5.3l flex fuel extended crank

[Gatto]

Hello everyone I have a 2007 tahoe z71 package and I am having a problem with extended crank. I put a fuel pressure gauge in it and while running it’s at a out 58-60 psi shut it off and it sat at 50 psi ish let it sit for 2hours and it dropped to 10psi then turned key on and jumped back up but had extended crank. But if I let it sit over night it fires right up normal. It dose gave a new fuel pump in it. It did the same thing before the new pump and after the new one it seemed fixed then after about 3 months it’s back . At this point I’m stumped other then maybe a injector stuck and flooding it and when it sits over night by then it’s all evaporated and starts right up. I’m I wrong on this. And if not how do I tell witch injector . Also it dose it on e85 and regular fuel . Oil dose not smell like fuel and is not thinned out .
thanks you in adanved .

 

[George B]

Can you explain in more detail the extended crank? Like, does it attempt to start and then require an extended crank?

 

[wsteele]

Hello everyone I have a 2007 tahoe z71 package and I am having a problem with extended crank. I put a fuel pressure gauge in it and while running it’s at a out 58-60 psi shut it off and it sat at 50 psi ish let it sit for 2hours and it dropped to 10psi then turned key on and jumped back up but had extended crank. But if I let it sit over night it fires right up normal. It dose gave a new fuel pump in it. It did the same thing before the new pump and after the new one it seemed fixed then after about 3 months it’s back . At this point I’m stumped other then maybe a injector stuck and flooding it and when it sits over night by then it’s all evaporated and starts right up. I’m I wrong on this. And if not how do I tell witch injector . Also it dose it on e85 and regular fuel . Oil dose not smell like fuel and is not thinned out .
thanks you in adanved .

Do you have a scan tool that you can watch live fuel trims? Are you getting any codes, MIL, etc.? Like P0300, etc.

 

[OR VietVet]

CEL's? Age of ignition parts? I have seen on the flex fuel rigs mentioned here that there is a special flex fuel solenoid or valve, for lack of a better term. I freakin' forget the name though, sorry.

Plus, welcome to the forum from Oregon.

 

[Gatto]

Can you explain in more detail the extended crank? Like, does it attempt to start and then require an extended crank?

No just cranks for longer and then starts

 

[Gatto]

CEL's? Age of ignition parts? I have seen on the flex fuel rigs mentioned here that there is a special flex fuel solenoid or valve, for lack of a better term. I freakin' forget the name though, sorry.

Plus, welcome to the forum from Oregon.

No cel and not sure one ignition parts except plugs are new.

 

[Gatto]

Do you have a scan tool that you can watch live fuel trims? Are you getting any codes, MIL, etc.? Like P0300, etc.

Yes to scan tool and fuel trims are fine with in acceptable range

 

[Gatto]

Only other thing I forgot to mention is once in awhile when it dose the extended crank you do smell fuel but not all the time.

 

[OR VietVet]

No just cranks for longer and then starts

Sounds like what has been said. Losing fuel pressure after shut off and bleeding back. Likely a fuel pump problem or injector leaks. Needs to sit o-night, attach gauge to see current pressure, then KOEO check pressure and then start and see what the pressure is and then when shut off watch to see if pressure drops sitting there.

 

[George B]

Can you see what the PCM thinks the engine coolant temp is when it happens?

 

[wsteele]

Hello everyone I have a 2007 tahoe z71 package and I am having a problem with extended crank. I put a fuel pressure gauge in it and while running it’s at a out 58-60 psi shut it off and it sat at 50 psi ish let it sit for 2hours and it dropped to 10psi then turned key on and jumped back up but had extended crank. But if I let it sit over night it fires right up normal. It dose gave a new fuel pump in it. It did the same thing before the new pump and after the new one it seemed fixed then after about 3 months it’s back . At this point I’m stumped other then maybe a injector stuck and flooding it and when it sits over night by then it’s all evaporated and starts right up. I’m I wrong on this. And if not how do I tell witch injector . Also it dose it on e85 and regular fuel . Oil dose not smell like fuel and is not thinned out .
thanks you in adanved .

It sounds like it may be flooding when it leaks down after shutdown. That might explain the normal start the next cold start, but the long crank when warm.

An injector(s) not shutting off completely could account for the pressure bleed and a flooded warm start. You might try a flood clear procedure when you expect the warm start long crank. If it catches briefly during flood clear, it might be time to take the injectors down for a test.

The bad news is your trims should be off some if the injector is not fully shutting off.

 

[Gatto]

Can you see what the PCM thinks the engine coolant temp is when it happens?

I will check that when I leave work today as it will more then likely have the extended crank.

 

[Gatto]

So I did another live data won’t let me post the recording of it but here are pictures idle ,1500rpm 2500rpm and engine off key on.

 

[Gatto]

Here are the others

 

[wsteele]

Nothing extraordinary in the Bank 2 trims. Do the Bank 1 trims look similar?

 

[tom3]

I'm not really up to date on the newer stuff, but could it be the fuel pressure regulator leaking back into the intake? Older models used vacuum to adjust pressure once the engine starts.

 

[wsteele]

I'm not really up to date on the newer stuff, but could it be the fuel pressure regulator leaking back into the intake? Older models used vacuum to adjust pressure once the engine starts.

Unfortunately the 07 MY (like a think the last two NBS models) has the fuel pressure regulator in the fuel pump assembly (in the tank), so the older style regulator next to the rail isn’t there.

 

[OR VietVet]

Yep, all with the pump.

 

[CaptainAmerica1]

What’s your alcohol content?

 

[OR VietVet]

What’s your alcohol content?

Not too bad right now but the 4th is still young! Plus, I am off tomorrow so I can sleep it off. Party on Garth!