Our Onan Genset, 3-cylinder diesel driving a 6.5 Kva alternator, is now benefiting from a similar tidy up to the one I did on the engine while Jacqui was in England. After not running it for 5 months I changed fuel filter, coolant and de-gunged the water intercooler. On start up I was horrified by a rhythmic metallic 'slap'. Suspecting a dropped valve I checked and set the tappets. Not the problem. Turning the crank with a spanner I felt for any resistance that shouldn't be there but nothing.
I fired it up again and the noise was still there. Out of desperation I opened each fuel injector feed slightly in case there was an air bubble. The first two didn't stop the noise, only causing a slight loss of smoothness and a spray of diesel, but the last one stopped the racket. Obviously something wasn't right.
The service manual is the typical 'only for idiots' and refers you to skilled mechanics for anything more than the blindingly obvious, so injectors were ignored, but with my much appreciated Dad's mechanical upbringing, a generous measure of common sense - something that I seem to see less and less of these days - and the use of a bench mounted vice courtesy of the marina workshop, their innards were accessible to clean. Number 3 pintle and tip were fused together with a solution of diesel gum and took the use of an electric drill's chuck to grip the delicate pintle round shaft and an electric heat gun on the metal tip to expand the outer casing. After a lot of swearing and grunting, and that was just Jacqui, I managed to slide the inner pintle out. After just a few minutes of careful cleaning with a kitchen scotch brite and some clean diesel the pintle slid in and out of the tip as it should. Amazing the difference a few minutes made.
The injectors are cleaned and rebuilt, re-installed and diesel lines hooked up and bled and the motor now runs like a good 'un. Whilst I was checking intently that the injectors were properly seated with no air or diesel bubbling out I noticed one of the cylinder head bolts had some signs of diesel around it so with a 13mm spanner I decided to just give it a tweak, and just to spoil all my 'smug with myself' feeling, the head of the bolt snapped off!
Bugger!
I calmy dismantled the diesel lines once again to gain access in preparation for the 'seldom works' extractor tool removal, I went to centre pop the broken stud to be able to drill centrally, and just as a precursor tried to tap the stud around with the centre punch, and for once It worked. After a few careful taps I was able to unwind the broken stud out of the block, amazing. I was at best expecting drilling and extracting and at worse removing the complete head to get mole grips and a blow torch to turn it out. There must be a God!
It's Sunday today so stores are shut, so tomorrow I will be active trying to find a replacement, but as it appears to be a fine thread, I'm not too hopeful. Last resort will be to weld a nut on top of the broken stud and use that until we return to part of the world where parcel mail is affordable without having to sell your left kidney.
I'll complete David's story from Monday morning when we set out on our hired motorbike to find our solution without selling any kidneys...
After we'd visited three chandleries and hardware shops our search for a replacement cylinder head was ongoing. Next we called in on the welder at Spice Island Marine. He sent us to the site mechanic who 'might have one in his spares box'. The mechanic was going for lunch and asked us to come back in an hour so we too went for lunch. An hour later we were back at his tool shop where he said he didn't have a bolt with such a fine thread.
We had now reached our last option - to have the welder attach a new nut onto the original stud. Although he was reluctant because he didn't feel it would be a strong fit – the original thread is high carbon steel and the nut regular stainless – he set one of his men on the job.
It was a hot afternoon and we were waiting in the shade of the awning outside the weld shop. I was daydreaming, David was looking at the accumulated pile of discarded bits and pieces. And then he spotted it under an old cloth; something that not only looked like, but was the same model Onan generator. It was a Eureka! Moment. Long abandoned but still with its six cylinder head bolts. It couldn't have been better – exactly what we needed
David asked if the old Onan was a current project? Did it belong to someone? No and no, just scrap were the answers. Last question – could we buy one of the cylinder head bolts? Mr Welder scratched his head for a moment, looked around the yard for inspiration and finally said 'yes'. One bolt purchased for the price of a small lunch. One kidney sale averted and problem solved.
The epilogue to this story is David was able to complete his service of the fuel injectors and the generator is once again running smoothly.
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