Fuel Injector Diagnostics: Thinking Through The Problem
There is almost no way to inspect the spray pattern of the fuel injector while it is on the vehicle, and it is impossible to inspect on a vehicle with direct fuel injection. You can, however, witness the symptoms of a bad injector.
VIDEO: Fuel Pump Voltage; Different Numbers On Different Tools?
Andrew Markel discusses the current used to drive fuel pumps, and how measuring it with a suite of diagnostic tools can determine the component’s health. Sponsored by Auto Value and Bumper to Bumper.
Smart Fuel Pump Diagnostics
If you are diagnosing a “cranks but does not run” or a “lean/stumbling under load” complaint, your first instinct might be a problem with the fuel pump. But, how do you assess the condition of the fuel pump without taking it apart?
Fuel Trim Theory And Operation
The modern engine measures two things extremely well, the amount of air going into the combustion chamber with the mass airflow (MAF) sensor, and the byproducts that are generated by the combustion event with the oxygen sensor. These measurements allow the engine’s computer to put the right amount of fuel and spark into the cylinder to give the most efficient and cleanest combustion event.
VIDEO: Negative Fuel Trim And Fuel Economy
Andrew Markel introduces a case study where a 2004 Chevrolet Impala has no codes, but is getting bad fuel economy. Sponsored by ProDemand from Mitchell1.
Acura Tech Tip: Chirping From High-Pressure Fuel Pump
With the hood open, listen for a chirping noise with the engine warmed up. If the noise is coming from the high-pressure fuel pump, follow the Repair Procedure in this Tech Tip.
Volkswagen, Audi Direct Fuel Injection System
For the past decade, almost every vehicle that Volkswagen and Audi has sold in the U.S. has been equipped with direct fuel injection. These FSI, TSI and GDI systems allow for better fuel economy and power. The switch to direct injection has also allowed Volkswagen to downsize its engines from 2.0L to 1.4L on base models without losing any power, while still improving fuel efficiency.
Giving It The Gas: When The Fuel Pump Isn’t The Problem
The most famous last words in automotive diagnostics are, “We’ve always done it this way.” In many cases, “always done it this way” consists of diagnosing a fuel pump by squirting some type of liquid or gaseous hydrocarbon into the air intake. Case in point, a 2011 Nissan Rogue had suddenly stalled on a busy summertime highway.
Rethinking Fuel Pump Diagnostics And Sensors
The technician diagnosed the 2011 Rogue as a bad fuel pump by squirting propane into the air intake. With propane, the engine runs, without propane, it stalls. But, after the fuel pump was replaced, the Rogue exhibited the same problem, which was a very slow, unsteady idle followed by an engine stall.
Fuel Injector Function Testing
If a fuel injector is not operating within set parameters, it can cause driveability symptoms and codes that can point to components other than a faltering fuel injector.
VIDEO: Checking The Voltage On A Fuel Pump
Andrew Markel explains how modern vehicles have pressure sensors that send out a voltage signal, and how a diagnosis can be made by measuring the signals with a scope. Sponsored by Auto Value and Bumper to Bumper.
The Duramax Dilemma: Injector Circuit Diagnostics
The owner of this GM Duramax was headed to Montana on vacation with his family and camper trailer in tow. After stopping for lunch, the owner was dismayed to find that his Duramax immediately went into “limp mode” as the engine started.
