The leaks just won’t stop... leak­ing

Canal Boat - - Ask The Experts -

Q I had a fuel leak from the lift-pump on my 1991 1.5 BMC en­gine, so I had the pump re­moved, the screws around the pump flange that holds the two parts of the pump to­gether were re­moved, the seal wiped clean, and the same seal re­fit­ted. All seemed okay, but af­ter an hour I found fuel leak­ing again from the same place, also oil run­ning down the en­gine block.

I re­moved the pump, parted the body, ran a small bead of sealant around the seal, re-as­sem­bled it and left it for a week, which cured the fuel leak. I also or­dered a new gas­ket for re­fit­ting it to the en­gine but un­for­tu­nately it wasn’t the cor­rect seal.

It seems my pump is a bit of an ‘odd­ball’. I’ve made sev­eral at­tempts to make and fit new seals us­ing dif­fer­ent grades of pa­per type ma­te­rial, I’ve tight­ened the fix­ing studs as tight as I dare, and I’ve even tried tight­en­ing when the en­gine is hot but I still have a slight leak. What would you rec­om­mend? ALAN CLARKE, via email

A TONY REPLIES: I sus­pect the pump mount­ing flange has been bowed over the years by over tight­en­ing and pos­si­bly an over-thick gas­ket. Check the flange by plac­ing a straight edge (a stout rule, for ex­am­ple) across the flange. If the flange is bowed and if you feel con­fi­dent, strip the pump, take the op­er­at­ing lever out, tape a sheet of emery cloth to a piece of glass, and rub the flange un­til you have re­moved the bow.

I am also con­cerned about the fuel leak. What you call a seal be­tween the two halves of the pump body is prob­a­bly the pump­ing di­aphragm. This needs the screws tight­en­ing with the di­aphragm held DOWN by the pump mech­a­nism; oth­er­wise you may split the di­aphragm and could fill the sump with diesel.

The pa­per gas­ket used is not very thick so I do not think the grade is crit­i­cal. You could try us­ing any sil­i­cone sealer: leave the pump slightly loose un­til it has set a lit­tle, then fully tighten it.

Check the flange isn’t bowed

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