4.0 Fuel Pressure
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Joined: Dec 2006
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From: Kitchener,Ontario,Canada
fo
Ford spec ; this from Haynes manual
KOEO 35-45 PSI
Idle pressure vacuum disconnected 35-45 PSI
Idle pressure vaccum connected 30-35 PSI
Open loop control should not cause the engine to run lean, since the injector pulse width is 10 times (or sometimes more) what it is with a warmed up engine in closed loop operation. This mode is operational for less than 5 mins, even in cold weather. You wont burn your valves during open loop, the engine temp, fuel trim & load factor are too low or rich for this to occur.
More important for your 02 sensors to be in top shape than the fuel rail pressure to be within 1-2 PSI. The O2 sensor is ultimately (with other engine sensors) what governs the AFR @ 14.66:1. This EEC IV or V ford system is adaptive & if fuel rail pressure is 35 PSI not 45 PSI the P/Width will be a little longer to correct the AFR & maintain 14.66 :1 ratio. I believe this accurate fuel control is one reason which helps these engines to be able to run one set of plugs for 100,000 miles or more !
HTH,
Aeroman.
Originally Posted by Aerostar1
I have always been impressed with Ford fuel injection versus GM. I took GM forever to catch up with Ford's tuned runner length, port fuel injection systems. I had several vehicles with GM's Throttle Body systems. They were an improvement over a carb, but not nearly as good as the tuned runner length, port fuel injection systems that Ford had. This was back in the 80's and 90's.
I don't mean to be particular about this fuel pressure, but it is important that it is correct to within 1-2 psi in the open loop modes. I have messed around with adjustable pressure regulators, and 1-2 psi makes a big difference. The injectors don't control the fuel flow regardless of pressure (like carbs), it is a function of BOTH the pulse width received from the ECM AND the fuel pressure. The ECM depends on the fuel pressure being a constant pressure drop across the injector at all times. I just want to know what is the constant pressure drop that the system is designed to operate with. It appears to be 39 psi, but I have not seen a specific value in the manual anywhere. In the open loop modes, if the pressure is running low, I could run the chance of the engine running lean. I just put new heads on this motor and I don’t want to burn the valves or anything.
I don't mean to be particular about this fuel pressure, but it is important that it is correct to within 1-2 psi in the open loop modes. I have messed around with adjustable pressure regulators, and 1-2 psi makes a big difference. The injectors don't control the fuel flow regardless of pressure (like carbs), it is a function of BOTH the pulse width received from the ECM AND the fuel pressure. The ECM depends on the fuel pressure being a constant pressure drop across the injector at all times. I just want to know what is the constant pressure drop that the system is designed to operate with. It appears to be 39 psi, but I have not seen a specific value in the manual anywhere. In the open loop modes, if the pressure is running low, I could run the chance of the engine running lean. I just put new heads on this motor and I don’t want to burn the valves or anything.
KOEO 35-45 PSI
Idle pressure vacuum disconnected 35-45 PSI
Idle pressure vaccum connected 30-35 PSI
Open loop control should not cause the engine to run lean, since the injector pulse width is 10 times (or sometimes more) what it is with a warmed up engine in closed loop operation. This mode is operational for less than 5 mins, even in cold weather. You wont burn your valves during open loop, the engine temp, fuel trim & load factor are too low or rich for this to occur.
More important for your 02 sensors to be in top shape than the fuel rail pressure to be within 1-2 PSI. The O2 sensor is ultimately (with other engine sensors) what governs the AFR @ 14.66:1. This EEC IV or V ford system is adaptive & if fuel rail pressure is 35 PSI not 45 PSI the P/Width will be a little longer to correct the AFR & maintain 14.66 :1 ratio. I believe this accurate fuel control is one reason which helps these engines to be able to run one set of plugs for 100,000 miles or more !
HTH,
Aeroman.
Last edited by Aeroman59; Feb 18, 2007 at 04:46 PM. Reason: in
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Originally Posted by khantyranitar
Wideband O2 sensors are used in production vehicles. Almost all Nissans, Toyotas, Hondas and Ford Made after 2003 use wideband O2 sensors, also known as fuel/air sensors. Our trusty Aerostar will not support wideband O2 sensors, the computer would need to be reflashed. BTW, the computer does make its decisions based upon preprogrammed pulse width, but they are part of a chart that uses data from the MAF sensor. So while the computer cannot monitor the actual mixture, it is not totally blind. Also, it does still read the sensor, and tries to prevent an overly lean mixture. This is how lean codes are set. If the sensor reads a lean condition during WOT, it sets a code. So long as you are getting at least 38 psi under a similated WOT, you should be fine.
That's right. I forgot about the MAF sensor. Still an open loop situation, but the ECM is getting some feed back.
I've got another question about the Aerostar ECM. How does it pinpoint a misfiring cylinder. I had a #5 cylinder misfire code (which I've corrected). Does the ECM determine this from "blips" in the crank position sensor, or does it listen to the knock sensor or something else?
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
no knock sensor in the 4L OHV...
Ford recommends clearing KAM when fuel pressure regulator replaced per service info
from Ford Service DVD
Misfire Monitor
The Misfire Monitor is an on-board strategy designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. The Misfire Monitor will be enabled only when certain base engine conditions are first satisfied. Input from the ECT, MAF, and CKP sensors is required to enable the monitor. The Misfire Monitor is also performed during on demand self-test.
The PCM synchronized ignition spark based on information received from the CKP sensor. The PIP signal generated is also the main input used in determining cylinder misfire.
The input signal generated by the CKP sensor is derived by sensing the passage of teeth from a 36 minus 1 tooth crankshaft position wheel mounted on the end of the crankshaft.
The input signal to the PCM is then used to calculate the time between PIP edges and also crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value and other criteria is met, then the suspect cylinder is determined to have misfired.
Misfire type A:
Upon detection of a Misfire type A: (200 revolutions) which would cause catalyst damage, the MIL will blink once per second during the actual misfire, and a DTC will be stored.
Misfire type B:
Upon detection of a Misfire type B: (1000 revolutions) which will exceed the emissions threshold or cause a vehicle to fail an inspection and maintenance tailpipe emissions test, the MIL will illuminate and a DTC will be stored.
The DTC associated with multiple cylinder misfire for a Type A or Type B misfire is DTC P0300.
The DTCs associated with an individual cylinder misfire for a Type A or Type B misfire are DTCs P0301, P0302, P0303, P0304, P0305, P0306, P0307, and P0308.
Ford recommends clearing KAM when fuel pressure regulator replaced per service info
from Ford Service DVD
Misfire Monitor
The Misfire Monitor is an on-board strategy designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. The Misfire Monitor will be enabled only when certain base engine conditions are first satisfied. Input from the ECT, MAF, and CKP sensors is required to enable the monitor. The Misfire Monitor is also performed during on demand self-test.
The PCM synchronized ignition spark based on information received from the CKP sensor. The PIP signal generated is also the main input used in determining cylinder misfire.
The input signal generated by the CKP sensor is derived by sensing the passage of teeth from a 36 minus 1 tooth crankshaft position wheel mounted on the end of the crankshaft.
The input signal to the PCM is then used to calculate the time between PIP edges and also crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value and other criteria is met, then the suspect cylinder is determined to have misfired.
Misfire type A:
Upon detection of a Misfire type A: (200 revolutions) which would cause catalyst damage, the MIL will blink once per second during the actual misfire, and a DTC will be stored.
Misfire type B:
Upon detection of a Misfire type B: (1000 revolutions) which will exceed the emissions threshold or cause a vehicle to fail an inspection and maintenance tailpipe emissions test, the MIL will illuminate and a DTC will be stored.
The DTC associated with multiple cylinder misfire for a Type A or Type B misfire is DTC P0300.
The DTCs associated with an individual cylinder misfire for a Type A or Type B misfire are DTCs P0301, P0302, P0303, P0304, P0305, P0306, P0307, and P0308.
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