Low fuel pressure causing a P0171 and P0174 trouble code
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- เผยแพร่เมื่อ 7 ก.ย. 2024
- 1999 Mercury Mountaineer 5.0 with a P0171 and P0174 DTC in memory. This is a great video on using fuel trim and freeze frame data to determine the cause of the lean condition.
Engine Performance Diagnostics chapter 4 pages 12-19
Symptoms
- low power
- lean exhaust trouble codes P0171 and P0174
- pinging
- hesitation
- surging
Fix
- replace fuel pump and fuel filter
Tests shown
- how to determine MAF sensor condition using BARO HZ data
- how to use freeze frame data to determine type of lean condition
- how to use STFT and LTFT at different loads to determine type of lean condition
- how to test fuel pressure with a gauge
- how to determine fuel delivery design
- how to measure fuel pump current with a scope
- how to locate the fuel pump inertia switch
- how to calculate fuel pump RPM
Tools used
- scan tool
- fuel pressure gauge
- Picoscope
- inductive low amp probe
Playlist
- (Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing
• (Chapters 14, 15,16) F...
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• Fuel psi less than 50 ...
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Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.
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You & Eric are awesome representatives for Rosedale. Wish I could afford to go there. The integrity that you guys give the automotive industry is invaluable. Hope you guys get some kind of sponorships someday like from an oil or parts company. Greatest respect for you two.
I CAN WATCH THIS VIDEO 1000 TIMES, AND NEVER GET TIRE OF IT, GREAT VIDEO LIKE ALWAYS PAUL!!!!!!!!! THANK YOU SO MUCH ,,,,,
Idle lean and lean under load, I learned something new today, thanks Paul.....
60psi is definitely the right PSI for that engine. Was working on a Explorer that would crank abound 8 seconds before starting and had the lean codes. Had 31 psi fuel pressure at idle, checked the specs and scratched my head at the ridiculously wide range they give. Searched online and many forums and determed that 60psi was the right pressure that year and engine. Replaced the pump assembly and it run perfect.
Yup. My 2000 Dakota R/T had those codes. I went through all the normal checks, replaced vacuum lines, replaced gaskets and now the fuel pump. I wanted to get all those easy less expensive things out of the way first.
@Thor7167 Great catch friend! I found out after filming that the fuel filter had just been replaced, so it is definitely the pump.
A plugged filter would have a higher amperage, however unless you know what the exact amperage of fuel pump should be it is tough to ID. I have seen plugged filters have only minimal difference in amperage readings before and after. Some pumps have internal relief valves which will also affect the amperage readings.
@supersport2778 17:51 is the end of the video, sorry for the abrupt ending, I had some stuff I had to cut out at the end. It didn't change the final call though which was a bad fuel pump.
You have to be careful making a call based on amperage however a plugged filter will certainly cause a higher than normal reading. I think the best advice for these situations is to replace both pump and filter. You could replace the filter and re-test if you desire. However in my experience when a filter is plugged so bad as to cause low psi, you have already hurt the fuel pump. BTW the filter in the vid. was just replaced so bad pump only in this case.
@supersport2778 I am not sure why, but set your video quality to 480p or less and it should be fine. I am using an HD camera but something must have changed with my settings. Thank you and let me know if this works.
thanks them are the same codes i just got.. and i watched some of you video and it showed me how to look at a couple of things and what to do to help narrow down the problem.. anyone who click thumbs downs is an ass and has never worked on vehicle in there life and needed help to figure out a problem. i got fords, kia and chevy but the codes are all about the same .. i make the same kind of video to help people.. and i get the same question from people.. my this is that is doing whatever, so what do you think lmao.. people come on we are not in front of you car its so hard to say what wrong with your stuff..these videos are to help point you in the right direction.. thanks for the video and info this should help me figure out moms kia
that is because we had it running before that shot. what you were looking at was called "rest pressure". If we had just connected the gauge then yes it would have read zero and when he turned the key on it would have jumped up in psi.
part 1: Nice video again. Fuel pump looks fine is actually very stable. Yes indeed Fuel pressure definitely low but talking about spec on that mountaineer I know for sure is 30-65 psi. Snap-on Verus is a nice generic scan tool but returnless old ford fuel system you have to consider also first of all to run KAM process. Then you must place the car in a dyno and run fuel pressure looking at FP% PID along with actual fuel pressure under 62% engine loads.
ScannerDanner doesn't check Mitchell...... Mitchell checks with ScannerDanner to confirm.
hahaha nice!
Hi im a tech at a shop now... im also the new kid and new to the business. Thank you for ur video.
4-6 on a typical PFI system and 8-10 on some higher psi systems (GM CPI for example runs 55-65 psi with this kind of amperage)
thanks for all you do brother watching your vedios is inspiring
@ScannerDanner Thanks for the reply.
The car was warm when It came to me and the lady who owns it had to take it to go to work so I only had like less then two hours to look it over, she said she'll be back one day this week. I'm not sure about the MAP voltage yet. The fuel pressure was 44psi at idle and held after turning the car off.
I didn't think about the purge solenoid, I will check that when the car returns.
I will keep you updated when the car returns.
Thank you very much.
-Tim
thank you, got a clear idea of what's going on with my car
SCANNERDANNER YOU ARE THE BEST ON EARTH, FULL OF 1OOO PERCENT KNOWLEDGE IN YOUR THOUGHTS. THE STATE OF CALIFORNIA IMPLEMENTED AN UPDATED
A REQUIREMENT FOR SMOG REPAIR TEST AND REPAIR FAILURE COURSES AND YOU ARE AHEAD IN YOUR TECHNICAL ABITITY. BLESS YOUR HEART AND YOUR FAMILY. THANK YOU, SIR.
i replaced the fpdm on my buddy's 04 f-150 it had the code "fuel pump driver module off line" me and my dad put it up on the hoist and the aluminum part of the fpdm was completely corroded. we took it apart after and found that water had got in and shorted a trace on the pcb to the ground plane. and now watching this i'm reassured it wasn't the fuel pump cause we didn't have the lean codes that this mercury had. Again thanks for all your videos man happy holidays!
yes that is correct, I think I use 4000-6000 as typical but it can go higher or lower than my spec and still be ok. Also fuel pump RPM isn't as important as pressure and volume delivery. Although a scope test of a fuel pump at times can be a very valuable test.
Especially with a dead commutator segment.
Had the same problem on my 1999 Ford ranger, v6 4.0. Turned out a weak fuel pump was throwing the codes.
hi ScannerDanner good video l have 97 ford expedition 5.4 l have p0171&p0174 & did smoke tester no leaks on the intake so far so I am .going to replaced fuel regulator & maybe like you said fuel issues thanks so much
+Oscar Alarcon check the MAF next
+ScannerDanner hii there i have a 07 ford expedition 5.4 wit 02s11 02s12 stuck rich
Either way is fine, just make sure you let me know when you put it up. Thanks Russ!
I am having almost exact fuel trim patterns on my 2008 expedition 5.4L with both banks lean. Fuel pressure also decreases under throttle. It also has long cranks but only when it’s sat a long time.
When I turn the key on engine off, the fuel pressure reading is sporadic. Sometimes it will only load about 20 psi until repeated, sometimes it will go to 40…I don’t want to sink more cash into the car so I’m trying to be sure it’s a pump. I have already changed the filter.
More context if you’ve read this far…I’ve had issues with this car intermittently sputtering about once a month, I thought I fixed it with new plugs and then after that I got a CE light and discovered lean conditions.
98 expl v6 sohc has two lines 7:30 so it has the vacuum difference range at idle and WOpen.
[Idle psi is usually about 8-10 psi lower than WOT/.KOEO]
@felplay vina there are mechanical poppet nozzels (mechanical injectors that are opened by fuel pressure) that will not open below 50 pounds of fuel pressure regardless of what the electrical injector part is doing
@jdubb408 There are three main designs, mechanical return, mechanical returnless and electronic returnless (Section 14 in my book). Each one we treat a little differently, but on all designs fuel pressure should NEVER drop under load or during the snap throttle test. On the mech. return type with a vacuum reg. Idle psi is usually about 8-10 psi lower than WOT/.KOEO
Wish I could go to your classes!!! You are such a good teacher!
@ScannerDanner I would say it is not a ford issue because I am able to meter this FP % pid on old returnless ford fuel system using OEM ford diagnostic tool. the PID for late model is: FRP% FRP# FRP which stand for fuel rail pressure supported by a FP sensors (tranducers).
I will get that camera. thanks for your videos. you are doiing a great job
Thanks for all your help with my 01 silverado. I've come to conclusion that i do have a fuel delivery issue. Its kinda baffling because after going through and checking all grounds i could find,cleaning the map sensor and egr valve looking at every connector for any obvious signs of trouble i have finally got my truck to run pretty good. Idles smoother and the intermittent misfire is gone. When i get on the Hi way and mat it the truck goes like a bat out of hell. I do notice a slight drop off around 80 or 90 though but is much better than before. However, my fuel trims are still out of the park. At idle im seeing upwards of between 30 and 40 % on short term and long terms steady at 25% on both banks. Im thinking the fuel pump is just not push enough fuel for computer to make corrections. If i wasn't see this on scan tool i wouldnt think there was a problem at all. No check engine lite on either
I should see around 55 to 60 psi on fuel pressure test on this 6.0 vortec correct?
cranking it should be 60 psi all day.
Your trim numbers are very positive at idle. (possible vacuum leak) What do they look like at 3000 rpm in park, with no accessory loads, steady throttle?
ScannerDanner fuel pump shat the bed today. At least thats what i think. Have to get it home and check it out. I'll let you know what i find. Ive been hunting chassis ground and cleaning them as i find them but havent crawled under truck yet. I'll get to that after i fix hot hard start on my buddies 69 road runner and carb issue on his old honda xl dp bike. Busy busy thats me. Thanks for all your help mr. Danner. You're the best. Holler at you soon friend. By the way does the abs/brake light issue on this truck share any common ground? Like mutual ground point locations do you know. These lights been coming on more frequently lately too
Not sure man. I'd have to look at a diagram. We can do that on my forum. It's free to join.
www.scannerdanner.com/forum/post-your-repair-questions-here.html
@@ScannerDanner
I have an 04 GMC Yukon, 5.3. Showing lean bank 1& 2, truck starts and idles great. But under load has an intermediate problem. When it does it 40mph is a stretch for it. It’s quite dangerous. Like u may pull up to a red light go to pull out n hope n pray you don’t get ran over. U can be driving 30 mins on highway doing great but all of a sudden it hesitates and you pray to make it back home. U can feel it hesitate, let off the fuel a little and it will go on but not if you push it. If u push it, it will get worse and basically go into limp mode or reduced power mode. Fuel pressure test shows 53 psi at start up and idle, 45 psi at 3000 rpms, 40 at 4000 and from 5000 to rev limiter it falls to about 30 lbs. under snap throttle test.
40 mph and below 2000-2500 rpms Seems to be the sweet spot were it will run but if u push it at all it hesitates, new acdelco fuel pump in July, fuel filter is built into pump, New Delphi maf in dec, new acdelco spark plugs n wires in oct. I did a fuel treatment and c-foam through throttle body and vac line, this past weekend which straighten it up for a couple days but it came right back, same as it did with all these parts I’ve listed. This thing has me puzzled. Been told fuel regulator but for the life of me I can’t find one on these fuel rails, been told fuel filter but this one is built into tank within pump housing. Here lately it’s been a coin flip on getting from home to work and back the 7 min drive each way. At lunch today it took 20 mins to make that 7min trip cause it was acting up so bad. It seems worse if it gets hotter, I can clear codes and drive 40 mph home 45 mins and it still hesitates if u push too hard but codes won’t come back for a day or two. I almost know it’s a fuel delivery problem just from the codes and what I’m seeing driving it. The fact it’s 2500 or 2000 rpms at 40 mph
But idk what to turn too next, I’m kinda stuck waiting for my new scan tool to come in to see the live data, n freeze frame data. I’ve always been the go fuel pumps are either dead or good no in between but this one has me rethinking that stance. But also thinking regulator if I could find one on it, or a fuel line restriction.
I fitted a fuel pressure regulator (PR217 for an American Buick V6 or 5.3 litre V8) which is adjustable,meaning that the regulator had to be adjusted inside a bucket of fuel outside of the tank due to the regulator being fitted inside the tank in the Commodore.
The closest setting I got was 60 PSI of pressure adjustment & the fuel trim has come down to 8.59% on bank 1 & 9.38% on bank 2 which is a nice change from 25% on both.
it does but it is more generalized and not vehicle specific. of course I give specific examples of what we're looking for with certain sensors but you cannot apply that across the board. fill out your name and email on my webpage and I'll send you some more information on it. thank you for your interest!
@victor35ma You are correct, it doesn't exist on this system. So it wouldn't be a Verus issue but a system design issue. Also, since this truck ran for 187,000 miles with the fuel lines that are on it, I would say line diameter should be fine, don't you?
The camera is a Panasonic HDC-TM60.
@ranacherian Thank you for responding! That makes me feel much better
My 99 Expedition 5.4 was reading 0 even with the switch and engine not running and then as soon as I started the engine the pressure went up to 31 psi and then it would jump up to about 38 when hitting the throttle. It stalled on me at a red light and sometimes it wont start in the mornings.
Always great information videos scanner
Of course! Section 5 (under causes of a fixed rich O2 or negative fuel trim numbers)
@amorozzo70 I think if you watch the videos right after the upload there is a sound quality issue until it is finished processing. Can you let me know if it is good now please?
It's just me but I like to see things diagnosed to the end. Fuel pump vs. fuel filter vs. fuel pressure regulator (if not built into the pump--you did say that the regulator on this vehicle is in the tank). I believe that the fuel filter should be changed anyway and first to see if that fixes the problem.
Thanks man. I wish you could too.
all of the returnless fuel systems will show a brief sudden drop on a snap throttle test. especially the electronic ones with no regulator. as long as it recovers quickly you're ok
i know at my BMW dealership we check the fuel pressure from the tank pump, usually around 450 kpa, and if that is good but the vehicle still has fuel codes we do a high pressure pump- but only cause theyre a common issue. im sure you could also look up fuel pressure by looking at sensor read outs on a verus or diagnostic machine, but ive never had to do that yet.
I had a E-150 with 2 fuel pumps-the low pressure pump (~3 psi) is in the tank and the high pressure is inline. You need two gauges since most gauges capable of reading the high pressure will not accurately indicate 3 psi. Some vacuum gauges can also read low psi fuel. If you have low psi, the high pressure boost pump is faulty. If you have 0 psi, the low pressure pump is faulty--the boost pump is not getting any gas. (Given that only one pump is bad and that the regulator and filter are good.)
@jdubb408 Is this freeze frame data you are quoting? If so my next step would be to look at live data both STFT and LTFT at idle, 1500, 2500 rpm. Can you so this and give me the numbers?
Wait, what? Refresh my memory please :)
As for the engine load data PID, I simply look at it for determining type of lean condition. If you have my book I have some case studies on that. To much detail to put here in a limited character box, sorry. In short, if lean condition is at idle = vacuum leak, if lean condition is under load = dirty MAF, low fuel pressure
Another great video!
Thanks again.
i finally brought mine to the ford dealer. even though my airflows on my mass air where normal looking. my baro frequency was in the 140's and im at 750ft elevation. so my computer thought i was at 4000 feet elevation. running 7 to 10 percent long term fuel trim. and my engine was pinging despite the knock sensor retarding it. i would get as high as 49 degrees advance off idle no load. and thats when it has a miss to it.my sensor is clean too. the baro readin is soo important on fords
@TRcustomengineering First, how does it run cold and at WOT? Are you sure the O2 is reporting accurately? If your not compare O2mv with tailpipe CO% and let me know how much CO is coming out of the tailpipe. What is your MAP voltage at idle and at 2000 rpm? How is the fuel pressure?(sucks to check on these if I remember right).
@victor35ma This is not an electronic returnless system so there is no FP% Pid. The tests you are mentioning apply to an electronic returnless fuel system. This one is mechanical. Also resetting the KAM would have nothing to do with fixing the low fuel pressure problem here.
Thanks for that. I'm currently dealing with a suspect pressure reg on a 2011 vx zafira at work. The waveform is all over the place. My next step was to check the fuel pressure with a gauge, it would jump to around 2 bar KOEO then drop to zero. Cranking would see the pressure steadily rise to 2.8 bar before spluttering into life. Compared to another vehicle and it was showing 4 bar KOEO and KOER. Can post the waveforms on the pico forum tomorrow if you want to take a look?
@ranacherian Can you double check the audio on your end please and let me know if it is fixed?
Refresh the page.There is nothing wrong with the video thanks!
@TRcustomengineering Oh and make sure the purge solenoid vacuum hoses are not reversed (if its possible)
Your welcome and thank you
@ScannerDanner In fact just a simple multimeter would have been good for this test. I really wasn't concerned about detail as much as what was the overall amperage.
YOU ARE THE MAN
2006 Explorer 4.0 L
Key on Engine off 207-276 kPa (30-40 psi)
Engine running 207-276 kPa (30-40 psi)
is this a question or a statement? Also, I believe your Explorer is an electronic returnless fuel system with a variable speed pump and no psi regulator and from memory, 30-40 sounds about right for idle speed on those
@94vettelover2 haha I will don't worry. You could buy my book though if you like:)
So it is running lean only under load. That is typically from low fuel psi or a dirty MAF sensor. But your honda is a MAP engine I believe so that rules out a MAF problem. Make sure your MAP is reading around 2.8v at WOT/KOEO. A test drive with a fuel psi gauge taped to the windshield may be in order, but be very careful and take a fire extinguisher with you. Was there any debris in the fuel tank when you changed the pump? (water, rust etc.) If so your injectors may be plugged
@ScannerDanner HiI didn't say electronic... but it is a returnless old ford system. if you replicated this in a dyno I said, you should run all monitor first for instance np_relearn... you know when you get DTC P1000 you are actually looking at incremental live data not real live data. so, reseting KAM in my opinion have a lot to do if you run the car in a dyno. didn't say KAM would fix it.
No it does not. What changes is the amount of fuel on the return line. The pump runs at full speed full amps all the whole time.
Although on a vacuum assist type regulator you will get a slight amperage increase due to the regulator requiring more psi to open it under no vacuum conditions.
thanks is corrected, thanks for replying
wait, are these negative or positive fuel trim numbers
My ford 1995 has a new fuel pump and new fuel filter and new fuel regulator, when I give gas the pressure increase but go down so fast is at 31 psi increase to 40 but goes down to 30 rapidly
of course the fuel filter needs to be replaced with the new pump. however a fuel filter alone would not have fixed this vehicle, it would have had higher than normal amperage on the pump with a plug fuel filter and it did not
Just here watching videos but my Acura does get the p0171 at idle when it sits for 10-15 mins I turn the car off and then start the car 5 mins later. I had my scanner hooked up and the freeze came said the intake temp was 139 but this is probably heat soaked from sitting but it’s 40 degrees outside. During the summer if I sit with the ac on it doesn’t happen. Come to think of it I just changed the purge solenoid last week and it’s more apparent now with the 0171 and 0174 codes. I do have a very small exhaust leak due to a gasket but it’s been leaking this entire time I’m sure if it and the code didn’t show up.
If the exhaust leak is near the O2 sensor or upstream of the O2 sensor. Fix the exhaust leak first!
hi, Paul. Great video. I have Honda Civic 1998 DX. Getting occasional P0171 (lean) whenever LTFT limit maxes out. STFT range at idle [ - 2.77 ~ + 3.00 ]. Upon acceleration STFT numbers plummet : 30 mph - 24%, 50 mph - 35%, 60-70 mph - 49% ( flat line on scan tool ). Once pedal released numbers drop to flat 0. Things done: new fuel filter, fuel pressure within specs (at idle) and open throttle (parked), swapped fuel pump, swapped ECU, voltage drop test on pump's power feed and ground (parked), ?
That happens to me in my toyota yaris 2007...we check everything..but this yaris does not have to check the gas pressure, so after discarding many possible faults ... we replace the gas pump and the problems will be finished, no more checking engine light or to lean bank 1 and p0107 codes on my board! !!
I LOVE YOUR VIDEOS.Would even probley pay for them(although keep doing this way :)
very very useful video... keep it that way!
I agree, someone should call them and tell them to hook me up :-)
on a obd2 upper end car, a good scanner - 100 bones- will give you freeze frame data of the environment at which point in time the code was triggered - faster and more robust diagnostic I got a cheap 80 buck one at walmart - roadi ngs 100 - gives freeze fr and real time o2 volts, short and long fuel trims , engine operating temp - , maf performance , map sensor
you dont have to look for weather cause the barometric pressure can be had from map reading and ect will be average 5 hours temperature of engine....lol - engine off so there is no vacuum and key in on position but no start.....lol
Thanks Russ, I just read your email, I'll get back to you soon, very busy right now
I have those codes on my 99 E350, and if I hear clean the MAF or check the PCV one more time I'll go postal, since I personally have done so, along with trace all the vacuum lines in the doghouse.
I am directing all help requests to my forum. Sign up (it's free) and create a new post. Be sure to add a name under "alias" as this is the name that will appear in the post.
Here is the link to the forum.
www.scannerdanner.com/ForumRetrieve.aspx?ForumID=3226
Thanks
Done all the same here on my f150
STILL COULD BE:::
....fuel pump
...fuel sending unit
....bad torque converter
...bad catylitic converter
...untraced vacuum leak
....intake gasket bad
....crack in the intake
....bad computer
.....bad fuel injectors
.....clogged fuel filter
AND MUCH MORE!!!!!
Get rid of the ford,,,get a Chevy and never look back
I HAD a Silverado ,,,NO ISSUES EVER
SOLD it to buy the f150 super crew for more room....WORSE DECISION EVER!!
even more issues then this
Mike T Bullshit, Chevy and their plastic intake, I have a friend with one that needs the intake gasket replaced, costs $1500, people like you always gotta come on here and try to play my brand is better than yours. Dads Chevy has ignition issues, being a 2001 it doesn't qualify for recall, so he gets to eat the cost of repairing it, have to remove the bed to replace the fuel pump, and the driving lights keep blowing out. BTW my E350 has been trouble free for 12 years, racked up 148,000 miles, and you don't walk away from a wheelchair conversion to start over unless you are wealthy, which in that case you'd just get it fixed.
Sure! What type of fuel delivery is it? Electronic returnless, mechanical returnless or mechanical return type? Also is it possible you could send me the FP wiring diagram? I don't have access to that vehicle nor have I ever even heard of one :)
I have a ford focus mk2, European version and it doesn't have a MAF sensor. Could p0171 he generated because of the swirl flaps that have gone bad?
@ScannerDanner So, I changed the res on the video and was able to watch it to 17:51 where it stops and wont play forward no matter what I try. Just wanted to let you know, although the res change did let me hear you until it stopped at 17:51. Look forward to your videos and thanks!
Thanks for sharing your knowledge
Hi Paul I do have question about fuel pressure, 02 gm Yukon no codes symptoms starter only when I push the accelerator. Fuel pressure 50 lb, when it should be 60 to 65, with 50 lb low why it won't start up?
i fix 2 ford explorer 4.0 v6 today classic p0171 p0174 mitchell said fuel pressure between 30 to 65 i checked fuel pressure first truck was at 38psi at idle second truck 40 psi at idle and arround 34 underload the fix fuel pump and i confirmed the fuel pressure have to be at 60 psi i replace the fuel pump and check again stft when -20% just like scannerdanner teach in class total fuel 5% thats a fix. from now on i burn 60psi in my brain for any ford with 4.0 soch and 4.0 ohv same as 5.0 ohv with return less system electronic fuel control thats another deal
thank you, so I am thinking on that fuel pump you have here on the demo if that pump is weak not enough fuel pressure you will have that one running at low rpm because amps is ok??
I heard of a formula to find out about the rpm if the fuel pump has 8 commuters I should set the cursor in between the 8 hump to get the delta time, the ms it took to complete the 8 hump divide 60.000/delta time = to rpm is that right ?? and most fuel pump runs at 3,000 to 6.000 rpm ??
Geez, the 5.0 was still around in '99? Is that a record for an engine family? 260cid-5.0.
Big fan of your videos!!!
I've ran into that problem at least a dozen time on those explorers
Hey, so if I'm aiming for a weak fuel pump on a car, should revving it up to 3k rpm while it's stationary cause the LT to rise 20+%? My roommate's fuel trim goes up during acceleration on the road (up to about 24% by the time you're at 50mph) but if I rev it while the car is stopped, it stays down at normal levels of about 0-4%. Idle speed trims are also 0-4%
I already ruled out MAF through both cleaning and swapping the good compatible MAF from my car to hers, and she has 2 newer OEM A/F / O2 sensors.
There's really no drivability problems here, just the leaning out while driving, and I'm thinking this might be why her catalyst monitor is never triggering ready no matter how many times I do the driving parameters to make it ready (coolant temp, IAT, etc all in order). Never throws a P0420 either though.
much respect
What is a 'weak pump?' It seems like they should work, or not. My Toyota has 185k miles, I replaced filter around 150k miles though they say never needed. I've had a slow start as you mention for a while. I now get P0171 and can't find it anywhere. I tried two new MAF sensors and code kept returning. No vac leaks. I've tried fuel treatment a few times to clean injectors. I can't find a shop as thorough as you - here they just want to throw parts at it, at my expense. I did take it to a shop to confirm vac leak with smoke test, he merely suggested MAF sensor and valve cover gasket for $500! Worse, he promptly dismissed my mention of fuel pump.
You definitely need to confirm good fuel pressure under load!
Pump impellers wear out, increasing clearance, reducing pressure.
Nice review.
Hey paul, looking for some help here. I went through some water a few weeks ago. When I got home I checked my air filter and it was soaked. Replaced air filter and dried everything up. The next day a p0174 code came on. Truck runs fine still so I just cleaned my MAF.....no luck. So I have already changed the MAF and both right bank O2 sensors. SES light is still on. Any thoughts? Pulled the freeze frame data today if this helps anyone take a guess on whats causing this.
Load value-88.24%
Coolant temp-186.8
STFT B1-7.81%
LTFT B1-33.59%
STFT B2-8.59%
LTFT B2-33.59%
RPM-2062
Vehicle Speed-77.05mph
i have a 2001 lincoln ls v6 133k and im having problems Symptoms
•Car will only rev up when warm (200°+)
•po174, po171
•horn not working
•cut off at when idling to long
•catalytic converter glows red
• check engine light won't come on
♢ what I done so far
* clean fuel injectors and test them
*Replace ignition coils
*Replace tps, all 3 pcv and egr sensor
*Cleaned maf and IAC
*Change spark plugs
*removed exhaust system no change in engine performance
* spread around engine for vacuum leaks with Carbon cleaner no change in engine
Lp Liverpool what is your fuel pressure?
Idk didn't do a fuel pressure test but i did just test the maf sensor and with a multimeter and scan tool on the mm i got 1.10-1.20v at 850-950 rpm and on the scan tool i got .8-.9v at 850-950 rpm so my question is. Is it my pcm or maf
Lp Liverpool neither, your using a different ground point than the PCM and it is common for the actual numbers to be off from scan data slightly. you need to do a fuel psi test next.
ScannerDanner Premium but what about my catalytic converter glowing red
Lp Liverpool you have lean exhaust codes and lean symptoms. a lean misfire will pump all kinds of unburned fuel and air at that cat.
Oh! What luck , I was sent a dud pump or one that has failed on Ebay !!!!
The stall pressure (i.e. the pressure of the fuel pump with the gauge connected to the fuel supply) is only 50 PSI which isn't enough pressure for the Chevy LS1 engine which is tuned to run at nearly 60 PSI from the factory - I had to do that test to rule out any possibility that the fuel pressure regulator may have failed or isn't up to par which is 58 PSI , so it looks like I won't have to Shell out any money on a 4 bar fuel pressure regulator which the car runs as standard,I did have a pressure rating of 65 - 70 PSI when I fitted the other pump in 2011 so I am not sure if that fuel sender unit was been fitted with a 4.5 bar regulator or that I have read that a 255 litre per hour pump will give a higher pressure reading than stock ????
That pump is still returning about 2 litres per minute back to the fuel tank when the injectors are at 100 % duty cycle (2016 cc's per minute in total for all 8 injectors).
I ended up ordering one of those Japanese 150 litre per hour fuel pumps from Malaysia for about $16 AUD so I am going to see how that one goes,the one I ordered from Melbourne also has a faulty non return check valve inside of it as well & I'd say the pressure bypass valve isn't doing its job if its bypassing fuel at 50 PSI so I will see if I can get my $30 back for the pump next week.
Mine is tuned to put out 276 kilowatts out at the flywheel (same power as the stock LS2 in Oz) so needs about 117 litres per hour to fuel it under load so the fuel injectors are flowing at 97 % duty cycle at full throttle.
The fuel trim has been at 22.66% on both banks as the ECU is trying to compensate for the lean mixture by moving to a different block in its memory to widen the injector pulse width so once the new pump has been installed this or next week,I'll let you know if that fixes the lean condition,I'd say the injectors can't atomize the fuel properly (i.e. bad spray pattern) due to the lowe pressure so hopefully they will run with a narrower pulse width soon.
When checking amperage on pump circuit, would a bad pump cause a high amperage reading? I'm thinking of this like a bad starter and pulling too many amps on the circuit...
Typically no, the pumps fail from poor brush contact so current is low. BUT, I've certainly seen mechanically frozen pumps draw excessive current
Thank you sir paul!
Thank you!
@fivefortyeye540i Of course! I just got a new toy that's all.
I'm having a similar problem with a 2003 BMW E46, the car is a bit of summer fun and as such I dont usually leave much fuel in it, recently ran it to keep things moving and it threw a code for misfire with low fuel and now I have lean codes for bank 1 and 2, is this likely to be the pump slow failing? Thanks
A weak pump will certainly have throw lean codes
Fuel Filter #1 issues
I have to replace the fuel pump in my 2002 Holden Commodore this week (runs the Chevy LS1 drive train) & I'm wondering why no fault codes could be detected by my scan tool.
The Maximum fuel trim value that was achieved was 25% on both banks (lean) & the fuel pressure is at 47 psi when it should be at almost 60 psi.
The only fault code I've ever read was a P0443 which was related to the emission control system (air leak).
Is the 25 % fuel trim at idle or under load? If it doesn't max out in low rpm, that might be why it haven't triggered a code.
trim numbers are positive. I put dashes just for the speed reference intervals. Car is using almost twice more gas than supposed to after highway driving. Some other lying sensor ? ( Extra info: previously replaced cracked manifold at the O2 sensor housing and melted cat. Possible mechanical damage consequences ? )
You should do a video where you look at sertain sensors to no for sure the maf sensor is no the fault also how to calculate maf flow