How to do a fuel pressure leak down test on a 2004 4.2 i6?

[Sqrly]

I know how to check the fuel pressure but I also want to check for leak down. I'm looking for leaky injectors.

On my 2004 the schrader valve is at the fuel filter and before the pressure regulator.

Q: Can the regulator affect the pressure leak down test?

 

[TJBaker57]

I know how to check the fuel pressure but I also want to check for leak down. I'm looking for leaky injectors.

On my 2004 the schrader valve is at the fuel filter and before the pressure regulator.

Q: Can the regulator affect the pressure leak down test?

Sure can!

So the issue with testing for leakdown becomes:

Is it leaking back into the tank??

Or leaking from one or more injectors??


Is a 2004 a single pipe system or two pipe?

Can't remember. Will have to research that.

 

[TJBaker57]

Thinking yours has the regulator in the engine bay,,,, since I seem to remember you mentioning checking the vent line for fuel smell.

 

[Sqrly]

Sure can!

So the issue with testing for leakdown becomes:

Is it leaking back into the tank??

Or leaking from one or more injectors??


Is a 2004 a single pipe system or two pipe?

Can't remember. Will have to research that.

I can show you which system it is.

I'm going to assume I need to plug the return line off the regulator to see if the injectors leak down with something that would hold at least 80 psi, to be safe. I don't want to spray fuel across the garage.



Image Source: https://nemigaparts.com/cat_spares/epc/gmc/56s-t/

 

[Sqrly]

Would you happen to know what this, I think it's a schrader valve, is for? It seems to be on the vapor recovery line.

 

[TJBaker57]

Would you happen to know what this, I think it's a schrader valve, is for? It seems to be on the vapor recovery line.

EVAP system test access port.