Bigger electric pump for fuel polisher.

pcatterall

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I have made up a fuel polisher as per many old threads and used an ordinary CAV filter ( cheap and cheap filters)
The delivery output end is just a flexible pipe which I can shove into either fuel tank ( via the tall dipping tube or into a jerry can.
It works fine but struggles to pump fuel up from the tank round the system and back into the dipping tube ( about 3 feet head from the fuel level)
If I pump into a jerry can held at tank level it takes about 40 minutes to fill the 5 gallon tank.
I cannot see or recall what size the original pump was but would like something that will give a decent rate of pumping.
Can anyone suggest the size of pump which would cope better?
 

Lon nan Gruagach

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First thing to do is check the flow rate on the filters.
Then look for a pump that will do that flow rate at the head you want, note that most pumps are rated at flow rate OR head, and there is approximately a linear trade off between.
Naturally remember to check the pump is suitable for diesel.
 

superheat6k

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Mine uses a Holly pump. Not cheap new, but sometimes pop up on Ebay for a few quid. Mine has been very reliable and will pump to some head - at least 2 m.
 

Trundlebug

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I have similar to Little Ship but bought mine from ASAP, some are much cheaper but I haven't looked at the detail

http://www.asap-supplies.com/search/fuel+pump

Aside from that there are a couple of points from above that I would have concerns about though
1. Using gear or impeller pumps is not a good idea with filters - they're far too high pressure and could force particles through the media. Wrong type of pump to use altogether for this application
2. Using CAV filters is cheap yes and will filter out the solid black gunge which is the waste product of the bug, but they don't remove the cause of the problem which is moisture in the fuel. Much better to use a Fleetguard filter with suitable filter head, I use FS1221 filters which remove 95% of moisture and there are others which remove 99%. The CAV remove 0%. Having filtered the diesel I noticed the colour of the fuel was noticeably lighter from being quite a dark brownish red to a pinky clear red.

I appreciate the Fleetguard filters are more expensive, at around £12ea than CAV (which I have as my primary filters on the fixed installation so I still use them) but still much better value and better performing than Racor which everyone seems to rave about. And of course compared to getting someone in to polish your fuel (av £100 ish a time) considerably cheaper to do it yourself. Also the Fleetguard filters last much much longer. I used about 1 or 2 per tank on my heavily contaminated 2x 40 gall tanks.

For further guidance speak to Fleetguard Technical services (their website was cr*p last time I tried a few years ago) in Rugby and they're both knowledgable and helpful.
 

Lon nan Gruagach

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Thanks for all the info guys. I see the ASAP pumps rated at 121 lph. I guess this at level so how do I factor in pumping up to say 3 or 4 feet higher?

iF i specs 8 feet then halve the flow rate (ish), if it specs 16 feet then 1/4. if it specs 2 feet then get sucking.
 

Lon nan Gruagach

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Don’t understand this ( appologies if obtuse!!) The secification given is just 121 litres per hour. I assumed this meant pumping level. I wanted to know how to calculate the output at 4 feet.
if you mean this one http://www.asap-supplies.com/marine/electric-fuel-pumps/12-volt-electric-fuel-pump-for-diesel-and-petrol-306550
The significant numbers are:
flow at zero head: 121 lph
min pressure 4psi (about 11 feet of diesel)
max pressure 7psi (about 20 feet of diesel)
max dry lift 300mm.

So, if it needs to suck more than 300mm up before any diesel reaches it, it wont do.
max pressure is what I would look for and assume zero flow at that head.
it is reasonable to use a straight line graph of flow vs head (pumping height)
From the info we have 121 lph at zero head and zero flow at 20 feet head.
For a centrifugal pump a good estimate of flow at 4 feet would be 90 lph.

From how these pumps work I assume that up until the minimum pressure 4 psi back pressure (11 feet of diesel) then it will still be running at its maximum flow of 121 lph

Thats all good until it meets the filters, they will add their own back pressure (head), if you can post a link or part number for them it might be possible to calculate that.
 

rogerthebodger

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This http://www.asap-supplies.com/marine/...-petrol-306550

Is a piston pump where the pumping stroke is spring driven and the return is solenoid driven. This means that the maximum pressure is determined by the spring and size of the piston. The advantage is that it the flow is blocked no damage will not take place as the maximum pressure is limited by the spring. Also the flow rate will be determined by the resistance of head like the filter and as the filter gets blocked the flow will reduce until the resistance of the piping, head and filter equals the max pump pressure

The kind of pump you need is a positive displacement pump where the flow is only dependent on the size of the pump and the speed it is driven. Gear, vane and positive piston pumps are the type that will pump the same volume no matter what the resistance is up to a point (strength of the pump and piping) bursting pressure.

The ones I posted early are the type you need.

I fitted the one in the asps URL as prime pumps at allow easy bleeding but I am replacing these with hand priming bulbs which IMHO are better.

The ASPS pump was designed to replace the engine mechanical lift pump mainly on motor vehicles with boot mounted fuel tanks.
 

superheat6k

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When assembling your rig it is suggested to be more effective to place the separator filter in the inlet line because the pump's action breaks up globules of water into far smaller particles that might then simply pass through the filter rather than agglomerate and then separate.

Mine uses a Baldwin separator with a clear bowl, along with dripless instant connectors to plug into.
 
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