Author Topic: Low pressure fuel pump  (Read 701 times)

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Offline califkid_66

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Low pressure fuel pump
« on: Friday,July 05, 2019, 04:33:40 PM »
I need advice on what pump to get and how  to set it up i have no idea how it works i have a low pressure regulator but there is no return iand i heard the pump doesn’t stop pumping so what happens to the pressure build up
On my wedge with solex i have the T between the pump and carb and its a return for exess presure  and goes back to the tank

Im looking to setup for my crossflow  low pressure electric pump and will be using the car for road use  its just i don’t know why no return 
Can someone explain what happens where does the pressure go i cant find info
Thanks for your help

Offline jbcollier

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Re: Low pressure fuel pump
« Reply #1 on: Friday,July 05, 2019, 07:21:57 PM »
The wedge engine has a return to maintain a constant supply of cool fuel because the exhaust manifold is right under the carb/intake.  The crossflow hasn’t the same heat load in the carb/intake area and does not need a return line.

I used a 4 psi max Facet pump.  Works very well.


Offline surfguitar58

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Re: Low pressure fuel pump
« Reply #2 on: Friday,July 05, 2019, 07:35:52 PM »
There is some good fuel pump advice I received from our more knowledgeable members in this thread: http://www.lotuseuropa.org/LotusForum/index.php?topic=2431.msg22971#msg22971

I have a Facet FAC-40178 "cube style" electronic fuel pump I'm willing to part with if you are interested. It is recommended for cars with "about 80 HP". PM me.

The FAC-40178 came installed on my TCS and worked great on my Twin Cam unless I really punched it, at which time the engine would sputter from fuel starvation. I upgraded to a FAC-40105 (rated for 150 HP, 3 to 4.5 psi max) and no more fuel starvation at high end.

Tom
"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away."
Antoine de Saint-Exupery

Offline jbcollier

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Re: Low pressure fuel pump
« Reply #3 on: Friday,July 05, 2019, 08:16:15 PM »

Offline califkid_66

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Re: Low pressure fuel pump
« Reply #4 on: Sunday,July 07, 2019, 06:49:18 PM »
Thanks for all you’re response my worries were that there was no return and was afraid of pressure build up because the pump doesn’t stop pumping but i just read that facet pumps have built in pressure relief so no stress on the carbs
So i guess they must all have built in pressure relief if they don’t have a return line
I just have to figure out what my fuel needs are
Thank again

Online BDA

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Re: Low pressure fuel pump
« Reply #5 on: Sunday,July 07, 2019, 07:05:21 PM »
I have a low pressure Facet cube fuel pump that I like. I've never heard of them going bad. I would also get a fuel pump relay that turns off the pump in the event of an accident.

Offline califkid_66

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Re: Low pressure fuel pump
« Reply #6 on: Sunday,July 07, 2019, 07:57:07 PM »
I was looking at the wiring diagram and its fused as a relay and its hooked to and oil pressure sensor  for safety so that if the engine stop for whatever reason the pump will stop at the same time

Offline jbcollier

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Re: Low pressure fuel pump
« Reply #7 on: Monday,July 08, 2019, 06:06:42 AM »
You can also just use a roll-over switch in the circuit.  It cuts the power with any impact.

Offline surfguitar58

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Re: Low pressure fuel pump
« Reply #8 on: Monday,July 08, 2019, 06:33:39 AM »
For whatever it's worth, this is the filter-shutoff-pump-switch set-up I'm using in my TCS. The red topped thing is the impact/roll-over switch. It cuts power to both the fuel pump and the normally-closed shutoff valve on impact. (Push the red topped button to reset.) There is some debate as to whether the shut-off valve is necessary or not. The Facet data sheet (http://www.facet-purolator.com/tech-information/ ) says the fuel pump I am using does not have a positive shutoff built in. Since the top of the fuel tanks are above the float bowl on the carbs, I thought it would be best to include a separate positive shut-off. This whole assembly lives in the "C" section of the frame just below the carbs with easy access to the reset button.

Tom
"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away."
Antoine de Saint-Exupery

Online BDA

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Re: Low pressure fuel pump
« Reply #9 on: Monday,July 08, 2019, 06:45:43 AM »
Looks good. It's hard to tell. Are you plumbing with -6 lines. That's the appropriate size in spite of the fact that the pump has 1/8 FNPT ports. -4 is too small.

edit: I think that's true even though I reminded myself that my 1275 Midget race car (110+ hp, 7500rpm) used -4 to its SUs! Also, I believe all the fittings for Weber carbs are -6.
« Last Edit: Monday,July 08, 2019, 06:50:11 AM by BDA »