You don’t have to be a certified mechanic to troubleshoot a diesel engine. All you need is a bit of mechanical aptitude and some basic tools. You have to determine what happened right before the breakdown. This is called the story line, it’s a blow by blow sequence of events that will help you determine the cause of the failure.
By the way, if your diesel engine is electronic you may find yourself towing it to a dealer who has a scanner to get the codes out of the On Board Diagnostics System. BUT there are still checks you can perform before you call the hook.
Always check the simple things first!
Diesel engines require air and fuel to run.
This is investigative information that will guide you to a possible solution. You have to ask the driver of the vehicle the following questions.
1. What was exactly going on when the engine quit?
2. Were there any dash gauges or warning lights acting up?
3. Were there any unusual noises?
This will help you get some clues on any contributing factors that could give you some troubleshooting wisdom. If the engine was hesitating or losing power you could be looking at air in the fuel. If the engine just quit instantly you should check the ignition system, fuel transfer pump and engine shutdown solenoid.
Here Are Some Basic Checks You can Follow up With: Mostly for a rough running engine condition before it quit.
1. Is the fuel tank topped up? I know this is a lame question but it’s happened before.
2. Is there gas in the tank instead of diesel? Again, I’ve seen this happen before.
3. Check the fuel filter and make sure it is full of fuel. This determines if you have a fuel starvation problem or not.
4. Check for water in the fuel separator, the first filter closest to the tank. They have a bleed off valve at the bottom of the housing.
5. Check for fuel leaks at the lines and fittings.
6. Check the air filter for any restrictions. This won’t cause a no start unless air intake is totally blocked off.
7. Make sure you are getting fuel to the injection pump. Crack a line before the injection pump and crank over the engine to determine if the fuel transfer pump is working.
8. Crack open an injector fuel line at one of the cylinders and crank over the engine.
Are there signs of pressure or a foamy substance? The latter means there is air in the fuel.
By this time you will have determined where the problem is in the fuel system. Once you nail down a general theory to what component is at fault you can do some digging and pick some brains at the local repair shop. These procedures will help you possibly find a problem along the way, get some experience and save a few bucks.
My name is John Whelan and I have over 32 years of Heavy Duty Mechanic experience. For more tips and tricks on troubleshooting a diesel engine and other mechanical systems come on over to my Mechanic’s Blog and take a tour or send me a question.