Mechanical Vs Electric lift pump

Hadenough

Hadenough

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I am revamping my fuel system, new pipe work throughout, new filter for each tank, three way valve between tanks in tandem with a three way for the returns. Proper job I hope. My existing mechanical lift pump is normally absolutely inaccessible, in fact I have only seen it today for the first time after removing the heat exchanger. The pump draws from dip tubes so no gravity options..I am contemplating removing the mechanical pump, blanking it off and replacing it with an electric pump in an accessible location. I know all the arguments about electrical dependancy and the beauty of being able to keep a diesel running without battery power but the idea appeals. Thoughts please?
 
Sole diesel engines use the little square facet pump as standard. I know cos I saw one on display in the chandleirs here in Lanzarote yesterday. I would go with one of these and carry a spare. You could even have two plumbed in parallel. They cost about £40 so not big cost issue.
 
You need to first get an idea of the actual throughput of the existing pump before you can specify an electric pump.
 
Because it's 30 years old and even if I replace it as a preventative measure if it ever fails in the future I can't get at it without dismembering the engine bay! Question actually was - what does the motherhood think of an electric lift pump as opposed to a mechanical one?
 
Hadenough said:
Because it's 30 years old and even if I replace it as a preventative measure if it ever fails in the future I can't get at it without dismembering the engine bay! Question actually was - what does the motherhood think of an electric lift pump as opposed to a mechanical one?
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In answer to your question, I reckon it's an unnecessary complication. Mechanical lift pumps are essentially reliable. There are lots of other inaccessible bits of your engine which might fail, but I doubt that it's worth trying to duplicate/replace them just in case.
 
Our engine came with electric pump, it's magic when filters are changed, bleeds the system a treat as pressure is there as soon as ignition is turned on with the engine stopped. I do carry a spare - just in case. Be careful about which electric pump, some have very low lift capability, mine came via Thornycroft.
 
Mechanical lift pumps are reliable but will eventually fail. Maybe not completely and the symptom on the engine will be fuel starvation causing lack of revs.
When this happened on my Thornycroft T80 I replaced the mechanical pump with an electric Facet wired to the engine ignition swtch. The old pump was removed and a blanking plate fitted. See attached photo. The advantages of an electric lift pump are that bleading the fuel system is so easy and the engine starts much sooner as the injector pump is primed as soon as the ignition is switched on.

http://www.fuelpumpsonline.co.uk/facet-cylindrical-pumps-12v-1821-c.asp

View attachment 46829
 
pvb said:
I wonder why most engine manufacturers fit mechanical pumps?
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Because they can last for 30+ years. Can be stripped and cleaned easily and cost very little to replace. I had an perkins engine with one of these lift pumps which had been in a machine used every day for years and although it looked if it had never been off since 1971 when I stripped it the lever which presses on the camshaft was badly worn which meant that the lever was not pumping as much as it should.
So on the boat I am renovating I have fitted a new lift pump (£18) kept the old one as a spare, and bought a £40 Electric Pump as a spare.
 
I would have thought the advantage of a mechanical pump is that the engine can continue to run even with total electrical failure - a valuable safety feature .
I would replace the mechanical pump with a new one and forget about it for 30yrs.
 
ghostlymoron said:
I would have thought the advantage of a mechanical pump is that the engine can continue to run even with total electrical failure - a valuable safety feature .
I would replace the mechanical pump with a new one and forget about it for 30yrs.
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The OP stated his mechanical pump is inaccessible without part-stripping the engine. (".... My existing mechanical lift pump is normally absolutely inaccessible, in fact I have only seen it today for the first time after removing the heat exchanger.....").

That is the other reason I recommended an electric replacement. He could just leave the old pump in situ and reroute the pipes to an electric pump.
 
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ghostlymoron said:
Yes but if it is now visible, its a good chance to replace it.
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And weighing up all the advice that is what I have decided to do. Mainly based on the ability to keep going even in the event of electrical failure. But also because of the evident long life of mechanical pumps. Thanks for the input.
 
Probably an unnecessary addition but I'd tend to have the backup of the electric pump and leave the mechanical. In 30 years and 3 engines I've never has a lift-pump go... there's a first time for everything.
Much more urgent and certain to fail - spare raw water pump and alternator.
 
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