T he mandate to reducediesel engine emissionsand increase engine per-formance and fuel econ-omy has resulted in

major technological advances indiesel engine fuel system designand sophistication.

The modern diesel engine issmoother running, quieter, morepowerful, and yet much moreenvironmentally friendly. The sys-tem can even diagnose its ownproblems.

This is all well and good. But amajor diesel engine problem iscurrently going undetected – andit is destroying these precision fuelsystems.

The problem is dirty fuel.Ten years ago, maximum diesel

fuel system pressures seldomexceeded 3,000 psi. Today’s state-of-the-art fuel system pressurescan be as high as 30,000 psi.

And therein lies the problem.The issue became apparent some

20 years ago – not in fuel systems –but in newly developed high-pres-sure hydraulic systems that utilizedservo valves. It was noted thathydraulic system component lifewas drastically reduced in the newhigh-pressure systems. And for noreadily apparent reason.

Pumps and valves that had pre-viously lasted tens of thousands ofhours in low-pressure systemswere failing in only hundreds ofhours in the new high-pressuresystems.

How does this relate to you andyour vehicles? The modern dieselfuel system is essentially an ultrahigh-pressure hydraulic system.So the same issues and parts fail-ures apply here.

In the case of the high-pressurehydraulic systems, it was deter-mined that ultra fine particles thathad not been a problem in lowerpressure (1,000 psi or less)hydraulic systems were the causeof reduced pump, valve and com-ponent life.

Particles in the 5 to 10 micronsize were determined to be themost abrasive particle size groupand were the cause of severelyreduced component life.

In particular, the 7 micron par-ticle was the perfect fit betweenthe micro-machined clearancesand would grind away on metalsurfaces, causing acceleratedwear. This would result inreduced pump pressures, servovalve orifice erosion and degradedsystem performance.

As a result of this hydraulic sys-

tem research, an InternationalStandards Organization cleanli-ness coding system was developedthat enabled lubrication engineersto establish target cleanliness lev-els for systems with operatingpressures beyond 3,000 psi. Byusing these cleanliness levels, sys-tem life was extended and broughtback to normal.

The ISO coding systemaddressed three particle sizegroups that were found to mostaffect high pressure componentlife – namely the 2 micron, 5micron and 15 micron size ranges.By utilizing ultra-fine fluid filtra-tion, the harmful particles couldbe eliminated and systems wouldbe less vulnerable to failure as aresult of contamination.

Since the modern diesel fuelsystem is essentially an ultra-high-pressure hydraulic system, thesame requirements for ultra-finecleanliness should apply directlyto our fuel systems, right?

Wrong.The fuel cleanliness issue begins

at the refinery. There, the finalfuel output filtration is typically 30microns. Particles smaller than 30microns are unfiltered and stillremain in the fuel.

And the problem only gets

7 8 H E A V Y D U T Y T R U C K I N G • O C T O B E R 2 0 0 3

S pecial Report

Trucking’s DirtyL I TTLE SE CRET

A M AJOR DIESEL ENGI NE PROBL E M H AS GONE UNDETECTED.AND IT’S DESTROYING FUEL SYSTEMS.

IT’S DIRTY FUEL.By Steve Sturgess, Senior Editor & George Morrison, Contributor

worse. After the diesel fuel hasbeen taken from the refinery itgoes through several transfersuntil it ends up in its final tank fordistribution to vehicles. By thistime, the fuel has picked up evenmore contaminants.

Poor ISO cleanliness levels canmean that for every gallon ofdiesel fuel entering that fuel sys-tem there are 263,719,875 parti-cles greater than 2 microns,49,163,365 particles greater than5 microns, and 1,006,810 parti-cles greater than 15 microns.

All of these particles are goingright through your fuel pumpsand fuel injectors.

Controlling Fuel QualityFuel filters at truckstops typical-

ly catch only 30 micron units andabove. Consequently, they don’tfilter any of the most abrasive 5-to 10-micron particles.

The same is true for truckengine filters – most of which arenominal 15-micron filters.

For most diesel engines, withevery gallon of diesel fuel burnedhundreds of millions of abrasiveparticles have cut their waythrough the fuel pump and injec-tor system.

As a result of this high amountof ultra-fine dirt contamination,high-pressure fuel pump andinjector life is going to be greatlyreduced.

Silently and gradually the fuelsystem degradation proceeds untildecreased performance finallybecomes noticeable or the truckjust quits running.

All during this process the truckuses more fuel, creates more pol-lution, develops less horsepower,and becomes less efficient eachday.

To this point, the typical truckoperator is unaware of the prob-lem. But there is much that can bedone to protect sensitive fuel sys-tems from dirt and contaminationby way of quality control andgood housekeeping with fuelstored at terminals.

First, the fleet must test thediesel fuel source to find outexactly what it is purchasing.Diesel fuel is the trucking indus-try’s No. 1 commodity cost ofoperation. Yet very few compa-nies regularly test their diesel fuelquality.

The recommended fuel testsshould be for cetane index plusISO cleanliness code.

If a trucking or constructioncompany has its own fuel tanks,fuel tests should be run for bothincoming and output fuel fromthe tanks. Often, fuel is being con-taminated by dirt already presentin storage tanks.

Poorly maintained storage tankscan also contain significantamounts of water, which results inmicrobe and algae growth that cancause fuel filter clogging. Theacidic by-products of microbe lifecauses tank inner wall corrosion,further increasing fine fuel con-taminants.

Once fuel quality and contami-nation are determined, a plan canbe implemented to reduce con-taminant levels.

Read the story beginning onpage 82 to learn how to clean upthat dirty fuel.

Co-author George Morrison, wasvice president of surface mechanicalsfor a large coal mining concern for18 years. His job also included themaintenance planning of over-the-road truck fleets. For the past 15years, he’s been the owner of anExxonMobil distributorship inColumbus, Ohio.

8 0 H E A V Y D U T Y T R U C K I N G • O C T O B E R 2 0 0 3

Because of the fine filtration, atwo-micron filter clogs easily.Dealing with this problem, fleets

simply increase the filter screen, but atthe cost of many thousands of dollars infuel system deterioration that will mani-fest itself as poor engine performance,fuel dilution of lube oil, failed pumpsand, more and more frequently, itseems, failed injectors.

Typically, the injector failure fromsolids contamination is progressive. Agradual loss of performance andincrease in smoke may well go unidenti-fied. However, as the injector spray holes

erode, the precise combustion isdegraded. Ultimately, wear in theinjector leads to slobbering andincreased fuel in the lubricating oil.At the same time, fuel economyfalls.

Water contamination, though,may well be more dramatic, result-ing in the tip of the injector beingblasted off.

And over the years, the cost of aninjector has escalated in parallelwith its increasing complexity andcloser manufacturing tolerances. Anelectronic unit injector is a signifi-

cant service item.Some maintenancemanagers are say-ing injector mainte-nance is a newline-item in theirbudgets, withreplacement atlower mileagesaccounting for asmuch as a 75-c e n t s - p e r - m i l eincrease in operat-ing costs.

THE HIGH PRICE OF INJECTOR FAILURES

This injector

failed due to

contaminant

exposure. Note

the damage to

the tip.

Tru c k i n g’s Dirty Little Secre t