Fuel Pressure Specs?

Check the fuel pressure with and w/o vacuum-if you pull the vacuum line from the regulator and there's fuel in it-replace the regulator-also test out the idle air control speed motor/throttle position sensor and EGR valve-

Six cylinder front wheel drive automatic 161,000 miles.

My car has the 3.0L OHV engine. I have been experiencing a loss of power and "miss" at highway speeds since I have owned the vehicle. I own both the Ford shop manual and the Ford emission control and diagnostic manual. Both show different specs for my fuel pressure. The shop manual says 50-56 psi (350-380kpa). The emission diagnostic manual says 39-65 psi (270-450kpa), both koer. I have monitored the fuel pressure while driving with my scan tool and it stays near 270 kpa and fluctuates slightly over and below that number. Turning the A/C on is when the problem is most noticeable, and I do not see a rise in fuel pressure when I do. I am thinking I should check the fuel pump driver module as I have already replaced the pump with another unit (used). Also, what spec should I look at?

39-65 psi is the correct spec for the pulse width modulated system.

So what is the 50-56 psi specs for in the Ford shop manual? Alldata.com lists both of these specs on their site for this car.

The 55 to 60 spec is for a vehicle that does not have PWM fuel pressure.

I assume you did because you said you have a fuel pump driver module which is only used with PWM.

So then is it normal for fuel pressure to stay at the bottom of the spec (270 kpa), fluctuating slightly up and down, though out the entire time you are driving? The fuel pressure stays steady on flat interstate, on hills, accelerating with the A/C on and off. Thanks for all your help.

Yes, that is the whole theory of that system. It adjusts to load. It has a vacuum sensor that feeds the PCM and it combines that info with speed, gear ratio, TPS, coolant temperature and air flow to make pressure decisions.

Thanks for all your help. I have one more question regarding this. I installed another fuel pump driver module and the fuel pressure went up to around 400 kpa at idle. I checked the pressure again with my scanner today at idle and got the same results. I checked the pressure with a manual gauge at the same time and got around 60 psi. I decided to drive the car and the more I drove the more the pressure dropped. I am baffled as I was sure the pressure would rise with load, as load increased while driving. I am just about at wits end on this. Thanks again.

I think your forgetting temperature. It runs a richer mixture when the engine is cold so it would not surprise me that the pressure drops with engine heat. I think your worrying about nothing here. The PCM is programmed to look for problems and will usually find them before you.

As far as the fuel pressure is concerned, I am sure you're right. I am just baffled at what is causing the car lose power (like a gently buck at highway speeds) and miss. All ignition components were tested at a local dealer and passed. I am going to put the vacuum pump I just purchased to use on Tuesday and begin checking for leaks. Thanks again. I really appreciate your help.

I saw no mention of plugs, wires or coils in your history. Those would always be the first things to look at with symptoms like that. You should be able to use a scan tool on this and see the actual misfire counts for every cylinder.

Also, make sure what your feeling is not the TCC jumping in and out of overdrive. That can feel like a miss too.

The plugs, wires and coil have been replaced. The original coil had a crack and was causing a misfire. I am not seeing any information about misfires with my scan tool. It shows everything as okay. I am noticing that it records the results of the diagnostic tests it runs on the EVAP system as sometimes high or low. I am going to check for vacuum leaks and take the vehicle to a transmission shop to make sure it is not the torque converter.

This problem intially started after the car struck on dog on the front right corner. After the initial impact my wife pulled over and shut the car off. Afterwards, she tried to start the car and it would not start. 15 minutes later it started with no problems, but over the last two weeks this problem persisted,starting and then not starting. One day She had filled up with gas and it would not start for 30 minutes at a gas station. Another day it would not start and we had to wait til the next morning for it to start( the car had an 1/8th of tank of gas at the time). We took it to an parts store and had the OBD II codes checked, no problems there. But once again the car would not start. The battery checked good and at no time had the fuel inertia switch ever activate. My questions are the following,
Is it the fuel pump, starter, or fuel pressure? If it is the fuel pressure, how do I fix the fuel pressure?

is the engine is turning over.

The engine will turn over and run as any other day when I start it for the first time. No problems occur while driving either. After the vehicle is shut off and we try to restart it nothing happens apart from the electronics turnning on. It will not crank over nor do I hear the starter engage. No sounds whatsoever.

you are going to have to do some testing the next time it isn't working to find where the problem is.

things it could be

starter solenoid
starter relay
park/neutral safety switch
ignition switch

i suggest we start with testing the solenoid.

While the engine is cool. Find your starter and notice the solenoid on it.
There will be the big battery cable going to it, and Then a smaller wire that energizes the solenoid.

Use a test light and probe that small wire,
have someone crank the engine over and you'll see the light come on.

Now you know where everything is and what the test light should do when everything is working.

we need to know if the test light comes on when the engine doesn't turn over.

[quote:afb1c6552e="bryank94"]The engine will turn over and run as any other day when I start it for the first time. No problems occur while driving either. After the vehicle is shut off and we try to restart it nothing happens apart from the electronics turnning on. It will not crank over nor do I hear the starter engage. No sounds whatsoever.[/quote:afb1c6552e] I have the same car, same problem. Dealer told me it's my starter, too many amps. I've very skeptical that this is a correct diagnosis.

2000 Ford Taurus wagon, **FLEX FUEL** V-6 engine running on regular E10. Began stalling intermittently. Would run rough for 30-60 seconds or so and then die, both while driving and while idling. Would restart just fine. Began happening more and more frequently and threw a Check Engine code (but I don't know what it was, repair shop says they “lost it”.) Then one morning it wouldn't start (mild Oregon climate ~55F overnight). Had it towed to an independent repair shop. They read the code and measured fuel pressure at the fuel pressure test port (on the very far end of the fuel injection rail from the gas tank) at 3psi. They diagnosed a bad fuel pump and replaced. Told me it was ready to pick up. It had been sitting out overnight. When I picked it up, it wouldn't start. With lots of cranking it finally started but ran extremely rich. Strong smell of raw gas out the exhaust and clouds of fumes (not burned oil, just unburned, rich exhaust). Gave it back to the shop. They read code P0191 and diagnosed a bad fuel flow sensor (device right at the beginning of the fuel injection rail) and replaced, but it didn't affect the problem. It will still sometimes have trouble starting and run very rich when starting from cold (cold = 55F). Without touching the throttle, engine can be shut off and started again and it will be just fine. Shop doesn't know how to proceed. I walked through with them their diagnosis of the bad flow sensor. Upstream of the flow sensor is an oval-shaped metal enclosure with fuel lines going in and out, and an electrical connection. They didn't know what this device does (neither do I). I suspect it might be the electronic fuel pressure regulator.

It is unlikely that there would be two bad components at the same time in the fuel delivery system. I suspect that the bad fuel pump was a misdiagnosis, and the bad flow sensor is obviously a bad diagnosis. There are two TSBs that might be pertinent – TSB14187 & TSB14041. But I don't understand completely the flex fuel system. What controls the fuel pressure to the fuel injection rail? What device senses the ethanol concentration of the fuel system? What is that oval box in the fuel line? What does the engine change in response to the ethanol concentration? What could be the true problem here that would fix the car?

Apart from the P0191, was any other trouble codes retrived? Seems there are a lot of unsolved problems for the flex fuel system

The automotive forum link was interesting – it shows that flex fuel issues can be very hard to troubleshoot. But nobody there was getting a P0191 code. That code was read by the repair shop; they didn’t mention any other codes along with it.

What is the description that goes with a P0191 code?

I know what basic elements need to be in the fuel supply system, but not what order they are in the Taurus. Do you guys have access to the vehicle manuals? Can you tell me how the components of the fuel system are laid out (what components, in what order, starting at the fuel pump and ending at the fuel injector)?

We do have access to Mitchell1 and Ford websites for such information but problem is the description of the system is rather vague and principles of operations are not very comprehensive.

Without any specific criteria it would be almost impossible to get information as the amount is vast so whatever information that you require, let me know so I can search for them. I will see what I can get about the principles of operations.

You mentioned the first mechanic lost it so I do not know if the trouble codes then was the same P0191 or it could have been others.

P0191 - Fuel Rail Pressure (FRP) sensor circuit performance. The test procedures are below.

NOTE:
On CNG models, if vehicle is a no-start, go to TEST HB

16) KOEO/KOER DTC P0191

DTC P0191 indicates FRP voltage signal is more than self-test maximum.
Possible causes for this fault are:
High Fuel Pressure
Low Fuel Pressure
Excessive Resistance In Circuit
Faulty FRP Sensor
Low Or No Fuel

Turn ignition switch to ON position. Ensure vehicle has at 1/8 tank of fuel. Turn
ignition switch to OFF position. Release fuel pressure. Connect pressure gauge
to Schrader valve. With engine running, check fuel pressure. Fuel pressure
should be within specification. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to TEST HB (natural gas vehicles) or TEST HC (all other models) .

17) DTC P0191, P1168 & P1169: Check FRP PID Fuel Pressure
Turn ignition switch to ON position. Using scan tool, select FRP PID from PID/DATA MONITOR & RECORD menu. If PID psi reading is not within 10 psi of fuel pressure gauge psi reading in step 16), go to next step (natural gas vehicles) or step 19) (all other models). If PID psi reading is within 10 psi, proceed as follows:

If DTC P1168 or DTC P1169 is not present, repeat QUICK TEST.
If DTC P1168 or DTC P1169 is present, clear DTCs. Road test vehicle 3-5 minutes at a steady speed. Stop vehicle and check for Continuous Memory DTCs. If DTC P1168 or DTC P1169 is present, go to next step.

18) Check Fuel Rail Solenoid

Using scan tool, access OUTPUT TEST MODE under ADDITIONAL SYSTEM FUNCTIONS. While observing fuel rail solenoid, cycle output on and off several times. If solenoid clicking can be heard or felt, exit output test mode and go to next step. If no solenoid clicking can be heard or felt, go to step 22.

19) Measure VREF Voltage

Disconnect FRP sensor connector. Turn ignition switch to ON position. Measure
voltage between VREF terminal and SIG RTN terminal at FRP sensor harness
connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts,
reconnect sensor and go to TEST C.

20) Check FRP Circuit For Excessive Resistance

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect
connector for loose, damaged or corroded terminals. Repair as necessary.
Measure resistance between FRP terminal at FRP sensor harness connector and
PCM connector terminal C40 (LS) or terminal No. 63 (all other models). Measure resistance between SIG RTN terminal at FRP sensor harness connector
and PCM connector terminal No. 91 (SIG RTN). Measure resistance between
VREF terminal at FRP sensor harness connector and PCM connector terminal
C20 (LS) or terminal No. 90 (all other models). If all resistance readings are less
than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair
open circuit.

21) Monitor FRP Circuit With Scan Tool

Turn ignition switch to ON position. Using scan tool, select FRP V PID from PID/DATA MONITOR & RECORD menu. If PID voltage is less than .2 volt (natural gas vehicles) or more than 4.8 volts (all other models), replace FRP sensor. If PID voltage is not as specified, replace PCM. Program PCM.

NOTE:
When in output test mode, voltage measurement must be made within 7 seconds of activating test mode.

22) Check Voltage At Fuel Rail Solenoid

Disconnect fuel rail solenoid connector. Using scan tool, access OUTPUT TEST MODE under ADDITIONAL SYSTEM FUNCTIONS. Turn all outputs ON. Measure voltage between VPWR circuit terminal (Pink/Black wire) at fuel rail solenoid harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit.

23) Check Ground Circuit

Measure resistance between ground circuit terminals at fuel rail solenoid harness
connector and negative battery terminal. If resistance is less than 5 ohms, replace
fuel rail solenoid. If resistance is 5 ohms or more, repair open circuit.

24) Check VREF Voltage To FRP Sensor

Disconnect FRP sensor connector. Turn ignition switch to ON position. Measure voltage between VREF and SIG RTN circuit terminals at FRP sensor harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range. Go to TEST C.

25) Check For Shorted FRP Signal

Disconnect scan tool from Data Link Connector (DLC). Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM harness connector FRP and SIG RTN terminals, between PCM harness connector FRP and VREF terminals, and between PCM harness connector FRP terminal and battery negative terminal. If all resistance measurements are more than 10 k/ohms, replace PCM. Program PCM. If any resistance measurement is 10 k/ohms or less, repair short in affected circuit.

At cold start the fuel pressure was 10 lbs (key on, no engine running). After starting engine fuel presure came up to 32 lbs very quick. Restarts the fuel pressure remained high. After waiting for a long period the fuel pressure would go back to zero and a step of turning key on and off ( not engine start) 3 or 4 times would bring the fuel pressure up to 40 lbs. Why is it taking so long for fuel pressure to come up. The initial 2 seconds of fuel pump before start does not seem long enough to bring pressure up to running pressure. Is this normal!
I kow it is not the fuel filter as I just replaced it, fuel pressure was to zero and it took 4 key (on and off) cycles to bring pressure up to 40 lbs. The normal 2 seconds doe not bring up the fuel pressure enough to start car efficently.

I need you engine size to look up specs, 3.0? 3.0 DOHC?
Flex fuel? or 3.4?
With the Key on engine off reading should be 30-45 psi and test the system like this:
4) Check Fuel Pressure Release fuel system pressure. Turn ignition off. Install fuel pressure gauge. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Command fuel pump on. Note fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step 10). 5) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, turn ignition off. Exit OUTPUT TEST MODE. If fuel pressure remains within 5 psi (34 kPa) of specification for 60 seconds, go to step 7). If fuel pressure does not remain within 5 psi (34 kPa) of specification for 60 seconds, go to next step. 6) Check Pressure Regulator Diaphragm With fuel pressure gauge installed, start engine and operate for 10 seconds. Turn ignition off and wait 10 seconds. Start engine again and allow to idle for 10 seconds. Turn ignition off. Disconnect and inspect hose from fuel pressure regulator. If hose is wet with fuel, replace fuel pressure regulator. If hose is dry, go to step 12). 7) Check Fuel Pressure; Test Drive Vehicle With fuel pressure gauge installed, disconnect and plug fuel pressure regulator hose. Ensure fuel pressure gauge can be seen by vehicle operator. Drive vehicle while noting gauge reading during heavy acceleration. If fuel pressure reading stays within 3 psi (21 kPa) of original pressure reading, go to next step. If fuel gauge reading does not stay within 3 psi (21 kPa) of original pressure reading, go to step 13). 8) Check Fuel Pressure Regulator; Test Drive Vehicle With fuel pressure gauge installed, reconnect fuel pressure regulator hose. Install vacuum gauge to intake manifold. Ensure both gauges can be seen by vehicle operator. Drive vehicle while noting gauges during heavy acceleration. Gauge readings should be as follows:  Fuel pressure gauge reading increases and vacuum gauge reading decreases.  Fuel pressure gauge reading decreases and vacuum gauge reading increases. If gauge readings are as specified, fuel system is functioning properly and testing is complete. If gauge readings are not as specified, go to next step. 9) Check Vacuum Supply Turn ignition off. Disconnect and plug fuel pressure regulator hose. Install vacuum pump to fuel pressure regulator. Start engine and operate at idle. Observe fuel pressure gauge while applying vacuum to regulator. If fuel pressure changes as vacuum changes, repair restricted vacuum source. If fuel pressure does not change as vacuum changes, replace fuel pressure regulator. 10) Check Fuel Pressure Regulator Leave ignition off and scan tool connected to DLC. Release fuel system pressure. Disconnect fuel return hose at fuel rail. Connect a separate hose to fuel rail and put opposite end of hose in clean, one quart container. Turn ignition on. Enter OUTPUT TEST MODE. Command fuel pump on. Note fuel pressure and fuel returning to container. Exit OUTPUT TEST MODE. Command fuel pump off. If fuel pressure is 35-40 psi (240-280 kPa) 35-40 psi with fuel returning to container, go to next step. If fuel pressure is not 35-40 psi (240-280 kPa) or fuel is not returning to container, replace fuel pressure regulator. 11) Check Fuel Return Ensure fuel return line is disconnected at fuel rail. Disconnect fuel return hose at fuel pump. Check return hose for restrictions. Apply 3-5 psi (21-34 kPa) compressed air to return hose. If air flows freely, replace fuel pump. If air does not flow freely, repair or replace fuel return hose.
If there is any gas in the vacuum line to the regulator, replace the regulator.

I did all the checks but it seems that all numbers are good so far with exception of Cold Start pressure (engine off) being only 10 lbs. If I cycle key 4 time the pressure comes up to 40 lbs. Vacuum working. Vacuum fuel pressure regulator working. Leak down test OK, waited 5 minites and no pressure loss detected. Pinced return line and pressure increased to 60 psi. Vacuum is -18 lbs. Fuel filter new.

It sounds like the pump itself is getting tired. Takes too long to get up to initial pressure specs. Or the filter is clogged.

Replaced filter but that was not the issue. Replaced Fuel Pressure regulator (easy to do) and this solved most of the problem. I do believe the Fuel Pump is getting lazy and will need to be replace soon. But for now most of the problem went away.

Ok We will be watching for any more on this!

1995 Ford Taurus 6 cyl

what is the average fuel pressure on a 1995 Taurus SHO with a 3.2 engine?

[quote:5680d36915="icy03"]1995 Ford Taurus 6 cyl

what is the average fuel pressure on a 1995 Taurus SHO with a 3.2 engine?[/quote:5680d36915]

It should be 37 to 43 psi according to the shop manual.

i have a 1995 ford taurus with 83,500 miles.when in hot weather the fuel pressure drops to 15 p.s.i. then drops to zero then dies.i replaced the fuel pressure regulator and filter. still has the problem .could this be the fuel pressure relay or fuel pump.thanks tim

[quote:cb5577cf39="timl"]i have a 1995 ford taurus with 83,500 miles.when in hot weather the fuel pressure drops to 15 p.s.i. then drops to zero then dies.i replaced the fuel pressure regulator and filter. still has the problem .could this be the fuel pressure relay or fuel pump.thanks tim[/quote:cb5577cf39]

Judging by the discription you have given, it is not the relay. Sounds like a pump problem.

agreed, sounds like fuel pump

I tested the fuel pressure after the regulator and is supposed to be at 39 psi but is only reading 30 psi so i replaced the fuel regulator, and the fuel pump and is still reading 30 psi except for when u accelerate the throttle and it reaches the correct pressure but as soon as u let off of the accelorator the pressure drops back to 30 psi. The main reason I checked the fuel pressure was because the car starts up and runs fine but when u floor the accelorator the engine bogs down and loses power the same occurs when driving and you floor it to get up and go but as soon as you let up off the throttle or even ease off the rpms pick up and so does the power. It almost acts as if its not getting enough fuel. But i Replaced the exhaust including the catylitic converter beacuse i thought it wasn't allowing enough air to escape but that didnt help. I also did everything you can do for a tune up. The car still doesnt run right.

10 psi low is quite a drop and needs to be check out immediately.

change your fuel filter and check the fuel lines for kinks and bends that dont belong there. make sure you put the filter on the right way.

let me know.