One way fuel valves - where best to install?

bleudanube

Member
Bought a couple of 8mm one way valves to overcome potential air locks or excessive cranking of the engine….so, where to install them?

a) between the fuel pump and carburettor?
b) between tank and fuel pumpnear the pump?
C) between the tank and the pump, but closer to the tank?
D) anywhere else?
e) a combination of the above… I have two of the suckers, so could put two in.

thanks as always. Sven
 

driven

1000+ Posts
Root cause of problem is probably valves/seats inside the fuel pump are worn.
They act like a one way valve anyway.

Failed valve and you will get no flow at all and a roadside stop
Replace diaphragm at same time :)
 

bleudanube

Member
This is more as an added safety/convenience step…. The pump has new valves as the old ones were completely corroded. Diaphragm was still in good condition.

you are right Bob, the valves in the pump are somewhat the Same thing… so maybe one valve near the tank would be most logical to keep the fuel in the line between tank and pump!?
 

richo

Member
Have bought them ( one way valves ) in the past and tested them on the bench.
From there they went in the bin.
None held fuel overnight, never mind a week.

Electric fuel pump if you desire near instant starts.
 

badabec

New member
I tried one, made no difference. If the car has been standing for some time, I prefer to crank away with the starter motor, gets the oil flowing. My oil pressure switch is set at 20psi, the light often goes out just before it fires.
 

Citquery

New member
Ken W and richo have suggested electric fuel pumps to minimise engine cranking prior to start up. I agree and have plumbed an electric fuel pump into the fuel system for this purpose - switched momentarily - to complement the mechanical pump.

Have others used this sort of setup and if so, what is considered the best electric fuel pump and plumbing arrangement?

Chris
 

andrewj

Member
Ken W and richo have suggested electric fuel pumps to minimise engine cranking prior to start up. I agree and have plumbed an electric fuel pump into the fuel system for this purpose - switched momentarily - to complement the mechanical pump.

Have others used this sort of setup and if so, what is considered the best electric fuel pump and plumbing arrangement?

Chris
I've put a fuel bulb off a peugeot diesel on my GS. Fuel pump is ok, so only use it if the car has not running for a few weeks.
 

andrewj

Member
Similar, but I got one of a 405SRDT. My experience with cheap and cheery ones was not good. Rubber went hard in a couple of years.
 
Ken W and richo have suggested electric fuel pumps to minimise engine cranking prior to start up. I agree and have plumbed an electric fuel pump into the fuel system for this purpose - switched momentarily - to complement the mechanical pump.

Have others used this sort of setup and if so, what is considered the best electric fuel pump and plumbing arrangement?

Chris
I use a facet style electric pump (ebay) mounted in the lines wherever you can suitably mount, to bring fuel up to the mechanical pump/carbys on my Alfa, if the car has been sitting for a week or so. I installed a press button under the dash.You can hear when it it's done its job as the note changes in the pump.
 

andrewj

Member
I use a facet style electric pump (ebay) mounted in the lines wherever you can suitably mount, to bring fuel up to the mechanical pump/carbys on my Alfa, if the car has been sitting for a week or so. I installed a press button under the dash.You can hear when it it's done its job as the note changes in the pump.
I like the idea of a push button for the electric fuel pump. Mechanical fuel pumps provide a degree of passive safety in a crash / popped fuel line or carburetor fitting. An electric a motor that will keep pumping fuel indefinitely once the motor stops is a bit scary 🔥🔥🔥
 

Hotrodelectric

Now go make me a sandwich
I like the idea of a push button for the electric fuel pump. Mechanical fuel pumps provide a degree of passive safety in a crash / popped fuel line or carburetor fitting. An electric a motor that will keep pumping fuel indefinitely once the motor stops is a bit scary 🔥🔥🔥
I don't know if Ford still does this, but they used to use an inertia switch that, in the event of a crash, would trip "open" and kill power to the fuel pump. Usually they were installed in the trunk, between the inner wall and the fender skin. Easy to install- just power in/power out- and I used them to great effect on all the street rods I wired.
 

andrewj

Member
Hi Hotrodelectric,

That sounds like a very elegant solution. Much easier that a tachometric relay.

Cheers,
Andrew
 

DoubleChevron

Real cars have hydraulics
I thought most used a tachometric relay ... you must over-ride it to initially start the cars, but unless the tacho pulse is great than 200rpm for example, it'll shut the fuel pump off. I like the idea of the electric pump being used as a primer pump from a push button :)

if you have an inpact switch ... best memorise where it is, so if the car ever cuts out .. you can check it (under the passenger front seat in my shitbox range rover .... .kids can kick stuff under the seat from behind and trip it).
 
Salvage an inertia switch from some dead recent model and use it to control the electric pump. Many later cars don't have one as the ABS/ESP is used to trip the fuel pump via the engine ECU. An older Berlingo (M49/59) has quite a nice unit with a rubber cap, as would a Xantia. You want a low pressure pump of the type that will 'tick' rapidly as it initially pumps up and then only every so often once it's up to a few psi. The classic SU diaphragm electric pump seen on many carby UK cars would suit, but there are modern alternatives. You have to make sure it's only very low pressure or you will overwhelm the float valve and flood it. One car I encountered had an electric fuel pump plus the ignition supply run via the oil pressure switch, so it would not fire until there is engine oil pressure. I thought it was overkill. A tachometric relay is used to sense for an ignition pulse in EFI cars, but none I have ever seen involves any kind of inbuilt inertia switch.
 

Hotrodelectric

Now go make me a sandwich
One car I encountered had an electric fuel pump plus the ignition supply run via the oil pressure switch, so it would not fire until there is engine oil pressure. I thought it was overkill.
Yah, a lot of GM cars had that. It was there more to protect the engine than a safety measure. Certainly usable as a safety, but to trip it you need to lose engine power. The inertia switch Ford used was on everything from IIRC 1990-2010. They might still be using it. Should be easy to find at your local breaker.
 

Citquery

New member
It occurs to me that this thread has diverged somewhat from the original topic - one-way valves - but it has stuck with the principle of (safely) minimising the work the starter motor has to do to start an engine which has laid idle for a while. I have used a momentary switch for the supplementary electric fuel pump (only activates the fuel pump while you press the switch); however, I have also employed quite a complex plumbing arrangement - involving one-way valves - to more or less keep the mechanical and electric fuel circuits separate.

I think, by implication, at least one contributor to this thread has set up a system where the electric fuel pump and mechanical pump are in line. The electric pump, when activated, pumps fuel through the mechanical pump to prime the system. When the engine is started, the mechanical pump is then sucking fuel through the electric pump. Is this an effective setup? If it works it's certainly far simpler than the complex plumbing arrangement I've used.

Chris
 
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