Engine circuit breaker tripping

[Mickeyrouse]

I have been having a devil of a time with a circuit breaker tripping on my Westerbeke 55B4. The engine will crank and run quite easily, runs for about 5 minutes, then shuts down. The circuit breaker in the engine wiring has tripped. I re-set it, and in a second attempt to start the breaker trips as soon as the key is engaged. If I let everything rest (cool?) for say 6 hours or so, it may start, run 5 min., then shut down. Same old drill. Or it may trip the breaker upon switching.
I have disconnected everything that runs from the main engine wiring harness: water temp sender, water temp alarm, oil pressure sender, oil pressure alarm, fuel pump, connections to the alternator, pre-heat, alarm buzzer, starter motor solenoid- all but the fuel shut-off solenoid. Still the breaker trips.
When I disconnected the starter solenoid, the circuit breaker behaved itself and acted normally. Thinking that pointed to the starter motor, I removed the starter (no small task, as you may imagine) and took it to two automotive starter shops. Shop #1 sez "yeah the motor is shorted but I don't know where to get parts for a Westerbeke." Shop #2 sez "nothing wrong with this but I'll clean it up for you." So he does, and changes the solenoid anyway.
Upon re-installation, same old story.
I have gone through the wiring harness as carefully as possible under the cramped and inaccessible conditions and found one spot that appeared to be rubbing with the block. Taped it, and put a piece of wire split loom over it. No difference. All I am left with is the fuel shut-off solenoid. (Incidentally, there is split loom the full length of the harness, and is unprotected only when it comes out of the harness to the appropriate terminal.)
I know I can take the fuel solenoid out of the circuit, and that the engine will run until the fuel in the injectors is combusted. The problem is that if nothing was wrong with it before, considering its inaccessibility and cramped conditions, the process of disconnecting it may create new problems. Kinda the "if it ain't broke,......" situation.
I have not checked the instruments, thinking "no way."
So thus two questions: is there any way to test that fuel solenoid while in the circuit?
And if there is, and it checks out, how do I get this @?&@!!! Westerbeke to run- and keep running without tripping?
For the insatiably curious, the wiring diagram in question is available on the Westerbeke website in a download of the 55B4 Operator's Manual.

[FamilyVan]

Your diesel engine shuts down when a circuit breaker trips? Is that common in new diesels?

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[Mickeyrouse]

This diesel has about 500 hours.

[dohenyboy]

What circuit is the breaker installed in?
Once a diesel engine is started, unless it has some kind of electronic control system (which I doubt) it will run without the key being on or any electricity
I would replace the circuit breaker but that is because I am lazy. It is probably reasonably accessible.
The general idea is that wires getting normal hot from the engine running will not cause a short which would trip the breaker. But maybe a breaker could trip from being old and too hot.

Those westerbeke solenoids do burn out if they go out of adjustment and that is probably what happened.

1. remove the wiring from the solenoid and
try testing the ohms on it, with the multitester, comparing each terminal to each other and to ground. Write down the readings, with all power off and engine cold
then when it stops after getting hot, try it again. if the readings are not the same, your solenoid is bad and you need to replace it.
I understand that the Westerbeke fuel solenoids are OFF unless they get current. So, if the breaker is tripping for some other reason, your engine will stop.
2. With power off and the breaker off, take off each lead from the solenoid and check the ohms between it and engine ground. then do the same when the engine is hot. there should only be a difference on the lead, if any, from the temp sensor
3. with power off
test for continuity between the circuit breaker and each lead to the solenoid. Find out which one has 0 ohms resistance.
try to start the engine with that lead off.
if it does not start, then you know that it the right circuit to check out.
prepare a jumper ahead of time from that terminal to the circuit breaker.
When the engine heats up and shuts down, remove that lead and put in the jumper instead. If the engine starts, your problem is that particular circuit. Don't run the engine long with that jumper. You do not know what else you might mess up. just check that it will start.

[Mickeyrouse]

I hope it's not common on anybody else's diesel.

[model 10]

Operate the fuel system without starting the engine. If it were the solenoid it would quit working in the same time. If it it is one of those stupid systems that relies on an energized solenoid to stay running, you got it.

[Mickeyrouse]

If a diesel has a fuel shut-off solenoid, (which this does) the ignition circuit must be "hot" for the solenoid to be in a "pulled and hold" state. Otherwise the solenoid shuts fuel off. Fairly common on newer and larger diesels.

[Mickeyrouse]

Circuit breaker has been replaced- same story.

[leftbrainstuff]

A mechanical diesel has no electrical load once running.

Do you have a high resistance in a fuel pump or glo plug circuit that is tripping the breaker? Sticky solenoid just partially making contact but not enough to engage?

What is the circuit breaker connected to?

What you describe is symptomatic of resistance heating.

Follow the wiring. When looking for the fault feel wiring. If its noticeably warm then start measuring voltage deltas. Anything measurable is suspect.

As a rule of thumb no circuit should be warm...

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[model 10]

Originally Posted by Mickeyrouse

If a diesel has a fuel shut-off solenoid, (which this does) the ignition circuit must be "hot" for the solenoid to be in a "pulled and hold" state. Otherwise the solenoid shuts fuel off. Fairly common on newer and larger diesels.

That is not how I would set up a boat. You only need to energize a solenoid for a few moments to shut off the fuel to the engine. Then it quits. You don't need to rely on an energized solenoid for your engine to keep running. Stupid on a sailboat.

[FamilyVan]

Originally Posted by Mickeyrouse

If a diesel has a fuel shut-off solenoid, (which this does) the ignition circuit must be "hot" for the solenoid to be in a "pulled and hold" state. Otherwise the solenoid shuts fuel off. Fairly common on newer and larger diesels.

That's a crazy set up. I was having electrical problems on my Perkins (5.108) this spring, got a jump from a tow truck at a lock wall and finished my voyage (another 100 miles or so) with no alternator belt.

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[FamilyVan]

Why does Perkins 5.108 auto correct to the stupid sunglass face?

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[Sardean]

What is the amps rating on the circuit breaker

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[unbusted67]

The tripped breaker might be cutting off power to an electrical fuel lift pump and that might cause hard starting. That's the way my Universal M40B is wired. The oil pressure gallery is wired to an electrical lift pump which shuts off when the oil pressure comes up. If it doesn't come up the engine will stall out. Kind of nifty really.

[Mickeyrouse]

It's not a question of hard starting- NOTHING works on the engine electrical circuit: no alarm buzzer, no fuel pump ticking, no panel meters, no cranky cranky, nada. When the circuit decides to work (meaning untripped breaker) the engine starts incredibly quickly- no clicking of the starter, no hesitant cranking- she's ready to go. Unless the breaker trips. (See above)