Fuel Pump or Fuel Regulator? Something else?

[decathlondriver]

I'm working on a 2001 Alero. While trying to start, it fires every now and then. I have put fuel into the intake and gotten it to start right up. I have replaced the fuel filter as well. I turned the key on and had the fuel line cracked open and it shot out a stream of fuel. The flow rate was similar to what you would see coming out of a drinking fountain. I have pulled the plug and it is dry.

I am left to believe the problem may be in the fuel pump or regulator. I'm not sure if the fuel pump can be working, but at too low of a pressure? And how do I check either of these? Could it be anything else?

[GTP Dad]

Check the fuel pressure. Connect a fuel pressure guage to the fuel rail. It looks like a fitting on a bicycle tire. If it is greater than 40 PSI you should be fine. If it is less then I suspect the fuel pressure regulator. It could be the fuel pump but the regulator is cheaper and easier to replace. Check the fuel pressure first and that should lead you to the issue.

If the fuel pressure is good however you may have an ecm issue that it is not sending signals to the injectors to open at the proper time. I don't suspect ignition issues but it could be a wiring problem

[decathlondriver]

Where is the shrader (sp?) valve at? Also, is the fuel pressure regulator the vaccumm controlled valve like thing that sits at the end of the fuel rail under the manifold? Finally, how much is a new fuel pressure regulator? pump?

Thank you so much for your quick response. It is very much appreciated!

[BNaylor]

It would be helpful if you could list the engine you have in your Alero.

If you have a 3.4L the Schrader valve is located on the rear fuel injector rail (right side of engine). The fuel pressure regulator would be located on the forward fuel injector rail (left side of engine) right by the UIM and throttle body.

[decathlondriver]

I pushed in the schrader valve earlier today with the key in the 'on' position and it sprayed for less than a second, and then nothing came out. I unhooked the returnline back by the filter and turned the key on, and fuel came out of this line while the pump was heard running. It was not at the same pressure that the fuel came out of the filter though. I am going to see if I can get a hold of a pressure gauge to put on the schrader valve tonight and give it a try. So far I am thinking that the pressure regulator is stuck halfway and letting the fuel bypass.

Do the injectors work off pressure? I guess the real question here is, if the pressure is below 40psi, say 30psi, would any fuel get sprayed into the engine? Also, just by looking at this system, am I right in assuming that the pressure regulator is on the output side of the fuel rail? So that when the rail hits a certain pressure it bleeds off to maintain that pressure with vaccum assist?

Once again, thanks for your help. I'm learning a lot.

[BNaylor]

Originally Posted by decathlondriver

I pushed in the schrader valve earlier today with the key in the 'on' position and it sprayed for less than a second, and then nothing came out. I unhooked the returnline back by the filter and turned the key on, and fuel came out of this line while the pump was heard running. It was not at the same pressure that the fuel came out of the filter though. I am going to see if I can get a hold of a pressure gauge to put on the schrader valve tonight and give it a try. So far I am thinking that the pressure regulator is stuck halfway and letting the fuel bypass.

Do the injectors work off pressure? I guess the real question here is, if the pressure is below 40psi, say 30psi, would any fuel get sprayed into the engine? Also, just by looking at this system, am I right in assuming that the pressure regulator is on the output side of the fuel rail? So that when the rail hits a certain pressure it bleeds off to maintain that pressure with vaccum assist?

Once again, thanks for your help. I'm learning a lot.

Lynn (GTP Dad) suggested checking your fuel pressure but you did not specify your engine size. The 2.2 Ecotec and 3.4L V6 have different fuel pressure specs. For example the 3.4L will typically have at least 55 psi fuel pressure with ignition to on (not start, pump prime). With engine running the pressure will be higher with vacuum disconnected off the fuel pressure regulator. With engine idling if you see a change of more than 7 psi by pulling the vacuum line off and on then the fuel pressure regulator is suspect. See pic below:



Good luck!

[decathlondriver]

I ended up trying pinching off the return line to see if I could simulate holding pressure. And it still did not start. I still was not sure enough of the diagnosis to spend the money on a pump or a regulator. I ended up taking it to the dealer. I guess the ignition something or another was not sensing the right key and such not letting the injectors work. So it had had nothing to do with the pump or the regulator. I definitely should have paid more attention to the injectors to see if they were actually working. The problem is, they are so difficult to get to. Anyhow, thank you all for your help. I learned alot.

[BNaylor]

The Passlock anti-theft deterrent system disables the fuel system. So if you are having Passlock problems that may be the reason for your problem. Most Passlock problems are the key cylinder which is part of the ignition switch or the body control module (BCM).

The only way to access the fuel injectors is to remove the upper intake manifold.