How to replace a fuel pressure regulator on 7.4 (454) gm engine. This is a 1999 k2500 suburban. Comment if you have any questions. Thanks for watching, hope this helps you!
So my '99 Vortec 7.4 started having a hard/long cranking warm start issue. It also threw the random multiple misfire code and I could smell raw gas with the engine running, but with no visible leaks. I thought I had an intake vacuum leak somewhere that was causing over-fueling, so I put together a home-made smoke generator to try to find the intake leak. . . However, here on RU-vid I learned that the Vortec's are plagued with this warm start issue, and that it is fuel injectors leaking, and that it is fixed by replacing all the injectors with new injectors because the refurbished ones have just been prettied up with some brake cleaner, bla bla bla. . . . The videos, or blogs I went through also kind of offhandedly said to replace the fuel pressure regulator too, since you are down in there. . . . Well, when I tore things apart, and got down to removing the top half of the intake plenum, I found about a cup, yes literally a cup of stale standing gas sitting down in the bottom of the lower intake plenum. I soaked it up with a towel, not a shop rag. . . . Over-fueling? . . . Yeah . . . Bad injectors? . . . Maybe. . . The injectors are port injectors. They don't put gas in the intake plenum. . . How did all that gas get down in the intake plenum? . . . I was just debating whether I should spring for $800 worth of new injectors, when I decided I should also rebuild or replace my fuel pressure regulator, so I was back here on RU-vid researching the fuel pressure regulator rebuild process. . . . A search brought up the @Schrodingers Box channel and a video on understanding fuel pressure regulators. . . . Go check out that video. . . The reality of how all the gas got into my intake plenum is that the fuel pressure regulator diaphragm is the only thing between the fuel coming from the fuel pump and the intake vacuum inside the intake plenum. . . . A bad/leaking diaphragm allows gas to get sucked and pumped directly into the intake plenum through the vacuum port connection thereby saturating the air in the intake and making a massively rich condition. . . . So, put a new fuel pressure regulator in, and then make a fuel injector tester setup (RU-vid) and check for injector leaks, clogs, and spray pattern to be thorough. . . You don't want to take things apart again for at least a few years. . . . If you find bad injectors that can't be cleaned or made to function properly, play the junkyard game, if you want, and find good replacements there. . . . Or you can just spring for an $800 set of new injectors. It's your time and your money. . . Oh, and don't forget the fuel pressure regulator. . . . Good video!
Came from day when I bought a book to do this sort of thing, read the book on small block Chevy rebuilding than DIY on 1st full rebuild. Ran the heck out of 327 for 20yrs. Spent good money on "Chevy shop manuals" when purchasing '96 3500HD new, two books stack 5" tall and are nearly worthless. Couldn't have fathomed we'd get such info from vids. :D Very helpful.
Th is was REALLY helpful. And like you said, you pass on the easy stuff and concentrated on what really mattered and made the job easier. We all appreciate what you did. Why didn't you do injectors at the same time??
fyi: I found a FPR for the 7.4L GM engine on Amazon that's ADJUSTABLE! Waiting for it to arrive now.... every regulator I've gotten from Rock Auto, Ebay and local parts stores has produced fuel pressures below the required engine injector specs. The factory injectors are spec'd to require 58 psi at idle and up to 63 psi when the throttle is increased to accelerate... the regulators I've been getting have all turned out to be at least 10 psi too low! Dead-heading my fuel pump it produces in excess of 85 psi, so there's nothing wrong with it it's these darn regulators that have been eating my lunch.
I replaced mine and did not have to remove the intake at all. I removed the distributor cap and had enough clearance to pull out the old fuel pressure regulator and pop in the new! Lol
I have a 2000 7.4L 427 that is doing some weird stuff. Its in a RV (Fleetwood Southwind) I have access from the back side so this should be easier for me. Idles fine, decent pressure on the fuel (50psi +) As soon as I put load on this thing, it won't give me more than about 2000 rpm and boggs out. I am interested in how you tested your fuel pressure regulator and what the symptoms were before you changed it out. Thanks for making this video!
very very helpful.. looks like i get to replace that fuel pressure regulator, that or the rubber hose is leaking from a mouse chewing on it.. dont know yet, just bought a 99 2500 suburban, not running, bad fuel pump, and the list continues lol
Great video. Very helpful and informative. I’ve got a K3500 Chevy pick up that’s due for a tune-up and has a misfire on cylinder 7. Hoping that this will help out with my issue or perhaps a bad injector since it was mistakenly filled with diesel at one point. Awesome RC videos too. Cheers from Central Valley CA.
:D I've run a tank of diesel thru old carburated industrial engine, ran fine but as I had heard the oil level comes up fast with blowby dilution, need to change oil right after. I can't see why it would damage injectors but they are expected to need replacement anyway I'm told...why I'm here with a severe miss on #4. Only "safe option" for injectors I could find available on Amazon were around $700 but as always parts cost is trivial compared to the labor, downtime, etc. Obviously going to change out psi regulator too.
@@Mrbfgray from what I’ve read; diesel is a little more viscous than gasoline and that messes up the fuel pump and leaves residue on the fuel lines and maybe the injectors too. Injectors do get pricey; I did consider getting a set of 8 new injectors ended up getting a set of 8…o-rings. :D haha. 2$ each ar o’reilly’s. Pulled out my fuel rails with injector and everything looks normal except worn out o-rings. A bad FPR (fuel pressure regulator) and a bad lower intake manifold will cause a misfire. Mine is on cyl7 and it’s intermittent.
@@oyeahboii Interesting about the o-rings, I don't want to take a chance of having to pull it apart twice so IDK. I wouldn't know for sure about diesel damaging anything other than the motor oil which it certainly does but gasoline would entirely flush out the diesel in no time I say.
The rubber vacuum line going to the regulator should be replaced while you have it apart. I have seen many rotted or dried out lines leaking air, the heat back down there where that vacuum line is, is a really hot area. I just use some fuel line that is the correct diameter to replace the vacuum line, fuel line lasts a long time. Why they couldn't put that regulator in a better spot is beyond me. I have to replace my fuel pump for the second time, only reading 20psi so truck barely runs if it starts at all. I will stress one thing, only use genuine GM replacement parts and sensors for any of the fuel system, electronics, or emissions systems period. I put in an aftermarket fuel pump and new it didn't put out enough pressure and didn't last but a few months and removing the fuel tank is not my favorite job🙁. This time I am cutting an access hole in rear floor. The MAF and MAP and temp sensors you must use genuine GM or you're asking for problems. I also used aftermarket injectors and another big mistake so paid for originals and have to install them. The quality and calibration of genuine GM parts its perfect for the onboard computer/ECM. You will pay more for genuine AC and Delphi GM parts but they work correctly and last. I have been a mechanic for 50 years and have learned the hard way. But what did I do???, used all aftermarket parts and now problems, I should know better, but tried to save some coin, hehehehe.😁 My 1999 Suburban K2500 7.4 4X4 is off road only now so I removed all emission stuff and only run the two front Oxygen sensors for fuel/air calibration, and runs fantastic except for the problems above. I also removed the EGR and all that stuff and the air pump. I also built duel large diameter exhaust with no CATS. Next, I will drop my 871 blower on it. OH, forgot to mention, I bought an aftermarket MAF sensor and it didn't work right, worse than the old original I took off, so now have to buy a genuine GM sensor and not cheap, so I wasted that money on after market junk. I also noticed the engine aftermarket temp sensor was not putting out the correct readings which is real important for the ECM, so need to get another good one this time. My mistake: What I did was decided to do a major tune up on this and ordered all parts at once and all aftermarket, I am talking allot of parts including the crank sensor and distributor, every sensor on this truck I bought after market. I have a computer scan tool that tells me everything that is going on, what all sensors are doing and putting out, etc. And this is how I know what aftermarket parts are screwing up, and that I made some big purchase mistakes. I also replaced the fuel pressure regulator but it is working fine, so far? Thanks for the good video. OH, this engine distributor is locked in one position. It has a different hold down clamp that is square so you can't turn/adjust the distributor. Its similar to a cam sensor basically. If the timing chain gets real worn it can put the sensitive distributor timing off. If the chain and gears are worn just a little its no problem. You can have someone with the correct laptop scan tool check the coloration of the distributor compared to the crank position and tell if the timing chain is worn bad. I love my 4X4 suburban. There getting hard to find now. And mine has the towing package so heavy duty everything.
Your old FPR is missing the very small o-ring. My guess is you left of in the rail which would explain why you're having to use a friggin c clamp to keep in compressed so you can install your clip.
Taking off upper intake on my 1997 C 3500 Sierra pickup truck not lifting High enough broke off plastic and fuel injector assembly clip.... watched metal clip go in as I noticed structure was broken and fidgeted with it with my hands... down into the intake.
Sounds like a nightmare scenario! Like the night I was fishing with my phone in my lap and stood up and watched it skim off the edge of the boat into the lake. Hope it worked out better for you.
On the intake on the drivers side with the open hose that looks like the pcv valve is there a hose that hooks up to that or is it just a suction breather for the intake?
Good job!!! I have a cpl questions. 1.Was the regulator leaking internally into the intake giving you a rich condition? 2.What was the symptoms that the truck was displaying for you to complete this task? 3.Did this fix the symptoms? The reason I ask is I am getting ready to do this job tomorrow.
Yea I’ve done some research and it’s pointing to that irk pressure regulator. My 99 big block Burban after it’s warmed up and been running will not start right away. Act like a carb motor. And at the 3rd try it will start and blow a ball of black smoke and smell raw fuel. I’m going to replace it and see if it fixes my problem. I will update you on that. Thanks.
Juan Vazquez yes I will let you know. I live in Arizona and it’s 115 right now so I haven’t gotten around to it but when I do I will post or reply with the results.
R. Robles I just got my truck done 2 day’s ago... so far the truck has been running pretty good no complains!!... I didn’t remove the intake, all I removed was the air box, brackets on the back on top of the distributor cap, and (distributor cap)... it’s a tight fit but it can be done!! Good luck🤟
I find it easier to remove the throttle body (leaving the cables connected to it) and lay it over into the driver's side of the engine compartment, leave AC lines connected to compressor no need to open that system! I am however having a heck of a time trying to find a new FPR that's got the correct psi ratings.... auto parts stores list some FPR's that "fit my truck" but are only 36 psi rated! WTF? Everything I read says this 7.4L engine requires 58psi at idle to run right, why would they want to sell me a 36 psi rated FPR then? :-\
I just stuck a new FPR that they assured me was rated at 57 psi, but it's actually only creating 54 psi and then dropping to 51 psi without vacuum (in other words, 54 psi is the max it will ever make!). It's just not right, it should go up to over 60 psi without vacuum.... and yes my fuel pump will produce over 85psi with the return line clamped shut so that's not the problem! I'm stumped right now.... hence I was Googling and came across your video.
Well, another problem, distributor cap shorting inside from center terminal to another that is close by. Actually burnt a hole in the cap plastic. What a shit design cap, normal caps are much better. And as usual intake has to come off unless you want to torture yourself. Do not use an aftermarket rotor and cap, they don't last guaranteed. While intake is off, replace the fuel regulator and intake vacuum sensor up front by the radiator hose on top of engine, easy to get to with intake off. And also replace the ignition module that is mounted to the coil bracket, again, easy to get to with intake off. These parts are not too expensive so do it. If you feel like it, replace the distributor metal rotor sensor in bottom of distributor. I did not see any codes for this shorting dis. cap. It didn't want to accelerate and acted like it was starving for fuel, which was strange, and then it would not start with huge backfires actually stopping the cranking of the engine. Also, pull your crank sensor out and check to see if it has been contacting the sensor rotor inside the timing cover. If so, slide a high-quality rubber Oring over it to hold it back away from the rotor a bit. Works perfect and also helps stop oil leaking. Even if it has not been touching the rotor, I recommend adding this Oring, a little more space between the rotor and sensor will not hurt performance. I used an air conditioner line Oring used on the truck that has the same approximant diameter as sensor. I hear they sell a spacer kit for these sensors, but an Oring works fine and fast. My first crank sensor was touching the rotor and leaking oil around the sensor when rotor hit it and moved it while running but it still didn't fail which was shocking. I also don't take the coil off the intake when removing the intake but do unplug the wiring. Intake comes out and goes right back in with coil mounted to it. My 1999 K2500 454/7.4L 4x4 Suburban LT lights the tires up through first and second gear, what a fantastic machine. This is a heavy truck to do that shit. The only change I made was building a custom dual exhaust out of 3-inch thick wall steel pipe exiting in front of the rear tires and no CATS but I do use the front two oxygen sensors and not the two rear ones. I retired in Mexico so no CATS, no problems. I used two turbo mufflers, one for each pipe.
