KA(M)D 300 Changing fuel lift pumps because they are old????

K

kashurst

Well-Known Member
Joined
10 Oct 2003
Messages
11,844
Location
Spain
Visit site
I have been advised that now my fuel lift pumps with an internal rubber membrane are 16 years old they need changing. There is nothing wrong with the existing ones, however allegedly if the rubber membrane fails, diesel gets into the engine oil and it's bye bye engine.
The pumps are @ £60 each and easy to change on my boat - so I may well do it anyway.
However is this a wise precaution, yet more boaty myths, or uneccessary fear mongering?
 
The lift pump is driven by the camshaft, so if fuel gets past the membrane it runs down inside the block to the sump.
I think its a bit extreme to say the engine will be destroyed as a gradual leak will show up as a slight rise in level on the dipstick and a major leak would more than likely result in the engine stopping because no fuel is reaching the injection pump. We only change pumps when they fail and I have only replaced about 7-8 in the past 25 yrs. Mine is 24 yrs old and still going strong.
 
Thanks for the replies- I suspected any failure would present itself as a rising oil level so giving advanced warning.
I will leave my alone for now and just do the usual oil checks.
 
K,

it's more likely you're going to have problems priming than anything else like runaway engines...
Don't know the one fitted on your KADs but having taken apart (and successfully reassembled) half a dozen times my yanmar 2GM generator lift pump, I'd suggest when you have nothing to do (and have new gaskets, or decent heat/diesel resistant instant gasket thing) to open one up and clean the tiny oneway "valves" they have in them. You can also assess the condition of the membrane. On the yanmar running at 3k rpm all the time after 1000h it was fine, just a bit of dirt...
All that assuming you CAN dismantle your lift pump and it's not fixed!

V.
 
Depending on style of pump, the lever pumps I have come across have a weep hole on the underside, diesel leak means rubber seal dead on the diesel side, but derv will not get into the engine, oil leak means the other rubber seal for the lever itself is dead.
 
Last edited:
for the record, the Mikuni one on Yanmar GMs will definitely leak diesel in the engine if membrane fails. Easier (and guess cheaper) not to have seals et al keeping diesel out of the crankcase, so just one seal to keep engine oil from getting out of the crankcase and a lever going all the way to the membrane.
Having said that, I doubt the Bosch ones on my IVECOs will leak to the engine
 
We had a couple of KAD lift pumps fail, all in one season. What failed was the pin that holds cam lever to the pump, the lever must have fell into the sump. Maybe a bad batch.
 
You must log in or register to reply here.

Share this page

Top