The en­gine’s a bit of a drip...

Canal Boat - - Back Cabin - TONY REPLIES… TONI, via email

Oil is drip­ping from the in­take man­i­fold on my BMC 1.8 where the air fil­ter is bolted to it. There is also a fair amount of smoke on start up at times al­though this clears af­ter a cou­ple of min­utes. Could valve stem oil seals be likely? Also, when tick­ing over for a while the en­gine seems to ‘miss a beat’, could the in­jec­tors need ser­vic­ing? There’s also a light weep on the fuel man­i­fold from where it goes on to the in­jec­tors. The en­gine starts and runs well but if I rev too much, I get black smoke.

QAFirst, have a good ‘mir­ror and torch type’ in­spec­tion of the rocker cover gas­ket. They are not the eas­i­est to re­new cor­rectly, es­pe­cially on the man­i­fold side.

Af­ter that, check the crank­case breather sys­tem for block­ages. As far as I can see, the sys­tem on the 1.5 and 1.8 are very sim­i­lar, al­though Cal­cutt seem to add a breather from the oil filler cap on some en­gines. The oil mist sep­a­ra­tion on th­ese en­gines is not the best so it is fairly com­mon for oil from the breather sys­tem to drip out of the bot­tom of the air cleaner.

As long as the en­gine is start­ing well from cold and de­vel­op­ing suf­fi­cient power, take the breather hose off the air cleaner and route a new length into a small milk or drink bot­tle in the en­gine tray. If it is oil mist, I doubt it would be worth­while hav­ing the en­gine over­hauled.

If the oil re­ally is trick­ling down in­side the in­let man­i­fold then valve guides are about the only source, but it is usu­ally oil mist from the breathers. I think that what you call the ‘fuel man­i­fold’ is the leak-off pipe that links the tops of the in­jec­tors. The most likely cause of such a weep is old, hard cop­per seal­ing wash­ers. A new set of wash­ers will prob­a­bly cure it. If the weep is at num­ber four in­jec­tor, in­spect the braz­ing where the pipe is se­cured to a small banjo union be­cause some­times the fuel fil­ter vi­brates and breaks the pipe or braze.

Th­ese BMC en­gines use pin­taux in­jec­tor noz­zles which have a very small spray hole on one side of the noz­zle. Th­ese spray when crank­ing to di­rect the fuel into the hottest part of the swirl cham­ber. The hole tends to block fairly eas­ily and, when they do, cold start­ing suf­fers. Your smoke on first cold start of the day is al­most cer­tainly just va­por­ised fuel (white) or a mix­ture of par­tially burned and va­por­ised fuel (grey). For a BMC this is very com­mon and not worth wor­ry­ing about as long as, in all other re­spects, the en­gine per­forms well.

I ex­plained the above be­cause of the slight mis­fire. Tak­ing that to­gether with the smoke sug­gests it might be worth hav­ing the in­jec­tors over­hauled, but be­fore you do that, check the valve clear­ances and re­move each glow­plug and test it across a bat­tery. Only con­sider the in­jec­tor over­haul once you are sure those items are okay. I am not sure hav­ing the in­jec­tors over­hauled will have a no­tice­able im­prove­ment though be­cause an odd mis­fire on idle is not that un­com­mon.

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