Fuel pressure test port

[gmcman]

So I hear the pressure is tested at the filter at least on the early models. Mine has a port at the rail, and the filter, I assume the port at the rail is for the injector cleaning but do all the early models have a rail port as well, or is this one just special?

 

[BRomanJr]

So I hear the pressure is tested at the filter at least on the early models. Mine has a port at the rail, and the filter, I assume the port at the rail is for the injector cleaning but do all the early models have a rail port as well, or is this one just special?

The test port at the engine is for EVAP Testing (green cap is always EVAP)

 

[mrphoenix80]

My 06 has one above the alternator on the fuel rail. However I don't have a fuel filter under the truck. So I think GM added them to the fuel rail after the filter delete. How else could you check fuel pressure?

If this is where you see the port it could have a newer rail on an older truck. I dont remember seeing a port on the rail on the older trucks with the fuel filter.

 

[gmcman]

Well now this leads to another question. Couple years ago during summer, about 1 min after I started the engine, A/C on, I would get a purge like a nitrous hose blew and smoke billowed out from the hood, lasted about 10 sec. This happened about 3 times total and never has done it since... I was thinking my fan clutch was weak and over-pressuring the A/C system.

After searching around about the EVAP and it's location, could this have been the EVAP or does the A/C do this if over-pressurized by the compressor and not from charging manually?

No codes were ever set.

 

[gmcman]

This is the port in question. Yes it does appear to be connected to the EVAP system...thanks.

What is said procedure for testing? I'm hunting down any possibility for a MPG loss....excess fuel possibly evaporating is not in the cards.

 

[MAY03LT]

What is said procedure for testing? I'm hunting down any possibility for a MPG loss....excess fuel possibly evaporating is not in the cards.

Whatchu trying to test?

 

[gmcman]

Basically kicking the tires.

I want to go over the ole girl head to toe, make sure things aren't on the edge of failing. Been looking for causes of slight fuel mileage issues and I know winter gas is a large player, but other things were out of whack....namely the upstream O2 sensor which has changed things already.

 

[mrphoenix80]

Yes that port is for the evaporative emission system for the fuel system. That is where you would hook a smoke machine to test for small leaks. However the onboard system tests for leaks as small as .020"! So if you have a leak it will code. no code=no leaks.

The other issue of a cloud of "smoke" I have only seen once and not on our trucks. I had a A/C system overpressure once on a E350 and the safety valve blew off and did exactlly what you describe. I dont know but that is my guess. If your system was overcharged that could happen. The cans for sale at the parts store are ok, but if you put in to much you can acctually hurt the performance of the A/C

The A/C system has nothing to do with the EVAP system so I would say they are not related.

On my 06 the fuel pressure test port is located on the fuel line at the rail. directlly above the alternator and right behind the lift bracket. I dont know what good it is because it looks like a pain in the to get at.