Eberspacher fuel pick up baffling

[Bikerwookie]

The main tank on my boat is shallow and wide. The eberspacher takes it's fuel from the bottom but sucks air if we sail with it on. We race so don't really want the 120ltr tank full.

Any ideas on stopping it happening other than fitting a day tank?

 

[pvb]

In the circumstances you've described, a separate day tank would seem to be your only option.

 

[vyv_cox]

You have the option of taking the Eberspacher fuel from the engine fuel line. Mine is Teed into the line after the primary filter but others use one of the blanked off nozzles on the filter itself. Eberspacher themselves do not recommend this method but it has worked perfectly well for me for many years. There is a full description under Heating on my website.

 

[savageseadog]

A lot of people say you shouldn't use an outlet from the main engine filter as it will let air into the fuel system. Please ignore them and do just that, there is a non return valve in the pump so it can't affect the engine. One thing you should do is fit a valve or stop cock so you can remove your heater or carry out servicing.

 

[martinaskey]

Agree with both the above.
Fitted Eberspacher 4 years ago with supply from spare port on the CAV filter.
Isolation valve fitted just after filter which is kept closed unless using the heater.
Eberspacher seemed concerned about the heater competing with the engine for fuel but the flowrate to the heater is low and I've never had a problem.
And I like the idea that the heater runs off filtered fuel too.
M

 

[Hypocacculus]

+1

ours also draws from the fuel filter. But then we've only got a little 20hp engine. It might be different if it were sharing the fuel with a monstrous engine.

 

[Cardo]

A lot of people say you shouldn't use an outlet from the main engine filter as it will let air into the fuel system. Please ignore them and do just that, there is a non return valve in the pump so it can't affect the engine. One thing you should do is fit a valve or stop cock so you can remove your heater or carry out servicing.

Feel free to ignore as per above, but we had this exact same setup and suffered for quite some time with the engine dying frequently, often at problematic times. Eventually tracked it down to the Eber, and discovered the non-return valve in the pump seemed to have failed and air was being sucked in via the Eber pipe instead of fuel from the tank.

A shut-off valve to the Eber would get around the above issue, and when the Eber was running we didn't suffer any issues due to the suction from the heater. We still chose to change the Eber setup so it takes its fuel from a standpipe in the tank, instead.

 

[savageseadog]

Feel free to ignore as per above, but we had this exact same setup and suffered for quite some time with the engine dying frequently, often at problematic times. Eventually tracked it down to the Eber, and discovered the non-return valve in the pump seemed to have failed and air was being sucked in via the Eber pipe instead of fuel from the tank.

A shut-off valve to the Eber would get around the above issue, and when the Eber was running we didn't suffer any issues due to the suction from the heater. We still chose to change the Eber setup so it takes its fuel from a standpipe in the tank, instead.

If the eber non return valve wasn't working then the pump couldn't work properly either. It might work if primed and gravity fed but wouldn't be able to pump against gravity. The problem with drawing off the tank is dirty fuel of course, the filter in the pump is tiny and it's a pain especially if it's in the usual inaccessible place.. Best solution of all would be a separate filter.

 

[vyv_cox]

Based on what Eber say on my website a takeoff from the filter will work best when the tank is higher than the filter. Personally I cannot understand their statement that the small pump cannot draw from a large pipe, seems to contradict the laws of hydrodynamics to me.

 

[lw395]

Another option is a filter in the eber feed which has enough capacity to 'store' any air picked up until it can be bled. I used one of those cheap plastic inline jobs, it was clear so you could see the air, obviously keep it away from any hot bits.
Also fit 1/4 valves or something so you can prevent the fuel running back.
It only takes a few cc of air for a weberbasto to fail to start and shut down.

 

[maby]

The standard Eberspacher way of drawing fuel off the tank is designed to ensure that your heating cannot leave you out of fuel. If you tee off the fuel feed to the engine, or let the tube get down to the bottom of the tank, you could run it dry with potentially dangerous consequences.

 

[savageseadog]

I use an outboard tank because the heater is too far from the main tank and filter. The out board tank is ideal because the outlet is built in, it has a handle to take it off and fill it etc etc.

 

[chewi]

Based on what Eber say on my website a takeoff from the filter will work best when the tank is higher than the filter. Personally I cannot understand their statement that the small pump cannot draw from a large pipe, seems to contradict the laws of hydrodynamics to me.

I would think that the excess volume to prime an oversize supply pipe using the tuny pump might cause the the controller to conclude it has no diesel supply at startup.

 

[vyv_cox]

I would think that the excess volume to prime an oversize supply pipe using the tuny pump might cause the the controller to conclude it has no diesel supply at startup.

Once all the pipework is full, surely it makes absolutely no difference how large it is? In the situation that the Eber hose is drawing from a somewhat larger hose, or the filter, I cannot see how that is any worse than drawing from the tank.

 

[chewi]

Once all the pipework is full, surely it makes absolutely no difference how large it is? In the situation that the Eber hose is drawing from a somewhat larger hose, or the filter, I cannot see how that is any worse than drawing from the tank.

Agreed once the pipe is full it would make no difference, but at startup if the hose is fine it will take relatively few pumps to lift the fuel to the eber to fire it, but If the pipe is large it will take more pump cycles , and the controller could time out.

 

[vyv_cox]

Agreed once the pipe is full it would make no difference, but at startup if the hose is fine it will take relatively few pumps to lift the fuel to the eber to fire it, but If the pipe is large it will take more pump cycles , and the controller could time out.

I don't think so. Every stroke of the pump moves the same volume of fuel, regardless of the hose size.

 

[chewi]

I don't think so. Every stroke of the pump moves the same volume of fuel, regardless of the hose size.

Quite so, so won't a 8mm hose size take 16 times more pump cycles to prime than a 2mm hose?

 

[vyv_cox]

Quite so, so won't a 8mm hose size take 16 times more pump cycles to prime than a 2mm hose?

Well I would not have thought so unless the pump was trying to fill voids in the hoses, which once everything was up and running would not be there.

 

[David2452]

Based on what Eber say on my website a takeoff from the filter will work best when the tank is higher than the filter. Personally I cannot understand their statement that the small pump cannot draw from a large pipe, seems to contradict the laws of hydrodynamics to me.

Really? try sucking up water with a two foot straw....easy, now try sucking it through a two foot 22mm tube..... not so easy, A heater installed to spec will always work, one that for instance takes fuel from an engine filter may or may not work depending on the amount of lift, so if one understands that it can be a valid reason to do so, but most installs done that way work simply because somebody couldn't be bothered to do it properly and got away with it rather than understood what they were doing. Admittedly my colleagues and I only see them when things have gone wrong, but poor, or rather inappropriate fuel supply arrangements are a common cause of poor starting, flame outs and even total failure to start.

 

[David2452]

The standard Eberspacher way of drawing fuel off the tank is designed to ensure that your heating cannot leave you out of fuel. If you tee off the fuel feed to the engine, or let the tube get down to the bottom of the tank, you could run it dry with potentially dangerous consequences.

Exactly so, the standpipe (or dip tube) is cut after measuring the depth of the tank at the insertion site, running out of fuel due to heater usage is not uncommon on inland craft in the winter, they can get through quite a bit when used in anger, also the small bore tube can more easily be blocked buy crud from the bottom of the tank.