Fuel shutoff solenoid problem

[henry pounds]

I changed the key ignition switches on our 43 ft Bayliner (twin Cummins diesels) because I thought one of them wasn’t working. What a mistake. They seemed to work fine but after about 10 minutes both engines died. The fuel shutoff solenoids were both burned out according to the mechanic who looked at the boat but he looked at the switches I installed and said that they couldn’t have been the cause. I don’t want to replace the solenoids (they are expensive) without knowing what happened or even if the solenoids are really burned out. Only the wiring is burned. I have inquired at several places but nobody has got back to me. Any help would be appreciated. Thanks in advance. Henry Pounds

Topic

[Tony Athens]

HOW COULD? Happened right after changing a key switch?

1) A high resistance ground connection caused by corrosion

2) The “suck-in” high current coil in the fuel solenoid ( 40 amps or so) stayed energized for some reason and it got too hot. Are you sure the magnetic switch under the starter ( that controls the “suck-in circuit thru the start switch circuit) shows ZERO sighs of rust corrosion?

3) Better recheck the “key switch” and wiring–Curious———–Why did you need to change the key switch?

Post some really good pics.

Tony

[Len Morrison]

Fuel Solenoid short

I was replacing an impeller in a pump that runs off my starboard Cummins 6BTA motor. I closed the engine access hatch and went to the lower helm and started the motor. No problem. I was trying to activate the electrical clutch on the pump when I smelled smoke. I tried to stop the motor using the engine shut off switch
but nothing. Managed to switch motor off. Opened the hatch and the engine room was full of smoke. I traced the heat to the fuel cut off solenoid. The wires had burnt through the connection and the wires on top of the solenoid had melted. I undid the wiring harness and pulled it through to where I could check the rest of the harness. Only the wiring to the cut off solenoid was affected. I traced the black wire all the way to where it earths out on the block and its burnt. How could the switch short create so much heat. Is this a common problem. I have a new solenoid and I can rewire the affected section. I am concerned as to how the short occurred in the first place

[henry pounds]

Further question

Thank you Mr. Schmidt. The logical question is could the new ignition switches I installed have caused the solenoids to stay in the crank position thus causing them to burn out? Whatever the cause was, it resulted in the wiring being melted together causing the system to short so could the solenoids possibly still be OK? I’m going to try to do the test you suggested and find out.

[Corey Schmidt]

What can typically happen with shutoff solenoids is that if they are stuck in the “SUCK” or CRANK position, they can get burned out easily as that can consume 10-20 amps while stuck in this mode. Only way to test is to pull the solenoids off and test them with a battery, then assess the wiring to ensure that nothing is shorted, corroded, etc.

Resources:

Fuel Shutoff Solenoid Wiring 101

Starter, Crank & Fuel Shutoff Solenoid Wiring

https://www.sbmar.com/wp-content/uploads/2015/11/B-C-wiring1.pdf

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