Electric fuel pump in place of raw water pump??

[ruvane]

I'm looking at using a car electric fuel pump in place of the impellor one on my Volvo MD11. Is this is really stupid idea or might it work?

A couple of points bother me, which is why I haven't actually done this yet. What's the flow rate meant to be on the raw water pump and can the electric one match this?

Given that the flow is tiny with the thermostat closed, might the high pressure of the electric pump damage something? Obviously the original is sort of self regulating with the rubber impellor being able to flex and not force anything.

How would the electric pump stand up to water instead of fuel, and possible salt water? One year? 5 years?

Any thoughts? TIA.

 

[LORDNELSON]

I believe there is usually a small by-pass on the termostat to avoid build up of pressure; you might check your engine manual. What happens if your electric supply to the proposed replacement pump fails? The advantage of the original mechanical one is that it should continue to pump cooling water until the engine itself stops (except, of course, when the impellor fails!)

 

[Bilgediver]

Forget it.....You need lots of available flow in gallions per minute for when the thermostat opens and for cooling the exhaust. This will NOT be achieved by a fuel pump which delivers a few litres an hour!!!!!!!!

JOHN

 

[Phoenix of Hamble]

Plus, if you lose your batteries, then the engine will keep on running with an impellor, but with an electrical pump when you lose power, you also lose your engine....

 

[Rick]

Almost universal view will bw "bad idea"! As a get-me-home last ditch fix, you might try cooling using a 12v galley style water pressure pump, but they aren't rated for continuous operation. I think going down the path of electric pump is likely to end in disaster and big expense replacing the entire engine. Is the idea just because of the price of a new water pump?

 

[William_H]

The idea is not bad if it is set up as a standby pump in addition to the existing mechanical pump. A lot of engine failures seem to stem form raw water pump failure. You would need bypass hoses and possibly non return valves. Consider an intank pump for fuel injected cars they are centrifugal rated for continuous operation and pump a fair bit I think. or try a bilge pump. good luck olewill

 

[ruvane]

Thanks for all the replies.

Anyone know the flow rate of a good condition, raw water pump like the Johnson F35 or similar small unit?

I suppose the reliability issue boils down to which fails most often; mechanical raw water pump, alternator or 100% duty cycle electric pump?

 

[Avocet]

I recently ran a little 12 hp diesel with the water inlet to the pump in a bucket of water. I was just flushing the engine out and it "drank" 3 gallons in less than a minute and that was only at about (I guess) 1500 RPM! I suppose at full revs, it might shift 6-10 gallons per minute but I don't know how much of that it actually needs!