Troubleshooter

cooling circuit, which eventually falls into the muffler. When the engine starts, exhaust gas forces the excess water out of the muffler. But if the engine falls to start, the water can fill the muffler, eventually filling the exhaust as described earlier. That’s why Nigel Calder says, “If the engine doesn’t start, stop cranking and start thinking!”

Depending upon your engine and your mechanical skills, you might be able to overcome a hydro-locked engine, but for most of us it’s time to call a professional.

ENGINE CRANKS BUT WILL NOT START

Let’s assume that the engine cranks with its usual vigor, but will not start. Use caution when cranking your engine, because prolonged attempts or too many of them can lead to problems. Each try should last no longer than 5 to 10 seconds, and pause about 15 seconds between attempts. Every time you crank, a tremendous amount of current flows into the start circuit, and excessive cranking will create high temperatures that can damage components. As for the number of attempts, you want to avoid hydro-locking the engines as discussed earlier.

No rule of thumb determines the safe threshold, due to the variety of configurations. If the engine has not started after several attempts, you can close the rawwater intake seacock, but you must be prepared to open it immediately if the engine starts, otherwise you may ruin the impeller.

Diesel engines used to need three things to run: air, fuel, and compression. Now a fourth element has been added: a properly working engine computer or ECU.

If your engine ran yesterday, chances are that air is not a problem (clogged filter, blocked exhaust). If it has been running well (not smoking, starting reliably), then compression will not be a likely suspect. That leaves us with fuel and (on newer engines) the computer.

Fuel problems might be simple. Perhaps you changed a filter and left a supply valve closed, pinched an O-ring, or inadvertently bumped against a valve handle and cut off the supply. Inspect valve positions at the tanks and filters first. Look at the fuel level inside the primary filters to see if they are full. A clogged primary or secondary fuel filter falls low on the list of possibilities. This condition usually occurs gradually, and on the previous day’s run high vacuum pressure would have been noted on the primary filter. A clogged primary or secondary filter would eventually limit engine rpm during the run, not suddenly overnight. If you recently changed the fuel filter, it is possible you introduced air into the system. On older engines the air can prevent the engine from starting, but