Volkswagen’s clean turbocharged direct injection (TDI) diesel engine offers high mileage between refills and more than 50% better fuel economy than similarly sized gasoline engines. With a potential 43 miles per gallon on the highway, you can get up to 795 miles per tank, in a car that emits lower CO2 commissions than 93% of other vehicles. The TDI is available in new Volkswagen cars like the Passat, Golf, Jetta sedan and Sport Wagon, Beetle and Beetle Convertible, and Toureg.
To keep your TDI running at peak performance, it is important to understand how it works and how to maintain it.
What makes a TDI engine different
The secret to TDI’s success lies in the engineering. Replacing the indirect injection of older diesel models, the new models use a fuel injection system that sprays atomized fuel directly into the main combustion chambers and not into the pre-combustion chambers. This process is combined with forced induction with the turbocharger that increases the amount of air that passes to the engine cylinders and an intercooler to decrease the temperature and density of the turbo charge air.
The result for you, the buyer? More fuel is injected and burned, so you’ll notice higher engine efficiency and more power, along with more torque and lower emissions.
Fuel requirements for TDI
The Volkswagen TDI engine runs on diesel fuel (petro diesel) or certain types of biodiesel fuels. The trade-off for the engine’s technical prowess is that it is picky about the type of fuel it needs. In the US, VW recommends number 2 diesel fuel, which has a higher cetane number than number 1 fuel and a lower viscosity. Proper fuel straight from the pump is common in Europe, but some US drivers must use additives or premium diesel to make sure cetane levels are correct.
“Misfueling” your TDI engine with regular gasoline instead of diesel can be a costly mistake. Some older VW models were more forgiving, but putting the wrong fuel in a modern TDI engine will damage the fuel pump and ruin the engine when fuel passes through the fuel system. That system on 2013 vehicles has been redesigned with a fuel tank hatch to prevent you from inserting a gasoline nozzle instead of a diesel nozzle into the tank.
The cost of accidental fuel starvation can range from roughly $ 100 to pump out the wrong fuel and replace filters to over $ 8,000 to replace the entire fuel system. Most of these repairs are not covered under warranty.
What can you diagnose yourself?
Your local VW dealer has an excellent service department that can keep your TDI engine running strong. Regular maintenance costs are roughly the same as professional service for a gasoline-powered VW. However, if you are a competent yard mechanic who enjoys doing your own car repairs, there are a few situations unique to a TDI that you can diagnose yourself:
- If you hear noises, are they “normal” for your TDI engine? Most drivers notice popping in the steering column, popping of the EGR and pressure control valves, and a thud from the shoulder valve when the engine is turned off. These noises indicate adequate performance, not a problem, but as a new TDI owner you must learn what to ignore and what to pay attention to.
- Engine won’t start or reluctant to start? While the car is in neutral, turn the ignition to the run position to see if you receive a check engine warning or glow plug lights. If not, you may need a new battery as the motor is not receiving power.
- Does the engine start? If you see check engine or glow plug lights on the dash, but the car makes noise when you try to start, it may be low on fuel, corroded wires leading to the battery, or loose connections.
- Do you have a fault in “relay 109”? If the check engine light or glow plug comes on and off, you may have a 109 fault that requires the relay to be replaced. If that doesn’t work? You may have a faulty ignition switch or security system. You can also see the glow plug light if you have a burnt out brake light.
- Does your engine smoke when fully revved after a fill? You may have gotten a low quality fuel tank.
A Volkswagen TDI engine offers the best in performance and efficiency, but they are particular engines that require very specific maintenance and repairs. Always remember to replace defective parts with genuine Volkswagen replacement parts, or choose your local VW service department for professional service from certified and experienced mechanics.