FuelPressure Regulator (FMU) Installation Instructions
Purpose of the RisingRate Regulator
The Cartech regulators are designed specifically to addfuel to modified EFI engines (turbos, superchargers, andnormally aspirated). This is accomplished by using the manifold vac/pressure to drive the fuel pressure up as the boost rises, orwith the N/A engines, as the vacuum goes toward atmospheric.The three types have differing part numbers.
Types of Regulators
PN: 2025 Aftermarket turbo and supercharger (1/8 NPT)
PN: 2027 Hi-Flow aftermarket turbo and supercharger (1/4 NPT)
PN: 2022 Factory (OEM) turbo and supercharger
PN: 2023 Normally aspirated
1.)The rising rate regulators fit into the fuel system after thestock regulator, and in series with it. The regulator becomes thelast item before the fuel returns to the tank. Do notremove the stock regulator, as it still controls the fuel flowunder most manifold vacuum conditions.
2.) The regulators can bemounted in any position. For convenience, place the adjustmentscrews within easy access. The most difficult aspect ofinstallation is getting the fuel lines onto the correct fittings.
3.) Older model regulators made from castings (20002-20007), had labels ofIN/OUT on the barb bosses. IN isfor the fuel line from the stock regulator. OUTis the return line heading back to the fuel tank.The IN and OUT of the new regulators (2022-2027) areslightly different, as there is only an "IN" label. The blank port is the "OUT" port.
4.) Fuel fittings for the 2022,2023, & 2025 are 1/8 NPT. The 2027 has 1/4 NPT threads.Some form of thread sealant is advised. We prefer one drop ofLoctite per joint. In general, please avoid teflon tape as theresidue and debris can get into the fuel system if not extremelycareful. The threaded bosses on the regulators are strong enoughfor a zillion ft-lbs of torque, they will not crack. Theycan be stripped, but neither failure is warrantable.
The regulators are powered by manifold vacuum and pressure.The signal must come from the intake manifold, after the throttleplate. These will not work properly if the signal comesfrom anywhere else. There are two small hoses attaching to the regulator. The hose barbpointing directly at the center screw of the regulator is for the manifold signal line. The other hose barb fitting, exiting the brass needle valve, is the fitting for the check valve.
On occasion the regulators will not adjust to a sufficiently low rate of gain. In this instance, it is necessary to add the small restrictor to the signal line. This is provided for your convenience. The restrictor is non-directional, it can point either way.
Two functions are accomplished by the check valve. One, thesimple plugging of a small vacuum/boost leak. Second,vacuum is required to pull the preload spring under the centerscrew away from the valve so stock fuel pressures can be achievedunder manifold vacuum conditions. The check valve white end attaches to the 4" vacuum line and the line plugs onto the 10/32 hose barb exiting the needle valve. This allows venting the boost signal to atmosphere in order to adjust the rate of gain, while maintaining a seal under vacuum conditions. The black end of the check valve MUST blow off to atmosphere and MUST NOT be attached anywhere else.
Please keep in mind that the OEM or aftermarket status of thevehicle doesnt change if one swaps turbos on an OEMautomobile. It is OEM because the fuel system was designed forforced induction originally. That status doesntchange unless one changes the fuel system in some manner.
Only one adjustment isrequired of the NA and OEM turbo/supercharger regulators, whereasthe aftermarket turbo requires two adjustments. For the NA/OEMregulators, only the maximum pressure achieved is of interest.For the aftermarket, both the point of onset and the maximumpressure are adjusted.
In all installations, weurge tuning be aided with an air/fuel ratio meter and fuelpressure gauge.
The pump pressures needed to run the rising rate regulators varywith each type. The 2023's for the NA engines do not needmuch pressure and are always compatible with a stock/originalpump, provided it is in proper condition. TheOEM turbo/sc style units (2022) need pressures in the 70/80psi range tofunction well, while the aftermarket turbo/sc (2025/2027) will need a minimumof 95 psi for 7 to 8 psi boost. Checking the pump isdiscussed later.
NA Regulator, 2023
For the NA regulator, the center screw is the only adjustmentpossible. It determines the fuel pressure achieved at fullthrottle. Turning the screw clockwise raises the fuelpressure. There is no needle valve, check valve, or restrictor included with the 2023. All 2023 adjustments are made at idle with the signal line removed.
An approximate graph of fuel pressure is shown infigure 2023. This is an approximation only for the purposesof suggesting to you the general ranges of operation.
12 10 86 4 20
OEM System Regulator, 2022
The OEM turbo/supercharger requires more fuel if the boostpressure is raised beyond the factory level. Additionalfuel is only required for that extra increment of boost, and notthrough the entire boost operation. This adjustment iscontrolled solely by the needle valve. The amount ofincrease required is modest and is suggested by figure 2022.
2 4 68 1012 14 1618
Aftermarket Turbo/SuperchargerRegulator, 2025 & 2027
Two adjustment are necessary with this regulator. NA engines thatare subsequently fitted with forced induction often exhibitextreme leanness in the range of 4 inches of vacuum toapproximately 3 psi boost. The cause for this is that the turbo/sccan achieve atmospheric pressure in the manifold prior to thethrottle being fully open. Under these MAP/MAF and TPScombinations, the ECU lacks proper enrichment and a leancondition occurs. This is not as prominent in later modelODB2 automobiles where the O2 sensor feedback covers a broaderrange.
Pressure calculation: thefuel pressure required increases with the square of the boostpressure ratio:
Example: 6 psi boost is a pressure ratio of 1.41.With stock fuel pressure of 36 at zero boost, then:
Needed fuel pressure= (PR2 x Base Fuel Pressure) + Boost = (1.412 x 36) + 6 =77.5 psi
The first adjustment is offuel pressure is at the atmospheric pressure point, and can bestbe done at idle. To simulate passing through the zeropoint, the vacuum line must be removed from the regulator. The regulatorthen sees atmospheric pressure as a signal, same as zero on theboost gauge. Control of the fuel pressure at the zero pointis by the Allen screw in the center of the regulator.Clockwiseon the screw will raise the pressure. Once adjusted, plugthe vacuum line back onto the regulator and observe the fuel pressuredrop to the stock figure.A suggested pressure forstarters is 48 to 50 psi.Please understand, this will vary from engine to engine, and isnot a magic number. The magic number iswhatever pressure your vehicle requires to pass thru the boostonset without the lean flat spot. It is not unusual to seepressure anywhere from 40 psi to 55 psi. Use whatever worksbest.
The second adjustment, theneedle valve, controls the rate of gain of fuel pressure versusboost pressure. The lowest rate of gain is with the needle valvefully open, the highest, fully closed. Clockwise closes theneedle valve. Figure 2025 offers a typical guide to fuelpressure versus boost pressure.
Caution: There is a vaguelimit that exists with regard to the maximum possible fuelpressure. The industry "rule of thumb" ofinjectors jamming at 50 psi and the flow not increasing withpressure is not correct. It is possible for a very largeinjector (90 + lbs/hr) to jam at 100+ psi of fuel pressure. Atanything less than that, jamming is not going to happen.
0 1 23 45 6 78 9 10
Checking Pump Pressures
A brief check of the maximum fuel pressure available should alsobe done at idle. This is essentially determining the pumpspressure capability. None of the regulators can force apump past it maximum pressure potential. With a pair of pliers,squeeze the fuel line shut that connects our regulator to the originalfuel pressure regulator. When squeezed shut, the pump willbe forced to maximum output. Make sure the pressure available isconsistent with your intentions. In all cases, the pressuremust show, in this idle test, to be about 10 psi higherthan the desired fuel pressure, as the available pressure underreal load conditions will be less than that measured at idle.This test does not actually prove the pump to be adequate underboost, but if it doesnt pass this test, it is certainly awaste of time to continue with the same pump. In general, do not try to exceed 100-110 psi fuel pressure.
The maximum fuel pressureis controlled by the needle valve and must be determined whiledriving the car under boost. Start with the needle valveclosed, which is fully clockwise.It is unlikely the regulator willneed this adjustment, but the test also serves the purpose ofproving the pump will do the job needed. A weak fuel pump willcause a drop in fuel pressure as the engine is revved higher.If the pump cannot maintain the desired psi to the engineredline, it is not in satisfactory condition to feed the turbo/scengine and must either be replaced or supplemented with anauxiliary pump.
1. Jams at maximum fuelpressure:
Where should a fuel pressure regulator be installed? ›
In many cases, you can mount the regulator in a location to satisfy ease of installation, adjustment, and appearance. However, in the cases of high power applications, extra low fuel pressure systems, and high-g launches, it's best to mount the regulator as close to the fuel delivery destination as possible.Does a fuel pressure regulator need a return? ›
An adjustable fuel pressure regulator with return is required.Where does the hose on a fuel pressure regulator go to? ›
FPR Hose. This hose is about six inches long; it runs from the fuel pressure regulator to a small port under the intake manifold.Does a fuel regulator go before or after the fuel pump? ›
All pump flow, minus engine consumption, must always run to the regulator, wherever it is. Putting it after the fuel rail means all fuel must run through the fuel rail, and over the injector inlet, at all times. This ensures full flow is available to the injector in any instant.Can a fuel regulator be mounted upside down? ›
We advise no; keep the body above the horizon when mounted in a horizontal pipe, or mount it in a vertical pipe.What does the vacuum line do on a fuel pressure regulator? ›
The engine vacuum will draw on the discharge side of the injector pulling more fuel through the injector, so it will decrease the pressure at the rail to compensate. The result of a boost-referenced fuel pressure regulator is a constant flowrate across the injector regardless of the intake manifold pressure.Why is the fuel pressure regulator on the return line? ›
A return-style regulator offers a few benefits over Blocking Regulators: The regulator reacts faster to changes in engine load. It supplies more consistent and accurate fuel pressure. This reduces Lean Condition spikes.Does a fuel pressure regulator return fuel? ›
It's just in the tank, so the only fuel you have physically leaving the tank is what's going to be used by the engine. It just gets returned internally.” A mechanical fuel-pressure regulator is a simple device. Inside, you have a spring that controls a diaphragm.Can you block off fuel return line? ›
Any fuel going through the return line is simply fuel your engine did not need/could not use. Blocking or restricting the line only increases fuel pressure at the injectors. Blocking the line results in the fuel pressure just being the maximum the pump can push.What happens if fuel pressure regulator is stuck closed? ›
When the fuel pressure regulator gets stuck closed, it will cause more than needed fuel to enter the combustion chambers. The combustion of too-rich fuel results in black smoke which is released through the exhaust pipe.
What are the symptoms of a stuck fuel pressure regulator? ›
- Signs and Symptoms of a Faulty Fuel Pressure Regulator. ...
- Fuel Pressure Problems. ...
- You See Smoke. ...
- Your Vehicle is Stalling and Sputtering. ...
- You Are Hearing a Strange Noise.
The simplest way is to just listen for the hum of the fuel pump when you first turn your car on. You can also use an OBD II scanner.Does a electric fuel pump need a fuel pressure regulator? ›
Most lever style mechanical fuel pumps don't require a regulator and some electric fuel pumps even have the regulator built right into them, and eliminating the need to purchase an external unit.Should fuel pressure remain constant? ›
Fuel Pressure Test
After properly installing the gauge, secure it, and turn the ignition key to the on position, it should indicate fuel pressure. Next, start the engine; the fuel pressure should remain the same and increase with a snap of the throttle.
It is between 35 and 65 pounds per square inch (psi) on most vehicles.How do you mount a fuel pressure gauge? ›
How To Install A GlowShift Liquid Filled Mechanical Fuel Pressure ...Where do you put a fuel pressure regulator on a carburetor? ›
In a street/strip application we recommend running the feed line directly to the carburetors fuel log then placing the regulator on the return line side of your fuel log. This allows the fuel to flow unrestricted to your carburetor, but still regulates the pressure and returns the unused fuel back into the gas tank.How do you hook up a Holley fuel pressure regulator? ›
Holley Die Cast Bypass Fuel Pressure Regulators - YouTubeWhat happens when fuel pressure regulator loses vacuum? ›
A vacuum-operated fuel pressure regulator can fail in several different ways. In many cases, the diaphragm inside of the regulator ruptures, allowing fuel to be drawn through the vacuum line and into the engine's intake manifold. Such a scenario usually results in an engine that runs rich (too much fuel).Does my fuel pressure regulator need vacuum? ›
You do NOT have to have the regulator connected to vac as long as your bsae pressure is enough to cover accelleration demand, sustained high rpm operation without leaning (due to a momentary drop in system pressure)(which will be a "stumble" when punching the gas, and the inj can actually handle the increase in ...
Can a vacuum leak cause low fuel pressure? ›
End of dialog window. The only vacuum line on the fuel system I can think of is at the fuel pressure regulator. So in short, yes it could.How does a return style fuel regulator work? ›
Return-Style Fuel Systems
Think of a traditional return-style fuel system as an endless cycle. Your fuel pump (electrical or mechanical) constantly pumps gas from the tank, through a regulator, to either the injectors or carburetor. The fuel pressure regulator is charged with sending the excess fuel back to the tank.
- Once you have triggered the fuel pump, and you still have low or no fuel pressure, it could mean the fuel pressure regulator is leaking or stuck open.
- However, if the fuel pressure is high, it could mean the fuel pressure regulator is stuck closed.
Fuel Pump Pressure and Regulator Test - YouTubeHow much pressure should be in a fuel rail? ›
Required fuel pressure can vary depending on your vehicle's engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).What happens if the fuel return pipe is blocked? ›
If the fuel return hose becomes blocked or kinked it may cause the carburetor to flood from excessive fuel or pressure buildup. A flooded carburetor may cause engine stalling and hard starting until it is cleared, or enough fuel has evaporated.What are the symptoms of high fuel pressure? ›
- Check engine light.
- The exhaust gives off fuel smell.
- Low fuel economy and constant refuelling.
- Poor engine performance.
- Blackened spark plugs.
- Spark plugs that are wet with fuel.
- Restrictions in return line.
The only things that are likely to cause fuel not to return are either a failed fuel pressure regulator, or an obstruction in the fuel rail.What are the symptoms of low fuel pressure? ›
- Throttle Unresponsiveness. Every automobile needs an adequate fuel supply to its cylinders to operate correctly. ...
- Hard Starting or Can't Start At All. ...
- Engine Stalling. ...
- Engine Misfires. ...
- Turbo Lag. ...
- Whining Noise. ...
- Poor Engine Performance. ...
- Worn Spark Plugs.
A fuel regulator can often easily last the lifetime of the car. It is not very common that the fuel pressure regulator fails on most car models. However, it can sometimes happen, but there is no fixed time or mileage when you should replace it.
What voltage should a fuel pressure regulator have? ›
The voltage at idle will be approximately 1.2 volts rising to approximately 3 volts snap throttle. The fuel pressure control solenoid is a two wire device with battery voltage on one wire.Will a bad fuel pressure regulator cause a car to stall? ›
poor engine performance. a vehicle that won't start or stalls. continuous return fuel systems may suffer from leaks if the fuel pressure regulator fails.Can a fuel pressure regulator be clogged? ›
Answer: It's possible. The line can also be clogged. You may want to remove the fuel filter and open the ignition key and see if you get good fuel volume coming from the fuel tank.Can I use a tire gauge to check fuel pressure? ›
Check what is the pressure when on idle speed or at load and compare it with prescribed values. If you have a problem accessing a sophisticated fuel pressure gauge, you can check fuel pressure with a tire gauge.Can you check fuel pressure with obd2? ›
You can actually check fuel pressure with OBD 2 scanner, which will give you readings from the fuel pressure sensor. If you don't have a scanner, you can listen to a buzzing sound when you try starting your car, which indicates that the fuel pump puts pressure on the system.How do you test a fuel pressure regulator with a multimeter? ›
With the fuel pressure sensor disconnected, plug the multimeter into the diagnostic port of your car's computer. Plug the lead into the fuel pressure sensor, which should show “DFPT” on the multimeter display. You should also see “123db”, which is a reference to the distance between the sensor and the connector.Does a mechanical pump need a fuel pressure regulator? ›
Most lever style mechanical fuel pumps don't require a regulator and some electric fuel pumps even have the regulator built right into them, and eliminating the need to purchase an external unit. These pumps are typically low pressure units and were designed for use with carburetors only.Where do you put a fuel pressure regulator on a carburetor? ›
In a street/strip application we recommend running the feed line directly to the carburetors fuel log then placing the regulator on the return line side of your fuel log. This allows the fuel to flow unrestricted to your carburetor, but still regulates the pressure and returns the unused fuel back into the gas tank.Do you need a fuel pressure regulator for carburetor? ›
A fuel pressure regulator is always needed.How do you mount a fuel pressure gauge? ›
How To Install A GlowShift Liquid Filled Mechanical Fuel Pressure ...
Can a mechanical fuel pump make too much pressure? ›
Using the wrong fuel pump that delivers excess pressure can cause problems ranging from poor performance and lower gas mileage to flooding and carburetor damage. When the pressure is only a little over the required amount, your vehicle may sputter when you first accelerate from a stopped position.How much fuel pressure does a mechanical fuel pump? ›
Mechanical automotive fuel pumps generally do not generate much more than 10–15 psi, which is more than enough for most carburetors.Can you use a electric fuel pump with a carb? ›
It is becoming more and more common for people to use an in-tank electric pump to feed a carbureted engine. Many new engines simply do not have the provisions to use a mechanical fuel pump. Sometimes there is no room to have a mechanical fuel pump in the engine compartment.What should fuel pressure be on a carbureted engine? ›
Required fuel pressure can vary depending on your vehicle's engine and fuel system. Carbureted engines may require as little as 28 kPa (4 PSI), while modern multipoint fuel injected high-performance engines can require as much as 414 kPa (60 PSI).How much fuel pressure should a carburetor have? ›
Setting Fuel Pressure
Your system's fuel pressure should be generally set between 6 and 8 psi (measured at the carburetor) for a street engine (higher for a race engine).
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- AEM 25-300BK Adjustable Fuel Pressure Regulator. ...
- PTNHZ RACING Manual Adjustable Fuel Pressure Regulator. ...
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- Signs and Symptoms of a Faulty Fuel Pressure Regulator. ...
- Fuel Pressure Problems. ...
- You See Smoke. ...
- Your Vehicle is Stalling and Sputtering. ...
- You Are Hearing a Strange Noise.
It is between 35 and 65 pounds per square inch (psi) on most vehicles.What does a fuel pressure regulator do on a carburetor? ›
A fuel pressure regulator with bypass is a component that controls fuel system pressure using a spring and diaphragm that is either adjustable or preset. Fuel from the fuel pump flows into the inlet and exits the outlet of the regulator to the carburetor or fuel injection system.How do I check my fuel pressure without a gauge? ›
The best way to measure fuel pressure without a gauge is to use an OBD II diagnostic scanner tool. This will give you real-time engine fuel pressure readings, directly from the fuel pressure sensor. The safest method of checking the fuel system on a vehicle these days is by using an OBD diagnostic scanner.
Why are fuel pressure gauges liquid filled? ›
Why Liquid Fill? The liquid fill dampens vibration, mechanical shock, and pressure pulsations, enabling easier pressure readings. The liquid fill eliminates corrosion, moisture penetration and icing due to the ambient atmosphere.How do you install a fuel pressure isolator? ›
While the isolator is lying on a flat surface with the gauge side facing up, completely fill the isolator using a 50/50 anti-freeze and water mixture. Attach the 7/16”-20 adapter to the isolator, then using a small squeeze bottle, continue to fill the isolator and fitting, then cap off the adapter.