Troubleshooter

on most engines the cranking process will force the air out. If these areas check out okay, it’s time to take a look at the engine.

Most marine diesels use a solenoid to shut down the engine. They normally remain open, allowing fuel to flow. When you press the STOP button, current flows to the solenoid, closing the valve and cutting off the supply of fuel (in some cases, the current holds the valve open while the engine runs). These valves can fail and when that happens, no fuel can flow.

If you are familiar with this solenoid on your engine, you can often visually confirm that it functions properly. Your engine manual likely shows the location and function of this solenoid.

You can quickly rule out fuel issues by checking the return line. Remove the return line at the tank and hold the end over a cup while someone cranks the engine. If fuel is coming through, then the engine is getting enough fuel to run.

STARTING FLUIDS

Given our assumption that the engine has been starting easily and running well, issues related to compression and air supply would be longshots. Using starting fluid on a diesel engine should be avoided. You might void the warranty or damage the engine. If your engine has glow plugs, ether-based fluids can ignite and cause damage. Ether combusts at a lower temperature than diesel fuel, and that means it will ignite before the piston reaches the end of the compression stroke, throwing off the timing of the combustion cycle. Additionally, the starting fluid washes the oil off of the cylinder walls, leaving them dry during start-up, which accelerates wear.

If all else has failed and you must get the engine running, you can try spraying a small amount of WD40 into the air intake. WD40 contains enough lubricant to protect the cylinder walls and is less volatile than ether. Silicon spray lubricant works well in this application as well. Remember however, that an engine under warranty might be jeopardized. Use of any aerosol as a starting fluid should be a last resort. If the engine starts briefly and then quickly dies, you probably have a fuel delivery problem.

THE ECU

On newer engines (the year varies with horsepower range and manufacturer), a small computer (or ECU) controls its operation. A failed ECU—or a failed connector leading to the ECU—can prevent an engine from starting. In some cases the digital instrument panel at the helm gives you access to error codes. If you are lucky, the code reference can be found in the engine manual. In many cases the error code numbers are generic and can be found online. If the ECU has failed, you will only need one tool—your cellphone—and the number of the local tow company.