M DIAGNOSING RETURNLESS FUEL SYSTEMS
34March 2013Photoillustration: Harold A. Perry; images: Thinkstock & Wieck MediaMost of us are familiarwith the “traditional”fuel loop. Typically, thisstarts and ends in thefuel tank, and utilizesone or more pumps tosupply a high volume of fuel at highpressure to the injector rail. The pressureis usually maintained by a regulator attached to the exit end of the fuelrail. Any unused fuel is bled off by theregulator and returns to the fuel tank viaa return line. A check valve in the pumpprevents backflow and maintains residualpressure in the supply line to avoid hotrestart problems due to fuel boiling (vapor lock). These systems (see Fig. 1 onpage 36) have been the norm for manyyears, but are now on the wane.Returnless fuel systems, in contrast,supply only the fuel that’s currentlyneeded. This obviously eliminates theneed for a return line. From a manufacturer’s standpoint, there are two advantages—reduced assembly costs and reduced load on the evaporative emissions system. (The unused fuel returning to the tank in a looped system isusually quite warm as a consequence ofthe time spent in a hot engine compartment. Add in the vapor load resultingfrom high-volume flow and turbulence,and the evap system has a hard timekeeping up, especially in hot climates orurban stop & go driving.)So, how does a returnless systemwork? How does it “know” how muchfuel is going to be needed? The photoon page 36 and Fig. 2 show two slightlydifferent implementations. The setup inthe photo, found, for example, in someSaturn and Chrysler vehicles, simplymoves the historical fuel pressure regulator to the inside of the fuelfilter. From there, any excess fuel runsvia a short line back to the tank, avoiding the heat of the engine bay.Fig. 2 illustrates the setup now usedby many manufacturers. Here, all theaction takes place within the tank. Fuelis pumped into the supply line until it’sfilled and pressurized. The pressureregulator is an integral part of the pumpmodule, and all excess fuel bleeds offinternally within the tank.Since no fuel bleeds off via the regulator until the demands of the supply linehave been met, the system appears toDIAGNOSINGRETURNLESSFUEL SYSTEMSBY SAM BELLWell beyond the simple ‘crank/no-start,’fuel supply problems can cause arange of driveability symptoms. Theadvent of returnless fuel systemshas added another layer ofcomplexity to fuel supply diagnostics.“know” how much fuel is required. Butit’s easy, really; all it has to do is keep theline filled and pressurized.TestingTesting the fuel pressure in a traditionalloop system is fairly straightforward. Youmay connect a pressure gauge to a convenient port if one is available. Failingthat, your gauge can be connected inline before the regulator. Fuel pressureon most looped systems varies slightlydepending on engine vacuum, so besure to check the specs.Of course, fuel pressure is only part ofthe driveability analysis story; you alsoneed to check fuel delivery volume. If youhave a gauge like the one shown in thephoto on page 38 (top), you can connectit in series before the beginning of thefuel rail and read not only the fuel pressure, but the volume as well. (I also liketo be able to see the fuel as it flows. Bothaeration and major contamination showup readily even at high flow rates.)Don’t have a flow gauge? Whilethere’s no doubt that using equipmentwith a dedicated flow volume measurement scale is far easier and safer thanany other means, don’t despair. You canmeasure return volume by running ahose from the pressure regulator outputinto a suitable container. (A glasskitchen measuring cup will do.) Ofcourse, flow rate measurement requiresmeasuring time as well as volume, solook at a watch with a secondhand. Most cell phones have a stopwatch feature (see “Rate Calculator:How Much Is Enough?” on page 40 fora chart of common minimum rates).Pressure testing for returnless systems is quite similar. If no port is provided, you’ll have to connect in-line. Buthow do you check volume on these systems? Even an in-line flow gauge will
show only the amount of fuel actuallybeing consumed at that moment.To see how much that might vary, Iused my wife’s Scion xB. At a hot idle, its1.5L engine sips fuel at a barely perceptible rate: .02 gallon per minute (gpm), or.08 liter per minute (lpm). At 2500 rpm,consumption is still only .05 gpm (.19lpm). Finally, though—not that you’dever want to rev an engine this hard, ofcourse!—the little powerplant sucksdown as much as .12 gpm (about .45lpm) at 5000 rpm on a frigid morning. (Icheated and simulated this by substituting some very high-ohm resistors for thetemp sensors on a well-warmed engine. Imay be crazy, but I’m not stupid!)So how do we measure the availablefuel volume without going to such extremes? And how do we know howmuch is enough?Let me take these two questions inorder. To determine maximum fuel vol-ume delivery, I tried several tactics. Myfirst experiment was performed withthe engine off. I began by disconnectingthe fuel line under the hood, connecting my Zapp Fuel System Analyzer(FSA) in-line with a long piece of fuelline back to the tank, then commandingthe fuel pump on via my scan tool andmeasuring the resulting volume. Withno restriction other than hose diameter(about 8mm), I recorded .58 gpm, plenty for any situation. Since there was norestriction to flow, the pressure herewas essentially zero.Now I began slowly restricting theflow back to the tank, thereby increasingthe pressure. With a slight restriction, Iwas able to achieve a pressure of 20 psiwith a flow rate of .43 gpm. A moderaterestriction brought pressure up to 39 psi,while flow dropped to .25 gpm. As Ipinched off the line almost completely,pressure rose to 42 psi (the publishedspec) but flow dropped almost tozero. This verified that the system setpoint was, in fact, the advertised 42 psi,and that the fuel pressure regulator inthe tank was now controlling fuel flowby simply dumping all excess fuel internally.I conducted my next experiment withthe engine running. I reconnected theoutlet of the FSA to the inlet of the fuelrail, placing the FSA in series betweenthe pump and the injectors. I startedthe car and observed that the fuel pressure was the expected 42 psi. Now I began to slowly restrict the inlet hose ofthe FSA. Remember that before, as Iincreased the outlet restriction, thepressure rose from zero. Now I observed the opposite. As I began tocrimp off the supply line, pressure inthe FSA began to decrease. Interestingly, the engine continued to idle smoothly all the way down to a pressure of 20March 201335
DIAGNOSING RETURNLESS FUEL SYSTEMSFuelReturn LineFig. 1 Traditional fuel injection systems incorporate a high-volume pumpto ensure an adequate supply of fuelunder all operating conditions. Manyearly systems coupled a low-pressure,high-volume, in-tank “presupply” pumpto a high-pressure main pump. Moremodern systems locate the main pumpinside the tank. System pressures forsome TBI systems are as low as 13 psi,while other configurations feature system pressures as high as 75 psi.things being equal. Second. a smoothrunning engine is no guarantee of adequate fuel pressure. And third, excessive fuel trim corrections may indicate afuel supply problem.Photos & illustrations: Sam Bellpsi, or about half of that normally specified. Below that pressure, the enginebegan to stutter, finally stalling as fuelpressure dropped below 10 psi.But what about off-idle operation? Iused a throttle prop to hold enginespeed around 2000 rpm and repeatedmy experiment. Fuel trims once againgot a little crazy, but even at 15 psi, thelittle motor ran smoothly. Finally, I setthe throttle for 3500 rpm, achieving essentially the same result.I learned several lessons from theseexperiments. First, fuel delivery volumevaries inversely with pressure, all otherThis truncated return system, widely used on some Saturn and Chrysler vehicles, is across between the conventional fuel loop and the in-tank regulation of a “pure” returnless system. Here the pressure regulator and its return leg outlet are incorporated into the fuel filter assembly. There have been some reports of faulty (or possiblycounterfeit) parts causing either extremely high pressures or a total lack of pressure.most effective tools in my arsenal forrestoring proper driveability performance. The system I use allows me todisconnect both the fuel feed and return lines and to substitute my cleaningmachine for the tank and pump.Once the equipment is connected, thefirst step is a long cycle of cleaning theinjector inlet screens and the fuelrail. This is accomplished by running themachine’s built-in pump at a pressureabove the KOEO set point of the car’sregulator, allowing a filtered mixture offuel and cleaner to circulate continuouslythroughout the rail. This circulation provides a long period of contact betweenthe cleaning solution and the injector in-let screens, during which previously accumulated deposits can be dissolved andthen trapped in the machine’s filter.After 30 to 60 minutes of that initialcleaning, I fire up the engine to run onthe same cleaner and fuel concoction.(Unplug the car’s own pump or loop itsfeed and return lines together first, ofcourse!) Once the motor is running, Iadjust the pressure to a slightly lowerthan-normal level. In closed-loop operation, this causes the injectors to openlonger to achieve the same fuel deliveryvolume, allowing more time for a thorough cleaning of the injector’s innards. Iusually walk away at this point, lettingthe machine do the work until it runsPCMFuel Rail/InjectorsFilterService ConsiderationsAlthough admittedly less effective thanwhen coupled with off-car ultrasoniccleaning, a thorough fuel rail cleaningand engine decarbonization treatmenthave for many years been among the36March 2013PumpFig. 2 In-tank pressure regulation is the hallmark of the now-common “pure”returnless fuel systems used by most manufacturers. In addition to reducedassembly costs, OEMs see an advantage in reduced evap load.
DIAGNOSING RETURNLESS FUEL SYSTEMSout of fuel and stalls. (Since the prolonged low-pressure operation mayhave raised long-term fuel trim [LTFT],be sure to reset trims back toward normal, even if only by test-driving afterthe cleaning. And clear any codes orpending codes you may have set alongthe way, of course.)Obviously, this cleaning strategy cannot work on a returnless system becausethere’s no loop to allow for the inletcleaning cycle. In some cases, I’ve beenable to find an adapter to allow me toconstruct a loop (see photo left below). If you choose to go that route,make sure you check thoroughly forleaks when you both install and removeyour adapters. New O-rings are sometimes required, so be sure you havesome on hand before you begin.But what about inlet screen cleaningon the majority of returnless systems,where there’s no return port on the rail?You can use a pressurized cleaner or aconventional device like the one I use todissolve varnishes and similar deposits. But any attempt to force largeparticulates through the injector’s inletscreen is likely to backfire sometimesliterally! In some cases, there may be notruly good solution to this problemshort of pulling the injectors for off-carcleaning. Depending on the configuration and layout of the fuel rail, it maysometimes be possible to use a pressuredriven with the fuel tank very low, and Ihypothesize that excessive moisture condensation in the fuel tank may have beena factor. In the case of one of the Neons,I was faced with a floating misfire as theflakes shifted within the rail. Most ofthem eventually collected on the No. 3and No. 4 inlet screens.Variable Fuel PumpsIn the Thompson Automotive Labs FuelZapp combination pressure and flowtester, the large central gauge readspressure while the two smaller gaugesshow manifold vacuum and exhaustgas backpressure. A glass column andfloating ball provide volume data.test port to allow for inlet screen cleaning circulation to at least some of therail. Other alternatives may includedraining the rail and using a spraycleaner repeatedly, but this is not usually effective except in cases of large-flakedeposits, such as those described next.Some models have experienced internal fuel rail deterioration. I’ve seenmetallic flakes from these rails collect onthe inlet screens of some Taurus V6s andNeons. In most instances, these werecars that were frequently and habituallySome returnless systems can be easily reconfigured to allowfor conventional injector cleaning/decarbonization treatments to work. For example, in some Ford and Volvo products, the former fuel rail pressure regulator has been replaced by a Fuel Rail Pressure Transducer in order to produce a returnless system. Reversing the swap by putting aregulator back in allows easy and convenient access forsuch a cleaning. The hose shown here can replace the blockoff for the old regulator port on some products, allowingthem to be looped for cleaning. Note that there is no provision for pressure regulation directly with the hose; you’llhave to rely on your cleaning equipment for that function.38March 2013Complementing the basic returnlesssystems previously described is an additional technological wrinkle—the variable fuel pump. Both major versions ofthis idea are designed to prolong pumplife and reduce pump noise. One typeof system uses a dropping resistor, resulting in a two-speed pump. Here, thePCM monitors the voltage drop acrossthe resistor to verify low-speed pumpoperation and to calculate electrical current consumption. The other, a moretruly variable type of system, utilizes aPCM command to a pump-driver module, which, in response, provides a variable pulse width- or duty cycle-controlled power supply to the pump.In my experience, such systems incorporate a fuel rail pressure sensor to allowthe PCM to monitor pump performanceand more accurately calculate injectoron-time. In many cases, however, the reported scan data value for the fuel railpressure is substantially different fromthe actual pressure readings taken with aThese two fuel modules from a Chrysler Pacifica’s “saddle”tank demonstrate the complexity of some returnless systems’hardware. The driver’s-side module contains the pressurepump. The internally routed tubing carries the fuel across thesaddle to the passenger-side module, which contains the regulator and the supply line outlet to the engine. The regulatordumps any surplus fuel in the right-side tank, from which it’sthen siphoned back to the left side. Both modules contain fuellevel sending units. Their signals are combined before beingdisplayed on the dash gauge. Here the tank is being emptiedfor cleaning prior to the modules being replaced, so only theleft (driver’s-side) module is currently immersed.
DIAGNOSING RETURNLESS FUEL SYSTEMSgauge. It appears that at least some manufacturers have chosen not to measurethe fuel pressure as we mortals normallydo. Our gauge readings tell us the pressure above atmospheric. In most applications I’ve encountered, however, the reported values correspond to a relativepressure—that is, the pressure dropthrough the injector, from the rail to theintake manifold. This is not the gaugepressure, nor the absolute pressure,which is what the pressure gauge mightread if the vehicle could somehow betested in outer space.Absolute pressure should not be unfamiliar to us; after all, it’s precisely thesame frame of reference used in mani-fold absolute pressure (MAP) readings. To calculate the expected gaugereading to verify a reported Fuel RailAbsolute Pressure (FRAP) PID fromyour scanner’s datastream, simply addBARO if known, or normal local atmospheric pressure (about 14.7 psi at sealevel, roughly .5 psi less per thousandfeet above sea level) back into yourgauge reading. The result should bevery close if the sensor is accurate.But for those systems which reportneither absolute pressure nor gaugepressure, but instead report the pressuredifference between the fuel rail and theintake manifold (Fuel Rail PressureTransducer [FRPT]), the calculation is aRate Calculator: How Much Is Enough?While manufacturers’ specifications vary, a good rule ofthumb is to expect fuel delivery volumes in the range fromabout a pint every 15 seconds forsmall-displacement motors to abouttwo to three times that amount forhigher displacement or very high-performance engines. Most productionvehicles need no more than a quartof fuel every 15 seconds. Using equipment with a dedicated flow volumemeasurement device is much saferthan any other method.Here are a few more rules ofthumb: A typical gasoline engine uses less than one gallon of fuel tomake 1 horsepower for one hour. Asfuel pressure increases, fuel pumpdelivery volume decreases and pumpelectrical current consumption increases. Brake Specific Fuel Consumption (BSFC) varies considerablydepending on basic engine designand performance criteria. High-performance, naturally aspirated engines may operate in a range of .4to .5 lb./hp/hr., while their forced-induction counterparts are generallyin the range of .6 to .75 lb./hp/hr.Gasoline’s density is roughly 6.2lbs./gal. When choosing a fuel systemfor high-performance applications,standard practice is to oversupplyfuel by 20% to 25%, with the injectors operating at an 80% duty cycle.I created the table shown here using the Thompson Automotive LabsFuel Calculator provided with thecompany’s Fuel Systems l Zapp). The table assumes 100% volumetric efficiency,so naturally aspirated engines willrequire less fuel than shown, whileforced-induction powerplants mayrequire somewhat more. The volumes shown are absolute minimumrequirements to maintain adequatemixture formation. A substantial reserve safety factor of at least an additional 25% is the norm, with manysystems supplying as much as doublethe minimum required amounts.Displacement(CID/L) . 91.5/1.5 . 122.0/2.0. 152.6/2.5. 262.4/4.3Max rpm . 6000 . 7500. 6500. 5000Air (cu. in./min.) . 274,500 . 457,500. 495,950. 656,000Air (lbs./min.) . 12.12 . 20.21. 21.90. 28.97Fuel (lbs./min.) . .83 . 1.38. 1.5. 1.98Fuel (U.S. gals./min.) . .13 . .22. .24. .32Fuel (L/min.). .49 . .83. .91.1.21Overall: Approximately 1 2 gal./min. or .5 L/min. (roughly 1 oz./sec.) is usually morethan sufficient for normally aspirated gasoline engines up to about 5.0L displacement.40March 2013bit more cumbersome. To correlate yourgauge reading, add atmospheric pressure or BARO as before, then subtractMAP. If MAP or BARO are expressedas inches of mercury (in.-Hg), multiplythis number by .491 to convert it to psi.Here are a couple of examples. Inthe first example: FRAP reads 50 psi,elevation 2000 ft., direct BARO readingunavailable:FRAP – local atmospheric pressure 50 (14.7 – (.5 x 2)) 50 (14.7 – 1) 50 13.7 36.3 psiThis is the expected gauge reading.In the second example, the gaugereads 41 psi, FRPT reads 50 psi,MAP 11 in.-Hg, elevation 1000 ft.:Gauge reading local atmosphericpressure MAP 41 (14.7 (.5 x 1)) (11 x .491) 41 (14.7 – .5) 5.401 41 14.2 5.4 49.8 psiThis is very close to thereported FRPT PID. (The differencemay be attributable to current weatherconditions. High atmospheric [barometric] pressure is associated withgood weather, low barometric pressure with rain and storms.)As you can see, the gauge readingsfor the two methods of reporting thefuel pressure PID differ by about 12%,so it pays to know which sort of reporting system is used. If your databasedoes not provide a detailed answer, besure to check the PID KOEO. Sincethe engine is then off, MAP becomesequal to BARO. This means that systems reporting FRAP will show a PIDequal to your gauge reading plus localbarometric pressure (as before.)But what about systems showingFRPT, the pressure drop across the injector? Since MAP is now equal to localatmospheric pressure, the reportedPID should match your gauge readingexactly, allowing you to determine easilywhich type of system you’re dealingwith (see “What’s the Matter?” on page42 for help in diagnosing abnormalpressure, volume, or pump electricalcurrent consumption issues).Additional ConsiderationsNo discussion of fuel system diagnosis orservice would be complete without con-
DIAGNOSING RETURNLESS FUEL SYSTEMSThe chart below can help you diagnose fuel supply problems inconventional return-loop systems. To adapt it for use with returnless systems, install your pressure andvolume gauge in the feed line, thenrun a return line back to the tank using a suitable flexible neoprenehose. Slowly and carefully crimp thereturn hose until flow stops. Caution:Fuel pressure should reach the published maximum system pressure.Pump Current*System PressureWhat’s the Matter?Make sure all couplings are tightlysecured. Now slowly open your crimpuntil the pressure drops barely belowthe maximum just observed, thenuse the chart shown here.In the case of variable-speed (dutycycle-controlled or current-limiting)pumps, it may be necessary to bypassthe fuel pump driver module or relaySupply Volume (Flow)either through bidirectional scan toolcommand or physically at the modulewiring. If you have no other means ofmeasuring volume, have an assistantuse a well-marked measuring cup orsimilar device along with a stopwatchat the end of the “return” hose.Pump actuation using a typical remote starter (dead man) push buttonallows for a quick response in caseMurphy’s law tries to horn in on theaction.Look ForLow . . . . . . . . . . . . . .Low . . . . . . . . . . . . . .Low . . . . . . . . . . . . . . . . . . . Low pump circuit voltage; incorrect pump. Drivercommand or faulty module; inlet restriction (cloggedsock); weak pumpNormalto Low . . . . . . . . . . .Low . . . . . . . . . . . . . .Low . . . . . . . . . . . . . . . . . . . Fuel leak inside tank; coupler hose, internal pressureregulator fault, pulsation damper leak, clogged filterNormalto High . . . . . . . . . . .Low . . . . . . . . . . . . . .Low . . . . . . . . . . . . . . . . . . . Restricted fuel filter; faulty combo filter/regulatorassembly on truncated return systemHigh . . . . . . . . . . . . . .Low . . . . . . . . . . . . . .Low . . . . . . . . . . . . . . . . . . . Restricted supply (clogged sock); pump internallybound up (high mechanical resistance)High . . . . . . . . . . . . . .High** . . . . . . . . . . . .Low . . . . . . . . . . . . . . . . . . . Pressure regulator stuck closed; return line restrictedHigh . . . . . . . . . . . . . .High** . . . . . . . . . . . .Normal to High . . . . . . . . . . Faulty pump driver module; incorrect pump command*Pump current relative to normal known-good. iATNsponsors can find many such values in the WaveformArchives at http://members.iatn.net/.**High system pressure in a returnless system should golow if a return path is provided.whenever pump prices climb.sidering fuel quality issues. Excessive alcohol, water or other contaminants maycause serious driveability problems. Mostof us have experienced at least one nostart resulting from misfueling a gasolineengine with diesel. Excessive alcohol, tochoose another example, also can causeproblems, including aeration and leanrunning due to a split in the hose between the pump and the outlet from thetank, especially in older vehicles orwhere the wrong connecting hose hasbeen installed between the pump andthe tank outlet. Alcohol can also cause injector winding faults, spray pattern andatomization issues and performance ormileage complaints.Contamination may come in manyother forms underlying a variety ofcomplaints, including misfires, hesitation and lack of power. This is onereason why seeing the fuel supply inaction is so important. Where flowrates are high, contamination may bemore difficult to spot, but returnless42March 2013systems offer a very clear view of fuelat idle with the appropriate equipment.If you’re taking a fuel sample alongthe way, make sure you use a clean container made of glass or some other suitable material. Allow the fuel to stand forsome time so that any water or contaminants can settle out. Detecting excessivealcohol concentrations requires a bitmore work, but a number of simple kitsare readily available. Most producequantitative results in as little as two tothree minutes. Remember that the gojuice in most metropolitan areas is “oxygenated” with as much as 10% alcohol.Good fuel is usually readily transparent, although normally dyed to allow after-sale (or after-spill!) identification.Cloudiness or turbidity often accompany excessive alcohol and water content,but may also arise from very fine particulates in suspension. Friends who workas rental fleet technicians report encountering an increasing incidence ofapparently intentional fuel wateringConclusionReturnless fuel systems call for somenew diagnostic techniques, but attention to basic principles of construction and operation should go a longway toward helping to ease the transition. Basic fuel supply testing procedures can still be carried out withminimal adaptation, although somework may be required to square fuelrail pressure scan data with conventional gauge readings. The “deadend” fuel rail’s lack of a return linemay result in more injector inletscreen blockage, since debris is notreadily flushed away by ongoing flowthrough the regulator and back to thetank. In some cases, traditional on-carinjector cleaning may be ineffective,requiring new techniques, equipmentThis article can be found online atwww.motormagazine.com.
fuel loop. Typically, this starts and ends in the fuel tank, and utilizes one or more pumps to supply a high volume of fuel at high pressure to the injector rail. The pressure is usually maintained by a regulator at-tached to the exit end of the fuel rail. Any unused fuel is bled off by the regulator and returns to the fuel tank via a return line.
uses 2 primary types of RFS which are called Electronic Returnless Fuel System (ERFS) and Mechanical Returnless Fuel System (MRFS). The latter is the simpler of the 2 systems and controls the fuel ra
Fuel transfer pump (35) is mounted on the back of unit injector hydraulic pump (1). The fuel transfer pump pushes pressurized fuel out of the outlet port and the fuel transfer pump draws new fuel into the inlet port. Fuel is drawn from fuel tank (12) and flows through two micron fuel filter (11) . Fuel flows from fuel filter (11) to the inlet .
This control system is intended for use with a returnless fuel system and fuel pump that is capable of being pulse width modulated (PWM) at 25 kHz to control fuel pressure. A fuel flow rate of 65.6 G/H at 58 psi (400) kPa is needed. Because this is a dead headed system, a pressure relief
5-6 FUEL SYSTEM AND THROTTLE BODY FUEL TANK LIFT-UP Remove the front seat. ( 7-4) Remove the fuel tank mounting bolts. Lift and support the fuel tank with its prop stay. FUEL TANK REMOVAL Lift and support the fuel tank with its prop stay. (L7above) Disconnect the fuel pump lead wire coupler 10. Pla
Fuel Pressure: Fuel Pressure Regulator and System Pressure. Fuel System: Pumps, Relays . significant volume of fuel may come out. Be ready to catch all the gas in the filter . The 3 main things to check in the fuel circuit are the fuel pump relay, and the 2 fuel pumps. 1. Fuel Injection Relay Test
ATJ/F-24 fuel blend appears to result in accelerated wear in fuel-lubricated rotary fuel injection pumps. At various fuel inlet temperatures, the use of maximum concentration CI/LI in a 30% ATJ/F-24 fuel blend appears to retard the accelerated wear observed in prior fuel -lubricated rotary fuel injection pump studies.
fuel pressure to the fuel injection pump. The pressure regulator regulates the fuel at an absolute pressure of 150 kPa (22 psi) when the engine is at idle speed. The fuel injection pump increases the fuel to a maximum pressure of 200 MPa (2900 psi). The fuel injection pump delivers the fuel to the high-pressure manifold (Rail). The fuel .
Quality level according to API 6A - PSL 1, 2 or 3. 1. In the trunnion mounted design configuration, the ball is supported by bearing, held in position by the valve closures. This configuration allows to discharge any side loads on the valve body, enabling a smoother operation of the ball, minimizing the operating torque and reducing seat seal wear. 2. Anti-Blow Out stem design. 3. Standard .
