Replacement motor questions but hopefully fixable

[rockdogz]

So this is my first time pulling injectors. I was trying to pull the fuel pump fuse while the engine was running to empty the fuel rail but when I pull the fuse and the relay it keeps running. Any ideas?

 

[TollKeeper]

The fuel pressure has to drop off from the engine running. Give it a minute or 2.

 

[Rocket Man]

So this is my first time pulling injectors. I was trying to pull the fuel pump fuse while the engine was running to empty the fuel rail but when I pull the fuse and the relay it keeps running. Any ideas?

The fuel pressure has to drop off from the engine running. Give it a minute or 2.

Yeah it won’t stop immediately. And if you disconnect the fuel line without doing this, it won’t quit spraying all over immediately either! Just let it keep running until it dies.

 

[rockdogz]

It’s been 35 minutes…

 

[rockdogz]

Pic of fuses

 

[George B]

When you pull the injectors mind the O-rings. I once lost 4 of them down intake runners. I was lucky to get them all back by removing the intake.

 

[rockdogz]

It ran 40 minutes and never died

 

[Rocket Man]

It ran 40 minutes and never died

It should only take a few minutes, no sense letting it run more than 5. Either you’re pulling the wrong relay or you need to pull the fuse from the fuel pump control module. You can also disconnect the harness from the FPCM if you can locate it in the rear undercarriage. I just noticed you’re talking about a 2008 but this thread was posted in the 2000-2006 section so you might be getting us confused. A 2008 should have a FPCM.

 

[Fless]

Just noticed this thread is in the NBS forum.

On my NBS I pulled the fuel pump relay this morning -- getting ready to drop the fuel tank -- and started it up and it ran for maybe 2 seconds. Cranked it over again to be sure but it never started.

EDIT: might double-check that you have the right relay pulled.

 

[rockdogz]

It should only take a few minutes, no sense letting it run more than 5. Either you’re pulling the wrong relay or you need to pull the fuse from the fuel pump control module. You can also disconnect the harness from the FPCM if you can locate it in the rear undercarriage. I just noticed you’re talking about a 2008 but this thread was posted in the 2000-2006 section so you might be getting us confused. A 2008 should have a FPCM.

Shoot, yep I posted in the wrong forum. Any way to move it?

 

[Rocket Man]

Show us a pic of the inside of your fuse box lid with the diagram.

Edit: you’ll have to ask the mods to move it. @NathanJax @07Burb @Shaggy @yates ™

 

[Fless]

Shoot, yep I posted in the wrong forum. Any way to move it?

@soulsea please.

 

[soulsea]

moved

 

[rockdogz]

Thanks for moving.
So just pull the connector on the FSCM while it’s running?

 

[Rocket Man]

Thanks for moving.
So just pull the connector on the FSCM while it’s running?

That’s what I did with my 08 Silverado.

 

[wsteele]

Compression checked out ok. Tried new plug wire and spark plug, and swapped coils with cylinder 2 - the misfire stayed on cylinder 4. I suppose it could still be a lifter right? The compression test wouldn't rule that out because it would fail collapsed right?

Yes, you could still have a collapsed AFM lifter (#4 is an AFM lifter). The sure way is to pull the valve cover and inspect the #4 rockers. If they are both straight and one is not loose, you probably don't have an AFM lifter issue. Turn the engine over and watch to see if the rockers on #4 are operating properly, if the are moving up and down in time, it isn't a collapsed lifter.

 

[89Suburban]

As far as the VLOM, I had already been experiencing some oil leaking from somewhere higher on the block and I was going to replace the valve cover gaskets. I also have some small amount of coolant leaking somewhere although I don’t see it on the ground. I just need to add more to the reservoir monthly when it gets low. When I read about the VLOM issues of oil/coolant leaking I have a feeling it could be related.

There is no coolant leak possible from the VLOM, only oil. However, there are 2 crossover steam pipes on the top of the cylinder heads that have little gaskets on them that do go bad and slowly seep, but not enough to smell or see a leak. Something to check if you go diving into things.

 

[V327839]

I swapped in a later 5.3 motor into my 04 Sub z71. I then had unexplained coolant and oil loss. Turns out the motor has the Castec heads that were prone to cracking. I had to replace them. I don’t remember having knocking or codes but I guess it could depends on how bad the cracks/leakage is. Wish I had a better experience to share.

 

[Tonyrodz]

I swapped in a later 5.3 motor into my 04 Sub z71. I then had unexplained coolant and oil loss. Turns out the motor has the Castec heads that were prone to cracking. I had to replace them. I don’t remember having knocking or codes but I guess it could depends on how bad the cracks/leakage is. Wish I had a better experience to share.

In my experience the 862 heads crack too.

 

[Fless]

Thanks for moving.
So just pull the connector on the FSCM while it’s running?

Run out of fuel yet?