[Glidinghawk]

My 02 Firebird with the 3.8 will start but will not stay running. It did have a PO174 code earlier so I removed and cleaned the MAF sensor, replaced the alternator do to it acting up, replaced both O2 sensors and the fuel filter. Right now it doesn't have a code but will stall out seconds after it starts.

 

[Injuneer]

See you've also posted this topic as an add-on to another thread..... generally not a good idea.

Same answer I posted in response to your duplicate post:

Have you checked the fuel pressure? P0174 indicates it is running lean. Could be low fuel pressure, due to failing fuel pump, faulty fuel pressure regulator, etc. Have you checked for vacuum leaks?

 

[Glidinghawk]

I haven't checked the fuel pressure yet was my next step, have checked for vacuum leaks but can't keep it running long to check without a gauge.

 

[Firebird4Sure]

A good practice when changing out the fuel filter, is taking a before and after fuel pressure reading.

It gives you a good basis to go off of when you're experiencing this type of issue.

Fuel pressure when cycling the key, should be in the general area of 35-45 psi.

Running, should stabilize at idle around 41psi, and when the engine is under load, it should rise above that number. If not, that's a good indication your FPR is not working properly.

 

[Injuneer]

Fuel pressure when cycling the key, should be in the general area of 35-45 psi.

Running, should stabilize at idle around 41psi, and when the engine is under load, it should rise above that number. If not, that's a good indication your FPR is not working properly.

No. Those are (roughly) the specs for the 3rd Gen port injection and early 4th Gens. In later years GM raised the fuel pressure. The 2000 manual, which is the latest I have, shows the acceptable range for fuel prime pressure as 48-55 PSI for the 3.8L V6 (Ref Vol 2 Part 2 Page 6-1212) . 2002 should be the same.

 

[Firebird4Sure]

My apologies. I just noticed the cutoff year on my sheet was 1997.

 

[Glidinghawk]

Thanks, Gentlemen, I will post as soon as I get the results of the test.

 

[Glidinghawk]

Ok, tested the fuel pressure, after priming the system according to the steps the most that I can get is 20psi.Started the engine and it actually ran for a few minutes and the pressure dropped to 10psi and went into a rough idle. In my return line there is a fitting to test the return I am thinking. Is this where I would determine if it is the regulator or the pump?

 

[Injuneer]

Where is the fitting? The only thing in the return line is the fuel pressure regulator, sitting on a bracket above the supply line, above the rearmost injector. It will have a vacuum line attached to it. There is a "quick" connect, but you would have to insert the factory service tool fuel pressure test shutoff valve. Typically, only a dealer shop would have that.

Offhand, it sounds like the pump.

 

[Glidinghawk]

There are three lines that seem to be going back to the tank. I will try to attach a picture, in the picture there is a line with a green cap. The line is in the wrap with the supply and return line to the tank.

 

[Glidinghawk]

This is the valve

 

[Injuneer]

Says 3/8" on the line. Typically the 3/8" line is the supply line. The return line is typically 5/16" and comes off the fuel pressure regulator. But, there is a third line in the bundle, and that is the EVAP line from the carbon canister at the rear of the car to the EVAP purge system. That is a mix of fuel vapor and air purged out of the canister, and has nothing to do with the fuel rail, injectors, or pressure regulator.

What is written on the green cap?

 

[Glidinghawk]

All it says on the green cap is hand tighten only. At this point I believe that I have to agree with the fuel pump being the issue, unless the FPR could be stuck allowing most of the pressure to return to the tank.

 

[Injuneer]

One way to test for an open regulator is to pinch the return line. Problem is the hose on some of these cars is nylon (plastic appearing), and pinching it can damage it. My 94 is like that (or at least it was before I replaced all the lines with -AN fittings and braided S/S lines). Your lines appear to be rubber, fuel rated. You might be able to pinch the return line to see if the restriction raises the pressure.

Alternatively, while I am not a fan of replacing parts without proving them defective, the fuel pressure regulator should be a lot less expensive, and much simpler than replacing the fuel pump.

 

[Glidinghawk]

Pinched the return line off, no increase in the fuel pressure. Going to order the pump.

 

[Injuneer]

Next step is to decide whether you want to follow the factory procedure (remove exhaust, heat shields, and fuel tank), or cut a "hatch" in the package shelf...... much easier, been needs to be done correctly to avoid damage to the chassis, or expose yourself to the risk of fuel entering the passenger compartment in a wreck.

 

[Glidinghawk]

So, I dropped the tank and replaced the fuel pump, primed the system 3 times and my car fired right up. Seems to have fixed the issue, but don't know why I wasn't getting any kind of code for the fuel pressure. Thanks everyone for the assistance. Read a post about pulling the tank without dropping the rear axle, but found that it was the only way to get the tank out. Not to bad of a job took about 4 hours total from beginning to starting the car.

 

[Injuneer]

No code for fuel pressure. No fuel pressure sensor. There is a sensor for fuel tank (vapor) pressure, but that is something completely different. Where you would have seen a code is for "Fuel Trim System Lean", bank 1 (P0171); bank 2 (P0174).