Visit the Newsroom and browse the latest news articles and press releases to find out more about Delphi.

About Us

With a presence in more than 150 countries, and a global network of over 2750 service centres, Delphi aftermarket provides OE specification end-to-end solutions from components to sophisticated software solutions.

Resource Centre 5 min read

Analyzing a Failed Fuel Pump

Share Resource:
Diagnostics & Test Equipment How to Technicians 5 min read

Resource Highlights

In this article you will find out about how to analyze a failed fuel pump. We take you through different checkpoints to find the fault.

What can a failed part tell you? A lot... It tells a story. Take the following fuel pumps shown. These failed pumps were not a result of incorrect testing. All tests performed were valid and provided useful data for making a diagnosis, but more could have been learned. Were they worn out or did they fail for another reason?

The answers to these questions are important and without them, an accurate diagnosis is left to chance, inviting future problems for you and your customer. A failed-part analysis should always be conducted on failed fuel modules through close visual examination and some simple disassembly. Avoid a potential customer comeback with these simple steps.

First Checkpoint

Examine the electrical connectors closely and look for evidence of terminal overheating, especially at the terminals supplying current flow to the fuel pump inside the module. Badly charred and burnt terminals are easy to spot, but seemingly undamaged connections should be checked more closely for evidence of melting or bubbling near the electrical terminals. Any melting is an indication of excessive heating due to a poor electrical connection caused by a damaged vehicle body harness. If this type of damage is found, poor pump performance will occur due to this bad connection. The vehicle’s electrical connector must be replaced or repeat failures will occur.

Second Checkpoint

Examine the external strainer on the fuel module. Look for signs of dirt and/or rust contamination. Any form of dirt found in the strainer should immediately trigger an inspection of the fuel tank. A tank cleaning or replacement should be conducted, based on what is found.

It is important to understand how contamination entered the fuel tank so preventative action can be taken to eliminate future occurrences. Areas like the tank vent system should be checked to determine if contaminants entered through this area. If determined contaminants were “pumped” into the tank or intentionally added, it’s important to change fuel supplies or add a locking gas cap to the vehicle.

Third Checkpoint

Visually examine the fuel module bucket and internal strainer. Depending on the module design, you may be able to view the module bucket through an opening in the fuel module design. If not, the bucket may have to be removed from the fuel module through disassembly. What is important to note is what has accumulated in the fuel module bucket and internal pump strainer. Contaminants entering the fuel module bucket are indefinitely trapped, so the bucket will contain a contamination history of the fuel module.

A significant amount of contamination found in the bucket and internal strainer is a sure sign that the part failed due to contamination. This indicates there are other issues on the vehicle that need repair prior to the installation of a new fuel module.

Analysis of Actual Failures

These are actual scenarios showing failed modules. Since these issues were not identified during the initial diagnosis, the results were repeat failures. Upon such closer inspection, all the needed repairs could have been made. More important, a customer “comeback” would have been avoided.

Intermittent Starts Due to Bad Vehicle Wiring

This vehicle received three fuel modules over a five week time period. In each instance the vehicle would not start. Sometimes striking the bottom of the fuel tank would cause it to run. All modules were analyzed and failed due to a bad vehicle electrical connector, which had not been replaced in all instances. All three modules were damaged via a burnt fuel pump ground terminal. Although damage is not extreme, it is significant enough to create repeat failures.




All three modules failed due to a burnt “C” terminal, the ground path for the fuel pump.

Contamination Caused by Rusted Fuel Lines

On both parts, rust was found inside the bucket and on the pump strainer. External strainers of both parts show discoloration, but very little rust contamination. This vehicle received two fuel modules in less than a week. The reported issue was noisy operation and erratic fuel pressure. Both modules were analyzed, and found to have the fuel module bucket and internal strainer heavily contaminated with rust. The external strainers showed some discoloration, but had significantly less rust in them. The cause was a rusted return fuel line.

No significant amount of rust or contamination was found in the fuel tank because the source of the rust was the metal return line on the vehicle. The rust that was deposited went directly into the fuel module bucket, as the return line on this vehicle puts fuel directly into the fuel module bucket, not the fuel tank. Once the rust was deposited, it could not be removed. The fuel filter was not able to catch the rust because it was developing in the vehicle return line, downstream of the fuel filter.

Part One

Part Two

External strainers of both parts show discoloration, but very little rust contamination.

Part One

Part Two

On both parts, rust was found inside the bucket and on the pump strainer.


The specified form no longer exists or is currently unpublished.

Related article resources and products

    Part diagnostics fuel injection electronic test kit
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    Electronic Injector Test Kit

    With today’s Common Rail injector technology, it’s no longer sufficient to just measure resistance to check a coil’s health – you also need to measure inductance for an immediate and accurate assessment. Previously separate tools would have been needed for this. Not with our Electronic Injector Test kit. Otherwise known as the ‘buzz tool,’ or part number YDT720, you’ll be able to quickly test the electrical integrity of all makes of solenoid Common Rail injectors on vehicle. The simple,hand-held tool measures the injectors core criteria, allowing you to quickly compare values and identify if any are not within a comparable performance range, or confirm specific electronic failures which may indicate an unrepairable injector. You can also use it in conjunction with our solvent cleaning kit to resolve early-stage lacquering. All with just one tool, saving significant time and cost for the garage.
    Diagnostics & Test Equipment

    Pass-Thru Diagnostics

    Our DS-Flash™ pass-thru package does what its name suggests – it allows garages to ‘pass-thru’ to vehicle manufacturer’s websites to access valuable repair and maintenance information. With DS-Flash you’ll be able to perform dealer-level diagnostics, download software updates, reprogram ECUs and access OE technical data and service schedule information, without the need for expensive dealer-only tools. The full kit is compliant with VM programming requirements and comes complete with a DS-Flash™ VCI, cables, a battery support unit and a laptop PC, pre-configured for key brands. Users will also benefit from our 12-month support package, which includes training and technical support for both the equipment, registration to the VM web portal and installation and use of the VM software. So from now on, jobs that were turned away, or referred back to the dealer network, can now be managed in house.
    Part diagnostics fuel injection hd3000 high pressure tool
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    HD3000 High Pressure Diagnostic Tool

    Designed for specialist workshops, our patented HD3000, part number YDT840, simplifies the diagnosis of faults with current and future-generation diesel and gasoline high pressure fuel systems, on all vehicle types. With one tool users will be able to safely set and electronically control any pressure testpoint , up to 3000 bar, in order to investigate the full range of pressures and analyse the performance of the fuel injection system – previously this level of flexibility, accuracy and pressure capability could only be achieved with a system-dedicated test bench. Containing an electronic control device, hydraulic block and electrical device, it incorporates multiple dedicated test routines, as well as an IMV cleaning procedure. All this can be achieved without changing any ECU parameter, dismantling the fuel injection system, or taking the vehicle out on a road test – helping workshops save valuable time and deliver faster service turnarounds.
    Part diagnostics fuel injection lo35 low pressure tool
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    LP35 Low Pressure Diagnostic Tool

    Designed for the garage technician, LP35, part number YDT810, is a highly precise, ultra-fast, affordable hand-held tester for the low-pressure side of light, medium and heavy duty vehicles. With a single tool, you can perform quick and accurate pressure analysis across a wide range of positive and negative pressures, from minus one through to positive 35 bar -that’s why we called it the LP35. Unlike other entry level equivalents, it’s also compatible with most low-pressure circuits, as well as different fluids, so you’ll no longer need separate negative and positive pressure tools, saving both time and money. Add to this its static and dynamic functionality, and you’ve got a highly versatile, highly capable low-pressure tool.
    Part diagnostics fuel injection hd3000 high pressure tool blueprint
    Diagnostics & Test Equipment

    Fuel Injection Diagnostics

    Due to the design of today’s advanced fuel injection technology, electronic diagnostic tools require additional support to accurately trace faulty components – the ECU diagnostic software  can often go no further than failure mode identification, which does not always pinpoint the particular part of the system that has failed and can result in the unnecessary replacement of complete systems. That’s where we come in. We know exactly what is required when diagnosing this technology – after all, the chances are we designed and manufactured it in the first place. So, we’ve developed a range of simple, low-cost, on-vehicle diesel diagnostic tools to help you and your customer save time and money.
    Part diagnostics fuel injection sealed rail kit
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    Sealed Rail Diagnostic Kit

    Because Common Rail systems operate at extremely high pressures, any loss in pressure will have a knock-on effect on the vehicle – causing a progressive reduction in power and even a complete engine shut down. It is therefore imperative that any such issues are identified and resolved as early as possible. We have just the answer. Our Sealed Rail diagnostic kit, part number YDT850, provides simple, low-cost on-vehicle capability for all makes of Common Rail pumps and injectors. Consisting of a sealed rail pressure tester and injector back leakage measurement equipment, users can check the pressure being generated by a Common Rail pump and identify individual injectors that fail, meaning only faulty components will need to be replaced.
      where to buy

      Find out where to buy Delphi parts

      where to repair

      Find your nearest Service & Diesel Centres

      Select your Region