Engine and Instrument Failure

[Kernow]

I am new to the forum, so I hope I'm not posting this in the wrong place.

We have a Fisher 31 with a Beta 37.5 diesel engine, and both 12 and 24 volt power. When motoring on a dead flat sea in the Sound of Jura, and keen to get back to our mooring, I increased the revs on the engine to around 2100, at which point the engine and all the instruments cut out. After a couple of minutes the instruments came back on and I was able to start the engine again. This happened about five times, each time the cut out point was at slightly lower revs. I checked all the usual suspects on the engine - battery, air, water, fuel - all are as they should be. Both 12 and 24 volt alternators are fine, although I did notice that the 24 volt alternator ground strap had worked very loose. I've traced through all the wiring where the instruments and engine might 'meet' - VSR, fuel solenoid, ingnition - and all seems ok. With the help of a local boat mechanic and electrician, we ran the boat on the pontoon (suitably tied down and fendered) but we couldn't get it to shutdown again. It's possible that it was just a gremlin, though the simultaneous shutdown of both engine and instruments has got us worried and we'd like to get to the bottom of the problem. Can anyone suggest the cause? The only other thing I noticed was that the VDO wasn't showing and only flickered on intermittently - could that be a clue?

Sorry for such a long post. I'd be grateful for any suggestions.

[Zil]

has it cut out after you repaired the bad ground?

[Kernow]

Thanks for the quick response. No it hasn't. I found the loose connection back at the mooring. The loose ground was on the 24v side - domestic - could that have an effect on the engine/instruments?

[maine50]

Trace the wiring harness from panel to engine for abrasion/wear not just end points. If the instruments are still not working check the fuse that protects the harness which is middle of engine in front of starter. the fuse is a blade type and has 2 wires coming out of the harness. Tim

[Kernow]

I should have also said that according to Beta marine (I phoned their technical support) the only way to shutdown this engine if it has clean fuel, air and coolant is to energise the stop solenoid. They couldn't work out why the instruments also shutdown either. So something is putting power into the solenoid, unless I'm mistaken.

[Kernow]

Thanks Tim. I've done that, and checked the fuse (40 amp) and it's all good. In fact it looks brand new. Instruments all come back on again after a couple of minutes and work fine, until I put up the revs, and then instruments and engine both fail simultaneously.

[Cheechako]

is there a multi connector wire plug in the engine loom? sometimes these need to be cleaned or firmly pushed together. Not sure why a diesel would stop once running for an electrical reason.... i guess it must have a "no power= shut down" stop solenoid...? I think I'd want a solenoid that allowed running until activated....

[Kernow]

Thanks Cheechako. Yes, there's a multiconnector at the rear of the engine, protected by a rubber boot, which I've opened to check - it's all in excellent condition and firmly tied together by a cable tie. The stop solenoid is the the kind you prefer (me too) that is: power = stop.

[EveningTide]

As you said, something is putting power into the shutoff solinoid. Could there be some safety system, like over-rev, low oil pressure or something else that shuts down the motor to prevent damage? The instrument issue seems related but maybe from a different cause. Is there a relay that switches power to the instruments? Maybe instrument power is cut if the alternator stops making power (OK- that seems unlikely but think of something sort of like this). It's hard to guess how something is wired. And last of all, is this a modern boat that might have some computer monitoring or controling things? Then we have the possibility of a software bug.

[Kernow]

Thank you Evening Tide. To start at the end of your message - I am also confused as are Beta Marine, two very experienced mechanics and electricians at our local boatyard, and all the boat owners at our marina who have taken a look at the problem. The boat was launched in 1982, but a new beta engine was installed in 2006 by a very reputable boatyard. I bought the boat in 2008 and the engine has been, until this, utterly reliable. There are no computer controls. There is a VSR on the 12v side which also links, via the main 12v switches, to the instrument panel, but I had the VSR checked and that has been given a clean bill of health. Other than the VSR I don't think there is another relay that I can see. Nor, according to the beta manual, are there other shutoffs or bimetallic connections etc. it's a pretty simple set up in fact, which makes this confusing and frustrating. As you say, something is energising the solenoid, and de-energising the instruments, and then, after a couple of minutes, reversing it all to to de-energise the solenoid and energise the instruments. The only visible anomaly is the VDO which only occasionally flickers on.

[Cheechako]

well.... if a conventional diesel, then you must have a fuel problem and the electrical is coincidental. Once a conventional diesel is running it needs no electricity at all to continue. You could put a simple switch in line to the solenoid and leave it in the off position to ensure something isnt telling the solenoid to shut down. It really sounds like there are some electronic controls somewhere though. No controls to shut engine down if overtemp?, exhaust temp? low oil pressure?

[EveningTide]

Please educate me-
VSR = ?
VDO = ?
Thanks

[Kernow]

VSR is voltage sensitive relay: it distributes charge between the batteries in a dual battery setup. It is usually installed to charge the engine battery first, and then to switch the charge over to the service battery. It switches at 13.7 volts.

VDO is something in German, I think, but it is an LED in the tachometer that shows the number of hours the engine has run since it was first installed.

I read somewhere on a truckers' website that a faulty VDO can interfere with a diesel, but couldn't get anymore information than that, nor can I figure out how it could unless, in some way, it feeds back to the ignition switch and then to the stop solenoid. But that seems pretty unlikely.

[GordMay]

Originally Posted by Kernow

... VDO is something in German, I think, but it is an LED in the tachometer that shows the number of hours the engine has run since it was first installed...

“VDO” is a manufacturer of Hour Meters.
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