Symptoms of Bad Fuel Pressure Regulator and How to Test if it Has Failed

The main signs and symptoms of bad failing fuel pressure regulator and how to test if it has gone bad.
What is a Fuel Pressure Regulator?
A fuel pressure regulator maintains consistent gas pressure for the injectors to work properly.
High pressure can cause misfiring and increase vehicle emissions.
Low pressure can cause poor vehicle performance and bad acceleration or long starts.
Newer vehicles do not use a fuel pressure regulator. The computer regulates the speed of the fuel pump.
Symptoms of Bad Fuel Pressure Regulator
Long Start Times
Misfires (P0300 Code)
Black Smoke (Engine Running Rich)
Running Lean
Poor Gas Mileage
Poor Engine Performance
How To Diagnose a Bad Fuel Pressure Regulator
Check the vacuum hose for gas leaking out.
Check fuel pressure with a gauge.
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[@philltendo1480]

This was helpful thanks.

[@henrychavez918]

Great info

[@pierrelouischarles4454]

Thank you so much Sir

[@mikepettengill2706]

Thanks!

[@smalldog221]

Ok so it it the bypass control. Can you check function with a mighty vac on a regulator out of the box? If I apply vacuum will you be able to blow through the fuel section or does it require 30 plus pounds to open it?

[@stevebutler8028]

What should the vacuum reading be? Low vacuum causes a lean misfire, Right. ?

[@henrychavez918]

My 96 f150 is having this exact problems … how about a stronger pressure regulator, or heavy duty..regulator..??

[@Maine.1500]

My question is could a bad fuel regulator cause the fuel pressure to pulsate? Even after you’ve changed the fuel pump. This is for an ls swap

[@MarioSays713]

So my Corolla has this huge weird issue where it takes long maybe like 5-6 turns before it starts in a hot day (morning start) after engine has been running regular temp, stop at a store for 10-15 mins crank takes 7-8 turns. On a below 60 degree day this is no longer an issue anytime. Engine starts immediately. Is this a symptom?

[@Briax2]

will a bad regular cause it to crank up… odd? like slow as in not enough pressure so it’s a lag but not slow as in bad starter slow

[@mrbond191]

Hey man if I turn on my fuel pump with a scan tool am I supposed to hear hissing from the fuel pressure regulator because I've been having some serious fuel pump issues so I changed my fuel pump fuel filter because I'm having a loss of power when I accelerate at low speed and then my fuel pump would just give out

[@mrbond191]

Is it normal for it (fuel pressure regulator) to hiss if pressure is fed from the fuel pump?

[@carlorocky]

Is a fuel pressure regulator itself supposed to pull vacuum when the vacuum hose has been removed while at idle? Not the vacuum hose, but the regulator itself. Thank you

[@timhowell1220]

What if one of the injector is leaking and not the FPR?

[@billybobbarker3175]

GM 5.3 LS. Has the regulator on the fuel rail and a teeny tiny vacuum line to it from the manifold. The rubber on the vacuum line is cracked, so it must leak and not be proper vacuum at the regulator. This should cause a constant high fuel pressure, correct? Now the truck also has a recurring P0420 code. Could this tiny vacuum line leak be the cause? Engine otherwise runs super smooth and solid.

[@CWK090]

You should be able to tell if the vacuum line has a leak by blocking the end going into the FPR with your finger to check for suction. If there is any question, the vacuum line is inexpensive so replace it. Attach a fuel pressure guage to the schrader valve and note the fuel pressure rise at idle when the vacuum line is pulled off the FPR. In my GM 5.3L Flex fuel, it rises about 8 PSI, as I recall. The highest vacuum occurs at idle, pulling against the spring and diaphragm, opening the valve in the FPR and sending all of that unneeded gas back to the tank. Without vacuum at the FPR, there is way too much fuel pressure in the fuel rail at lower rpms. Disclaimer...I am not an ASE certified mechanic.

[@charlesmccormick4443]

All fuel pumps do not run in the key on position , some run while cranking .

[@augustinasnavickas5268]

My fuel presure regulator hose is shut and it dosnst connect to intake manafold. Could this cause misfire and rich condition, when accelarating fully car missfires and hesitates. Its fsi 1.6 engine Also spark plugs and coils are changed

[@quiryonwalker8356]

Hey what kind of car you got

[@davidwoods607]

Hello, just one question. I have a Kia creator 1.6cc.running rich even at idle. Gas in the oil and a intermittent misfire. Change all the coils injectors, charcoal canister and whole fuel pump assembly because the fuel reg. Is on on it. No shredder valve on rail. Any suggestions please?

[@HVAC_Mechanic]

I would pull the spark plugs one at a time and match them to a burn chart to see which is running rich and double test that injector. A Fuel Pressure Tester kit with a T fitting, placed inline, can be used to test the fuel pressure.

[@davidwoods607]

Thank you. I didn't really expected a reply will try your suggestion and let you know the results.

[@davidwoods607]

Just a word of thanks, I check the injections as you suggested and two of them were leaking. Never expected that because they were new,though aftermarket. Problem solved. Thanks again.

[@jamesortega8681]

based on your info it doesnt seem to be my fpr. if its running rich it means spark plugs would be black, so i checked my spark plugs and they a clean. so maybe it is running lean thats why im having long start times. heres where your info looks useful to me(pls correct me if im wrong) . you said if i turn off the key then pressure would slowly go down that results in long start times because it cant hold pressure. but this isnt the case with my long start time. first thing in the morning the engine is cold, my engine starts with one click no problem, but after its been running a few minutes if you turn it off again thats when it has a hard time starting back again. i try to do the on-off three times trick and it doesnt work. the only way it starts with one click again is to let the engine cool for about a half hour to an hour. so it losses pressure when its hot, but starts right up when its cold? my fpr is connected to the fuel rail theres no gas leaking through the vacuum hose i checked.

[@HVAC_Mechanic]

A component may be failing when it gets hot. I would test the fuel pressure when the engine is hot. A good OBDII scan tool should have fuel pressure readings or a fuel pressure gauge can also be used.

[@truthseeker1693]

I've got the same problem. Cold. It cranks right up. Drive one mile cut it off. Shop no more than 15-30 minutes and it wont crank unless I put it on the floor. Did this a couple months now when light turns green. Press pedal to go and engine stops. Have to press it to floor again to start. Once its running... I gently press pedal and very slowly take off On way home running about 55 I stomped pedal to floor and it took off. No hesitation all the way up to 90 and maintained that speed for half a minute and ran perfectly. Did notice when ideling fuelmpressure guage holds steady at 48.psi but when you cut it off pressure starts dropping. Mechanic thinks its pump, inline filter in tank OF COURSE!!! After video I'm thinking fuel.pressure regulator.

[@carlorocky]

@@truthseeker1693I have a similar problem. Did you ever figure it out?

[@nabil1992100]

Do you can help me please find the fuel pressure regulator in my Suzuki Grand Vitara 2011 2.4L ?

[@kanenscott8883]

If you can’t find it in the engine bay on the fuel Line then it’s most likely in the fuel tank apart of the fuel pump assembly as all modern car are moving it from inline to intank

[@kv.g3737]

Yeah. That pressure regulator is on the same connection with the fuel pump. The fuel pump is located inside the fuel tank.

[@pablo156v6]

suscribed!!!

[@redmist7747]

How do I know it’s the pressure regulator and not the fuel pump

[@thumbegg9421]

The fuel pump makes a noise when you turn the vehicle on.

[@knock904]

clamp off lines individually ..isolating each line

[@masonlittle9224]

You should hear the fuel pump turn on each time you cycle the key , if the regulator is bad It won’t start up good right after being turned off and when you first turned it on, it will idle rough , would definitely recommend checking the fuel pressure before you look into changing a fuel pump, also you can clean the fuel filter but I’d check the fuel pressure first

[@muhammadraza6345]

Blah Blah Blah Blah ...... Just lecture...! wr is demonstration.... ?