Question about 2001 Subaru Legacy

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Need to know the fuel system pressure on this engine. What is the set pressure for the regulator?

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Approx 43psi

Posted on Mar 24, 2011

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Fuel system on an 05 mustang is a return less system I'm going to turn it to a return and i have some parts fuel regulator,fittings, dual pumps , fuel line. So I'm i going to need a an electronic pump...


why?
ok the returnless system is totally differernt.
the regulator is in the pump and tank,
not knowing the reason, we can not help you,
running 2 pumps, huh? a lift pump and a pusher pump, what?
1: turbo added
2: for fun?
3: dont like loopless.

the stock system has a loop , its just dont leave the tank.
some cars have a mini tank near the fuel rail.
but most use the tank loop.
the pump is regulated then the return goes back to the main gas tank
immediately,.
the OEM Ford and others, puts a fuel pressure sender there.
because there is no vacuum regulator at the rail
the PCM then reads the pressure and adjusts pulse width to the injectors based on load .
The old system used vacuum to control the pressure directly
the new system Does not do that. at all.
there is no vacuum line going to the fuel tank
and at full throttle there is no vacuum at the injector tips
and as such will squirt too much fuel so the regulator drops the pressures about 6 psi. (from idle pressure)
see?
here is what needs to happen.
you just need a pump that works. and is rated for WOT fuel flow.
and the correct pressure set to factory spec, ford, pressure.
how.:
then use any manual regulator to set the pressure spec, pressure.
it never changes, then the stock fuel pressure sensor will report that
and the PCM does all the heavy lifting (calculations by magic)
that is how it works.

not knowing what you are doing so we can get on the same page makes all this impossible.
you are re-engineering the fuel system. so.... need to know that.

Im here,???
i want to go there. where and why.?
go to amazon dot com, type in greg banish books.
bingo read his books, (i have it on NOOK) for cheap.
it covers how loopless works and how it is tuned, to the finest details.

most folks down know why MPI systems drop 6PSI at wot.
it is because the reg is 1:1 reg for each pound of air pressure drop
so does the fuel pressure.
this magic on the old cars, keeps the differential pressure
ACROSS the injector the same at any throttle angle.
you car don't do that. at all. now.

and if you made it do that , id bet the PCM would go quite nuts.
it wants a static pressure. now.

Jun 06, 2014 | Cars & Trucks

1 Answer

What is the fuel pressure supposed to be


the 3.3L engine fuel system operates at 55 psi (379 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 46 psi (317 kPa). Without vacuum applied to the regulator, the 3.5L engine fuel system operates at 48 psi (331 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 39 psi (269 kPa).---------------------------------------------------------------------------------
Renault CAN Clip

Apr 18, 2013 | Cars & Trucks

1 Answer

I need to replace de fuel presurre sensor in a pontiac montana ,do i have to just replace the sensor ,o the sensor came with the fuel pump?thank you


Replacing the fuel pressure regulator, involves just replacing the regulator at the end of the fuel rail in the engine compartment, but fuel pressure sensor - does this mini-van have a fuel pressure sensor?
replacing the fuel pressure regulator: (1) locate it at the end of the fuel rail in the engine compartment,
(2) relieve fuel system pressure (3) disconnect fuel pressure regulator vacuum line. (4) remove fuel pressure regulator retaining screw (retain for re-use (5) using a shop towel to catch spilled fuel, lift & twist Fuel pressure regulator to remove it from the fuel rail. (6) remove/discard retainer and spacer bracket from the fuel rail. (7) remove fuel pressure regulator from the engine fuel return pipe. (8) remove/discard Fuel Pressure Regulator inlet O-ring (9) Check Fuel Pressure Regulator filter screen for contamination - if contaminated, replace Fuel Pressure Regulator. (10) Lubricate new Fuel Pressure Regulator inlet O-ring with clean engine oil & install onto the Fuel Pressure Regulator inlet. (11) Install the fuel return pipe onto the Fuel Pressure regulator (12) Install new retainer & spacer bracket into the slot on the fuel rail.
(13) Install Fuel Pressure Regulator onto Fuel Rail & tighten Engine Fuel Return Pipe nut to 13 ft-lbs (17 Nm). (14) connect Fuel Pressure Regulator vacuum line, (15) Install Fuel Pressure Regulator attachng screw & tighten to 76 in-lbs (8.5 Nm). (16) Inspect & verify that retainer & spacer bracket is engaged in the slots on the fuel rail. Grasp & pull on the Fuel Pressure Regulator.
to ensure that the Fuel Pressure Regulator is properly seated. (17) inspect for fuel leaks with this
procedure: On 2sec,(holy rollers), off 10sec will be left on, inspect for leaks while running.

Dec 11, 2010 | 2000 Pontiac Montana

1 Answer

Overreving with no power and excessive gas consumption air filter cleaned map sensor replaced fuel pump and filter


usually caused by busted diaphram in fuel pressure regulator allowing fuel to be drawn thru regulator directly to intake manifold. Pull vacuum line off regulator, plug line with golf tee, start car and watch to see if gas comes out of regulator. If yes, turn off car, replace regulator. The regulator sits near the fuel rail on the top of the engine as shown below. I will paste replacement instructions below from autozone.com in case you need to replace the regulator. Please let me know if you have any questions.
jturcotte_421.gif


Removal & Installation

4.2L Engine

  1. Relieve the fuel system pressure.
  2. Remove the air cleaner outlet resonator.
  3. Disconnect the engine wiring harness from the retaining clips at the front of the engine.
  4. Disconnect the fuel pressure regulator vacuum line.
  5. Clean any dirt from the fuel pressure regulator and the surrounding area.
  6. Disconnect the fuel return pipe.
  7. Remove the fuel return pipe retainer.
  8. Remove the fuel pressure regulator retainer.
  9. Remove the fuel pressure regulator.
  10. Inspect the regulator filter screen for contamination. If contaminated, replace the fuel pressure regulator.

To install:
  1. Install the regulator filter.
  2. Install the new O-ring on the fuel pressure regulator.
  3. Lubricate the fuel pressure regulator O-ring with clean engine oil.
  4. Push the fuel pressure regulator into the regulator housing on the fuel rail.
  5. Install the fuel pressure regulator retainer. Tighten the regulator retainer screw to 71 inch lbs. (8 Nm).
  6. Install the fuel return pipe retainer. Tighten the return pipe retainer screw to 71 inch lbs. (8 Nm).
  7. Connect the fuel return pipe.
  8. Connect the fuel pressure regulator vacuum line.
  9. Connect the negative battery cable.
  10. Inspect for leaks:
    1. Turn ON the ignition for 2 seconds.
    2. Turn OFF the ignition for 10 seconds.
    3. Turn ON the ignition.
    4. Inspect for fuel leaks.

  11. Install the engine wiring harness into the retaining clips at the front of the engine.
  12. Install the air intake resonator.

Dec 08, 2010 | 2002 Chevrolet TrailBlazer

1 Answer

Im gettin 11.9 mpg in 92 sonata 6 cylinder(3.0) I was told it could b my brain box. Would that be the engine control unit or the engine control module?


You have an engine control unit, but that is rarely the problem. Is your engine light on? If yes, let me know and I'll send procedures for extracting the trouble codes that may identify the problem.
If no engine light, the first thing I would check is the fuel pressure regulator. Pull the vacuum hose off the regulator and plug it with a golf tee. Start the engine and see if gas comes out the vacuum port on the regulator. Is indicates a busted diaphram. Even if the diaphram is good, I would then borrow a fuel pressure gage and run the tests below to make sure the regulator is working to keep the pressure at 39psi. Let me know if this isn't it or you have more questions.

  1. Relieve fuel system pressure.
  2. Turn ignition switch OFF and disconnect the negative battery cable.
When disconnecting any fuel system hoses, always place a shop towel to prevent residual fuel from spaying.
  1. Disconnect the high pressure hose at the delivery side. Using a fuel pressure gauge and adapter (09353-24000 or equivalent), install the adapter to the delivery pipe.
  2. Connect the negative battery cable.
  3. Activate the fuel pump, by applying battery voltage to the fuel pump drive terminal. Check that there is no leakage from pressure gauge or connections.

jturcotte_284.gif


Fig. Fig. 12: Fuel pump drive terminal location-Excel

  1. Disconnect the vacuum hose from the pressure regulator and plug.


jturcotte_285.gif


Fig. Fig. 13: Fuel pump drive terminal location-Sonata

  1. Operate the engine at idle and check the fuel pressure. Fuel pressure should be 47-50 psi (330-350 kPa).
  2. Reconnect the vacuum hose to the pressure regulator. With the engine idling, fuel pressure should be 39 psi (270 kPa).
  3. If the specified values are not met, make the necessary repairs, as indicated in the diagnosis chart.
  4. Shut the engine OFF. Check that the fuel pressure is maintained at the value indicated in Step 8, for approximately 5 minutes.
  5. Relieve the fuel pressure.
  6. Remove the fuel pressure gauge and reconnect the high pressure hose, using a new O-ring.
  7. Start the engine and check for leaks.

Nov 25, 2010 | 1992 Hyundai Sonata

1 Answer

If i put a little gas in the carberator and fight with my blazer it will start and stay started, but if i leave it for awhile, it will turn over but not start. i cant figure out if it is electric or...


Get a fuel pressure gauge and connect it to the rail for the fuel injectors to read pressure.

If the pressure is too low, it might be a bad fuel pressure regulator or pump:

Fuel Pressure Regulator Removal & Installation 2.2L Engine To Remove:
  1. Relieve the pressure in the fuel system.
  2. Disconnect the negative battery cable.
  3. Disconnect the vacuum hose from the fuel pressure regulator.
  4. Remove the pressure regulator mounting screw.
  5. Remove the fuel pressure regulator assembly with O-ring. Inspect filter screen for contamination. If contaminated, remove and discard.
Fuel pressure regulator removal/installation (2.2L SFI engine) gm-05-22-619.gif

To Install:
  1. Apply clean engine oil to the new pressure regulator O-ring and install the O-ring on the regulator.
  2. Install the regulator on the fuel rail. Apply thread-locker to the mounting screw.
    • Tighten the screw to 106 lb in (12Nm).
  3. Connect the negative battery cable.
  4. Use the following procedure to pressurize the fuel system and check for leaks;
  5. Turn the ignition ON for 2 seconds.
  6. Turn the ignition OFF for 10 seconds.
  7. Turn the ignition switch back ON to run the fuel pump again and pressurize the fuel system.
  8. Check the fuel rail assembly for fuel leaks.
4.3L Engine RPO L35 To Remove:
4.3L (RPO L35) Fuel meter body assembly gm_trk_sil15_02-04_43_fuel_metr_body_assy.gif

  1. Before servicing the vehicle, refer to the Cautions and Warnings in the beginning of this section
  2. Remove or disconnect the following:
    • Upper intake manifold (See: Upper Intake Manifold)
    • Fuel pressure regulator retainer clip (M) and discard the clip
    • Regulator (N) from the housing by twisting and pulling the fuel pressure regulator (N) and using a shop towel to catch any spilled fuel
    • Regulator seal O-ring (R) and discard the O-ring seal
    • Regulator filter (Q) and discard the filter
    • Regulator seal O-ring (P) and discard the O-ring seal
    • Backup ring (O) and discard the ring
  3. Cover the fuel pressure regulator housing to prevent contamination from entering the fuel system
To Install:
4.3L (RPO L35) Fuel meter body assembly gm_trk_sil15_02-04_43_fuel_metr_body_assy.gif

  1. Lubricate the NEW O-ring seals with clean engine oil
  2. Assemble the following new parts to the fuel pressure regulator:
    • Backup ring (O)
    • Regulator seal O-ring (P)
    • Regulator filter (Q)
    • Regulator seal O-ring (R)
  3. Install or connect the following:
    • Fuel pressure regulator with the vacuum tube pointing down
    • Fuel pressure regulator retainer clip (M)
    • Upper manifold
  4. Test drive the vehicle to confirm the repairs
RPO LU3 To Remove:
4.3L (RPO LU3) Fuel meter body assembly gm_trk_sil15_02-04_43_rpolu3_fuel_metr_body_assy.gif

  1. Before servicing the vehicle, refer to the Cautions and Warnings in the beginning of this section
  2. Remove or disconnect the following:
    • Upper intake manifold
    • Fuel pressure regulator retainer clip (E)
    • Regulator (F) from the housing by twisting and pulling the fuel pressure regulator (F) while using a shop towel to catch any spilled fuel
    • Regulator seal O-ring (J) and discard the O-ring seal
    • Regulator filter (I) and discard the filter
    • Regulator seal O-ring (H) and discard the seal
    • Backup ring (G) and discard the backup ring
  3. Cover the fuel pressure regulator housing to prevent contamination from entering the fuel system
To Install:
4.3L (RPO LU3) Fuel meter body assembly gm_trk_sil15_02-04_43_rpolu3_fuel_metr_body_assy.gif

  1. Lubricate the NEW O-ring seals with clean engine oil.
  2. Assemble the following new parts to the fuel pressure regulator:
    • Backup ring (G)
    • Regulator seal O-ring (H)
    • Regulator filter (I)
    • Regulator seal O-ring (J)
  3. Install or connect the following:
    • Fuel pressure regulator (F) with the vacuum tube pointing down
    • Fuel pressure regulator retainer clip (E)
    • Upper intake manifold
  4. Test drive the vehicle to confirm the repairs
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Nov 04, 2010 | 2002 Chevrolet Blazer

1 Answer

I have a 2004 Tahoe which has misfire problems (P0300). I changed the plugs, wires, fuel filter and air filter but problem still exist. The 4 plugs on the passenger side continue to file out and become...


Removal & Installation of fuel Regulators on
4.8L, 5.3L & 6.0L Engine To Remove:
CAUTION
Three styles of fuel pressure regulators and fuel rails will be used in this model year. Each regulator has a different "footprint" that consequently changes the size of the receiving port in the fuel rail. The regulator retaining clips are specific to each rail-regulator design and cannot be interchanged.
chevy_aval15_02-04_fuelrail.gif

  1. Remove the engine sight shield.
  2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure.
  3. Clean the fuel pressure regulator retainer and the surrounding area.
  4. Remove or disconnect the following:
    • Fuel pressure regulator vacuum line.
    • Fuel pressure regulator retainer.
    • Fuel pressure regulator.
  5. Remove the following parts from the fuel rail:
    • Backup ring (10)
    • Regulator Seal O-ring (11)
    • Regulator filter (12)
    • Regulator seal O-ring (13)
To Install:
chevy_aval15_02-04_retainer.gif

  1. Make sure the NEW fuel pressure regulator retainer is the right one.
  2. The tabs (1) are used on the straight vacuum port retainer (2), and the E85-straight vacuum port retainer (3).
  3. The angle vacuum port retainer (4) has no tabs. chevy_aval15_02-04_fuelrail.gif

  4. Install the following parts onto the fuel pressure regulator (9).
    • Backup ring (10)
    • Regulator seal O-ring (11)
    • Regulator filter (12)
    • Regulator seal O-ring (13)
  5. Lubricate the fuel pressure regulator O-rings with clean oil.
  6. Install the fuel pressure regulator and retainer. CAUTION
    Whenever the fuel pressure regulator is removed from the fuel rail NEW O-rings and a NEW retaining clip should be used on reinstallation.
  7. Connect the vacuum line.
  8. Tighten the fuel filler cap.
  9. Use the following to inspect for leaks:
    • Turn ON the ignition, with the engine OFF, for 2 seconds.
    • Turn OFF the ignition for 10 seconds.
    • Turn ON the ignition, with the engine OFF.
    • Install the engine sight shield.
8.1L Engine To Remove:
Fuel pressure regulator vacuum line gm_trk_sub15_fuel_press_reg_vac_line.gif

  1. Before servicing the vehicle refer to the precautions at the beginning of thjs section
  2. Remove the fuel injector sight shield as needed
  3. Relieve fuel system pressure (See: Fuel Pressure Relieving)
  4. Disconnect the fuel pressure regulator vacuum line (A) 8.1L Fuel pressure regulator retainers gm_trk_sub15_81l_fuel_press_reg_retainers.gif

  5. Clean any dirt from the fuel pressure regulator retainer and the surrounding area
  6. Remove the fuel pressure regulator retainer (I)
  7. Remove the fuel pressure regulator (H) from the fuel pressure regulator housing
To Install:
8.1L Fuel pressure regulator retainers gm_trk_sub15_81l_fuel_press_reg_retainers.gif

  1. Install or connect the following:
    • Backup ring (J) on the fuel pressure regulator (H)
    • New large O-Ring (K) on the fuel pressure regulator
    • Regulator filter (L) on the fuel pressure regulator
    • New small O-Ring (M) on the fuel pressure regulator
  2. Lubricate the fuel pressure regulator large O-Ring and the small O-Ring with clean engine oil
  3. Push the fuel pressure regulator onto the regulator housing on the fuel rail
  4. Install a new fuel pressure regulator retainer (I)
  5. Install or connect the following:
    • Fuel pressure regulator vacuum line
    • Negative battery cable
  6. Tighten the fuel filler cap
  7. Inspect for leaks using the following procedure:
    • Turn on the ignition with the engine off for two seconds
    • Turn off the ignition for 10 seconds
    • Turn on the ignition with the engine off
    • Inspect for fuel leaks
  8. Install the fuel injector sight shield
  9. Road test the vehicle to check performance
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Sep 02, 2010 | Chevrolet Tahoe Cars & Trucks

3 Answers

2000 Malibu Starts then looses fuel pressure I have replaced the fuel pump and the fuel pump relay still same problem


Keep in mind that you have several components there:
- Fuel Pump Sender Assembly,
- Fuel Pressure Regulator,
- Fuel Rail Assembly, and
- Fuel Injectors.

1.- Fuel Pump (Sender Assembly) - TESTING
Refer to the accompanying charts for fuel pump diagnosis and testing.

The fuel injection system remains under pressure, even after the engine has been turned OFF. The fuel system pressure must be relieved before disconnecting any fuel lines. Failure to do so may result in fire and/or personal injury.

eb744a2.jpg

Fig. 3.1L engine OBD system check to be done before fuel pump relay circuit diagnosis


26456ba.jpg

Fig. 3.1L engine fuel pump relay circuit diagnosis (1 of 2)


b3b739d.jpg

Fig. 3.1L engine fuel pump relay circuit diagnosis (2 of 2)


db78a73.jpg

Fig. View of the fuel pressure test port (Schrader valve)-3.1L engine

A - 3.1L engine fuel system pressure test (1 of 4)
B - 3.1L engine fuel system pressure test (2 of 4)
C - 3.1L engine fuel system pressure test (3 of 4)
D - 3.1L engine fuel system pressure test (4 of 4)

c8a9798.jpg

Fig. The fuel pump/fuel sender module assembly is mounted in the fuel tank


2.-
Fuel Pressure Regulator - REMOVAL & INSTALLATION

(the fuel pressure regulator, which is located on the fuel rail assembly)

NOTE:
Before removing the fuel regulator assembly, place a clean shop towel under the regulator to catch any fuel drips

  1. Properly relieve the fuel system pressure.
  2. If not done already, disconnect the negative battery cable.
  3. On the 3.1L engine, remove the intake manifold plenum, as outlined in .
  4. On the 2.4L engine, remove the fuel rail. Refer to procedure earlier in this section.
  5. Detach the vacuum line from the regulator.
  6. Place a shop towel under the regulator to catch any fuel that may drip out. Unfasten the fuel pressure regulator retaining screw, then remove the regulator by twisting and pulling it from the fuel rail.
  7. Remove and discard the O-ring seal. Inspect the filter screen for contamination and replace if necessary.
To install:
  1. Prior to assembling the pressure regulator to the fuel rail, lubricate the new rail-to-regulator O-ring seal with clean engine oil.
  2. Place the O-ring on the pressure regulator and install the pressure regulator to the fuel rail.
  3. Install the retainer or coat the regulator mounting screws with an approved thread locking compound and secure the pressure regulator in place. Tighten the mounting screw to 76 inch lbs. (8.5 Nm).
  4. If removed, install the fuel rail assembly to the engine.
WARNING The fuel return pipe must be connected before tightening the regulator retaining screw to prevent the regulator from rotating. Rotation of the regulator could damage the retainer and spacer bracket and lead to a fuel leak at the regulator inlet.
  1. Connect the fuel feed line and return line to the fuel rail assembly, use a backup wrench on the fittings to prevent turning.
  2. Attach the vacuum line to the regulator.
  3. On the 3.1L engine, install the intake manifold plenum.
  4. Connect the negative battery cable. Turn the ignition to the ON position for two seconds, then turn it to the OFF position for ten seconds. Turn again to the ON position and check for fuel leaks.

continue...

May 24, 2010 | Chevrolet Malibu Cars & Trucks

1 Answer

2002 sebring where is the fuel pressure regulator located?


The fuel system is under a constant pressure, even with engine off. before servicing the fuel filter/fuel pressure regulator, the fuel system pressure must be released.
CAUTION The fuel system is under pressure when the engine is running, 58 psi, plus or minus 5 psi. (400 kPa plus or minus 34 kPa). The fuel pump module contains a check valve to maintain some fuel pressure even when the engine is not operating. This will help to start the engine. Before servicing the fuel filter/fuel pressure regulator, the fuel system pressure must be released.

Hope this help.

Apr 02, 2010 | 2002 Chrysler Sebring

1 Answer

I need the operating fuel pressure for a 1989 Rolls Royce Corniche II.


Here it is and all the info you would ever need on the bosch k series.
spacerline.jpg “ This tech told me that the only way the fuse would quit blowing was by unhooking the coil pack. I was stunned at first, since the power to the coil is through a red/light green (R/LG) wire and from a different fuse than the solid red. ” ---> The K-Series fuel injection systems are continuous mechanical fuel injection systems used on a wide variety of European vehicles, including such makes as Volkswagon, Audi, BMW, Mercedes, Porsche, Volvo and Saab. The system is one of the most common fuel injection systems on the market today, but also is one of the least understood.
The K-Jetronic System constantly injects fuel into the engine as long as the car is running and air flow is present to move the sensor plate in the airflow sensor. The sensor plate is connected to an arm that pushes up on a plunger located in the fuel distributor. As airflow changes, the movement of the sensor plate and the plunger increase and decrease the volume of fuel injected into the engine. Since fuel is being injected constantly, fuel pressure will have a direct affect on driveability. As a matter of fact, fuel pressure is the single most critical element when diagnosing driveability problems in the K-Series fuel injection systems. An accurate fuel pressure gauge must be used when testing these systems, with a range of 0 to more than 100 psi. You will also need a digital volt ohm meter (DVOM) that can read milliamps.
You will work with three types of pressures when diagnosing these systems: system pressure, control pressure (also known as counter pressure) and rest pressure.
System pressure is the total fuel pressure produced by the fuel pump on a constant basis. The fuel pump must be able to maintain this pressure during all driving conditions from idle to wide open throttle. As a rule, system pressure will run about 5 to 5.5 bar pressure, or 75 to 85 psi (1 bar = about 15 psi) and the pump should be able to produce a minimum volume of 1 pint in 15 seconds. When deadheaded, the K-Series fuel pump will produce about 1.5 times the system pressure or about 110 to 120 psi. System pressure is a function of volume of fluid moved against a restriction, so to maintain system pressure at the desired level, there must be some type of restriction built into the fuel system. This restriction is more commonly known as the fuel pressure regulator. The fuel pressure regulator restricts the return of fuel to the tank by a calibrated amount, maintaining system pressure at the desired level. On early K-Jet systems, this regulator was a slide valve (also known as a push valve) internal to the fuel distributor. Fuel pressure could be adjusted by adding or removing shims from the valve. On later K-Jet systems, the regulator is the conventional diaphragm type.
Control pressure (or counter pressure) is the pressure that is metered to the top of the fuel plunger on a K-Jet system. By changing the counter pressure, the resistance to plunger movement is changed, allowing enrichment and enleanment of the fuel mixture to the engine. On a car equipped with K-Jet, this pressure is controlled by the warm-up regulator.
The warm-up regulator only compensates for engine temperature and is therefore a rather coarse control of fuel mixture. (Some K-Jet warm-up regulators also have a vacuum port to help with the acceleration enrichment and deceleration enleanment function.) Typical control pressures on a K-Jet warm-up regulator are 55 psi with the engine at full operating temperature and 20 to 30 psi on a cold engine. (The colder the engine, the lower the pressure.)
A car equipped with K-Jet Lambda also changes control pressure with a warm-up regulator (with pressures similar to a plain K-Jet system), but also controls lower chamber pressure in the fuel distributor by bleeding pressure through a frequency valve. By modifying lower chamber pressure, a change in volume of injected fuel is made, enriching or enleaning the mixture. The frequency valve is nothing more than an electrically duty-cycled fuel pressure regulator controlled by an on-board computer in response to an oxygen sensor signal. This system provides a more precise and rapid control of fuel mixture. Typical duty cycle on a properly running engine is 45 percent to 55 percent duty and fluctuating. A quick test of this system is to start the engine and test the frequency valve for vibration or noise -- it should vibrate. Also, unplugging the oxygen sensor will put the system in open loop and fix the frequency valve at a 50 percent duty cycle.
The KE-Jet system provides quicker response and more precise control of fuel mixture than the K-Jet Lambda system and is the current K-Jet system in use. This system uses a device called a differential pressure regulator to control fuel mixture in response to both engine temperature and oxygen sensor signals. In the KE-Jet system, counter pressure is broken down into primary counter pressure and control counter pressure. Primary counter pressure is the pressure applied to the top of the fuel plunger. This pressure stays constant and is the same as system pressure.
Control counter pressure is modified by the differential pressure regulator and is actually the lower chamber pressure in the fuel distributor. By modifying lower chamber pressure, the fuel mixture can be enriched or enleaned in response to temperature and oxygen sensor signals. Typical control counter pressures are 4 to 7 psi less than system pressure on a fully warmed engine and 17 to 20 psi less than system pressure on a cold engine (typical system pressures are 5.0 to 5.5 bar or 75 to 85 psi). The signal to the differential pressure regulator from the computer is measured in milliamps of current. To test this signal, a DVOM must be placed in series with the differential pressure regulator. Typical current values are 80 milliamps cold engine (15k ohm resistor in place of coolant temp sensor to simulate a cold engine condition); 120 milliamps during cranking (this is a crank enrich function to aid starting); and 8 to 12 milliamps warm idle. (Note: always check service manual for values.) These values correspond to the fuel pressures listed. In other words, at 80 milliamps current you should show 17 to 20 psi less than system pressure.
Rest pressure is the fuel pressure maintained in the system by the fuel accumulator after engine shutdown. The fuel accumulator is a large spring-loaded diaphragm that maintains a pressure of about 1.5 to 2.0 bar for 30 minutes or more after engine shutdown. This rest pressure provides for fast restart and prevents fuel percolation or boiling (vapor lock). Always check the service manual for the car line you are working on for proper rest pressures and times. Typical symptoms caused by accumulator problems are extended crank time and hard start hot.
With an understanding of the system and the proper tools, K-Jetronic fuel system service is a straightforward procedure that can keep your service bays full all year long. Give me a call if you have any questions!...did this help? Let me know...dc


May 11, 2009 | 2000 Rolls Royce Corniche

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