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IS THE FUEL PUMP PRESSURE ON 2004 300M CONSTANT OR DOES CHANGE WITH ENGINE SPEED?

I HAVE NO FUEL SUPPLY AT FUEL RAIL. WHEN I CHECKED THE FUEL LINE AT THE TANK THERE IS LOTS OF FUEL THAT COMES OUT WITH VERY GOOD PRESSURE WHEN THE IGNITION IS FIRST TURNED ON. WHEN CRANKING, THE PRESSURE & VOLUME IS DRASTICALLY REDUCED. AT NEITHER TIME THERE IS NO FUEL AT THE FUEL RAIL. IS THIS A PUMP PROBLEM, BLOCKED LINE, COLLAPSED LINE OR SOMETHING ELSE? NO VISIBLE TO FUEL LINE FROM TANK TO INJECTORS.

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  • Cars & Trucks Master
  • 14,585 Answers

Check the voltage at the tank for the fuel pump as you are cranking. If you lose power, replace the ignition switch. Key on and start up for the pump, are two different wires on the switch.

Posted on Nov 16, 2014

  • 5 more comments 
  • noclu3 Nov 16, 2014

    Key on power is 13.7v. Cranking power is 11.2v. The car quit running while driving at 50 mph in 85 degree low humidity weather. No preceding indications of possible problems. Won't restart. No codes except for low system voltage were set after, repeated starting attemps.

  • Randy Ohler Nov 16, 2014

    11 volts is plenty to power the pump. Low voltage is normal after trying to hard. So you have to look for blockage. I have never seen it, but a very clogged fuel filter could be your problem. It is just paper inside of it and could collapse. Most will give good pressure, just not enough volume. One other thing to check would be the fuel pressure regulator. Throw the pressure gauge back on it, turn the key on. It shouldn't drop more than a few pounds over about ten minutes. Then stay steady. When the pump stops running is when to take the readings. I don't have the exact pressure. But it should be around 60 pounds/407kpa's

  • noclu3 Nov 17, 2014

    I hooked up the pressure gauge to the fuel rail and have 50-55 psi while cranking. I don't know why there wasn't any fuel there before but there is now. I did bleed off the air in the line first. The Chysler service manual says 58 psi, +/- 5psi. It also states that the check valve on the output after the pressure regulator is supposed to be there to hold volume not pressure. I did notice though, that after 10 - 15 minutes that there was still around 45 psi. The car still won't start. How can I check that I'm getting power to the coils from the ecm? This engine has a coil on each plug. Could the

  • noclu3 Nov 17, 2014

    I hooked up the pressure gauge to the fuel rail and have 50-55 psi while cranking. I don't know why there wasn't any fuel there before but there is now. I did bleed off the air in the line first. The Chysler service manual says 58 psi, +/- 5psi. It also states that the check valve on the output after the pressure regulator is supposed to be there to hold volume not pressure. I did notice though, that after 10 - 15 minutes that there was still around 45 psi. The car still won't start. How can I check that I'm getting power to the coils from the ecm? This engine has a coil on each plug. Could the 36

  • noclu3 Nov 17, 2014

    OOPS! Our cat jumped on the keyboard & it got sent before I was finished typing! Could the alternator cause this? I did check for compression on cylinders 1 & 2 (both banks) to rule out timing belt. All belts have 80k on them. The night before the car quit running the serpintine belt went bad & also knocked the a/c belt off its pulley. The next morning I removed the a/c belt & replaced the serpintine belt only. The car started, ran and shifted fine. Later that afternoon after I left my sons house it quit & still won't start. We towed it home with a tow strap. About 40 miles. Thanks for all your help so far!

  • Randy Ohler Nov 18, 2014

    The fuel pressure is minimal, but should start the car. 58 pounds would be at key on. The pressure regulator will lose pressure over time, But it's main purpose is to supply enough pressure to push the gas thru the injectors. To check the coils. Pull the easiest on to get to, insert an old plug and ground the side of it to the metal part of the engine, crank it over, if you have spark, Most likely you have spark at all of them. No plug, use a screw driver and lay it close (1/4 to 1/2 inch) the a metal part of the engine. Watch for spark. If not spark, try one more. Still no spark I would go for the crank sensor. By the way, Have you had the codes read? I wouldn't discount the timing belt with 80K miles on it. But most are built to last 120K+. Your crank sensor is behind the harmonic balancer, But the wires come out the side, Since you threw a belt, this would be something to look at also.

  • Randy Ohler Nov 18, 2014

    Just a note, Fuel pumps will push 90+ pounds of pressure without the regulator.

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Changed my fuel pump on my 06 ford 500 now I can only start if I hold the fuel reset and it doesn't stay running for very long why does that happen how can I fix this


By fuel reset do you mean inertia fuel cut off switch ? Why did you change the fuel pump ? Are you aware of the fuel pump driver module ! Your vehicle has a electronic returnless fuel system . It is computer controlled , has a fuel rail pressure an temp. sensor .
The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to determine the pressure difference between the fuel rail and the intake manifold. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail. Both pressure and temperature signals are used to control the speed of the fuel pump. The speed of the fuel pump sustains fuel rail pressure which preserves fuel in its liquid state. The dynamic range of the fuel injectors increase because of the higher rail pressure, which allows the injector pulse width to decrease.
Inertia Fuel Shutoff (IFS) Switch The IFS switch is used in conjunction with the electric fuel pump. The purpose of the IFS switch is to shutoff the fuel pump if a collision occurs. It consists of a steel ball held in place by a magnet. When a sharp impact occurs, the ball breaks loose from the magnet, rolls up a conical ramp and strikes a target plate which opens the electrical contacts of the switch and shuts off the electric fuel pump. Once the switch is open, it must be manually reset before restarting the vehicle. Refer to the Owner's Literature for the location of the IFS.
The FPDM receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information on Fuel Pump Control and the Fuel Pump Monitor, refer to Fuel Systems in this section.
Electronic Returnless Fuel System (ERFS) The electronic returnless fuel system consists of a fuel tank with reservoir, the fuel pump, the fuel rail pressure (FRP) or fuel rail pressure temperature (FRPT) sensor, the fuel filter, the fuel supply line, the fuel rail temperature (FRT) sensor, the fuel rail, the fuel injectors, and a Schrader valve/pressure test point. For additional information on the fuel system components, refer to Engine Control Components in this section. Operation of the system is as follows:
  1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
  1. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.
  1. The PCM commands a duty cycle to the fuel pump driver module (FPDM).
  1. The FPDM modulates the voltage to the fuel pump (FP) required to achieve the correct fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. For additional information refer to Fuel Pump Control and Fuel Pump Monitor.
  1. The fuel rail pressure (FRP) sensor provides the PCM with the current fuel rail pressure. The PCM uses this information to vary the duty cycle output to the FPDM to compensate for varying loads.
  1. The fuel rail temperature (FRT) sensor measures the current fuel temperatures in the fuel rail. This information is used to vary the fuel pressure and avoid fuel system vaporization.
  1. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by the PCM.
  1. A pressure test point valve (Schrader valve) is located on the fuel rail and is used to measure the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.
  1. There are 3 filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/Schrader valve.
  1. The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.
  1. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
Go to you tube , there are videos how this system works an to test it .

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1 Answer

Fuel line location?


You did not mention type of vehicle but will give a general answer. If older vehicle with carb then fuel line comes from fuel pump right on engine and goes into carb with a fairly large metal line. On anything newer there are several lines because fuel injection requires constant high pressure in system. So fuel is pumped from a pump located in tank all the way through large line down length of car to fuel rail under hood. The fuel rail has a pressure regulator and whatever fuel is not needed is pumped back to tank in second line. These lines run together all the way from tank and are fairly large diameter. Bigger than brake lines. So look for two lines coming under vehicle to top of engine.

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How do I change the fuel pump in a 2009 GMC Acadia


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1 Answer

Where is the fuel sensor on a 1997 jeep grand cherokee


Have you checked the fuel filter? I would pull the fuel line apart before the filter to see if the pump is putting gas into the line. With key on, the pump should run for 2 seconds to pressurize the lines and fuel rail. And when the engine is cranking over, the pump should be running constant and putting gas into the line. If gas shoots out, possibly the filter is clogged or the fuel pressure regulator on the fuel rail is defective. If no gas comes out, possibly the pump filter sock is clogged or the pump is defective.
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Fuel pressure 1998 jeep grand cherokee 4.0 L V6


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.
  1. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to test port pressure fitting on fuel rail (Fig. 7).
  2. Remove vacuum line from pressure regulator.
  3. Start the vehicle.
  4. Note gauge reading. With vacuum line disconnected, fuel pressure should be approximately 269 kPa (39 psi).
  5. Connect vacuum line to pressure regulator. Note gauge reading. Fuel pressure should be approximately 214 kPa (31 psi).
  6. 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.
  7. 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.
  8. If fuel pressure is above specifications, inspect the fuel return line for kinks and blockage.

Capacity Test

  1. Remove the cap from the pressure test port in the fuel rail.
  2. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the pressure fitting on the fuel rail (Fig. 7).
  3. 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.
  4. 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.

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1 Answer

94 z28 chevy camaro fuel pressure check valve location and is there any other names for this item I recently installed a stock replacement fuel pump in my camaro I run 35psi which is low at idle unplug the...


do you mean the pressure relief valve, this is located normally on the low pressure or return side of your fuel rail, this is designed to maintain fuel pressure in your fuel rail constant, e.g. steady running requires steady pressure, acceleration requires increased pressure controled by engine vacuum, if it was on the supply line you can not regulate the pressure supplied to the injecters. stopped engine requires no pressure so the pump gets turned off with the ignitionf

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1 Answer

Was having trouble with my 1998 GMC 1500 5.7 with it dieing would restart and run for a few but got worse dieing and not starting so i took it in for a diagnostic test they said it had low fuel pressu


The fuel pump in the gas tank and the fuel pressure regulator are what controls fuel pressure-the pump builds pressure in the lines and the fuel rail on the engine, and when pressure is correct the pressure regulator keeps it constant by controlling the fuel return line from the fuel rail to the tank.
If your fuel filter is clean and not plugged, it sounds like the pump or the pressure regulator needs to be replaced. Even though the pump is working, it may be weak and failing. Some vehicles have the FPR inside the tank with the pump-You will have to check where yours is located. If it is located on the fuel rail, it can be checked to see if it is working right.
Good luck.

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1 Answer

Is fuel pump connected to the speedometer in any way??


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1 Answer

Where does the fuel line at the end of the injector rail run to on a 1991 rodeo


All fuel injected systems have a feed line to the engine's fuel rail to keep constant pressure at the injectors fuel entry point. A tiny bit goes into the engine cylinders when the computer allows the injector to open by a signal pulse.
And the rest of the fuel in the rail is pushed by the pump back to the gas tank by a Fuel Return Line (what you are seeing and the other line in all fuel injected systems.
Think about it. The pump is running constantly (with the engine), so to avoid pressure build-up, or having to continually turn the pump on and off, voila, put in a return line after a pressure regulator gets the pressure right in the rail, and let the excess go back to the tank. Pretty good idea: no stale gas left there on top of engine. I hope this helps you understand it better.

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3 Answers

1999 Grand Cherokee Limited, 95,000 miles, 6 cyl engine The Jeep stumbles, coughs and almost backfires when slowly accelerating from an idle speed. This occurs during the first 5-10 minutes the vehicle...


Hi.

If fuel pressure is low and you have already replaced the fuel pump, then the problem is usually the fuel pressure regulator. The pressure regulator is in same assembly with fuel filter. The assembly is located to the fuel tank, bolted to the truck's frame. The pressure is tested connecting a gauge like this : Set Sealey VSE952 to the port on the fuel rail. The pressure on Grand Cherokee must be around 49 psi plus or minus 5 psi. If engine runs but pressure is below 44.2 psi , check for a blockage in fuel supply line between fuel rail and fuel pump module (e.g.kinked line). If the line is not blocked, replace fuel pressure regulator and filter. Test pressure with and without fuel cap on.

Another test to be done is reading pressure, then shutting the engine off with the gauge connected. If pressure goes down too quick, then the regulator is defective. After 5 minutes the pressure should not go below 24 psi. If it does replace the regulator.

If regulator is OK check for leaks at the injectors that can cause fuel pressure drops.To check for injectors leakage clamp off the rubber hose of the pressure gauge tool between fuel rail and the port. If pressure staysr above 24 psi and before was dropping, then a fuel injector or the fuel rail is leaking.

Below a diagram representing the fuel rail and test port. The engines from same years like your six cylinder have the port and rail in the same position.


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Regards.

Ginko

Aug 04, 2011 | 1999 Jeep Grand Cherokee

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