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2000 Monte Carlo SS proper fuel pressure?

I want to check the fuel pump pressure on my SS so I called the dealer and was told 55 P.S.I. while engine is cranking. I don't know how to prevent the engine from starting while cranking. I do have 45 P.S.I. while running with vacuum line at regulator hooked up and 55 P.S.I. with it disconnected. What is the proper pressure and procedure? I can't seem to find that info anywhere. Thanks for your replies in advance.


  • edited May 2008
    for what reason are you checking fuel pressure?
  • edited May 2008
    Mechanic said pressure was on low side at 45 P.S.I. which it still is now after replacing fuel pump. I installed an aftermarket fuel pressure regulator and the fuel pressure dropped 5 P.S.I. and the performance dropped with it. I put the original one back in and performance went back up. I actually suspect a faulty injector but need to rule out the fuel pressure regulator first. I actually found moisture in one injector connector. After I cleaned and dried it my light throttle stumble went away but I can still hear a light misfire sound in the exhaust at light steady throttle and overall performance is down. I thought maybe if the aftermarket fuel pressure regulator reduced performance by dropping fuel pressure 5 P.S.I. then maybe raising it 5 P.S.I. would put me back on track. So I need to verify or rule out this theory by properly testing fuel pressure. I hope this clears things up a little. Thanks
  • edited May 2008
    A dirty fuel filter will drop fuel pressure. Try a can of Techron Fuel Injector Cleaner in a tank of gasoline. A 5 psi lower fuel pressure doesn't seem enough to be causing your problem. I would expect to see such a problem, possibly, under hard acceleration, not at idle.
    Haynes or Chilton's Repair Manuals are sources of instructions on how to check for fuel pressure, with vacuum connected to the fuel pressure regulator, or not connected. It will, also, have the specified fuel pressure values. You can acquire such a manual?
  • edited May 2008
    Thanks for the responses on my SS issue. The fuel filter is a year old, and yes it does'nt have the pick-up it always had. On an upgrade you rarely had to push more on the accelerator to climb the hill. Now you have to push down a decent amount and it kicks down one gear and sounds real throaty through the air intake. It kind of feels like the difference between a car full of people and luggage (and maybe a small trailer) and just one person in the car (no trailer or luggage)! I have not had good luck with generic manuals. I usually break down and get the factory shop manuals but, I don't want to spend the money right now. My Daughter is getting married this summer so I have to pinch pennies!
  • edited May 2008
    Your public library has FREE automotive repair information, in book form and on line. Some libraries have free access to, for free. Ask a liberrian.
    Test the fuel pressure with the engine under load. You can load the engine by putting the A/T into DRIVE and raise the engine speed to 2,000 rpm. Or, you can drive the car (with the fuel pressure gauge on a long hose and laid on the windshield), and load the engine by keeping pressure on the brake, and observe fuel pressure.
    The performance problem may be in the ignition system, or the fuel injectors. A repair manual (of any type) could help you troubleshoot.
  • edited May 2008
    Your fuel pressure is regulated by, as you've seen, a fuel pressure regulator. To check the pressure, you'd want to know the pressure with the regulator regulating, and with it not regulating. Not regulating might be considered the raw pressure the fuel pump is capable of supplying, as compared to the pressure the regulator regulates to.

    The "pressure while cranking" might be more appropriately called "unregulated pressure". You can measure it by simply removing that which operates the regulator, which is engine vacuum. If you remove the vacuum hose, the regulator is rendered inoperative. It's much simpler though, to just measure the fuel pressure with the ignition switch on but with the engine not running or cranking. Just turn the key on, don't try to start the engine, and read the pressure. The pump will only run for two seconds or so, so read the pressure quickly. If you miss it, turn the key off and try it again.

    As for regulated pressure, as you've seen, just read it with the engine running. If you have 45 psi with the engine running, I'd suspect you have no problem with fuel pressure. If you can't find what the pressure should be, you haven't tried very hard. Check a Haynes manual for what your running fuel pressure should be. I'd guess 45 psi is plenty.
  • edited May 2008
    I replaced the fuel filter to rule that out. I am going to my local Chevy Dealer next to ask them the proper procedure and if need be I'll purchase a new fuel pressure regulator. Just to let you know, I've been putting STP injector cleaner or gas treatment in the gas regularly since the car was new. I will keep you folks posted. Thanks...
  • edited May 2008
    The Chevy Dealer said 55P.S.I. when key first turned on or at idle with vacuum line disconnected! I'm at 55P.S.I. so pressure to the injectors is good. Part throttle acceleration is ok since I cleaned the one injector connector. Overall performance way down. Intake very throaty. I noticed what looked like a cloud of blue smoke behind me when I first punch it, also I smell rotten egg smell also. The only time I ever smelled that was after I cleaned the throttle body. Could to much fuel be the issue? My daughters Saturn used to do that because of a faulty temp sensor telling the computer the engine was always cold(thought it was blueish but was mostly blackish). Gas mileage is down overall on the SS. I actually replaced the sensor on the SS because the temp guage in the dash was reading a little high. It reads ok now as far as the guage goes. I probably replaced it not long before the problems started and it is possible the cloud is blackish. I will check further. Lastly I have noticed a very slight lifter tick as it drops to idle?? I have been very religous on my oil changes, 3000miles or less. The car has 126,000miles on it and it never burned oil! I'll keep plugging away at it so hopefully other people won't have to!
  • edited May 2008
    There are usually two engine temperature sensors, one for the gauge and one for the computer. The Coolant Temperature Sensor is usually right in the same vicinity as the gauge temperature sensor.

    Modern PCM computers do adapt to the conditions of the engine, i.e. they learn the best injector pulse width to arrive at the correct air/fuel ratio. If you change a part the computer has to relearn the correct values for fuel map. This may take some time.
  • edited May 2008
    I did'nt notice a second sensor in the area. I'm sure it would look kind of like the one I replaced. However, Here is the list of parts replaced: TPS, MAF, Plugs, plug wires, fuel pump, fuel filter, put original coil packs back on (nothing wrong with them, thats another story!), upper intake gasket, throttle body gasket, tested ICM, crank sensor, cam sensor, and just now the battery. My wife says that the car is ticked off at me for taking her to Belle Tire for tires, struts, strut tops, and an alignment! She had all these strange men violating her! Ha! Maybe I best keep my hands off for a couple of weeks, and drive her like my wife does! Thanks for the input!
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