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Re: FUEL PUMP PRESSURE
Fuel pressure should be around 40-44 PSI at idle, if u replace the pump the correct pump has preset pressure, if the pressure is to high then the regulator may be stuck, it is near the injectors on the fuel supplu rail.
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You should have a test port on the Fuel Supply rail, use a tool from a local auto parts "Tool Loaner program" where you can borrow tools for free,w/a deposit of course,then follow the steps provided;
MPI Fuel System Pressure Test
The MPI fuel system used in vehicles equipped with a 4.OL engine employs a vacuum balanced pressure regulator. Fuel pressure should be approximately 55-69 kPa (8-10 psi) lower with the vacuum line attached to the regulator than with the vacuum line disconnected. System fuel should be 214 kPa (31 psi) with the vacuum line connected to the regulator and 269 kPa (39 psi) with the vacuum line disconnected. CAUTION: Some fuel may be discharged when connecting fuel gauge to fuel rail.
Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to test port pressure fitting on fuel rail (Fig. 7).
Remove vacuum line from pressure regulator.
Start the vehicle.
Note gauge reading. With vacuum line disconnected, fuel pressure should be approximately 269 kPa (39 psi).
Connect vacuum line to pressure regulator. Note gauge reading. Fuel pressure should be approximately 214 kPa (31 psi).
If fuel pressure is not approximately 55-69 kPa (8-10 psi) higher with vacuum line removed from regulator, inspect pressure regulator vacuum line for leaks, kinks or blockage. CAUTION: Fuel pressure will rise to as much as 655 kPa (95 psi) when the fuel return tine is pinched shut, shut engine down immediately after pinching oft fuel return line.
If fuel pressure is low, momentarily pinch shut the hose section of the fuel return line. If fuel pressure remains low, inspect the fuel supply line, fuel filter, and fuel rail inlet for blockage. If fuel pressure rises replace fuel pressure regulator.
If fuel pressure is above specifications, inspect the fuel return line for kinks and blockage.
Remove the cap from the pressure test port in the fuel rail.
Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the pressure fitting on the fuel rail (Fig. 7).
Start the vehicle. Pressure should be approxi- mately 214 kPa (31 psi) with the vacuum hose connected to the pressure regulator and 269 kPa (39 psi) with the vacuum hose removed from the pressure regulator.
If the pressure is not to specification, check the following before replacing the fuel pressure regulator:
4a - Inspect the fuel supply and return lines/hoses for kinks or restricting bends
4b - Check the fuel pump flow rate. A good fuel pump will deliver at least 1 liter of fuel per minute with the fuel return line pinched off. If the fuel pump does not pump adequately, then inspect the fuel system for a plugged fuel filter or fuel pump inlet filter (sock). Fuel pump flow rate can be done by connecting one end of an old A/C gauge hose to the fuel test port on the fuel rail and inserting the other end of the hose into a container of at least 1 liter capacity. Run the fuel pump by installing a jumper wire into diagnostic connector terminals D1-5 and D1-6. Be sure to pinch off the fuel return line or most of the fuel will be returned to the fuel tank.
Check your fuel pressure it should be 60-66 psi with key and engine off.These engines need at least 52 psi to open the popet valve inthe injectors to allow fuel thru.If you don't have 52 psi then replace the fuel pump and filter.
First clean the idle air control valve with a non-chlronated brake cleaner or replace it with a new one.If that did'nt help check your fuel pressure it should be 9-13 psi with the engine running anything less you will need to replace the fuel pump and fuel filter.
Hi, don't you have the 4.3 liter engine with sequential fuel injection? If yes, then your injectors are not working. Can you hear them click when the engine is cranked? If not, the problem may be with the camshaft position sensor or possibly the anto-theft system. Is the secuiity light on? Is the engine light staying on? Please check fuses 5 and 10. See diagram below.
The only thing left in this system is the fuel pressure regulator. You need to check pressure before the regulator and after the regulator if there is the problem then you need to replace it. I hope this helps. Don't forget to rate my answer.
replace your MAP sensor(manifold absolute pressure) the map sensor is the computer for your fuel pressure regulator telling how much pressure. Unless your tahoe runs like **** going up hill than it inevitably your fuel pump
I have a 97 gmc sierra .This truck is the same as the chevy ok.Its a 350 5.7 liter 4x4 Z71.I took it to auto zone which was my first mistake.They put it the scanner and said bad O2 sensor.Ok so which one is it i said.They dont know.Well there four (4) O2 sensors in this truck i hope you know that.I had to replace all four of them before i had to take it to a real shop.It seems the fuel pump i replaced a week earlier with an auto zone fuel pump was bad.Ive changed my feul pump 4 times now and have 235000 miles on still running.You need to get your fuel pressure checked.It should be 65 psi to start it and 55 psi to run it.If the pressures are good it could be a different O2 sensor or maybe the mass air flow senor.My last option would be the fuel pressure regulator because it seems to be a waste of time and money.I would get that fuel pressue checked first.Good luck.