that?

OP, you can try capping the return fuel line temporarily. I use vacuum caps and one of those fuel line hose clamps. Prime the system and this is what your fuel pump is able to produce at maximum pressure.

When I was doing troubleshooting on my 99 Silverado I recall my pump maxed out at 100 psi. That truck still has the original fuel pump and it's at 260k-ish. I've only done that once.