Where Is The Fuel Pressure Going?

In this video Eric O. has a look at a Cadillac that will not hold fuel pressure. Fuel pressure on a return type fuel system can leak one of three places. It can leak out the pressure regulator externally and internally allowing fuel to bleed back down the return line. It can leak out of the injectors and it can also leak back on the pressure side if the fuel pump check valve is bad. The question is how do you know where it is going!? Pay attention we are about to find out!
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Disclaimer:
Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair 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 South Main Auto Repair, 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 South Main Auto Repair.

[@mistersunflower4156]

You have the best videos, informative, clear, no distractions, no distracting music, no dead air time. Just the facts

[@d-s-ll2378]

One of the best fuel leaking teaching, efffective actions, no bubbling. highly respectful. many thanks, 👏👏👏👏

[@johndavis4800]

Been a few years since I pulled wrenches for a living , but apart from a few dribblers and odd shaped spray patterns, injector failure was fairly low on the ladder of anticipated failures. Which is kinda amazing considering how many millions of times they have to cycle to get you down the road...if I'm not mistaken my old 68 square back had Bosch injectors which never seemed to fail.

[@Fireship1]

Very methodical troubleshooting. I've been fixing cars for 25 years and I'm always learning some new trick or tip from you! Thanks for making all your videos for the KZbin community.

[@gradyhernandez4699]

2.4 caravan

[@gradyhernandez4699]

Not all have a vacuum line me on pressure regulator

[@jon316love9]

If you had been an instructor years back at vocational school, I’d be an auto mechanic today lol. Excellent video, easy to follow and understand. Great Job!!

[@Aardvark49]

I'm just a DIYer, but am really learning a lot from your showing how to step through a diagnosis. Thank you.

[@winfoley]

Just today-same problem - put pressure guage on fuel line out of tank and found the check valve leaked back. New fuel pump assy being installed. Will check, then recheck at rail. Very good on your presentation.

[@jimandnena4]

97 Explorer Limited suddenly dropped from 15 to 8 MPG around town. 150K on the clock, wife's car and I do all the maintenance. Surfed looking for fuel pressure numbers and Alexa led me to your channel where I have been subscribed for awhile. Great content as always and well done. Thanks

[@Vercus100]

Wow, when you said "it might just be your time" in the beginning, I have never laughed so hard during an SMA video. Pure genius. This is just one of the reasons I'm a big fan. Keep it up!

[@Xmvw2X]

Great video. I have a fuel pressure loss in my Subaru that I need to troubleshoot, and this is spot on for evaluating what's wrong, helps me out a ton for plan of action.

[@FPVREVIEWS]

the most complete diagnosis discussing the several possible options for the fault. this helps a lot., Thanks !!

[@TaekwondoFitForLife]

This is an amazing mechanic! Very good Sir, and you’ve helped me to go somewhere with an issue I’ve got on my older f150 with a 4.9 EFI. Thanks so much Sir! Wow, yes it was definitely spraying like wide open like no injection was there like you have equated on this video! Never will have thought an injector could as you say leak the volume it did… just wow, wide open like not there…

[@SEKI14000]

Another great South Main Auto Repair - Eric O video! Excellent examples on how to systematically go about diagnosing a fuel pressure problem.

[@spelunkerd]

Excellent demonstration of how those old fuel systems work.

[@suharinos]

Old?, thats how they work today.

[@letsfly7562]

South Main Auto you TRULY ROCK and your skills are A-1.

[@gould3063]

Hell of a great video! Well explained and now I know how to check the system better! I have a few more issues to check before ripping out the pump. Appreciate your knowledge! Keep up the great work buddy!

[@MarkMattioli]

Followed your advise with a job that came in today for non start, purchased a fuel pressure tester and turned out to be fuel pump pipe inside fuel tank had split and was leaking internally not holding fuel pressure!! Life saver 100% answer! Proved and verified. Just had the happy job of dropping fuel tank and replacing split pipe. 👍

[@JeffTheHokie]

I had a similar problem on my ranger. Mine wasn't a hard pipe. It was a split hose inside of the pump assembly. I noticed the split hose about a day after I replaced the assembly. Now for the cost of 2 inches of hose and 2 clamps, I have a spare pump if I ever need one.

[@dandearman2871]

I like your plumbing setup on your fuel pressure gauge. Like they say, necessity is the mother of invention.

[@Mr032789oscar]

This is too much of a coincidence. Im currently dealing with residual pressure lost. Thanks so much for video.

[@Batti2323]

Thank you for your thorough demonstration of isolating this problem. I really appreciate your methods and presentation!

[@richardbambenek2601]

"Safety squints" Your funny expressions are one of the things that make your channel so much fun.

[@roberthayes6329]

A nod to AvE for sure. 🤘

[@_AndromedaGalaxy_]

i like the term "Bitch Mittens" aka gloves.

[@bobkmac]

Awesome video... I've been looking for ways to determine why my LS won't hold pressure with the key off. Unfortunately I don't have one of those T fittings. I believe my issue is either the pump check valve or pressure regulator.

[@jondwyer3037]

educational as usual Sir Eric. Ive got a vauxhall (General Motors) Astra active 1.6 inline 4 with fuel injectors similar to those on the cadillac .I ve had problem with the upper sealing rings blowing out cause over presure at the pump in the tank.

[@OneAuto]

Great methodical diagnosis Eric.

[@turkraja255]

seriously this video is very informative. very precise diagnosis. thank you eric o. thank you very much for great stuff.

[@lightningsmokerXx]

Eric i got home late and got on the pc and was like damn ,.....no sma videos....and then i hit refresh and bam! you uploaded one. Timing perfection.

[@miker252]

I want to thank you for this video! My 2000 LeSabre, while hard starting, was running pretty well. It wasn't backfiring like with a leaky pressure regulator. (I'd changed it 5 yrs ago only later to find it had been the subject of a recall a decade before it failed.) While I don't have your tools, I do have a gauge manifold and a small compressor. Following your method, with no external leaks, I determined it must have a faulty pump and replaced it. Inspecting the old part, I found a pin hole leak in the plastic flex line, bleeding pressure back into the tank, between the pump discharge and the top of the assembly. Oh yeah! Bonus. I also now have a working gas gauge.

[@sharedknowledge6640]

Great video showing the logical steps. I think the BMW N63 V8 had a similar issue with a failed injector hydrolocking the engine and destroying it (with dealers charging $25K+ to replace the engine). The ECU monitors the fuel rail pressure and could, if manufactures wanted, detect a key on no-crank injector leak and then throw a code and prevent you from cranking the engine. When you shut your car off it could easily detect a fuel rail leak and throw a code and even perhaps prevent cranking until the code is reset. That's a bit extreme but it might have saved BMW, and apparently GM, some engine replacements. And the injectors should be designed even if stuck open to limit the max flow to something that hopefully wouldn't hydrolock an engine just from the 2 second fuel pump prime and then being cranked. But yeah, at this point this Caddy is basically scrap.

[@Happy4Go2Lucky]

So glad you picked my car. 2003 Cadillac Deville has the same coil pack and configuration shown on top of the engine. After having replaced the intake manifold gaskets on a 1999 Chevrolet Malibu LS , it took me seven months cause I’ve never done that sort of work before, I was elated to do the Cadillac Deville job in 3 hours. I gave up on replacing the gaskets as I noted in my last comment -they kept popping off. But the car is relatively easy to work on. I’ve replaced a wheel bearing assembly. I wish somebody would make a video about how you get the wheel bearing through that hole without breaking off the ABS sensor or whatever the hell that gizmo is that sticks out and breaks off. I used to play with Rubiks cubes and these wooden puzzle cubes so I tried every combination I could think of, but could not get that wheel bearing assembly through the hole with without breaking off what I thought was the ABS gizmo. I also gave up on replacing the fuel injector O-rings that have 106,000 miles on them. There’s a plastic ring at the bottom that keeps the O-ring 1/8 inch off the bottom. The Fel-Pro O-ring replacement kit does not have those plastic rings. If you try and take the O-ring off you break the plastic ring. And working on the Chevy it was impossible to replace the fuel injectors because the clips that hold the injector to the rail would go flying and get lost somewhere in the engine. So that was a job that never got done. I got all these Amazon fuel injectors that will never be used because the clips are so horrendous. I did not try the clips on the Cadillac engine. Everything on the Cadillac is so much better than on the Chevy for being easy to work on. My biggest gripe about the Chevy is the AC has never worked right. The 1999 Chevrolet Malibu seems totally accessible for the AC components except the condenser. If you look at the Cadillac condenser it looks like you just open the hood and out it pops. Not so with the Chevy. I find the Chevy is a nuisance to work on. But the Chevy gets 20 miles per gallon with a leadfoot in city driving. The Cadillac gets 14 at best. The Chevy is ideal for city driving and shopping trips. The Cadillac with the starter motor buried under the Plenum is better designed for interstate driving.

[@tedtolentino4955]

thank you for this video. It thoroughly explains in logical fashion how to diagnose a fuel leak. Please keep up the good work.

[@lucianoromero777]

I’m gonna try this on my Pontiac 2.4 1998 GT. Same exact issues, Loss of pressure slowly going to check everything you did in the video. Thanks much I wish I had a mechanic in my area like you

[@arciefan]

The word is deluge. It deluged the cylinder. And if Hannah had not have shut her down it would have deluged SMA with fuel. Excellent and another enjoyable video to watch Eric. Thank you so much !

[@timothybarney7257]

arciefan I wonder if that injector came off of an engine running nitromethane? Had the flow rate!

[@anthonykendrick1418]

Great video. Perfect timing for me to see this one because I'm currently dealing a similar situation on a 1989 F-350 dually with a 460. This will help guide me to thru the process to narrow down what my issue is. Thanks a bunch for showing us this process.

[@nothingbutperformance8037]

thats crazy! never saw an injector leak that bad either! great video as always keep them coming! wow that injector is crazy

[@j.cbaker6179]

You are Very thorough and it is nice to learn from someone that diffenly knows what to do. I greatly appreciate watching your videos. Thank you

[@sandyande]

brilliant was just dealing with a neighbours car with low pressure fault only reading 0.5 bar! new in-tank pump with built in regulator solved it cheers Eric, sandy

[@errorcodeguy456]

Great job explaining the three places fuel could go! Keep up the good work on your videos.

[@robertweir9034]

Eric O. This is an excellent presentation into diagnosing an event I have seen to date. No one does them better. Process of elimination was right on. Don't want to sound like a brown noser but, you are my hero. All that in twenty minutes. if your not getting paid somehow on these videos, something is wrong in internetville . Bless you sir.

[@iamdru1223]

💯💯💯💯💯💯💯💯💯

[@neilhannman169]

Agreed. One of the best diagnosis videos I've seen on the Tube. Thx for posting it!

[@rickhewitt5995]

3es ree redd er by ßßaaaaaaaaaaaaààààßaasaaaaaàaaàaàaaaàaaaaaaaaaaaaaàaaaàaaàaaaàaaaaaaaààaaaaàaaaaaaaaaaaaaaaàà sea aa area At

[@redwoodhd6217]

Great video Dr. O! Just had a Yukon on Friday doing that exact same thing, customers bringing it back Monday now I have a new approach for it. thanks for all the helpful information.

[@stevebaska2577]

Eric you're my hero I just love watching your mind diagnose things. You're my mentor. Thank you hope we can meet someday

[@REPOOCNITSUJ]

Have a car IDENTICAL!!! to this in my stall right now. I remembered watching this a while back, and had to find it again tonight. Can't wait to get there in the morning and pull my injector to see if it sprays like this one did.

[@ddilink]

I enjoy your videos. I like the problem solving logic as well as the close ups. I'm a little hard of hearing so the clarity of the audio is important to me.

[@TheBikeMechanic]

Just about to get started on my 2001 Nissan Xterror with a hard start when warm.... that was an epic discovery of the leaking fuel injector! Damn son!!!

[@steveburge4321]

I enjoy watching your diagnosis....you make What you're doing look easy. Your experience has obviously been gained through many hours of work. I only wish I could find someone like you to fix my car in barrie Ontario Canada! Thanks and ( look out scotty ) this guy knows his stuff too!

[@johnh8546]

Look out Scotty if you are talking about Scotty Kilmer he has never put out a video near as good as Eric. If he does know as much as Eric he has never shown it in a video I have seen.

[@Anonymous-it5jw]

Good call; good practical procedure to follow, but no Brake Kleen, no acetylene torch, and no explosions to liven things up. I guess you noticed that beginning at around 2:20 or 2:21, you can see gas dripping out of the T-connector at the point where you connected it to the pressurized fuel line - it happened each time you turned the fuel pump on. That little glitch could throw us DIYers off the correct diagnostic path.

[@DougFlood-jh9ew]

Great video. You make it so simple to understand. I am getting a p0171 and p0174 code. I was thinking weak fuel pump as the regulator seemed to be working, when vacuum line is disconnected the pressure goes up with no leaks. When car is shut off the pressure drops. After watching your video and seeing how you pinched off the return line l did the same. My pressure was much higher than when the car was running and it was maintained after the car was shut off. Final outcome was a bad fuel pressure regulator. Much easier to replace than a fuel pump. Thanks a million for your video. Doug in Canada

[@williamstidham2163]

Your the man, We look on and feel like top notch mechanics till we see our problems somewhere else’s,

[@phillippaul8578]

Awesome diagnosis sir....1st class !

[@jeremymorgan1683]

im a huge fan of your show i have bin wrenching for over 20 years and im still learning new things with your show

[@assignmeanameplease]

Great Video Eric, you are always a step ahead of me:) I was thinking that a thermal camera would be a good way to see if an injector was staying energized by seeing which one was hottest, but then you mentioned the thermal camera! I was also thinking that seeing which injector was COOLEST (due to the fuel flowing through it) might be a quick way to pin down the culprit.

[@davidljohnson8514]

Excellent excellent video this individual does an excellent job in explaining so much in almost less than 20 minutes.

[@exploringgodscountry]

I've been chasing my tail. I hopped up an LQ9 (basically an LS2) a bit with a custom valvetrain, cam, Johnson Lifters, rocker rollers... Then threw it in my 2001 Tahoe. Engine runs like a BEAST no issues (except P0300 code on occasion but due to bigger cam?) Bought new Delphi injectors (I now see they have very BAD reviews on Amazon). Long story short. I can warm the engine up. Then turn it off and say go in the store. When I come back it doesn't want to start. I have to crank the engine for several seconds before it will turn over. It starts perfectly under all other circumstances. I've been chasing my tail trying to tune issue out with no luck. Bad injector? I am buying stuff to diagnose. Bit nervous to pulse injector in cylinder w/ engine off like some tutorials I've seen. Have to finish watching your tutorial.

[@billcovert3473]

Bar engine over to relieve cylinder hydo lock. Man that brings back old memories of hydro locked Cummins truck motors which had holes in the liners from cavitation filling cylinder with coolant. To evacuate lock up bar engine in reverse engine rotation, thus allowing the fluid to escape out the exhaust value. After 3 or 4 rotations the cylinder is cleared allowing engine to be started, leave radiator cap loose and haul another load of logs. So bar reverse rotation to expel fluid.

[@gertis7420]

Just the video I was looking on how to test the fuel pressure regulator part. Thanks for sharing

[@1darslars]

Thank you for making this video was chasing my tail trying to find fuel pressure loss - ended up being bad fuel pressure regulator.

[@t_158]

Take off the vacuum line and if there is signs of gas fuel pressure regulator always the issue in this case

[@Atetus94]

You are The best car KZbinr! Thank You so much for Your videos, that I can learn from!

[@pontiacsrule8761]

This guy has the best informative videos. I'm still catching up on all of them.

[@yambo59]

The new Northstar firehose injection system-!

[@jeffburtonnottheracecardriver]

yambo59 that's hilarious!

[@baxrok2.]

Epic injector fail for sure Eric. Sweet catch on video! Lots of good info in this one. Thanks!

[@BuzzLOLOL]

My '79 Caddy Seville EFI Olds 350" had that problem... getting 1 MPG... raw gasoline dripping out the end of the tailpipe... Caddy wanted $180 for a new injector, so I blew air through it backwards from an air hose while jumping it open with 12 volts and it cleared the clogging crud out of it... worked fine there after... still have the car... Caddy wanted $400 for pair of new rear air shocks, so bought universal ones for $50/pair... Wanted $90 for front muffler and $60 for rear resonator, so put four $15 turbo mufflers on it... quieter than stock and less back pressure!

[@77.88.]

You did a great through video and covered all the fuel diagnoses bases well done and thanks, Old retired wrench!

[@Dugar1]

Wow that's amazing the flow rate of that injector. Again awesome video Mr.O

[@joetiller1031]

Good find Dr. O., if it was mine a trip to the salvage yard.

[@rwrobs777]

Excellent video Eric O !!...I picked up 2 used GM fuel line adapters (J37287 ) on Ebay for cheap...less than $100... each has the inline shut off valve....no more pinching off the lines with vice grips !!

[@chrismunos7741]

I'm using the last segment tomorrow! Awesomeness!!! Spewing is the descriptive word that I'd use for that injector!

[@oh8wingman]

Instead of pulling the injector rail and the injectors like you did, could you not pull the plugs and check for one that is fouled with fuel? You're going to have to pull at least one to overcome the hydro lock in any case.

[@joewahrerMotorcycleMan]

Man I learned a lot...I'm working on a Polaris Ranger and all your information enabled me to fix it and I thank-you!

[@stargazer9172]

Great video! Good editing. To the point. Made the diagnose look easy

[@DependableAutoTruck]

very good information you made it so simple . never seen a injector spray that much wonder if the end is blown out

[@mikechiodetti6737]

Good Diagnostic testing! You found the gusher!

[@johnworkman5121]

I’ve learned so much lol thanks I’ve filed that away...I just watch random videos by you just trying to get better at diagnostic

[@netocruz5080]

Thanks man, learn a lot with this video, now let me go to my 460 and check all the injectors, thank you.

[@tasmaniandevil7610]

Thanks for the explanation Im having lean issues myself

[@steventorres4296]

YOUR VERY GOOD AT WHAT YOU PRESENTED EASY TO UNDERSTAND THANK YOU

[@Veritas_mens]

Great video Eric. Never seen an injector leak like that before!

[@diagnosticcheck9803]

Hey eric thanks for the great video. to save time on finding out which cylinder is leaking you could pop the spark plugs out and hold a gas analyser over the plug hole. The hydrocarbons would go though the roof on the leaky cylinder and that would definitely be yar prablem lady.

[@maverickbryan7579]

Yes you are a good person to help people understand

[@stephenrogers5386]

One of the best videos I have seen on this subject.

[@eddiecuttsjr.5482]

Very Nice Diagnosis. You know your stuff !! Nice to see. Gonna check out my 454 she is leaking off her fuel pressure at about the same rate. Thanks a lot, I appreciate you explanation and time. Thanks again..

[@LunaDaSavage]

Bro you are a BOSS. I hope I can get to your level of experience and knowledge someday. Thank you for sharing

[@randrobinson443]

great work Guys... now if I just had all those tools

[@MrGreencheetah]

"Holy Crap Biscuit!" -- that was a thoroughly enjoyable romp through learning some cool stuff!!! Great video and you're a pretty clever guy!!!

[@rayhope7957]

using "holy" and crap together is an oxymoron....

[@davidtrautman6482]

Nice work but that would have been my first guess with the fuel rich condition along with the hydrolock. However, thanks for the thorough diagnosis. No wonder it was hydrolocked

[@wilfredomendoza9932]

This is the best testing procedure that i has ever seem, i really enjoy it thanks for the info.

[@kristianhermann5971]

Awesome video - love the clear explanation - thanks Eric O!

[@jamesadams2333]

Introducing the all new General Motors Northstar Rich Edition! *Replaceable Head gaskets still included! Buy one now! Sorry I just had to say it! Incredible work as always!

[@MrBlazenBruce]

Awesome Diagnostic video Eric !, Keep up the great Content, Even As a Certified Tech It helps to be shown other ways of Diagnosing !

[@evansjeanbaptiste1431]

You are wickedly nice at what you do bro. Respect ✊🏿

[@krookdfinra]

very informative and in depth fuel diagnostics

[@josesolorzano8403]

Thanks buddy I got the same problem

[@mkdayton321]

Having the problem with 1997 Tacoma, replaced all injectors. Going to do pressure regulator next. Starts hot fine and runs good, cold start hard and have seen a little gas leakage around regulator.

[@notejones9927]

I have learned it for you thanks eric

[@stevebirchmeier8082]

Great job of troubleshooting. I am currently trying to figure out a cyl 7 misfire situation on this same engine. I have replaced spark plug, boot, swapped coil assemblies and it stays with the cylinder. I have 35psi fuel pressure with key on and at idle. Misfire counters are worse at idle than higher rpms. I have replaced the fuel pump for a bad sending unit. The low fuel pressure concerns me. Any thoughts. Thanks Eric for sharing the knowledge.

[@freddy2064]

"There's your problem lady", lol. Great video Eric. Nice call on not cranking that thing over. Talk about hydrolocking jeeez!.

[@gouveiaclassicos]

Top marks for this video show the right way of doing diagnose

[@whitetiger8652]

Nice job Eric. Definitely a major leak going on there

[@RussellBooth1977]

I had that problem in my 1986 model Holden VL Commodore in 2008 which ran a Nissan RB30DE engine that I built for it in 2003,it ran the original 3 litre Nissan block ,rods & crankshaft but the rest of it was from a 1995 mode R33 Skyline RB25DE engine so it was a 24 valve engine,not the original 12 valve engine. Well,water leaked past the windscreen then into the ECU then shorted the injector driver out, I cleaned the ECU out with electricial contact cleaning spray & I found that number 4 fuel injector was jammed open. I went to the Japanese wreckers later that week & picked up a fuel injector to suit a Nissan SR20DE engine out of a Nissan Pulsar as it was the same fuel injector as the Skyline injector. Replacing the fuel injector fixed the problem !

[@cw2lido]

Wow! That's a bad injector! Great video! Thanks for sharing!

[@opl500]

there's your problem lady

[@AntonioClaudioMichael]

Good methodical Diagnosis Eric O very informative on How to Narrow down Fuel Pressure Psi Bleeding off Rapidly man That Fuel Injector is Just Gushing that explains why the engine was locking up Good Video as Always @SouthMainAutoRepairLLC

[@jackle842000]

So what all symptoms can a fuel pressure leak down cause? No start? Slow to start? Huge loss of power? Thanks for the video!