What's the best way to power an electric fuel pump?

Ulrich

Member
I need to connect an underbonnet Facel electric fuel pump (see pic). It's already connected to earth, so I need to find a handy positive connection somewhere under the bonnet if possible. I'd kind of like the pump to have its own dedicated switch inside the car, rather than it coming on with the ignition too. I guess the power supply should be fused? Does it need to run through a relay? I'm not terribly good with electrics so any helpful advice would be much appreciated.

Just to put things in context, this car was restored some years ago although one or two of the details were left unfinished, the pump connection being one of them, so it's never actually been connected up in the right way. I've run it with a lead directly from the battery just to see how the engine runs (it runs very nicely by the way), but I need a more permanent connection.IMG_3433.JPGIMG_3433.JPG
 
You can have a dedicated pump switch, but that switch must be controlled by an ignition switched live, other wise you could turn off the engine and walk away leaving the pump running if you forget (and you will) to switch it off.
You should also have an inertia cut off switch in the feed line to kill the power to the pump in the event of an accident.
IIRC I picked up an ignition controlled live in the rear corner of the drivers knee bin. It is best to fit an inline fuse, it will not need a relay.
Inertia Safety Switch
That Facet may overwhelm the floats in the SU's, so you may need to fit a pressure regulator and peg the pressure to the carbs at 3 psi or less.
 
I would immediately forget, you're right, best to go through the ignition. I'll look for power where you suggested - is there a cable colour I should look for? I read another thread that suggested taking power from fuse 19-20 (gauges, stop lamps, reverse lamps flashers) - not sure if that would be ok too?

Definitely a good idea to fit an inertia switch, my '96 xj6 has one, and they definitely make a car safer. As for fuel pressure, the car has an edelbrock fitted although I'm not sure which model - would that need a regulator too?
 
I would have to look in the car to refresh my memory as to where I took the feed.
I vaguely recall that I found a single bullet connector that came off the heated rear screen switch, made that into a double bullet connector to take off a feed for the pump, however it would need confirmation. Wherever you take it from you need to make a note and leave it by the fuse box, or in a knee bin. Then when the pump stops you know where to look for the problem.
Those Facets can deliver around 7 psi so you need to check the Edelbrock spec, it may be circa 4.5 - 5 psi.
These regulators work well Malpassi Petrol King Racing/Motorsport/Rally Regulator For Carburettors | eBay

edelbrock carb fuel pressure - Google Suche

Connect up a pressure gauge and see what you have before shelling out your hard earned.
 
I'm sure I'll find a point in there somewhere to take some electrons from, a double bullet connector should do the job alright - it's been so long since I messed about with old cars and wiring I'd forgotten they existed! Many thanks for the helpful suggestions and advice - very much appreciated.
 
Hi, You're looking for a white wire for ignition feed, Fused ign is green so be aware.

Colin
 
You should also have an inertia cut off switch in the feed line to kill the power to the pump in the event of an accident.
Agree.
An alternative is to power the fuel pump through a relay, linked to the oil pressure switch. Only powering the feul pump when oil pressure is present, thus if the engine stops, lack of oil pressure stops the fuel pump. This catches a fuel pipe coming lose, oil pump failure etc. This has saved me an engine more then once in the past.... (Pressure relief stuck open. Oil scavenge pump drive failure)
With this setup you need to also power the pump when the starter motor is being cranked to allow fuel flow at startup; although if using carbs maybe not.
 
I used a tachometric relay in my fuel pump circuit - you hit the key and it will go for 2 seconds and stop to prime. If the car stalls it will also stop. Just another option instead of the inertia box.
 
I may be corrected, but I thought the Facet pumps shown in the picture were all 'pushers' and meant for fitting with gravity feed to the inlet? We have fitted quite a few of these to rally cars and all have been at the rear of the car. Agree with post regarding the pressure, these pumps are pretty high and sometimes need a regulator in the line. We have just fitted a 'HUCO' suction fuel pump to our Lotus sprint car in the engine bay. These are designed to be mounted at the front of the car and have an outlet pressure of 3psi. Ideal for the Weber carbs. See how you go. We always relay our pumps. I know its something else to go wrong, but saves overloading the current wiring harness.
 
Many thanks for the answers and advice everybody, so I'm thinking I'll go with a relay, plus an inertia switch, powered from the white coloured ignition wire mentioned above. I'll report back when I've made some more progress. There's also some welding to do on the corners of the car, not as badly rotted as it could be fortunately, but still needs plenty of fresh steel, so there's plenty to do. Thanks again!
 
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