Fitting an electric fuel pump

Thanks all again!!
Like Sarnia I do have a fuel polisher and use it to transfer fuel from one tank to the 'working' tank or to a jerry can which I may 're-polish' or syphon into the working tank ( using a bulb and pipe).
I guess I could have a valve and connection to my primary filter for priming and emergencies. ( I believe that I would have to beef up the electric pump though as it struggles to lift from the 'spare' tank when it is low)
The info on the mechanical pump is interesting, I had thought it was fixed but do vaguely recall that on priming the filter it gets easier when it is full .
 
I have an electric pump in line with the mecahnical lift pump on the engine, as the "head" was possibly too great for the engine pump. This works absolutely fine, and as others have said makes bleeding easier.

One note of caution which I have not seen in the thread. One big advantage of a marine diesel (of the realatively uncomplicated type) is that even if you experience a total electrical failure, as long as the engine is running, it will keep on running. If you switch 100% to an electric pump, your engine would pretty soon packj up.
 
Stemar said:
There's the potential for a big bonus if the pump is fitted between the tank and the primary filter.

A pair of filters can be set up in parallel, with both primed & ready to go. Run on one, with a spare in reserve. Should on filter block, it's seconds to switch to the other and you could change the duff one while the engine's still running - as long as the pump has sufficient capacity, you could even prime the new one on the go. I have a similar setup, though gravity fed, so I doubt I'd get away with priming if the engine's running at much more than idle.
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Running two in parallel is fine, I am presuming they feed a common supply to the high pressure side, providing each can be isolated with valves, to enable replacement and bleeding prior to reconnecting to the common feed and the other one closed for replacement.
 
Leighb said:
I have an electric pump in line with the mecahnical lift pump on the engine, as the "head" was possibly too great for the engine pump. This works absolutely fine, and as others have said makes bleeding easier.

One note of caution which I have not seen in the thread. One big advantage of a marine diesel (of the realatively uncomplicated type) is that even if you experience a total electrical failure, as long as the engine is running, it will keep on running. If you switch 100% to an electric pump, your engine would pretty soon packj up.
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Total Electrical failure. Do you have any examples of how that could happen? I can't think of that scenario.
 
Sarnia said:
Running two in parallel is fine, I am presuming they feed a common supply to the high pressure side, providing each can be isolated with valves, to enable replacement and bleeding prior to reconnecting to the common feed and the other one closed for replacement.
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Yes, I have stopcocks upstream & down, for each filter. Plan A was a Y tap each side. but 4 stops were half the price of 2 Ys..
 
My engine is a marinised 1.6 Ford diesel. I replaced the CAV filters that came with the boat with larger spin ons having had problems with dirty fuel (finished up having to clean the tank anyway). At the same time I fitted an in-line electric fuel pump in case the new filters had too much friction for the lift pump. The fuel tank is below the level of the engine and the filters above it. The pump is between the primary filter / water separator and the engine filter.

Once the system is bled the electric pump does not seem to make any difference. I have started and run the engine without it, and left the electric pump running after the engine is stopped without problem. Where it may have helped was when the primary filter was getting blocked, I discovered the blockage during pre-sea checks so the electric pump had probably kept the engine running OK during the previous passage that involved 24hrs of motoring in a long swell.
 
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vyv_cox said:
I have found the answer to my question at http://www.cdxetextbook.com/fuelSys/diesel/comp/dieselliftpump.html The pump does not work in the way I had assumed, it is not the force applied by the cam-driven lever arm that pumps the fuel, it is the return spring.

'Atmospheric pressure at the fuel tank forces fuel along the fuel line, to open the inlet valve. Fuel flows into the pumping chamber. The eccentric keeps rotating, and the rocker arm is released. The spring exerts force on the diaphragm, to pressurize the fuel in the chamber. This pressure closes the inlet valve, and opens the outlet valve, letting fuel be delivered to the injection system.

If the system doesn’t need all of the fuel delivered, the pressure in the outlet fuel line rises to the same level as in the pumping chamber. That holds down the diaphragm, and keeps the diaphragm return spring compressed. When this occurs, the split-linkage in the rocker arm, allows the lever to maintain contact with the eccentric, without acting on the diaphragm pull-rod.'
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I don't see how the fuel tank opens the inlet valve. I ran one for years with a top feed tank below lift pump and primary filter.

The Yanmar pump will lift a head of fuel ( workshop manual test - fit hose to inlet pipe and operate cam @ 800mm above a container of fuel....) - so the pump is causing suction on the inlet side.

I agree it recycles when the outlet reaches a certain pressure. I've had one apart - but it was a while ago.

I seem to remember at the time the inlet valve flap is on the reverse side of the inlet port wall - held closed by a weak spring.
Moderate pressure internally will not blow past the spring - but when it reaches its operating peak - it forces the inlet spring open - essentially pumping the same fuel back and forth along the inlet supply hose ?

it made sence at the time - looking at it.
 
Amazed that his simple question has attracted 4 pages of "advice" and even the great engineering guru of this parish was rather stumped and had to research.

I can assure you that it is acceptable to fit an electrical pump in series between the tank and the mechanical lift pump. This is standard fitment when using, for example keel tanks.

For further confirmation read Beta installation instructions
 
third engines said:
Amazed that his simple question has attracted 4 pages of "advice" and even the great engineering guru of this parish was rather stumped and had to research.

I can assure you that it is acceptable to fit an electrical pump in series between the tank and the mechanical lift pump. This is standard fitment when using, for example keel tanks.

For further confirmation read Beta installation instructions
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My generator has a mech pump and electric pump in series. It works fine with both running and also just the mech pump running. The mech pump can suck through the electric pump. It was installed like that when I purchased the boat so had no reason to change it. It does make bleeding the system very easy but I don't as a rule run the electric pump as there is no reason. The generator does not have a return to the fuel tank.
 
I think that fitting an electric pump would be worthwhile just to make it easier to Prime they system. Having it available in case of mechanical pump failure would be a welcome bonus full stop nooooo I meant.
Slight dictating malfunction. I found that you have to spend more time editing the dictated text then you save by speaking full stop oh oh no not again.
 
Standard equipment on Island Packets is an electric pump situated after the Racor primary filter and before the Yanmar lift pump.
This pump is only used for bleeding the low pressure side of the system and AFAIK-it makes no noise when the ignition is on-must have a free flow when not working so the fuel can pass through.
A simple spring loaded switch allows bleeding when required. When it pressures the system it slows down and clicks like the old SU fuel pumps to show the system is full.
When I prepared a Kawasaki powered sidecar race outfit in a previous life I used the cube type Facet pump with a simple restrictor and return loop.
The restrictor was in the return loop and was adjusted in bore size to give the correct feed pressure to the carbs. In a diesel engines case it would be the required feed pressure for the lift pump.

I hope this helps.
 
nemodreams said:
I don't see how the fuel tank opens the inlet valve. I ran one for years with a top feed tank below lift pump and primary filter.
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That's always what happens, it's just physics. Pressure is reduced at the pump by the action of the diaphragm moving away. Atmospheric pressure then drives fuel into the space vacated. We just short-cut it by saying the pump sucks it in.
 
On the Grumpy Uncle's old BMC, we have, in this order.
Fuel tank >in line filter > small cube type facet pump> twin CAV filter>engines lift pump>secondry filter on engine>injection pump...
The 12v facet pump is really used to prime filters after changing ect, although we do use it when we start the engine, but in truth I have seen no evidence of this actually helping? (advice from the tinternet!)
There was a filter supplied with the facet pump but, again interweb advice, apparently it could have possibly been too fine for diesel fuel so we chose to use the cheap in line petrol type filters in front of it (Amazon bag of 6 for a few quid).
Had this set up for a while now with no issues what so ever. The facet pump does not have to be running as the fuel easily pulls through it via the lift pump.
 
third engines said:
Amazed that his simple question has attracted 4 pages of "advice" and even the great engineering guru of this parish was rather stumped and had to research.

I can assure you that it is acceptable to fit an electrical pump in series between the tank and the mechanical lift pump. This is standard fitment when using, for example keel tanks.

For further confirmation read Beta installation instructions
Click to expand...

This is just the situation I have with 2 keel tanks, with an electrical pump on each tank and a switch over for the fuel pump and return line to each tank. One thing to remember is a simple in line filter before the pump, which actually is really easy to replace and clean if it gets crudded up.
 
Reading this with interest. Few questions that some might know now though.

1. I have a yanmar 1gm10, would fuel still pass through this mechanical fuel pump if it failed at any point?
2. Does anyone know of any pumps that use the same hose size and allow fuel to flow through when switched off?
 
GrahamM376 said:
+1

Our pump starts as soon as the key is turned and the engine just sups what it needs, the rest being returned to the tank clean after the filters. Brilliant for filter changes, no manual bleeding necessary.
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+ 1 I used one on my 4108 - much easier for bleeding.
 
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