Chasing down fuel issue on the Taurus. Might just be a weak fuel pump..

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Nov 29, 2021
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OK well the latest thing to be going on with the Taurus is "low power under full throttle when it is hot" (like driving around for a half hour, hour.) It acts pretty well around town but drive it long enough (two hours) "around town" (local road, traffic lights, 50ish mph) and it will eventually buck and sputter from lights, with low to no power. Even stall. Then turn back on after 30 seconds or so and run okay/fine.

Narrowed it down to fuel.

Codes being set WERE: P0171, P0174, P0191, P0420, P0430.
Occasionally once or twice when it was at its worst: P2197, P2198.

Codes being set on the regular (now) are: P0430, P1000 (of course as a result of seeing what comes back.) Research seems to indicate P0171 will set when either STFT or LTFT goes above 24.2%. (Possibly.)

According to Ford forums, the pressure should be around 40 most or all of the time. https://www.taurusclub.com/threads/fuel-pressure-regulator-or-fuel-pump.149272/

One mentioned vacuum lines and a way to test by taking one off, not sure how to do that test but I'm open to it.
Another mentioned IAC..

Ok moving on. Action taken so far: Fuel filter replaced about a month ago. Was there improvement? Yesterday, absolutely.. Car no longer stalls, but I can repeat the failure (as a mechanic or technician, Step 1 is always to verify the complaint.)

I think it's either just a weak fuel pump or faulty FPR, Ford might call it a FRPS or Fuel Rail Pressure Sensor. This is a 2004 Vulcan, not a DOHC Duratec.

The weak fuel pump may be fooling tests, I did remove the FRPS on a cold engine today and "clean it." (Why? Because the seller that has a replacement even down to an O-ring already on it is away until March 20th.) https://www.ebay.com/itm/3542741835...BgGD0szSvM95a26xfxoUN5i8qEkW4qpIaAioQEALw_wcB I've always been of the belief that perhaps before you replace a sensor, try cleaning it. (Particularly true if you're trying to keep crappy Autozone, Advance Auto, O'Reilly, Pep Boys parts off your vehicle. I've wasted too much money at these stores in my life. Stores full of crap. New Year Resolution. OE or quality NOS or other quality parts.. online purchase usually checks all boxes there. Especially on weekends when dealers are closed and online is a better choice anyway.) So I cleaned the FRPS.

MAF sensor cleaned with battery disconnected and MAF spray twice. Doesn't seem to be the issue, as per observations over weeks with scan tool.

Here is a shot upon deceleration. The numbers don't tell the whole story.. although LTFT2 always seems slightly higher than everything else, sometimes around +7%. O2 sensors dont look great here (mirroring each other) and sometimes look OK. P0430 wants to set no matter what, Cataclean be ****ed. Starting to think that stuff doesn't do anything.

Screenshot_20230305-033648_Torque.jpg


I'm thinking (or at least speculating)the weak fuel pump was setting P0191, as P0171 amd P0174 never came back after fuel filter change...

Why don't the numbers tell the whole story? Well, before fuel filter change, the STFT would always go stupid high, like 50%, 66% .. before the car stalled and set P0191 (and once or twice the P2197 amd P2198.) At its worst, it wouldn't want to restart except for after minutes (and always in traffic.) Like a flooded engine. Or not having fuel delivered. Didn't have an eye on the fuel pressure at that time, but I'm sure it was down around 8-20psi during those episodes.. facilitating long crank, and engine not wanting to fire, the flooding is speculation on my part (maybe it was fuel starved not flooded.)

On these Fords, you have to measure the fuel pressure AT the rail anyway, since Ford made the spec relative to manifold pressure or vacuum or something. I read it in a thread once but. There is not a Schrader valve.... just one thing about these post-01 or post-03 Fords. I'm not 100% on it but wanted to mention.

Here is the guide video I used to remove, clean (sprayed WD40 let it sit = clean) and replaced, installation opposite of removal, the FRPS.



Present plan of attack or at least what I am thinking: 1. Order new FRPS shown in the EBay link 2. Install it. On cool engine as per in video 3. Monitor for change 4. See if that does it.

Got the money for a fuel pump ready if all of this is having people frustrated, saying It's a weak fuel pump. Could be. I see fuel pressure dip to 16, 12, 8psi in its current configuration.. fuel filter changed, original fuel pump in there from 2004, FRPS only removed (and put back on) at all today. Didn't look too bad. Fuel was in the rail, I imagine it should be.

Fuel pumps don't seem to be very expensive, I did not immediately see a Motorcraft one. Some come with the whole assembly some are just the pump? Tank has to be dropped down.. fun. Rusty bolts and straps make that the LAST thing to be addressed, as you start small then go to the largest..

I also note that the oil did smell like fuel, this is what made me concerned and do a deep dive into all of this. Sharing my observations over the last month or two with you so we can determine the best course of action.

Anything to add about the Ford's fuel issue?

Aside from.......

Screenshot_20230305-044318_Chrome.jpg


.

Fuel pump ?????..
 
My '89 bull had a fuel pump that would heat up after driving a while and slowly lose pressure. Put a few gallons of fresh cool gas into it and it would get me back home. It was better after initially changing the filter but that was short lived.
Was a warm weather issue in my case, finally took it for a ride and came home and let it idle with a gauge on it for a long time until I got a solid verification.
 
It seems like it wants to fumble (down to about 9.5 to 10psi now) when it is fully warmed up and you floor it. At its worst. Sometimes it only drops to 26 and sometimes it doesnt drop at all... Then it has no/low power.. runs but wants to stall. If you shut it off then right back on, fuel pressure jumps to 55 or 47 psi then seems to stay "right around 40" while driving around. Seems to run fine when cold.

The spec is as it is read through the fuel rail pressure sensor. It will NOT match a mechanical gauge. In fact, a mechanical gauge is of very little help on that electronic retunless system.

You really have to drop the tank to get to the fuel pump.. is the hard part the "rusted bolts" moreso than changing the pump? And less gas in the tank means less weight? I'll continue to monitor and it is running better.. but the malfunction (sets P0191) only happens fully warm and if you "floor it." (Like you may have to, sometimes. Part of the range of ability on the car.)

I'm thinking fuel pump but I will continue to monitor.

But it could also be clearing up crap in the tank ......


Not fully understanding "duty cycle."

That's normal. Ignore the specs unless you have a scan tool that can read fuel pressure. The spec is as it is read through the fuel rail pressure sensor. It will NOT match a mechanical gauge. In fact, a mechanical gauge is of very little help on that electronic retunless system. The pump would have to be nearly dead for a mechanical gauge to work. The 2 do not match because the FRP sensor is referenced to manifold vacuum and the mechanical gauge is referenced to atmospheric air. To get the 2 to match, you will need to unplug the vacuum hose to the FRP to get the FRP referenced to atmospheric air like the gauge is.

When using a scan tool to determine a pump problem, you'd not only look at pressure but also percentage of pump "on" time (40psi at idle with 23% duty cylce from PCM is good, but 40psi at idle with 45% duty cycle from PCM is bad). Then you'd also have to use an oscilloscope to check the output of the fuel pump driver module to ensure it is ramping up the pump "on" time per the command from the PCM (just because the PCM is commanding it, doesn't mean the driver module is running the pump right).... the twist there is that whatever duty cycle is present on the PCM data PID, the FPDM will double that (25% command from the PCM is 50% from the FPDM to the pump, 50% command from the PCM is 100% on command from the FPDM to the pump).

What you are seeing when you see the pressure raise and low, is the pump turning on and off... there is no pressure regulator. The PCM watches the fuel rail pressure sensor (FRP) and commands the pump on enough to achieve target pressure. Target is 40psi on cold fuel, and up to 55 psi on on hot fuel. pressure is NOT targeted on engine load like old returnless systems that used a vacuum operated pressure reg and return line.

Here is how it works. http://www.babcox.com/editorial/us/us120532.htm

Any codes? a dying fuel pump will set a P0191 (FRP performance) and often a P0148 (Fuel delivery error)... along with P0171 and P0174 (bank 1 and 2 lean)

If you don't have those... move on and leave the pump alone.
 
Not fully understanding "duty cycle."
That is the key to diagnosing a bad fuel pump, as the article you just posted explains.

Good pump: Duty cycle 25 at idle 33 WOT
Bad pump: Duty cycle 40 idle 50 WOT

Can your scan tool read the fuel pump duty cycle? Ideally plot it on the same graph with the FRP reading.

The sensor appears to be working properly. It shows a pressure drop at the same time the engine stumbles or stalls, symptoms of starving for fuel. When the PCM sees a pressure drop, it increases the duty cycle, which makes the fuel pump try to run faster, which should increase the pressure.

Higher than normal duty cycle also could be a clogged filter. How well did it run immediately after replacing the filter? If there is a lot of crud in the tank it can clog up a new filter.
 
That is the key to diagnosing a bad fuel pump, as the article you just posted explains.

Good pump: Duty cycle 25 at idle 33 WOT
Bad pump: Duty cycle 40 idle 50 WOT

Can your scan tool read the fuel pump duty cycle? Ideally plot it on the same graph with the FRP reading.

The sensor appears to be working properly. It shows a pressure drop at the same time the engine stumbles or stalls, symptoms of starving for fuel. When the PCM sees a pressure drop, it increases the duty cycle, which makes the fuel pump try to run faster, which should increase the pressure.

Higher than normal duty cycle also could be a clogged filter. How well did it run immediately after replacing the filter? If there is a lot of crud in the tank it can clog up a new filter.

It ran pretty well! Was run to E purposefully to make changing the filter as easy as possible.. and by "Ran to E" I mean running on fumes, mechanic had to add about a gallon or two of gas to get it through the lines since it was a crank no start after prime. But that was literally a "it ain't got no gas in it" kinda situation.

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It ran very well after that, definite improvement. No more P0171, P0174, or stalling. Just occasional acting up. (Also, no more P2197 or P2198. P0191 did recur, always on the low power, engine stumbling, type of situation. Either starved for fuel or faulty sensor itself throwing that, after reading more about Fords and how they do their fuel system, no Schrader valve and all.. I decided we can't condemn the fuel pump just yet.)

As I type this, I am letting it idle. The last screenshot will be that. Torque Pro. I havent found a free Forscan that works.

Seems to be going in the right direction. Here are some new data points.. did not add throttle % because I've heard on these, it's not accurate (says about 16% when car isn't moving .) All screenshots taken by a professional driver at the wee hours of the morning like 4a.m. on open roads.

Cruising

Screenshot_20230309-052002_Gallery.jpg
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Fuel trims go.negative upon tapping the brake (usually)

Slower:

Screenshot_20230309-052015_Gallery.jpg


Fuel pump blips up to about 42psi or so.

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Code P0430 is pending. Do not know if it will set. O2s just don't look the best.

Maybe it is clearing up .....

Here is after about a half hour-40 minutes operation before I shut car off and start my day.

Might be moving in the right direction here.

If it doesn't continue to improve or act up again I may have DIFY second fuel filter change because they have a lift and it takes 5-10 minutes on a lift...
Screenshot_20230309-052404_Torque.jpg
 
Here is latest diag shot. Here it is after being driven around town, gas "topped off," Fords you can usually top then off quite a bit . (Some say to not do that but I'm looking at fuel pressure and driveability.)

Again beginning to suspect a clogged fuel filter. I put the Flow measurement on the screen.

Until then? Will see if it clears up. Only codes setting are P0420 and P0430. Which aren't fuel....
Screenshot_20230313-050843_Torque.jpg


Climbed to about 53psi about 5 minutes later...

Screenshot_20230313-051248_Torque.jpg


Short log. Car started: 6:25a.m. Still full hot. Idling. Almost no idle loping. Started right up. (Gotta keep warm!) Fuel pressure: a BEAUTIFUL 52.3 psi.

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Let's see where it is at at 7.

Screenshot_20230313-062716_Torque.jpg


P0430 wants to set on the regular...

Screenshot_20230313-062759_Torque.jpg


6:42 about 50-ish psi hot idle
Screenshot_20230313-064228_Torque.jpg


(logging so we can see data points, how it is acting. No throttle blip introduced, that tends to set a P1270 which takes some time to go away)

Here's at 6:52. Fuel pressure climbing..

Screenshot_20230313-065223_Torque.jpg


Feeling perhaps a slight stumble/possible misfire but nothing too bad.


I have a Ford Taurus 3. 0L OHV VIN "U" it has a sharp surge while driving, from idle through the power band.
While checking the fuel pressure Alldata listed the pressure as 30-55 psi key on engine off and 26-45 psi engine on.
I get 60 to 61 psi key on engine off and 55 to 57 psi at idle and the pressure bounces up and down "at idle" from 55 to 57 psi.
Alldata is kind of vague on troubleshooting the fuel pressure sensor.

That's normal. Ignore the specs unless you have a scan tool that can read fuel pressure. The spec is as it is read through the fuel rail pressure sensor. It will NOT match a mechanical gauge. In fact, a mechanical gauge is of very little help on that electronic retunless system. The pump would have to be nearly dead for a mechanical gauge to work. The 2 do not match because the FRP sensor is referenced to manifold vacuum and the mechanical gauge is referenced to atmospheric air. To get the 2 to match, you will need to unplug the vacuum hose to the FRP to get the FRP referenced to atmospheric air like the gauge is.

When using a scan tool to determine a pump problem, you'd not only look at pressure but also percentage of pump "on" time (40psi at idle with 23% duty cylce from PCM is good, but 40psi at idle with 45% duty cycle from PCM is bad). Then you'd also have to use an oscilloscope to check the output of the fuel pump driver module to ensure it is ramping up the pump "on" time per the command from the PCM (just because the PCM is commanding it, doesn't mean the driver module is running the pump right).... the twist there is that whatever duty cycle is present on the PCM data PID, the FPDM will double that (25% command from the PCM is 50% from the FPDM to the pump, 50% command from the PCM is 100% on command from the FPDM to the pump).

What you are seeing when you see the pressure raise and low, is the pump turning on and off... there is no pressure regulator. The PCM watches the fuel rail pressure sensor (FRP) and commands the pump on enough to achieve target pressure. Target is 40psi on cold fuel, and up to 55 psi on on hot fuel. pressure is NOT targeted on engine load like old returnless systems that used a vacuum operated pressure reg and return line.

Here is how it works. http://www.babcox.com/editorial/us/us120532.htm

Any codes? a dying fuel pump will set a P0191 (FRP performance) and often a P0148 (Fuel delivery error)... along with P0171 and P0174 (bank 1 and 2 lean)

If you don't have those... move on and leave the pump alone.

Last but not least.. 7AM. 60-62psi idle. Again.. slight stumble/possible misfire, not silky smooth but not bad. Fuel filter ???? Shutting off car.

Screenshot_20230313-070003_Torque.jpg
 
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A little bit of an update on the Taurus, since Spring/Summer driving season is almost upon us and we just had a freak-ish cold weather windstorm, with blowing snow and much moisture/sleet/strong wind.. no real "snow" to speak of. This car has had doors freeze and not shut in strong winds. So. 2004 Ford Taurus, VIN U the Vulcan 3.0L SES, updates:

1. First observation: The car runs "pretty much perfect" when the tank is full. Even 3/4. Seems to run just about perfect. Only one low fuel pressure event, coming up on the hill somewhere between Exit 98 and 91 GSP SB, there are actually two hills.. if you're at speed (75, 80MPH, cruise set) the engine will floor it to get up the last of the hill at its steepest point.. of course, you can manually introduce WOT if you "need to" (blow out that carbon!! Nice and hot, ram air..) . So after driving it around "pretty much for two hours," the cruise control maintaining speed got the fuel pressure to drop to 15.1 psi/7/8.9/ some low number, until cruise control is disengaged and then the fuel pressure numbers come right back up to normal. P0191 sets and you can feel the bucking from fuel starvation. ONLY happens WOT after driving around "awhile;" if WOT is not introduced, it will NOT do that. And it seems to handle that well when cold. This is as per Waze, it measures the FRPS sensor which gives fuel pressure at the rail, can even watch for fuel pressure bleeding down and it does not, it does hold pressure if you leave key in Run position with engine off. (KOEO)

Has me thinking either fuel pump or clogged fuel filter, as the fuel flow measurement sometimes seems a bit low. Not sure what spec is. Could be new filter got contaminated with stuff in the tank, as suggested by Mr. @mk378 - I wasn't even sure that can happen but apparently it is not unheard of. So new fuel filter can again be changed.. can't hurt anything.

2. Car did not want to start this morning. Not really sure why. It eventually did start, then run rich from all the cranking over a half hour.. almost like something froze? I'm sure that makes no sense. Went straight from Crank No Start, being careful not to beat the starter up too bad, to eventually started, sputtered a little then cleared up, running rich until evening out. Maybe that is why it either set or penned code P2196 after that. What shows as a greyed-out code on Waze shows as "set" on a Snap-On Verus or MaxiSys, the shop I go to has a Snap-On unit. Apparently, it does everything, and "that code set" means "change that part," ......

3. Way to keep car running smooth until we see if a fuel filter change yields change is to keep the tank full and just cruise on highway. Seems to have power to deliver. All issues were with tank about 1/4 full.. not sure why having this car seems to generally dislike having lower fuel level. At least that is when it seemed to set all the codes, have driveability issues, and have wonky fuel pressures/STFTs etc.

Present pending codes are both P0420 and P0430. They both seem to eventually set. Magic fluids that say they turn off these codes do not seem to work. They seem to work for other people. (I would link DIY Dave's video of trying Yamalube Ring Free Plus review, but has an oil-burninf 1ZZ-FE and isn't the issue I'm experiencing here. Apparently the stuff turned off his P0430. Weird.)

So. Still thinking filter or pump.. wanted to update. This way, I avoid spraying fuel all over my driveway and invoking the wrath of an HOA where I live. I still mess with the cars. Just not obviously. Mom's car is almost sorted out.. we noticed the stalling a few months ago, and while it really could use some new O2 sensors, it could use a brake rotor more, and we really want to be 110% sure before we condemn the pump because it's still possible the new fuel filter got plugged up.. from Autozone.

Motorcraft FG-1060 Fuel Filter on the way.

Fuel pressures pretty much always 38-42psi driving around...

That's the update. Wanted to be as detailed as possible.

Mental note to change the fuel filter on my car. 128K miles is clearly too much. Did you cut it open and post pictures of it here?

@zzyzzx I think, because that is an EXCELLENT idea, I'm buying a hacksaw with blades that can cut steel because the shape, I'm just not sure I can cut it like I can oil filters. I got a cutting device but for oil filters. I'd love to share with the class.

MAF is right around 5.0g/s with car in drive; right around 4.0g/s when in park/neutral/KOER (Engine Running.)

And. Oil level does not appear to be rising.. I suspected FPRS (P0191) issue because this car previously had an oil level that rose by itself. Oil smelled of fuel. Since a FRPS is basically an FPR, I did change that. It seems pretty much exact where it was just a couple days ago so.. that is a good sign.

Reading taken just now.

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So, did you change the filter?

Because all this obsessive posting, as well as your clearly abusive driving, will not solve the problem. You are not chasing anything down.

You are posting. You are obsessing. You are continuing to drive the car.

By the way, full throttle on a car with a running problem is a good way to cause more problems. Like frying an exhaust valve from a lean burning cylinder.

Just put a filter in, and see what you gain.
 
So, did you change the filter?

Because all this obsessive posting, as well as your clearly abusive driving, will not solve the problem. You are not chasing anything down.

You are posting. You are obsessing. You are continuing to drive the car.

By the way, full throttle on a car with a running problem is a good way to cause more problems. Like frying an exhaust valve from a lean burning cylinder.

Just put a filter in, and see what you gain.

The filter should be changed again soon, it was changed about a month ago.

I'd have to buy stuff to measure "PWM" ... I inquired what that was etc.

I made an informative post and you're welcome to your opinions @Astro14
*edit: @Astro14 I'm not trying to sound angry or snippy or any type of way, I do plan on getting fuel filter changed, I wanted to post up "any and all" info about this car's problem and I agree.. Filter change is prudent, I don't think I have the hardware to properly look at PWM, I looked it up, apparently a Multimeter can't switch fast enough to read it. May need a new purchase.

Wanted to say that before anything "spiraled."
 
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If you've changed the filter recently - then it isn't the filter. It's rarely the filter.

An almost new filter won't cause this, unless the tank is full of rust and plugs up a new filter (this is rare, but can happen to cars that sit for a long time in humid climates, or cars that have evap system leaks).

Time to take another action - verify that the fuel pressure reading from the OBD monitor is accurate - put a good gauge on it.

If it's still low, then change the pump.
 
An almost new filter won't cause this, unless the tank is full of rust and plugs up a new filter (this is rare, but can happen to cars that sit for a long time in humid climates, or cars that have evap system leaks).
Been there, done that. Not sure if it was the tank that rusted out or if I bought gas that was pumped from the wrong end of the holding tank, but after multiple fuel filter replacements I got tired of it plugging up randomly and changed the tank.
 
O-K got it to act up.
This tells me it could be the pump or the filter. To @Astro14 point, this car has sat a while in Florida....
Could still be the pump...

This is after driving about 2 hours on a long stretch of highway with nobody on it. Test repeated for lowest numbers . Drives fine, except for WOT.. I did find FPDC in Torque Pro, thank you to @mk378 for the mentioning it.

3rd shot is right after letting off throttle.
Codes that want to set/are on now: P0191, P0420, P0430

Codes that DO set: P0420, P0430

It's improving (no stalls!) but still not 100% good.

Screenshot_20230318-053209_Torque.jpg
Screenshot_20230318-053323_Torque.jpg
Screenshot_20230318-053329_Torque.jpg


*correction... did NOT pend nor set P0191. Even with the WOT test looking at FPDC...

Screenshot_20230318-054417_Torque.jpg


It (other than. This instance) drives very smooth....

Screenshot_20230318-062904_Torque.jpg


Full tank hot it only went 37 on FPDC

Screenshot_20230318-071138_Torque.jpg
 
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It is looking and acting better.

Watching for fuel.pressure drop at various at-speed/WOT/fully warmed events. If no change.. I'm calling it, as the fuel pump. Got a Motorcraft filter too (new filter was from Autozone) but this should be resolved very soon.

Some screenshots. The at speed one is from the York PA trip, near the end of it. The second is the one idling presently to keep warm.

Preliminary research indicates that Bosch makes Motorcraft pumps, making me wonder if Advance and AutoZone etc (that carry Bosch) is suitable.. as "only a few manufacturers actually manufacture the fuel pumps." If pump is condemned. Had a bad experience with an Airtex pump once. It also cost 3x the price of an OE/OEM pump.. and was smaller....
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Appointment for fuel pump remove/replace tomorrow. Before car leaves someone stranded.

We are all but certain (there is a LOT of info in this thread) that that is what the issue is, anyways.

Screenshot_20230321-183251_Gallery.jpg
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Yes everything looks like starving for gas though FPDC goes up to the max, indicating the pump is weak. You'll be back up to triple digit speed in no time.
Abuse the Vulcan V6😤
They run on 87 and complete indifference
Thrash it to within an inch of its life :ROFLMAO:
It will do triple digits, but only just :D
Ford Taurus I salute you, you're charging up San Juan hill now, I don't know if your gonna make it back, but god speed 🫡
 
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