Air Out of Fuel System

[interceptorxr7]

Whats the proper way to get air out of the fuel system? I parked on an incline with an almost empty tank and I guess it sucked in air. Ive bled the system via the schrader valve on the drivers side of the intake. It worked for yesterday morning but when I went to go somewhere last night it wouldnt start. The fuel pump was kicking on, and the fuel filter is new.

[Bill Wheats]

Fill the tank up with gas and run the starter. The air should purge quickly.
You may have a problem with the pump, sock, or the flex line going to it????

[interceptorxr7]

After it wouldnt start I put 3 gallons in it then took it to the gas station and filled it up. Last night when it happened I didnt hear the pump prime the system. This morning it primed but wouldnt start. Some problems, dunno if they are related but..
-When you turn on the car the fuel gauge goes down to 1/4 but after you start it up it returns to full or wherever its suppose to be.
-I have a code P0138, but the CEL isnt on and the light isnt burnt out.

[Bill Wheats]

You should connect a fuel pressure gauge and start running some tests.
You may have lost your pump or fuel pressure regulator.

[rat]

You don't have to get the air out. It is a return style system. The fuel flows from the tank to the injectors, whatever is left goes to the regulator, then the tank. It is a loop. Sounds like you have other problems.

[S15vortecpwr]

i have never bleed air from fuel systems before

sounds like you have other problems as stated

[interceptorxr7]

If im going to have to replace the fuel pressure regulator then im probably going to upgrade to the MFI unit since I have to tear into the upper intake. The previous owner said that it wouldnt start one day so he replaced the fuel filter and it helped it. Maybe my pump is going out, I dunno. Every fuel pump ive had fail on me have just caused a no start situation.
Once the truck starts you can drive it all day without problems, its just when it sits overnight or for a few hours.

[S15vortecpwr]

i have seen fuel pumps do strange stuff,

put a fuel press guage on it and see what it does

[interceptorxr7]

Ok I went out and got a fuel pressure gauge and tested the pressure, results are as follows:
Gauge on after truck sat all night: 0-5psi
Key on, Engine off: 60psi
During cranking: 45-50psi
Engine on: 56psi
When I shut the engine down: 55psi

So yeah its definitely losing pressure somewhere, and also it took a couple tries to get it going. Im gonna check what the pressure is after I let it sit for the day, but its probably going to be nonexistent again.

[Bill Wheats]

Sounds like the fuel pump regulator or the check valve before the pump may be clogged.
You want to check the pressure with the key on run after a couple of seconds.

[interceptorxr7]

You mean with the key on engine off or with the engine running?

[Bill Wheats]

When you turn the key to RUN (not start) The primer relay will power the pump for about ~4 seconds to build starting pressure.
You want to note that pressure and watch how long it holds. There really is only two ways for it to bleed off without a leak in the fuel injection.
1. Fuel pressure regulator
2. check valve (usually real fast)

If it's leaking down pressure, then you will need to pull the fuel injector cover and look for washing.

[interceptorxr7]

Yeah I did that and got 60psi and it held it for a good 5 minutes until I just started it then it dropped to 57-58 psi while running. In the 2 hours that it sat it went to 54psi. Wheres the cover so I can check it?

[Bill Wheats]

sounds like the problem is gone

[interceptorxr7]

I just checked it, the pressure was down to 30psi... Took a couple tries to get it started, but it started and the pressure went to 60psi.

[Bill Wheats]

Try this next time; Turn the key to run, wait ~5 seconds then hit the starter.

[rat]

The pressure will bleed down after a while. I have an aftermarket regulator on mine and it bleeds down in a couple of seconds. If yours is holding that long you are good. The pressure is also suposed to do that when you idle. This keeps the pressure differential across the injector constant.

[interceptorxr7]

Why would it throw a P0138 code? If the cat was bad wouldnt it throw a catalyst below efficiency code? When that O2 sensor goes bad does it give hard starts?

[interceptorxr7]

I searched around and read that it could be the CTS? If my fuel system is working correctly according to my tests, then this might be the next place to look right? My temp gauge doesnt go above or stays around the line between 100-210. So if my math is correct thats only 155-160 degrees?

[Bill Wheats]

You may have just sucked up some bad gas. I'd add some sea foam to the next few tanks and see if the problem solves.
How old is the P0138?
The PCM doesn't look at the O2 sensors at startup.
Clear the code and see if it comes back.
As for the Cat the simple test when the engine is hot; connect a vac gauge to the intake. Raise the RPMs to about 2.5K and hold it. If the exhust is restricked, then the gauge will drop towards Zero till it chokes out.

[interceptorxr7]

It never did it until I let it sit on an incline with a low tank, so that could be the case.

Thanks everyone for you help

[interceptorxr7]

I dunno how old the code is, but its not causing the CEL to come on. Whats the easiest way to reset the ECM on these trucks? Just remove the negative cable, because I did that before I had it scanned and it was still on there.

[S15vortecpwr]

remove both batt cables and touch them together for about 20 minutes. this desipates the capacitors in the ecm and makes it lose its memory.

[interceptorxr7]

It started right up this morning without trouble. I did notice something though...

1) My MAF was upside down, like the connector was digging into the radiator hose
2) a relay with a whole bunch of wires going to it (3rd one) fell off the clip and was just laying on some coolant hoses.

The battery is disconnected right now, so We'll see if it helps any getting rid of the code.