Lotus Elan

Mechanical fuel pump by-pass

PostPost by: Heuer » Tue Mar 29, 2016 4:19 pm

I want to by-pass the mechanical fuel pump but I am having difficulty finding a 5/16" female to 1/4" female adapter. Anyone know of a source, web site or part number of something suitable?

Thanks
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PostPost by: dougal9887 » Tue Mar 29, 2016 7:14 pm

Are you trying to join something up to the 1/4" nylon fuel pipe? If so what?
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PostPost by: Heuer » Wed Mar 30, 2016 9:13 am

I want to join the nylon fuel pipe to the braided pipe going to the carbs by-passing the mechanical fuel pump. I am planning to use an electric pump but want to keep the mechanical pump in situ to easily revert back to standard. I have had three mechanical pumps fail, one original and two new - the last installed in September and it looks like the diaphragm has failed after being left standing over winter. My concern is if I leave the pump in circuit fuel could leak into the block.

Can't seem to find an adapter both of which have the same thread, sizes I was referring to were the nuts.
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PostPost by: oldchieft » Thu Mar 31, 2016 8:03 pm

why do you need to by pass it?

In the past I have run an electric pump after the mechanical to prime the float chambers on a Ford x/flow with twin DCOE's

Just press a switch to prime then run as normal after.

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PostPost by: dougal9887 » Fri Apr 01, 2016 6:47 am

To my knowledge you won't find a coupling suitable for the existing internal compression nuts used at the fuel pump.
I used a 1/4" compression ? 10mm hose tail to connect the 1/4" nylon to 8mm braided hose.
https://www.bes.co.uk/products/071.asp?EPBOE=#8991
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PostPost by: Heuer » Fri Apr 01, 2016 2:37 pm

OK, thanks. I checked the mechanical pump and the diaphragm is in good order so I have left it in circuit besides it probably acts as a fuel pressure regulator to some extent.
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PostPost by: Quart Meg Miles » Fri Apr 01, 2016 9:34 pm

Heuer wrote:OK, thanks. I checked the mechanical pump and the diaphragm is in good order so I have left it in circuit besides it probably acts as a fuel pressure regulator to some extent.

Oh no it doesn't, it increases it! If you put two pumps in series you need a regulator before the carbs.

Jon, I'm surprised you put the electric after the mechanical; my problem is getting the petrol from the tank to the engine bay.
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PostPost by: oldchieft » Sat Apr 02, 2016 1:46 pm

Quart Meg Miles wrote:Jon, I'm surprised you put the electric after the mechanical; my problem is getting the petrol from the tank to the engine bay.


It was a low pressure SU pump, same as fitted to Moggy 1000, so I mounted it in a similar place.

But you can do the same with a high pressure pump, like the old Mini mounted at the back.

It worked find, as it was a Morgan that did not get much running and built in priming was handy.

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PostPost by: jk952 » Sat Apr 02, 2016 7:36 pm

Meg,
There is always the $7 solution for priming, the outboard motor fuel tank type primer...and worked great again just today for my after winter first start-up....

image.jpeg and


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