pg edit :pg edit 11/19/14 3:19 pm page 1 c gasoline ... the results once you’re safely...

Carbon, whose name de-rives from the Latin car-bo, meaning coal, is thefourth most abundantchemical element in theuniverse by mass after

hydrogen, helium and oxygen. It waswell known to ancient Egyptians andSumerians, and doubtless to their pre-decessors and contemporaries as well.Our modern recognition of carbon

as an element dates to the work of An-toine Lavoisier in 1789. Because car-bon freely forms long chains of stablecarbon-to-carbon bonds and combinesreadily with hydrogen, there are morecompounds containing carbon than allthose containing any other elementscombined, except for hydrogen. And,indeed, carbon chains accompanied byhydrogen are the basis of every organiccompound, including, of course, gaso-line, petroleum, propane, ethanol, etc.In fact, all life on earth is carbon-based.In our work we deal with a broad ar-

ray of hydrocarbons, ranging from fuelsto plastics, from belts and hoses to oilsand greases. My focus here will be onhydrocarbon fuels, particularly gasolineand various “gasohols” (mixtures ofgasoline and alcohols, whether ethanol,methanol or isopropanol), and dieselfuels. We’ll be looking at a variety of car-bon compounds arising from processeswithin the modern engine—some inten-tionally produced and others not.The familiar combustion chemistry of

gasoline goes something like this: gaso-line + oxygen + (compression + heat) =water + carbon dioxide + more heat.However, in the real world such idealcombustion simply doesn’t occur withtotal regularity, so we’re left with variousbyproducts of incomplete combustion,most famously carbon monoxide (CO)and unburned hydrocarbons (HC). Toadd an additional layer of complication,modern fuel blends contain a wide vari-ety of additives designed to work as de-tergents, stabilizers, antiknock com-pounds and the like. So-called oxygenat-ed fuels mix in one or more alcohols orsimilar oxygen-containing organic com-pounds with the base fuel stock. Finishoff the cast of characters with unwantedcontaminants such as sulfur or even wa-ter, and you’ve got a potentially nastybrew in the tank.

36 December 2014

GDI:GASOLINEDEPOSITSINSIDE?

GDI:GASOLINEDEPOSITSINSIDE?

Gasoline direct injection allowssmaller displacement enginesto develop more power, alongwith improved fuel economy.

But your shop may have to dealwith some of the unintended

side effects of this technology.

Gasoline direct injection allowssmaller displacement enginesto develop more power, alongwith improved fuel economy.

But your shop may have to dealwith some of the unintended

side effects of this technology.

BY SAM BELLBY SAM BELL

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Pg_EDIT_:Pg_EDIT_ 11/19/14 3:19 PM

Changes in combustion chambertemperatures and pressures must alsobe factored in: Too high a temperatureand you start producing oxides of ni-trogen (NOX); too low and you canflood the engine with unburned fuel(HC). Suffice it to say that once thecombustion event has taken place, abroad array of carbon-based com-pounds is produced (see “What’sCooking?” on page 41).

While most of this material will exitthe vehicle as exhaust waste gases, someblowby will find its way through the pis-ton ring end gaps and into thecrankcase. Once these blowby gases aredrawn out of the crankcase, they’re thenreintroduced into the intake where theymix with the incoming air prior to pass-ing through the intake valves and intothe combustion chamber. Similarly, asmall volume of exhaust gases may alsobe reintroduced into the intake via theexhaust gas recirculation (EGR) systemin cars so equipped, or via valve overlapand partial sequestration within the dy-namic operating parameters of a vari-able valve timing system.

Historically, raw fuel from carbure-tion or, later, centralized (throttle body)fuel injection would mix with theseblowby or EGR gases and dissolve mostdeposits the gases might have left tomark their passage. I can remember thefigurative siren’s call of opening up thethrottle on a seemingly deserted stretchof highway to “blow the carbon out.” Ican also remember the real siren’s wailshortly after I flashed by the radar car at120+ mph one night. Let’s just say thejudge was nonplussed by my explanationat the time.

When intake valve deposits became asignificant driveability problem in themid-1980s, gasolines were reformulatedto incorporate more robust detergentpackages. The advent of port injectionreduced the solvent effect in the throt-tle body area and the upper reaches ofthe intake plenum, but at least stilllargely reduced or prevented the accu-mulation of carbon deposits on the in-take valves and passages. (Prior to thisera, there was generally little or no needfor throttle body cleaning.)

Recently, however, the increasinglywidespread adoption of gasoline directinjection (GDI) technologies (see the

37December 2014


sidebar on page 42) has led to a resur-gence of carbon deposits within theentire intake manifold and, quite criti-cally, within the cylinder head’s intakeports and on the intake valves them-selves. Whether it’s called GDI, FSI,DFI, SIDI, Skyactiv or EcoBoost, it’sdirect injection.Field technicians report that both the

Lexus IS 250 and VW’s FSI offeringsare beset by a veritable plague ofclogged intakes. Later Lexus modelssolved the deposit problem with a dualinjector approach. This system couplesthe primary direct injector used duringstratified charge operation with an auxil-iary port injector which operates underhomogenous charge conditions specifi-cally known to help scrub away intakedeposits. While this strategy certainlyincreases upfront manufacturing andproduction costs, it may prove effectivein the long term, especially when bal-anced against lost customers alienatedby disassembly and cleaning costs thatcan easily range as high as $1200 a pop.Meanwhile, the diesel world has seen

similar problems arise in the wake ofthe adoption of EGR and throttleplates. There are well-documented cas-es of diesel intake airflow restrictions of80% or more.

Symptoms & DiagnosticsWhat clues should lead you to check forcarbon buildup? You may encounterone or more misfire codes (P030x), es-pecially on cold start-up and driveaway,often accompanied by a P0316 code ora proprietary P13xy code, indicating amisfire within the first 1000 revolutionsafter start-up. While it’s possible thatyou might encounter a rich conditioncode such as P0172 or P0175, or themore generalized fuel trim malfunctioncode P0170, often there may be noDTC to tip you off.The most common driveability symp-

toms resulting from carbon buildup inthe intake are a lack of power (especial-ly at higher engine speeds), a failedNOX emissions test and/or excessiveping on acceleration. Cold-start difficul-ties, including cold rough running orcold stalling, may also occur, and are es-pecially common in Valvetronic-equipped BMWs. Datastream may

show unusually large negative fuel trimcorrections, especially at higher enginespeeds or on hard acceleration. Abnor-mally low mass airflow (MAF) readingsduring wide-open throttle (WOT) ac-celeration or Calculated Load valuessubstantially below 100% under thesame conditions may be other tip-offs.On turbocharged applications where

WOT-calculated load values often ex-ceed 100%, look for lower-than-normalfigures. (As usual, have an assistant driveor, better yet, use your scan tool’s movie,graphing or recording mode, then re-view the results once you’re safelyparked.) Unfortunately, neither thesesymptoms nor the occurrence of any ofthe DTCs mentioned are exclusive tocarbon buildup, so you’ll have to findways to rule out other causes, which

might include worn intake lobes, a con-taminated MAF sensor, excessive fuelpressure, leaking injectors, etc.On some applications, a quality flexi-

ble borescope, the thinner the better,may allow you to see the intake portsand valve heads well enough to pindown the diagnosis. A small-diameterscope can sometimes fit through a ma-jor vacuum port, such as that for a brakebooster, purge or PCV hose, to allowyou to maneuver it out of the plenumand downstream to one of the intakeports. Often, however, this approachwill not be practical. A good alternative

is to use your borescope (possibly with asecurely attached mirror) through aspark plug hole. Carefully rotate the en-gine by hand until the intake valves foryour cylinder are fully open. If yourscope shows you a rounded mass abovethe valve’s head, you’ve found the car-bon you were looking for.Speaking of scopes, can you identi-

fy carbon buildup by looking at a vac-uum waveform? The answer is a con-ditional maybe, at best. If the buildup isrelatively uniform, it will affect thewaveforms of each cylinder approxi-mately equally, so you’d need a verygood library of known-good waveformsfrom known-clean engines. Even then,the buildup would have to be pretty sig-nificant before it would rise to de-tectable levels at low to moderate en-

gine speeds. If you had a known-goodwaveform in your library from some-where above 4500 rpm, you might beable to pick up a good clue from thevacuumwaveform.What about compression testing?

For cranking compression pressures tobe affected, you’d need an almost com-pletely obstructed intake. Even at idle,only the very worst obstructions wouldrestrict the incoming air sufficiently tobe measurable. As is the case with vacu-um waveforms, only under the veryhigh airflow rates of near red-line oper-ation will lesser deposits be detectable.

GDI: GASOLINE DEPOSITS INSIDE?

Photographs of black carbon hiding down black holes are notorious for not showing muchof anything except blackness. What you can see in this photo is a small amount of carbonbuildup on the head of the valve. Next step is to get that stuff out of there.

38 December 2014

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While some manufacturers havetried to pin the blame for carbonbuildup on the use of low-quality fuels,field data shows that even the assiduoususe of so-called top-tier fuels fails toprevent the problem completely. Notsurprisingly, frequent short cold-weath-er trips do seem to exacerbate the is-sue. Overall, there does not yet appearto be a good preventive solution towhat is essentially a design problemwhich, if nothing else, fails to accountfor current real-world North Americanfuel formulations.

We’re not alone, either. Techniciansin Australia and New Zealand also re-port similar problems. Part of the diffi-culty stems from slower-burning com-ponents of the fuel blend. Many ofthese “heavy-fraction” molecules sur-

vive the combustion process and exit,only to find their way back into the in-take tract whose relatively cooler sur-faces prove ideal to condense them outof gaseous form. Log on to http://www.toptiergas.com/retailers.html for a cur-rent list of approved fuels and moretechnical information under the “de-posit control” tab.

A couple of requirements for thesetop-tier fuels are of some particularconcern. One specifies an ethanol con-tent of 8% to 10%, while another spec-ifies a minimum sulfur content of24mg/kg, or 24 parts per million(ppm). Newly adopted EPA require-

ments for gasoline fuels will reducethis level to 10 ppm in all gasoline fuelsby 2017. According to the EPA, thecurrent emissions standards, whencombined with the reduction of gaso-line sulfur content from the current30- ppm average down to a 10-ppm av-erage, will result in “dramatic emis-sions reductions for NOx, VOC, directPM2.5, carbon monoxide (CO) and airtoxics. For example, in 2030, whenTier 3 vehicles will make up the major-ity of the fleet as well as vehicle milestraveled, NOx and VOC emissionsfrom on-highway vehicles will be re-duced by about 21%, and CO emis-sions will be reduced by about 24%.”

European gasoline regulations al-ready limit sulfur to 10 ppm, perhapsaccounting, at least in part, for the fact

that versions of the same problematicengines do not appear to suffer asmuch from carbon buildup under Eu-ropean driving conditions. New fuelformulations are constantly being de-veloped and tested, so there is somehope for the future.

In the meantime, BG Products andWynn’s, among others, offer chemicalsand equipment designed to removebaked-on intake deposits. The proce-dure should be performed only out-doors or after connecting the vehicle toa very good exhaust extraction system toavoid filling your shop with toxic fumes.(Of course, this precaution should be

taken for any procedure that requiresrunning a vehicle indoors for an appre-ciable length of time.)

The BG approach starts with addinga can of one of their gasoline enhancersto the tank before warming the engineto normal operating temperature. Youthen install a fogging device by thethrottle body and set a throttle prop tohold at about 1200 rpm. The fogger isconnected to a pressurized dispenserfilled with one of the company’s propri-etary chemical blends formulated todissolve baked-on carbon deposits fromthe valves and passageways. The fogprocess continues for about 15 minutesand should be followed by an equaltime of running without the fogging toclear out any residual chemicals.

Wynn’s Direct Injection Power 3(DIP3) claims to be even easier to use:Remove the air cleaner, hold thethrottle of the previously warmed en-gine at about 2000 rpm and spray inabout 200mL of the fluid in shortbursts, being careful not to stall theengine or exceed 3000 rpm. Let every-thing stabilize for a minute or more,then reinstall the air filter.

As usual, I’d recommend followingup either of these services with an oiland filter change, since some of thatnasty soup will undoubtedly find its wayinto the sump. Don’t forget to includethis cost in your estimate, as most GDIengines require carefully formulatedsynthetic (read: “expensive”) oils in anattempt to minimize wear on the high-pressure injection pump plunger andthe camshaft lobes driving it (see “Tak-ing the Plunge” on page 43).

In general, “soft” carbon deposits aremore readily dissolved than “hard”ones. If you were able to see the de-posits before starting your work, youmay learn to tell them apart and predictthe likelihood of success in foggingthem off. Sometimes a second round oftreatment may be required, so be sureto verify the effectiveness of your workprior to performing that oil change.

If the deposits were heavy enough tocause DTCs to set or a noticeable per-formance problem, simple chemicalmethods alone are unlikely to be fullyeffective. And there are some potentialpitfalls for the unwary as well.


40 December 2014

Considering the amount of work that was required to reveal it during a decarbonizing service,one would hope that the oil separator for this PCV system will never be as accessible again.It would be a disservice to the customer to pass up the opportunity to clean and reseal it.


Side Effects May Include . . .One of the bigger worries about decar-bonizing services is that a large chunk ofcarbon may break free. In the worstcase, it may block a valve open, possiblyallowing a catastrophic piston-to-valvecollision. Or a piece may pass into thecombustion chamber and even ignite.In rare cases, this may cause a backfirein the intake side or may merely inter-fere with correct ignition timing withinthe combustion chamber. Alternatively,such a dislodged chunk may stick to oneof the combustion chamber surfaces,raising the effective compression ratioand possibly causing ping and excessiveNOX production, or it may pass throughinto the exhaust stream.

Ford has recently expressed concernabout thermal (overheat) damage to theturbochargers of some of its EcoBoostengines after decarbonization services.Ford’s official position is that no suchservices are currently approved for itsEcoBoost products. For vehicles stillcovered by the factory new-car warran-ty, there’s an exchange cylinder headprogram in effect. For out-of-warrantyservice, Ford at one time recommend-ed walnut shell blasting, although theircurrent preference appears to be headreplacement. There are also scatteredreports of catalytic converter damage,whether blockage or partial meltdown,imputed to such events. Misfires havebeen reported as well.

As always, it’s best to let your cus-tomer know about these potential issuesbefore they arise. As a practical matter,this means informing him, as part ofyour initial explanation, of the proposedservice. Use care and follow the manu-facturer’s directions scrupulously. Aboveall, don’t blip the throttle until the ser-vice has been completed, as suddenchanges in airflow are more likely to dis-lodge such chunks of carbon.

I have never been a fan of fear-basedselling, yet it’s obvious that selling this asa preventive maintenance service be-comes much easier when you mentionthe potential negative consequencesthat might occur should your customerwait too long. Recommendations forservice frequency vary greatly frommodel to model, and even from year toyear in some cases. For the worst-af-

41December 2014

Circle #22

The products of completecombustion are water and

carbon dioxide, but there areplenty of byproducts resultingfrom imperfect combustion.These fall into three broad cate-gories—incomplete combustion,combustion byproducts andpostcombustion oxidants.IInnccoommpplleettee ccoommbbuussttiioonn in-

cludes unburned hydrocarbonsand partially burned hydrocar-bons such as aldehydes, ketones,carboxylic acids and carbonmonoxide. Also in this categoryare thermal crack products andderivatives such as acetylene, eth-ylene and hydrogen, pure carbonsoot and polycyclic hydrocarbons.(Polycyclic aromatic hydrocar-bons, or PAHs, include severalhighly toxic compounds and havebeen identified as likely to causecancers and lower IQs, and ad-versely affect development.) CCoommbbuussttiioonn bbyypprroodduuccttss in-

clude the nitrous oxides from at-mospheric nitrogen, and sul-furous oxides from sulfur impuri-ties in the fuels. (In addition tobeing among the most danger-ous eye-irritants known, both ni-trous oxide and sulfurous oxidecompounds are also implicated inacid rain. Sulfurous oxides in suffi-cient concentration can also de-grade the performance of oxygenand air/fuel sensors, and degradecatalytic converter performance.)PPoossttccoommbbuussttiioonn ooxxiiddaannttss in-

clude important smog-formingcompounds such as ozone, or-ganic peroxides (powerful bleach- ing agents often also used in ex-plosives) and “tear-gas” peroxy-acetyl-nitrates, all formed whenexhaust gases are exposed tosunlight.All in all, the ingredients of this

stew are an unsavory bunch. Thevast majority of exhaust gasesmake it out the tailpipe; their ef-fect on the rest of the planet is adiscussion best left for anothertime. Unfortunately, though, asmall percentage of these com-pounds makes its way into the in-take manifold whether directlyvia an EGR system, or incidentallyvia the PCV system or via turbu-lence during periods of valve over-lap. The relatively cooler surfacesof the intake tract readily con-dense these gases, allowing themto build up and do their mischief.

WHAT’S COOKING?


fected models—those most prone tocarbon accumulation—5000 miles maybe a good interval, while for othersevery 15,000 to 30,000 miles will be of-ten enough. Unfortunately, I don’t yetknow of any reliable source of informa-tion on this point, especially sincedriving style and conditions causepronounced variability. Seasonal andregional variations in fuel formula-tions further complicate the question.Most Euro-brand techs seem to favorchemical cleaning annually or every15,000 miles as a maintenance item.BG Products offers a limited warrantyto owners who use their three-part in-duction service at least every 15,000miles.What should you do if you encounter

a heavier carbon buildup? There aretimes when no amount of external

chemistry will work to safely break upbaked-on carbon deposits, although asecond round of cleaning will turn outto do the trick often enough to make itworth a try. But for those times wheneven a follow-up chemical treatmentproves ineffective, most manufacturersspecify blasting the crud off with a wal-nut shell medium. Don’t use any kind ofabrasive media here! Rule 1: Read thedirections first. Rule 2: Follow them, es-pecially the parts about safety glasses,gloves and a face mask.The most common procedures call

for removing the intake manifold to ex-pose the head’s ports. Rotate the en-gine by hand in its normal direction ofrotation so that the intake valves forone of the cylinders are completelyclosed. Mask the intake ports of theother cylinders. (Corrugated cardboard

makes a good masking material; markthe bolt or stud holes, punch themwith a Phillips screwdriver, fasten thecardboard in place using appropriatehardware and follow up with maskingtape.) If you’ve removed anything else,such as a valve cover, mask those ex-posed innards as well. Load in a freshbatch of shells and fire away into thefirst set of intake ports.You’ll have to stop periodically to vac-

uum out the spent shells and dislodgedcarbon. Keep blasting until everythingis scrupulously clean, including the farside of each intake valve. Clean out alldebris, then mask off that set of portsand advance the engine until the nextcylinder’s intake valves close. Repeatuntil all the valves have been excavated.Large and small pieces of shells or car-bon deposits are likely to be lurkingthroughout your work area. Time youspend cleaning them up now is timeyou won’t have to spend correcting anydamage they might cause later. Includethis time in your estimate from the start.If any debris got onto a threaded studor down a threaded hole, clean it out soit doesn’t prevent you from hitting thecorrect torque specs on reassembly. Insome instances it may be necessary touse a tap or die to clean the threads ad-equately.It’s a good idea to clean up the rest

of the intake while it’s off, and youmay as well service the throttle body,too. Will you need new intake gasketsor O-rings? Probably so in most cases.Ask your favorite dealership parts con-tact for the skinny on what their techsdo or do not actually replace on en-gines of similar mileage. When indoubt, replace.Many vehicles will require reinitial-

ization of the throttle after cleaning.Make sure you have the technical re-sources to perform this service, orarrange for a mobile service to providethem for you. Once again, make sureto include any additional costs in yourinitial estimate. If there’s somethingelse in the area that ought to be ser-viced soon and will become significant-ly more expensive to unearth again—an oil separator, for instance—you maywant to offer to package it in with thecurrent job. Most customers will ap-


42 December 2014

Léon Levavasseur, a French engineer who also pioneered the first V8 en-gine layouts, invented the first viable gasoline direct injection system

over 100 years ago. The earliest applications were all in aircraft engines.Although several automotive manufacturers dabbled in the technolo-

gy, it was not until 1955 that Mercedes-Benz, using a modified Bosch me-chanical diesel pump, introduced the first “modern” car sporting directinjection—the gull-wing 300SL. The technology was simple enough: Alow-pressure pump supplied fuel to a high-pressure injection pump. Thischain-driven injection pump featured its own crankshaft. Like a miniatureengine, the pump used its pistons to pressurize the individual fuel linesfeeding each injector. Refinements including temperature and barometricpressure compensation were achieved via mechanical controls.

GDI works a lot like a diesel, where fuel is injected directly into thecombustion chamber just after the end of the compression stroke. Pres-sures may exceed 200 bar, or about 3000 psi. Modern controls allow mul-tiple injection and ignition events during a single power stroke.

You may well be asking yourself why GDI is suddenly such a big dealafter 100 years. GDI offers several potential advantages of considerableinterest to automakers striving to meet increasingly stringent fuel con-sumption and emissions regulations worldwide. These include:

•Decreased cold-start emissions, cut in some cases by 25% or more.•Greater fuel economy. Unlike previous “lean-burn” or “stratified

charge” systems that generally maxed out around 25:1, GDI offers real-world light-throttle cruise air/fuel ratios of 65:1, and, in some applica-tions, even leaner mixtures during trailing-throttle deceleration.

•Increased power and performance.•Decreased carbon footprint, especially for carbon dioxide.Additionally, GDI allows higher compression ratios and pairs well with

turbocharging, allowing an increased level of performance previously at-tainable only by higher displacement engines. The use of smaller displace-ment engines can greatly multiply fuel savings without sacrificing power.

GASOLINE DIRECT INJECTION (GDI)

Pg_EDIT_Carbon:Pg_EDIT_ 11/19/14 3:26 PM

This article can be found online atwww.motormagazine.com.

prove the additional preventive main-tenance work if it’s presented properlyas an add-on option at the outset.

ConclusionWhile gasoline direct injection enginespresent numerous theoretical advan-tages, real-world automotive applica-tions have been plagued by persistentand widespread carbon deposits onand within intake valves and ports.Current fuel formulations alone can-not effectively prevent all such prob-lems. Incidences of premature pres-sure pump and camshaft failures aremost commonly encountered wheremanufacturers’ oil specifications have

been ignored, although ultimate lifeexpectancy for these components is of-ten substantially shorter than that ofother valvetrain parts even when thecorrect lubricants and drain intervalsare used. Future advances in lubri-cants, engine design, combustion con-trol and fuel formulations will deter-mine GDI’s ultimate fate.

Meanwhile, GDI-equipped vehiclespresent a new array of diagnostic chal-lenges and service opportunities. Asusual, those shops and technicians whotake the time to study and understandthis new technology’s strengths andweaknesses and who invest in propertraining, tooling and equipment will be

well-positioned to assist their custom-ers. Periodic chemical intake cleaningcan be a valid and valuable preventivemaintenance service for GDI engines,but it must be performed early enoughto be effective and carefully enough toavoid damaging the engine and associat-ed downstream components, includingturbochargers and catalytic converters.Deeper cleaning via walnut shell blast-ing is appropriate for engines that fail torespond to chemical cleaning becauseof heavier deposits.

43December 2014

Most GDI systems in current production use acamshaft-driven high-pressure pump to feed their

injectors (see accompanying photos). Both the lobespushing on the pump plunger and the plunger itself ex-perience significant forces. The sliding contact betweenthe two pieces can result in very rapid wear.Most manufacturers specify carefully engineered syn-

thetic oils for this application. Not every synthetic meets

the standards, so be sure you check before you pour in thelube. There have been numerous reports of prematurefailure of these components. In many cases, these may oc-cur even during the new-car warranty period. SeveralOEMs have denied coverage when the customer cannotdocument the use of factory-approved oils. Current legisla-tion in effect in almost every state requires you to specifyboth the brand and viscosity of oil on your customer in-voices. If you haven’t been doing so, this would be an ex-cellent time to start. My advice? Use the factory-specifiedoil every time, and explain to your customers why you’re

doing so. Most will understand and appreciate your con-cern; after all, it’s their investment you’re protecting.Be sure to use a suitable filter that will provide ade-

quate protection over the life of the oil change. If you’reusing something other than the OE filter, choose a rep-utable brand and look for an assurance of longevity, suchas “extended use” or “long-life.” A statement such as“meets or exceeds manufacturer’s specifications” is not

necessarily enough. The specs in question may be limitedto thread size and burst-strength alone, ignoring issueslike microporosity and filtrate (dirt-holding) capacity.And, of course, be sure to follow through on the cus-

tomer education aspect by explaining both the proce-dure and the need for checking the oil level periodically.After all, there are some cars with a four-quart sump ca-pacity for which oil consumption of a quart every thou-sand miles is “acceptable.” If the drain interval is 10,000miles, you could be looking for an additional six quartsbetween changes.

TAKING THE PLUNGE

The bright wear on this trilobed cam attests to the considerableforce it exerts on the GDI fuel system’s high-pressure pump plunger.

If you need to remove the pump housing, be sure to counter-hold the hex on the outlet pipe (shown here pointing down-ward) as you remove the fitting leading to the rail. If the pipeloosens up from the housing, the assembly must be replaced.

Pg_EDIT_Carbon:Pg_EDIT_ 11/19/14 3:27 PM

pg edit :pg edit 11/19/14 3:19 pm page 1 c gasoline ... the results once you’re safely...

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