Maerin’s been troubled with intermittent engine shutdowns, coming at random times, with no clear cause. Since the engine fires back up without hesitation, an air problem is not the likely culprit, more likely is a problem with the fuel shutoff solenoid and/or the wiring involved in that control circuit. A momentary drop in voltage or an intermittent connection would cause the fuel solenoid to de-energize, and the engine would shut off just as if the key switch were turned off. Cummins designed this control to keep the engine running while energized, so loss of voltage for whatever reason results in engine shut down. One could argue the logic in this control method, but that’s what they designed. Unnerving, at the least, and a very high pucker factor goes with. Because there is a mechanical as well as an electrical component to the problem, they can be difficult to troubleshoot. The intermittent nature of the problem only compounds the difficulty.
In troubleshooting the problem, I’ve had some great suggestions from the T&T list, and also found some related information on boatdiesel.com forums. The information on boatdiesel.com recommends completely disabling the solenoid, a great tool for troubleshooting. I’ve been asked how that’s done, and offered to post some photos and a bit of explanation of the procedure, which is relatively simple- as follows.
The engine here is a Cummins BT5.9-M 180 HP with a Lucas CAV type injection pump, and the solenoid is energize to run. This procedure is for this particular application. Since the solenoid pulls and holds a plunger away from the internal valve in the pump, removing the plunger and spring has the same end result. Plunger removed, the engine will continue to run without any 12V power. To shut the engine down, simply rotate the manual fuel shutoff lever (arrow).
The solenoid assembly is on the lower half of the pump towards the rear, near the distributor head. The solenoid is threaded in place, and has an o-ring seal. It’s not particularly easy to access, but should not be exceptionally tight. Remove the assembly, there will be some fuel escape, it helps to have the fuel lines shut off to the engine. I shut the fuel supply off and ran the engine to reduce the fuel pressure beforehand, then shut off the return valve to isolate before removing the solenoid. Remove the control wire, remove the solenoid, then remove the plunger and spring assembly and set aside. Replace the solenoid (sans plunger). Some air will enter the pump, put it all back together, open the fuel valves, and with the throttle wide open- against the stop- crank the engine. It may stumble as the air moves to the injectors, when it catches, pull the throttle back and the engine should smooth out in a minute. Now, you have a true “no voltage required” diesel. To shut it off, rotate the spring-loaded fuel lever CW until the engine stops.
At the same time, another T&T lister has suggested wiring a temporary latching relay and pilot lamp onto the terminal that powers the solenoid. Any power interruption to that circuit will result in the latching relay dropping out. It won’t reset when power is reapplied, so it will accurately diagnose the control end of the equation. My plan is to run with the solenoid plunger removed, and the latching relay assembly in place. If no shutdowns occur, and the latching relay stays energized the entire time, I’ll have conclusive proof that the solenoid is the culprit, and I can obtain a replacement when convenient. Nice to know a way to keep the engine running when a small but key control element goes TU!
Todd & Belinda on 26 Dec 2011 at 7:46 AM #
In this situation I have simply hoisted sail to keep said vessel underway. I agree with the “pucker” factor though! 🙂 Merry Christmas 30 degrees here