The leaks just won’t stop... leaking
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