Electric fuel pump safety switch

[Gary_Ash]

I used a Facet low-pressure electric fuel pump on my 1932 Studebaker Indy car replica to feed the four carbs.  There is also a fuel pressure regulator in the fuel line from the pump that limits max pressure to about 2.5 psi.  I've read in a number of places that a shut-off switch for the fuel pump should be added to stop the pump if you crash.  Modern cars use inertia switches which trigger on a 10G impact, like hitting another car at 25 mph or a stone wall at 15 mph.  That seems to be a good type to use because it doesn't care if the engine is still running or not.  These are readily available for $50-$75.

 

Two other types are available.  One is connected to the oil pressure line or gallery and opens the connection if the oil pressure drops below 10-25 psi.  That's good if the engine stops, but older engines may have fairly low oil pressure when idling and warm, might cut off fuel flow when not required.  These are cheap at $10-$20.  Another type is electrical, connected to the ground (distributor) side of the coil to look at pulses, maybe $60-$75.  Both types are intended to stop fuel if the engine quits.  The first type would also shut off the engine if you lose all oil pressure, a good thing.

 

Has anyone installed one of these safety switches?  What type did you pick and why?

[Bloo]

I've done pretty much all of those things years ago. Lately I just don't use electric fuel pumps.

 

Oil pressure is probably not a great idea for the reason you mentioned. It worked OK for me, but I don't really consider it a good idea. You can wire a relay, probably a DPST if I remember correctly, in such a way that the pump comes on with the starter, and then it goes and "hunts" for oil pressure. When it finds some (because the oil pressure warning light switch opened), the fuel pump comes back on.

 

Checking for pulses at the ignition is done with a "tachymetric relay". These are French, and mostly used in Peugeot and Volvo. They work fine. They also handle the job of turning the pump on to get a little fuel in the carbs before starting. There are several kinds, and In the late 90s and early 2000s some of the versions were becoming unavailable. As many Volvos as there are here in the US I imagine some version for a later 240 or 760 still exists, but maybe not. It might come down to opening an old one up and resoldering the cracked solder joints, a common problem.

 

If I were doing it today, I would definitely use an inertia switch. The ones used in old Alfa Romeos and Jaguars should be avoided. The contacts probably should have been silver plated or something and are not. They are unreliable. The earliest Ford ones (Large, 2-pin, from around 1984-85) should be avoided like the plague. They trip too easy. I vote for the Ford 3-pin one from around 1987-88 and probably much later. You could find these screwed to the inside firewall of Ford Rangers back when you could still find late 80s small Ford Rangers in junkyards. In regular Ford passenger cars you will usually find the switch inside a rear quarter panel accessible from the trunk.

 

There is probably something more recent that works well, but I am not familiar with more recent options.

 

Edited November 6, 2023 by Bloo (see edit history)

[Don Jr.]

I have the Ford inertia one located in the cockpit under the seat of my 2 man car. If for any reason it trips the riding mechanic can reset it. I can switch from a hand pump when a riding mechanic is available or switch to hand pump going solo.

[SMB]

I use the Revolution  device.   I like the fact that it has a 3 second prime when the ignition switch is turned on.   That can be repeated before cranking the engine.   It shuts off the pump when the engine stops.

More information in the link.

 

https://www.revolutionelectronics.com/Products/Fuel_Pump.html

Edited November 8, 2023 by SMB (see edit history)

[Fordy]

On 11/6/2023 at 12:57 PM, Don Jr. said:

I have the Ford inertia one located in the cockpit under the seat of my 2 man car. If for any reason it trips the riding mechanic can reset it. I can switch from a hand pump when a riding mechanic is available or switch to hand pump going solo.

I have the same one readily accessible by reaching under the dash on my Triumph Spitfire. I have it wired to a master relay that drops out fuel pump, ignition circuit and everything else under the hood plus all instruments on the dashboard. Never used it yet but give the dash a good thump to knock it out for a demonstration - so it works.

Steve