Eberspacher fuel pick up baffling

[chewi]

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.

That's what I understand priming means.

I think we may be disagreeing about the words, rather than the engineering.

 

[vyv_cox]

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.

I cannot claim your expertise in heating systems but I know a bit about pumps. A positive displacement pump, given the same suction head, doesn't care if the suction pipework bore is 1mm or 1 metre. Plenty of pumps are used directly from vessels and tanks with no suction pipework whatsoever.

 

[David2452]

Plenty of pumps are used directly from vessels and tanks with no suction pipework whatsoever.

I' sure you are right but those pumps have some kind of a head if connected direct to a tank otherwise they would be sucking on air, the solenoid pumps used in these heaters hate sucking but push well, a bit like the old Morris minor -v- Mini pump, both looked identical but the Mini one one was mounted close to the tank instead of the engine bay like the Moggy for the same reason, the larger bore pipes can get drain back which is easily overcome by the larger engine pump but not by a heater pump, even with the correct bore tube Wallas provide a modification which turns the fuel on and off at the tank to overcome the backdrain issue when the tank is below the heater as their pumps are mounted in the heater so can not be located close to the tank. In practise unless there is a small amount of head these pumps do not cope well with larger bores, especially when they get some wear on them.

 

[Bikerwookie]

Looks like it will have to be a day tank then if we have no other suggestions.

Anybody just use the return from the engines pump to fill the tank? Along with an overflow back to the main tank once it's full I thought it could save having a seperate pump.

Any ideas on quantity a 3ym20 puts back down the return hose at tick over and 3000rpm?