Can a fuel pump suck?

[dgadee]

I have teed into my engine fuel line and then put a one way valve. From that I have a rise of 1m and about 3m to a fuel pump which I want to use to fill a day tank for my Sig marine 100 diesel heater. The pump was tested with short fuel lines and worked, but in place it doesn't. Might it be be that these things don't suck very well and that I should put it at the start of the line to the day tank rather than at the end?

 

[Daverw]

Suggest that you need to put close to the feed tank as they don’t have much of a suction head

 

[rogerthebodger]

Most pumps will suck to a greater of lesser extent. The amount depends on the design of the pump.

One issue with diaphragm pumps is the input and output non return valves could be held open by some grit of muck.

I have several of these as primer/bleeding pumps and do pump air

 

[Caraway]

Is it an electric pump? Try putting it directly after the valve, so it is pushing uphill.

 

[dgadee]

Is it an electric pump? Try putting it directly after the valve, so it is pushing uphill.

Yes, I think just a pump from a car engine. Not sure where I got it from.

 

[dgadee]

Would it replace the valve do you think?

 

[vyv_cox]

Would it replace the valve do you think?

Yes, a positive displacement pump, i.e. one with valves, will act as a non-return valve, assuming the valves are seating correctly. But see Rogershaw's point, a bit of dirt will hold the valves open. Ideally pumps should always have a suction strainer.

 

[NormanS]

Initially, the pump will be trying to pump air until the fuel reaches the pump. You either need to find a way to prime the pump with fuel, or better still, resite the pump to the Tee piece. Pumps are always better pushing, than pulling.

 

[scottie]

I have teed into my engine fuel line and then put a one way valve. From that I have a rise of 1m and about 3m to a fuel pump which I want to use to fill a day tank for my Sig marine 100 diesel heater. The pump was tested with short fuel lines and worked, but in place it doesn't. Might it be be that these things don't suck very well and that I should put it at the start of the line to the day tank rather than at the end?

Most heater installers would advise against using T connection into fuel supply lines as I understand

 

[[159032]]

Initially, the pump will be trying to pump air until the fuel reaches the pump. You either need to find a way to prime the pump with fuel, or better still, resite the pump to the Tee piece. Pumps are always better pushing, than pulling.

#4

 

[dgadee]

Most pumps will suck to a greater of lesser extent. The amount depends on the design of the pump.

One issue with diaphragm pumps is the input and output non return valves could be held open by some grit of muck.

I have several of these as primer/bleeding pumps and do pump air

What are they called?

 

[JumbleDuck]

Some fuel pumps are intended to be sited by the tank and mainly push. Some are designed to be sited by the engine and suck. OP, I have a couple of spare ones, brand new, knocking around. PM me if you're interested.

 

[rogerthebodger]

What are they called?

Universal electric fuel pump

New 12 Volt Universal Electric Fuel Pump, 4-6 PSI | eBay

 

[vyv_cox]

Most heater installers would advise against using T connection into fuel supply lines as I understand

I think you are correct but mine has worked faultlessly for many years with a T in the hose downstream of the primary filter. A kind of half-way house is that many add a nozzle to a CAV filter and take the heater supply from there.

 

[lw395]

It's often a question of priming.
I'd use a syringe to draw some fuel through it.
And maybe put a little inline filter right before it, to trap any air and let you see what's happening.

Possibly the extra non-return valve needs too much suction to open it?

 

[[159032]]

Universal electric fuel pump

New 12 Volt Universal Electric Fuel Pump, 4-6 PSI | eBay

They are coming from India, via the US.

Better to get a known make from a UK supplier. I've used Facet on projects.

FACET 40105 Fuel Pump | 3.0-4.5psi Solid State | Fuel Pumps Online

.

 

[rogerthebodger]

They are coming from India, via the US.

Better to get a known make from a UK supplier. I've used Facet on projects.

FACET 40105 Fuel Pump | 3.0-4.5psi Solid State | Fuel Pumps Online

.

I was just using that one a an example mine can from a local motor spares shop so would be available in most local UK spares shops

 

[dgadee]

Most heater installers would advise against using T connection into fuel supply lines as I understand

Yes, but this is just to intermittently fill a gravity day tank so I would think it should be ok. I could always put a shut off tap in place of the one way valve if there's a problem was my thinking.

 

[dgadee]

Moved the pump to near the tee (kept the one way valve) and the day tank can be filled. It pushes better than it pulls. I think it is an old eberspacher pump, so not very fast at filling but then it will only be used every now and then.

 

[dgadee]

Just to say day tank was a great success over the past few days - no pulling out the wee tank to fill it in the cockpit, so heater was run for many hours (even when not needed) and day tank topped up at the press of the button.

These Sig Marine heaters are really, really good. Loads of heat without using any power. And the glow of flames! Overpriced here, unfortunately, at £800 before you get the bits for chimney, day etc. I brought mine back in luggage from NY at much lower price. If it cost less I would tell everyone to get one for UK cruising. Better value than the expensive Eber type, though.