How does a solid state petrol pump work.

[nmauduit]

Slightly off topic, but related, several people have mentioned on here about a safety cut off device if fitting an electric fuel pump. What have people found to be the best and simplest to install?

I've fitted a intertia/fuel cutoff switch (used part off a Ford), you'll see photos on the internet, this is the model with a red knob that protrudes when it's been shaken (like after an accident), which moves a steel ball inside and and opens the contact; one can re-establish the contact by pressing the red button. It was very easy to fit, upper right corner of my trunk, on the wire that feeds the pump.

I'm also planning to add an engine off safety feature using the oil pressure switch and a relay (no fuel pump when loi pressure below 20 PSI, plus a temp switch to by pass like a priming pump), but have not done that yet. It's still winter here it seems...

[Mick6186]

On my 130/5 with dellortos I hated having to spin the starter for at least 30 seconds to fill the carbs with my mechanical fuel pump. I have now fitted a Facet pump between the mechanical pump & carbs. This is operated via a switch in the cabin and when the ticking noise changes the Facet is switched off and the car starts immediately with minimal strain on the starter . The mechanical pump seems to be able to push the fuel through the Facet no problem and there is no accident risk as the pump is not live once switched off before starting. I did have a rubber bulb device but noticed cracks starting to appear in the cheap rubber so binned that idea,
Mick

[billwill]

It's one of those things where you just have to guess, as hopefully it will never actually get invoked.

I for instance, bought a 2nd hand inertia switch from ebay and have fitted it, I think it was from a Land Rover but only afterwards did I discover that though they look the same there are many different ratings/specifications of inertia switches, so I've no real idea how much of a bump will trigger it nor whether the inertia ball (?) will stay in place during fast cornering (or braking) in my Elan.

Though I can't see inside the switch it seems to be a biggish steel ball held against a light spring onto contacts by a magnet, strong shocks dislodge the ball & then the spring prevents it reaching the contacts again until it is manually pressed down. I can dislodge it manually for test purposes by hitting the side of the switch with the edge of my hand.

It looks the same as the one fitted by the factory into my Reliant MPV diesel, but I doubt if it has the same rating.


~~~~~~~~~~~~~~~~


Earlier I published here an untested circuit diagram for using a relay with the existing oil pressure switch to switch off the fuel pump.



The priming switch should be a push button (non-locking) so that you can't leave it ON.

[john.p.clegg]

I fitted an inertia switch from a Mondeo , after some spirited driving the performance was really down , it seems some of my cornering was enough to activate the switch , hence High Pressure EFI pump turned off and just the Facet was feeding the injectors.....

John

[chrisbeck]

Interesting post Eric. This is something that has been concerning me for some time, if my Elan has sat for a while I take the plugs out and spin it over to prime the carbs, hardly ideal.
So I take it the mechanical pump is able to pull fuel through the electric pump okay once the car is running? Was there a reason you chose not to install it after the mechanical pump as suggested by Mick6186? I am very wary of over pressurising the original spec. (nylon) fuel feed line from the tank to the engine.
BTW, Diff access hatch? Is that a retrofit to make oil changes easier?

[ericbushby]

Hi Chris,
It was a bit speculative at the time, but I chose that pump because it would fit in the corner of the spare wheel well, also because it was reputed to be noisy and because it was cheap, ?12.60 ish. The apparently identical Facet pump is about ? 65.00. I wanted to be able to hear it ticking so that I knew when the carbs were full and I could release the switch.
Comparing it with blowing into a pressure gauge where I can blow about 2 psi. it needs less than 1psi to open it`s valves so I did not expect any problem.
It is just that it is out of the way there whereas the engine bay is a bit busy with the Filter King regulator fitted and I always seem to be rummaging about round there.
I do not know the output pressure, but I doubt if it is higher than the engine pump (about 7psi as far as I know) and as soon as the pressure builds up when the carbs are full I let go the priming switch and it changes to suction as normal.
The access hatch was from an idea on this forum. We did four cars in the local club. It is a 4" waterproof boat hatch. A hole saw and a bit of filing to fit it. We found that the fibreglass is not flat and would tend to distort the hatch so I made aluminium backing rings to stabilise it.
It now takes longer to remove the floor and spare wheel than it does to check the oil level.
If you need any more info. please ask.
Eric

[Quart Meg Miles]

[quote="chrisbeck" I am very wary of over pressurising the original spec. (nylon) fuel feed line from the tank to the engine.
[/quote]

I've not had any problem after five years but fitted a proper union after the pump, which is a Facet Posiflo, and the regulator is after the mechanical pump. (I've Zinger'd the tank since the picture!)

My car won't run without the electric pump in hot weather, or when the engine is hot, and the mechanical pump had been supplied as "refurbished" by St Wlikins. Seems I'm the only Elan owner to suffer vaporisation with new alcohol-loaded fuel.

[zoom]

Hi Eric,

I don't think you've had a definitive answer to your original question, though the fuel slipping past the piston sounds about right..and I can't improve on that. I had a type 14 Elite with an SU electric pump, and that did indeed stop ticking once the carbs were primed (in fact it used to stop altogether quite often, the only breakdowns I suffered in 10 years with the car. A sharp tap with a small hammer would always cure it!) For what it's worth, I have a Facet silver top (cylindrical) pump on my S4/Dellortos, fitted in the same place as yours and it does exactly as yours does - ticks madly until bowls are full, then carries on ticking, but at a slightly lower rate. I also fitted a 'filter king' pressure regulator then binned the mechanical pump, but must now fit an inertia switch.

Simon

[ericbushby]

Simon,
I think I may have inadvertently added some extra reliability.
If the pump does turn out to be cheap junk, then I am running on the engine pump anyway.
If the mechanical pump fails (again) then I can go home by linking out the priming switch and running on the electric pump. I only just thought of that.!
Cheers
Eric.

[chrisbeck]

[quote="chrisbeck" I am very wary of over pressurising the original spec. (nylon) fuel feed line from the tank to the engine.

I've not had any problem after five years but fitted a proper union after the pump, which is a Facet Posiflo, and the regulator is after the mechanical pump. (I've Zinger'd the tank since the picture!)

My car won't run without the electric pump in hot weather, or when the engine is hot, and the mechanical pump had been supplied as "refurbished" by St Wlikins. Seems I'm the only Elan owner to suffer vaporisation with new alcohol-loaded fuel.

Posiflow tank & delivery 105-498.JPG

[/quote]

'Quart Meg Miles': Can I ask where you got those elbow connectors? I would like something robust to connect the flexible to the nylon pipe. Thanks, Chris

[Bigbaldybloke]

Just for info, I used to work in the oil and gas industry and we used similar looking plastic pipe on pneumatic instruments operating at 100psi so if it?s the same and the joints have been correctly made, it?s highly unlikely your fuel pump will cause them any problems pressure wise. I?ve replaced mine with a copper pipe right through with a short braided flex pipe at each end.

[chrisbeck]

Thanks ?Bigbaldybloke?, I am also ex. Oil & Gas and recognise what you describe. I would expect to see a compresssion fitting with an olive. With hindsight I wish I?d run something more robust through the chassis during the rebuild than a new ?nylon? line. I?ve not had any problems but it?s a bit scary to see the line passing through the tight gap between body and chassis just after it exits the boot! I guess I could run a replacement in copper, at least with a Spyder chassis it?s easy to strap to the tubes.
I haven?t opened up the existing joint between the nylon and the flexible from the tank, I suspect it is simply inserted with the jubilee clip compressing the flexi. I would want something more substantial if adding a priming pump in the boot.
Chris

[Quart Meg Miles]

I've not had any problem after five years but fitted a proper union after the pump, which is a Facet Posiflo, and the regulator is after the mechanical pump.

'Quart Meg Miles': Can I ask where you got those elbow connectors? I would like something robust to connect the flexible to the nylon pipe. Thanks, Chris

I bought them locally from IES Fluid Technology but I can't find the invoice from them with part numbers. There will be a similar outlet near you and all you need to tell them is the hose and pipe end diameters. Make sure your hose is alcohol tolerant and buy it to fit the pump ends.

My elbows were both in two parts which screwed together, one end for the hose and the other for the particular pipe: tank output or nylon tube, the latter also needing a small metal tube inside it to take the gland pressure.

There isn't much space around the tank and you can see that I managed to get the hoses between the tank and bulkhead but the hose bends were rather tight. Two pictures show 1) my mounting, which allows my spare wheel, and 2) Alex Black's Sprint fitting which might not. (My picture is after I moved the regulator to following the mechanical pump and I leaned the pump over to reduce the bend).

.

[chrisbeck]

Thanks Meg, very comprehensive, Chris

[Washer]

Hi,

I notice that you use the 'jubilee' type of hose clip, in my experience these are not a good option for small diameter pipes due to the screw mechanism not conforming/changing to the decreasing circular shape of the pipe when tightened. The type of clip that consists of a screw and nut with the 'clip band' sliding underneath seem a better choice to me. I did have a supply of plastic clips that were tightened by squeezing a ratchet toothed mechanism which were excellent at ensuring a 360 degree grip of the outer pipe, 10+ years later those fitted are still fine.

Cheers,
Mike