rotrax
Well-known member
The elderly but up to now very reliable Westerbeke 8KW Generator on our boat started to randomly stop. It would instantly restart and run for some time before stopping again. Although I am very well versed in diagnostic techniques, the fault never manifested itself when I got the spanners and multimeter out. I did have an inkling of what the fault would be, and was eventually proved correct.
Being wise beyond my years and not prepared to spend hours looking for a non existent fault in confined quarters, I soldiered on. Eventually, my mental diagnosis was found to be correct. It stopped, would not keep running unless the heater plug switch was operated. Bingo!!!
The stop solenoid has two windings. When the unit is turned off, the magnetism is removed and the plunger spring pushes the rod into the pumps fuel stop mechanism. Turn the unit on ready to start, a current is sent along one of the windings, a fairly small current. This is not enough to pull the plunger out and allow fuel to flow. Operate the heater plugs and the solenoid is fed, through a heavier winding with enough current to open the fuel supply, allowing the unit to start. Once running, when the heater plug switch is released, the heavy winding is not fed, but once the plunger is pulled back by the generated magnetism, the light windings magnetism is enough to hold it open, keeping it running normally.
It was this lighter winding that had failed. I removed the solenoid and took it home. With it removed, the unit ran perfectly. By poking my finger into the solenoid hole and pushing the stop lever inside, it stopped.
At home I set it up in the lathe, turned the end off and removed the guts. It had that nasty 'burnt winding' smell. I replaced the electic guts with a manual cable operated rod, using the origonal internal spring and a bit of 6mm bore alloy tube, a bit of 6mm steel rod, a bit of alloy plate and strip and a motorbike brass spoke nipple modified to be a solderless nipple. A simple angle bracket screwed to the now hollow solenoid body became the fixed cable support.
The only cost has been a 17 quid 3 metre stop control cable from that wonderful old fashioned 'we've got everything' car spares shop in Littlehampton called "Going Spare".
The stop cable will take the place of the stop switch on the panel, keeping it looking good and keeping it simple. I could have got a new solenoid but it is an obsolete model and the only source was the US. Too much hassle and I might have ended up with the wrong part. Anyway, as my old mentor, race sponsor and all round top engineer Bill was fond of telling me "An Engineer is a bloke who can make for a tanner wot anyone can buy for a quid!"
Cant wait to get it installed and tested !
Being wise beyond my years and not prepared to spend hours looking for a non existent fault in confined quarters, I soldiered on. Eventually, my mental diagnosis was found to be correct. It stopped, would not keep running unless the heater plug switch was operated. Bingo!!!
The stop solenoid has two windings. When the unit is turned off, the magnetism is removed and the plunger spring pushes the rod into the pumps fuel stop mechanism. Turn the unit on ready to start, a current is sent along one of the windings, a fairly small current. This is not enough to pull the plunger out and allow fuel to flow. Operate the heater plugs and the solenoid is fed, through a heavier winding with enough current to open the fuel supply, allowing the unit to start. Once running, when the heater plug switch is released, the heavy winding is not fed, but once the plunger is pulled back by the generated magnetism, the light windings magnetism is enough to hold it open, keeping it running normally.
It was this lighter winding that had failed. I removed the solenoid and took it home. With it removed, the unit ran perfectly. By poking my finger into the solenoid hole and pushing the stop lever inside, it stopped.
At home I set it up in the lathe, turned the end off and removed the guts. It had that nasty 'burnt winding' smell. I replaced the electic guts with a manual cable operated rod, using the origonal internal spring and a bit of 6mm bore alloy tube, a bit of 6mm steel rod, a bit of alloy plate and strip and a motorbike brass spoke nipple modified to be a solderless nipple. A simple angle bracket screwed to the now hollow solenoid body became the fixed cable support.
The only cost has been a 17 quid 3 metre stop control cable from that wonderful old fashioned 'we've got everything' car spares shop in Littlehampton called "Going Spare".
The stop cable will take the place of the stop switch on the panel, keeping it looking good and keeping it simple. I could have got a new solenoid but it is an obsolete model and the only source was the US. Too much hassle and I might have ended up with the wrong part. Anyway, as my old mentor, race sponsor and all round top engineer Bill was fond of telling me "An Engineer is a bloke who can make for a tanner wot anyone can buy for a quid!"
Cant wait to get it installed and tested !
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