Post rebuild issues

[j91z28d1]

To me..

Turn over = Starter turns the engine.

Start = Engine turns and ignition occurs and now the engine is running under it's own combustion power.

Engine Runs = The starter turns the engine and ignition occurs and now the engine is running under it's own power.

For example: The engine turns over but doesn't start = the starter spins the engine but ignition doesn't occur and so the engine isn't running.

kinda.. but there's ON as well. that sometime needs to be explained as well.

to me, turning the ignition ON, is just the first key click. dash lights up. but some people call ON the engine actually running. these are usually new to understanding cars and think of the ignition switch on a car like a light switch in their house. I turned my light switch on but my light didn't come on. they think of cars the same way. not the extra steps that a car needs to start an engine. and then these new electric cars which you do just hit the on button complicated even more. whole they go thru a while sub routine to check for high voltage isolation and stuff. plus those you hit the start button to turn them on, but you can hold the start button without hitting the brakes to put them in the accessory On mode.


anyways.
step 1. key on, one click, eng off.

then key turned to start, starter engages, spinning the engine over, can also be called cranking over the engine.(throw back to hand cranked cars I guess)

engine starts is when you can release the ignition switch from the start position, spring returns it to ON and the engine stays running.

 

[iamdub]

It does not. Tried the 3 sec/5 sec this morning and it wouldn't turn over (start). Came back 5 min later and it started right up.

So it cranks but doesn't start. It still sounds like a fueling issue. Only, instead of the check valve keeping the fuel from flowing back in to the tank, I'm now wondering if you have a leaking injector(s), puddling fuel into the intake and cylinder(s).

Next test: After sitting, when the problem would usually occur, hold the throttle pedal to the floor and crank for about ten seconds. Or, just hold it until it stops cranking on its own (PCM will automatically stop it after about ten seconds). Release the pedal and try to start it as normal. Let us know what it does.

 

[tkdgirl]

if you mean the starter is not cranking the engine over at all with the key, and then you come back 5 mins later and it does. that's most likely electrical. and would need more info like what's happening with the lights while this no crank is happening. as said above, we all don't use the same terms to describe stuff, but little misunderstandings can lead a totally different path when trying to trouble shoot over stuff on here.

Every single light on the dash turns on when it cranks but doesn't turn over.

 

[tkdgirl]

Not that it means anything but I ran Torque Pro and here are the results. Everything was ok except all the EVAP stuff. I also ran the data on the Fuel Pressure/Trim Sensors. When it was idling while the test was running, it seems to sputter a bit. 2011 Denali XL with Flex Fuel

 

[tkdgirl]

So it cranks but doesn't start. It still sounds like a fueling issue. Only, instead of the check valve keeping the fuel from flowing back in to the tank, I'm now wondering if you have a leaking injector(s), puddling fuel into the intake and cylinder(s).

Next test: After sitting, when the problem would usually occur, hold the throttle pedal to the floor and crank for about ten seconds. Or, just hold it until it stops cranking on its own (PCM will automatically stop it after about ten seconds). Release the pedal and try to start it as normal. Let us know what it does.

Will give this a try in a bit, thanks!

 

[tkdgirl]

So it cranks but doesn't start. It still sounds like a fueling issue. Only, instead of the check valve keeping the fuel from flowing back in to the tank, I'm now wondering if you have a leaking injector(s), puddling fuel into the intake and cylinder(s).

Next test: After sitting, when the problem would usually occur, hold the throttle pedal to the floor and crank for about ten seconds. Or, just hold it until it stops cranking on its own (PCM will automatically stop it after about ten seconds). Release the pedal and try to start it as normal. Let us know what it does.

The first method, no turn over. Just crank. All dash lights on. It did not stop on its own, BTW. Released the pedal, turned back on and it started right away.

 

[Fless]

Has it run an evap drive cycle, or have the codes been recently cleared? Had any prior trouble with the evap system?

I'm with @iamdub, either a leaky injector or a stuck (or intermittent) purge valve on the engine. Either one could dump some fuel (or vapors) into the engine, causing a crank-but-no-start condition.

For the evap, have a purge and seal test performed. For the injectors, test for injector balance and leakdown. Those are standard tests with a good bidirectional scanner.

 

[swathdiver]

...If it's not the fuel pump what the hell is going on?

Can you tell me what year your truck is again please?

 

[tkdgirl]

Can you tell me what year your truck is again please?

2011 Denali XL with Flex Fuel

 

[iamdub]

The first method, no turn over. Just crank. All dash lights on. It did not stop on its own, BTW. Released the pedal, turned back on and it started right away.

Okay... I'm gonna be "that guy"... PLEASE don't use the term "turn over" here, especially in this context. It's really confusing and contradicting. It slows down the helping process when we have to ask for clarification and wait for a response before we can proceed. In a thread discussing if the key is being turned, or if the starter turning, or if the engine's crankshaft turning, etc., just say if it cranks (as it should when you turn the key) and if it starts ("fires" up and runs on its own). If anything, it's half the words to type. I don't mean to sound cranky (or is it turn overy?). Just wanna help get this figured out as accurately and efficiently as possible.

So, when you hold the pedal to the floor and crank the engine, it's not supposed to start. This is a factory function called "Clear Flood Mode". It stops the injectors and spark plugs from firing. It's to pump excess fuel from the cylinders should they become flooded for whatever reason. The idea was to test if you had a faulty injector(s) leaking down and flooding a cylinder(s) when it was parked. In addition to the wet fuel dousing the spark, this would also cause the fuel system to not be pressurized upon startup, causing a hard start (extended cranking) condition. As Fless mentioned, the EVAP purge system is another source for excess fueling to occur.

I assume the problem is pretty consistent, especially after it sits parked over night. Tomorrow morning, before you turn that key (leave yourself a note if you have to!), hold the pedal to the floor and crank it for ten seconds again, release the key, release the pedal, then crank it to start as normal. Hopefully it'll start and run normally. There may be a slight stutter, but it should still be a definite difference. Trying to get consistent test results here to narrow down the possible causes.