Present work deals with the failure analysis of fuel pump in transport utility vehicles. The fuel pump assembly failed at 70536km. Various types of failures in pump and its different components are analyzed. Failure mode and effect analysis (FMEA) of the acquired data has been carried out. The pump components with substantial contribution in failure are determined using risk priority number analysis and the failure causes are postulated. Using scanning electron microscopy (SEM) for pump parts as rollers and cam plates the types failures are observed. Presence of water in fuel tank indicated the reason for rusting of bottom surface of tank. Pitting failure due to rust particles has been identified in pump parts after SEM observations. Energy Dispersive Spectroscopy (EDS) of pump parts has also been carried out to identify levels of unnormalized constituent elements responsible for failure. From EDS presence of oxygen responsible for oxidation reaction with iron is identified. Significant percentage of oxygen at different locations indicated the presence of moisture in the system. Remedial measure to avoid pump failure has been suggested in present work.

1. Contents lists available at ScienceDirect
Engineering Failure Analysis
journal homepage: www.elsevier.com/locate/engfailanal
Short Communication
Failure analysis of fuel pumps used for diesel engines in transport
utility vehicles
Vikas Radhakrishna Deulgaonkara,⁎
, Kundan Pawarb
, Pratik Kudleb
,
Atharva Raverkara
, Amod Rautc
a
Department of Mechanical Engineering, Marathwada Mitramandal's, College of Engineering, Karvenagar, Pune 411052, MS, India
b
Helical Auto Technology Pvt Ltd, Pune, MS, India
c
Dynomerk Controls, Pune, India
A B S T R A C T
Present work deals with the failure analysis of fuel pump in transport utility vehicles. The fuel pump assembly failed at 70536 km. Various types of
failures in pump and its different components are analyzed. Failure mode and effect analysis (FMEA) of the acquired data has been carried out. The
pump components with substantial contribution in failure are determined using risk priority number analysis and the failure causes are postulated.
Using scanning electron microscopy (SEM) for pump parts as rollers and cam plates the types failures are observed. Presence of water in fuel tank
indicated the reason for rusting of bottom surface of tank. Pitting failure due to rust particles has been identified in pump parts after SEM ob-
servations. Energy Dispersive Spectroscopy (EDS) of pump parts has also been carried out to identify levels of unnormalized constituent elements
responsible for failure. From EDS presence of oxygen responsible for oxidation reaction with iron is identified. Significant percentage of oxygen at
different locations indicated the presence of moisture in the system. Remedial measure to avoid pump failure has been suggested in present work.
1. Introduction
One of the important components for passenger vehicles or buses using fuel as diesel is fuel-injection pump. Fuel pump not only
distributes the measured amount of fuel to the cylinder but also assists in controlling engine speed. A typical fuel-injection system
comprises of pressure generating system, motion transmitting system, control system, hydraulic delivery system and a system or unit
to handle overload [4]. The fuel-injection pump is indirectly driven by the crankshaft through gearing arrangement. Fuel injection
system includes several components possessing motion relative to each other, however no separate unit is used for lubrication as fuel
itself acts a lubricant during the fuel pump action. In present work a total of 89 fuel-injection pumps were analyzed for different types
of failures. Failure of pumps occurred at 70536 km far before the actual life of 200,000 km stated by original equipment manu-
facturer. Fuel pump failure is faced by all state transport systems and present work is conducted in one of the state central workshops
utilized for regular maintenance and bus body building. The failure data collected is analyzed using various techniques and remedial
action is devised which further affected the performance of fuel-injection pumps.
2. Investigation of fuel pump failures
Fuel pumps under consideration failed due to improper functioning of the pressure generating, hydraulic delivery, control systems
and overload control unit. Part wise failure data is collected and analyzed. Major systems, system components and causes of their
failure are enlisted in Table 1.
https://doi.org/10.1016/j.engfailanal.2019.07.048
Received 16 May 2019; Received in revised form 12 July 2019; Accepted 18 July 2019
⁎
Corresponding author.
E-mail address: vikasdeulgaonkar@gmail.com (V.R. Deulgaonkar).
Engineering Failure Analysis 105 (2019) 1262–1272
Available online 21 July 2019
1350-6307/ © 2019 Elsevier Ltd. All rights reserved.
T

2. Failures of major fuel-injection components are shown in Figs. 1 to 4.
For eighty-nine fuel pumps, partwise failure data is gathered. The gathered data is represented in Fig. 5. In this, number of times
the component failed is represented on ordinate while the component is represented on abscissa.
2.1. Failure mode and effect analysis (FMEA) of fuel pump components
Failure mode and effect analysis is systematic and step-by-step process used for failure analysis. It evaluates processes for failures
and gives inferences for preventing them with efficient quality and reliability. In present work FMEA of fuel pump parts is conducted
by listing failures of all components, failure causes and effects. In addition to this the severity of the failures, their actual occurrence
and detection were also figured out. Further to prioritize the components for experimental analysis, risk priority number (RPN) is
calculated related to every failure. Failure analysis of eighty-nine pumps has been carried out. While carrying out the analysis, each
component of the pump causing failure is accounted. In this work, we have actual failure data for each component and the same is
utilized during the analysis [1]. The failed component and number of times the same failed in a total of eighty-nine pumps was
enlisted. Failure of pump occurred due to a total of thirteen components and the number of times the failure detected was also
observed and noted during failure analysis. The component, number of times the component failed and number of times same was
detected is enlisted in Table 2.
To conduct risk priority number (RPN) analysis, the number of times the component failed is treated as occurrence (O), the
number of times the failure was detected is considered as detection (D) and a severity number (S) is assigned considering severity of
failure. RPN has been presented in Table 3. RPN is the product of S, O and D. The calculation of same is carried as RPN = S * O * D.
e.g. RPN of Lever bush = 4*8*10 = 320. Table 3 shows the detailed failure mode and effect analysis along with risk priority number
evaluation for every failure. (See Table 3.)
From above table, the components with RPN greater than 600 are selected for further analysis. Prioritizing the components by
their RPN, it is observed that cam plate, rollers, time device piston and supply pump possess RPN above 600, indicating that these are
major contributors for pump failure. The above results of RPN analysis are plotted in Fig. 6, which is further used in decision
regarding experimental analysis. The results from risk priority analysis are plotted in graphical format and the components prioritized
Table 1
System components and their failure causes.
Fuel-injection pump system System component Failure cause
Pressure generating system Supply pump Friction between vanes and rotor arising due to dry run, presence of water and thermal expansion of
vane
Pressure control valve Frequent expansion and contraction due to temperature variation
Motion Transmitting System Drive shaft Torsional fatigue, excessive load, key slot expansion and improper gear shifts
Cam plates Pitting due to fuel impurities, dry run and water presence causing corrosion
Roller plates Pitting due to fuel impurities, dry run and water presence causing corrosion
Hydraulic delivery system Hydraulic head Accumulation of burrs and impurities
Head Spring Corrosion due to water
Control system Fulcrum lever system Play due to continuous acceleration
Overload controlling unit Time device piston Expansion due to dry run of pump
Solenoid valve Clogging of fuel impurities resulting in choking
Fig. 1. Original and failed cam plate of motion transmitting system in fuel pump.
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3. for further analysis.
3. Discussion of failure causes
From the above predicative failure mode and effect analysis, the components identified for failures of fuel injection pump includes
cam plates, rollers and timing device piston. These three components with RPN greater than 600 are major contributors in pump
failure. It is observed that cam plate and rollers, fail due to pitting. One of the main reasons of pitting, is water being flashed on hot
metal surfaces. However other failure reasons include but not limited to rusting, corrosion, abrasion, etching, spalling, fuel oxidation
etc. [2]. All these phenomena of failure except spalling, include water as an agent. Iron oxide is produced when water encounters
with steel and causes the contacting material to rust e.g. fuel tank. This rust gets introduced into the system as hard particulate and
cause wear. Combination of water with acids in fuel causes corrosion of pump parts leading to failure [6]. Absence of enough
thickness of lubricant film causes abrasion. Sources of water getting introduced into the system include but not limited to, on delivery
from fuel stations, human error, leakage into tank which occurs due to high pressure washing, rain and ground water. Condensation
phenomena in fuel tank causes formation of water which further passes into the system. Humidity is also major contributor for
formation of water in fuel tank which further gets into fuel pumps. At high pressure, hydrocarbons and water molecules are in-
troduced into the fuel pump from fuel tank. This water droplet when meets any of the pump components, gets settled on it and
Fig. 2. Original and failed roller plate of motion transmitting system in fuel pump.
Fig. 3. Original and failed pressure-control valve of pressure generating system in fuel pump.
Fig. 4. Original and failed drive shaft of motion transmitting system in fuel pump.
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4. reduces the lubricant oil film thickness. Once the thickness of lubricant is reduced the metal to metal contact of pump components
occurs leading to failure. The water molecules deposited into micro-cracks on metal surfaces, beneath the extreme pressure gets
decomposed and releases hydrogen in a mini-explosion that enlarges cracks and creates wear particles.
4. Experimental analysis of failure in cam plate and roller of fuel pump
The experimental analysis of the above-mentioned components is carried using SEM and EDS. SEM or Scanning Electron
Microscopy of the failed parts is carried at magnification level of 500×. EDS or Energy Dispersive Spectroscopy conducted in present
work confirms the failure reason by indicating oxygen content. SEM observations of cam plate surface are shown in Figs. 7, 8 & 9.
Fig. 7 shows the 500× magnified view of cam plate surface. It is observed that rust particles are responsible for deteriorating the
quality of surface finish of cam plates. During operation these rust particles adhere to surface and score the surface, due to this, pits
are formed on the surface leading to pitting corrosion [3]. Fig. 8 1000× magnified view shows the scale formation on the cam plate
surface. A thick layer of scale can be clearly observed, which affects the functioning of cam plate and consequently leads to pump
failure. Fig. 9 2000× magnified view shows the pit dimensions. Pits of diameters as large as 20 μm are observed on the cam plate
surface (shown in Fig. 9 are 10.54 μm) and 18.06 μm, which further becomes housing for water leading to rusting and pitting
corrosion. Pitting corrosion, or pitting, is extremely localized corrosion leading to formation of small holes in the metal. Driving
influence for pitting corrosion is the de-passivation of a small area, which becomes anodic while an unknown but potentially vast area
becomes cathodic, leading to very localized galvanic corrosion. The corrosion penetrates the mass of the metal, with a limited
diffusion of ions. The mechanism of pitting corrosion is same as crevice corrosion. Scale is hard mineral coating and corrosion deposit
made up of solids and sediments. Scaling occurs because of high temperature water containing carbonates or bicarbonates of calcium
and magnesium.
Figs. 10 to 12 indicate the surfaces observed under SEM. Fig. 10 viewed 500× magnification shows surface pits formed due to
pitting corrosion.
Fig. 11 viewed under 1000× magnification shows rust particles inserted into the cam plate. It can be observed that the rust
particles present on the surface deteriorate the surface finish of the roller which further affects the pump functioning. Fig. 12 viewed
0
2
4
6
8
10
12
14
16
Fuel pump components
Occurences
Fig. 5. Occurrences of failure versus components of fuel pump
Table 2
Occurrence of failure in components of pump and their detection.
Name of the Component Number of times the Component Failed Number of times the failure was detected
Lever bush 06 10
Cam Plate 19 09
Rollers 14 09
Adjusting Plug 01 10
Body 10 03
Shim 05 10
Drive Shaft 11 03
Lever Shaft 08 09
TD Piston 12 08
Solenoid Valve 02 06
Supply Pump 05 07
Spring 05 08
Pressure Valve 02 07
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5. Table3
FailuremodeandeffectanalysisandRPNevaluationoffuelpumpparts.
ComponentFailuremodeEffectSCauseODRPNRecommendation
LeverbushFriction,wearInaptaccelerationoractuation04Overuse&excessfriction0810320Replacementafterstipulatedtimespan.
CamplatePitting&RustingErroneousfuelsupply07Wateremulsions&fuelimpurities1509945Avoidwatermixesandimpurefuel
RollersPitting&RustingInaccuratefuelsupplyandnoise07Wateremulsions&fuelimpurities1409882Avoidwatermixesandimpurefuel
AdjustingplugFrictionImpropergoverningaction02Frictionamongplug&fulcrumlever011020Ensureadequatelubricationandreplaceincaseif
needed.
BodyFriction&ShearImproperpumpfunctioning06Excessivetightening&fuelimpurities1003180Avoidexcessivetighteningofboltsandrepairifneeded
ShimThermalstressesNegligibleplay01Friction&Wear051050Replaceincaseoffailure
DriveshaftTorsionalfatigueNomotiontransmission10Inaptgearshifting&strengthreduction
duetocorrosion
1103330Ensurepropergearshiftingbyoperator&avoid
corrosion
LevershaftTorsionalforcesImproperacceleration05Overuse&abruptactuation0809360Replaceafterspecificperiod
Timedevice(TD)PistonThermal&Contact
Stresses
Failuretoadjustfuelsupply07Dryrunning&waterlogging1208672Avoidwatermixinganddryrun
SolenoidchokingInsufficientfuelsupplyduringoverload
situation
05Fuelimpurities020660Ensurefuelfiltration
SupplypumpFrictionalwearand
corrosion
Inadequatepressureinpump08Waterinfuel&dryrun0507280Watermixingtobeavoidedandremovemarkingsby
polishingsurface
SpringCorrosionFailuretoregulatefuelsupply06Waterinfuel0508240Watermixingtobeavoided
PressureValveThermalstressFailuretoregulatepressure07Dryrun020798Replaceifrequired
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6. Table 3
Unnormalized oxygen and iron percentages.
Spectrum Number Unnormalized
Oxygen (%) Iron Fe (%)
s2 10,758 14.71 55.06
s2 10,760 11.51 76.10
s2 10,757 7.31 81.32
s2 10,761 4.78 83.90
0
100
200
300
400
500
600
700
800
900
1000
Pump Components vs RPN (Risk Priority Number)
Risk Priority Number
Fig. 6. Risk priority number versus components of fuel pump.
Fig. 7. SEM observation of cam plate rust particles and pits due to surface corrosion.
V.R. Deulgaonkar, et al. Engineering Failure Analysis 105 (2019) 1262–1272
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7. Fig. 8. SEM observation of cam plate scale formation.
Fig. 9. SEM observation of cam plate indicating dimensions of pits on surface.
V.R. Deulgaonkar, et al. Engineering Failure Analysis 105 (2019) 1262–1272
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8. under 2000× magnification shows scale and pits formed on the roller surface due to occurrence of water emulsion into the system.
Energy Dispersive X-Ray Spectroscopy (EDS or EDX), a chemical microanalysis technique is used in combination with scanning
electron microscopy in present work. The water presence is depicted by the oxygen content as evaluated from the spectrum analysis.
EDS image viewed in 1000× magnification is shown in Fig. 13.
For each portion of the surface a spectrum number is assigned. The corresponding spectrum for each number is plotted between
Fig. 10. SEM observation of roller surface indicating pits on surface.
Fig. 11. SEM observation of cam plate indicating rust particles & pits.
V.R. Deulgaonkar, et al. Engineering Failure Analysis 105 (2019) 1262–1272
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9. Fig. 12. SEM observation of roller surface indicating scale & pits.
Fig. 13. EDS observation of cam plate indicating oxygen and other elements.
V.R. Deulgaonkar, et al. Engineering Failure Analysis 105 (2019) 1262–1272
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10. cycles per second per electron (cps/eV) volt vs kilo electron volt(keV). At spectrum number s2 10,758 the level of unnormalized
oxygen is depicted is 14.71%. and corresponding iron level is 55.06% leading to iron oxide (rust) formation. Plot for s2 10,758 is
shown in Fig. 14.
From similar analysis of remaining spectrum numbers as s2 10,760, s2 10,757, and s2 10,761 the unnormalized iron and oxygen
percentages are evaluated from graphs like graph 3 of all remaining spectrum numbers. The unnormalized oxygen and iron per-
centages are tabulated in Table 3.
5. Conclusion
Fuel pump failure data has been collected and analyzed for eighty-nine pumps. The number eighty-nine quantifies enough fuel
pumps to have a substantial insight for understanding the pump failure. Failure in different components of fuel pump and its
occurrence during initial phase gives enough insight for failure analysis. Further from this data, failure mode and effect analysis has
been carried out for all components of fuel pump. Water presence in the fuel pump system has been identified as the primary reason
for pump failure. Components which failed critically were identified and selected using risk priority number analysis. For components
whose risk priority number is above 300 are impact fuel pump life and quality and were cam plates, roller surfaces, time device piston
and supply pump. SEM of these components has been carried out to identify the failure modes and it is observed that these com-
ponents fail due to pitting corrosion. Outcomes from EDS shows presence of excess oxygen leading to oxidation thus confirming the
presence of moisture [5]. The presence of water in the injection system is due to malfunctioning of water-separator requiring periodic
repair and maintenance. Further, a water in fuel sensor that detects the excess amount of water in separator which gets introduced
into the system is suggested to be installed at the bottom of fuel filter and connected to the electronic circuit unit that alerts driver to
address it, hence the pump life and performance can be enhanced.
6. Recommendation to avoid fuel pump failure
The significant cause of pump failure is the intrusion & emulsion of water in fuel line. The fuel line has a water separator that
separates water from fuel tank and prevents it from entering the fuel pump, however it operates till its capacity, after which the
excess water needs to be manually removed. This excess water gets intruded into the fuel pump causing failures. Hence, an automatic
sensing system that identifies water in the separator and alerts the operator even before the engine is cranked is recommended. A
water in fuel sensor detects the presence of water in diesel fuel and gasoline using the difference of electric conductivity between two
electrodes through water and fuel. Detection of water in fuel can prevent or too much extent reduce damage, the water could cause to
fuel injectors. Presence of water in engine fuel system causes injection system damage, hard starting, loss of power, misfiring, surging
or stalling. Water in fuel sensors are placed at the bottom of a fuel filter water separator which provides a space at the bottom of
2 4 6 8 10 12 14
keV
0
1
2
3
4
5
cps/eV
FeFe
O
C
Mo
Mo
Ti
Ti
Cr
Cr
Mn
Mn
Ni
Ni
Fig. 14. Spectrum for s2 10,758.
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11. separators for collection of water. The signal generated is further transferred to electronic control unit or dashboard indicator, giving
alert to the operator that the filter needs to be addressed.
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