Why My Diesel Car Won’t Start: Help Tips

There’s nothing worse than running out the door for work or an appointment and finding out my diesel car won’t start. Did I leave my lights on? Did I forget to get more fuel? Simple reasons like those are great for sorting things out quickly, but what if there’s more going on under the hood? How do you know if you should replace the glow plugs, injectors, or fuel filters? Let’s break it down and read more about the possible reasons and where to go from here.

Top 5 Reasons Diesel Car Won’t Start

Diesel engines can just about run forever with proper maintenance. But every car owner knows that feeling of dread when they turn their key, and nothing happens. Here are the top 5 reasons a diesel car won’t start.

1) Defective Glow Plugs

On some diesel cars, glow plugs aid the combustion process by heating up the air in the combustion chamber. This can be more important in cold weather or if you are experiencing pressure issues with your diesel engine. When a glow plug module malfunctions, you may experience a hard start, or your diesel car won’t start at all. Your service technician can use a voltmeter to test whether the glow plugs are working.

2) Faulty Injectors

Diesel engines are internal combustion engines utilizing either a two-stroke or four-stroke cycle.  They include a fuel pump, fuel line, and injector nozzles. The combustion of diesel fuel inside the engine’s cylinders is what generates the engine power. The fuel injection system injects diesel fuel into each of the cylinders. Over time your injectors can develop varnish deposits, clogs, leaks, or wear. Your service technician can check the operating temperature of each cylinder with a digital pyrometer. Differences in temperature between cylinders suggest that one of them is faulty and requires replacing.

3) Clogged Fuel Filter

Not all diesel fuels are created equal. Some fuels are cleaner than others. That’s why you should always buy your diesel fuel from reputable retailers. The fuel filter(s) in your diesel car can become clogged with debris, which can cause issues with starting. You should replace the diesel car fuel filters according to manufacturer recommendations. Most owner’s manuals suggest changing the fuel filters every 10,000 to 40,000 miles. Discuss your driving style and performance needs with your service technician to see if that guideline works for your vehicle.

4) Dead Battery

A very common reason why a diesel car won’t star is a dead battery. Depending on your diesel make & model, you may have to inspect two batteries. Also, when temperatures drop during winter, so does a battery’s ability to hold a charge. For example, a battery will have 100% power at 75-80 degrees F but will drop to only 46% at 0 degrees F. Regular battery maintenance is relatively quick and easy to do yourself. Here’s a checklist to get you going:

• Check the cable connections are tight.
• Clean off any corrosion from the terminals.
• Test the battery’s charge (or check the indicator on the battery case).
• Make sure to warm up and run your vehicle for a while before turning on any auxiliary electric components (including A/C, radio, phone chargers, etc.).

5) Disrupted Fuel Delivery 

A disruption in fuel delivery is a common problem with diesel engines. Air can penetrate the fuel system via old fuel lines or through a bad fuel pump. The air bubbles disrupt the consistent flow of fuel and can create issues when starting your car. 

Water can also affect adequate fuel delivery. Since diesel fuel is hygroscopic, a water separator is installed to remove excess water. If the water separator is not drained regularly, it can damage fuel injectors, affecting engine efficiency and possible engine failure. Your service technician can perform a diagnostic service to track down what components are at fault.

Diesel Car Won’t Start: Routine Maintenance

We’ve all heard the saying,” An ounce of prevention is worth a pound of cure,” by Benjamin Franklin. Well, when applying that principle to auto maintenance, you could say, “Routine maintenance done today saves me money tomorrow.” And it would be true. Auto manufacturers, service technicians, and gear-heads around the world agree: Performing routine maintenance guarantees your diesel vehicle will last longer, drive better, and have a higher resale value.

Schedule Service

If you don’t want to troubleshoot your diesel starting issues yourself, the ASI-Certified Technicians at Wentworth Automotive have you covered. They will be happy to discuss all your diesel auto needs, from maintenance to repairs. Visit them online or call (858) 541-1044 to schedule your service.