Electric Fuel Pump Inertia Switch

[sunbeamowner]

I have noticed in previous discussions that there are a few Alpine owners out there using an electric fuel pump instead of the manual one. This conversion has many advantages however there seems to be one point that has not been spoken about or mentioned. Inertia switch. On modern day vehicles there is an inertia switch added to the fuel pump circuitry . This is to prevent the fuel pump operating in the case of a collision. This means if you don't have an inertia switch ,your fuel pump will continue to pump fuel as long as the ignition is on (unlike the manual pump that only operates when the engine is running). The fuel pressure of the the pumps installed by owners might be only a few pounds but that is still a lot of fuel to be pumped into a hot engine bay whether the driver is incapacitated or not.

 

[husky drvr]

I have noticed in previous discussions that there are a few Alpine owners out there using an electric fuel pump instead of the manual one. This conversion has many advantages however there seems to be one point that has not been spoken about or mentioned. Inertia switch. On modern day vehicles there is an inertia switch added to the fuel pump circuitry . This is to prevent the fuel pump operating in the case of a collision. This means if you don't have an inertia switch ,your fuel pump will continue to pump fuel as long as the ignition is on (unlike the manual pump that only operates when the engine is running). The fuel pressure of the the pumps installed by owners might be only a few pounds but that is still a lot of fuel to be pumped into a hot engine bay whether the driver is incapacitated or not.

Inertia switches and safety are brought up for discussion periodically. It never hurts to discuss ways to stay safer, thanks for bringing the topic up.

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forum.sunbeamalpine.org

If a poll were done for those with electric pumps, it would be interesting to note the percentages for the following groups:

A> have inertia switch installed.

B> intend to install inertia switch but haven't done so yet.

C> aren't worried about it because it's not an issue.

Have a good day,

 

[alpine_64]

If a poll were done for those with electric pumps, it would be interesting to note the percentages for the following groups:

A> have inertia switch installed.

B> intend to install inertia switch but haven't done so yet.

C> aren't worried about it because it's not an issue.

Have a good day,

Or...I have option D.

Pump is wired so it only works if the motor is running. This is a PITA if the car has been sitting ages as if it doesnt start data you have to jump the pump to fill the bowls.

 

[Bill Blue]

I found the oil pressure sensitive switch to be a headache on a Buick I owned. It had main bearing issues and low pressure. would die while waiting at a long red light or road construction. Much prefer the Ford inertia switch. The one I'm using has been called upon twice to perform its duty. 100% success.
Bill

 

[Acollin]

Why do people switch to an electric fuel pump?
Do other alterations make an electric fuel necessary?
Andrew

 

[alpine_64]

Why do people switch to an electric fuel pump?
Do other alterations make an electric fuel necessary?
Andrew

Different people have different reasons.

An advantage of an electric pump is it won't create cam wear and there is no place where petrol can seap into oil if the gaskets fail.

I switched when I went to 2 X 40 dcoe carbs. I found that at sustained open throttle the bowl would slowly drain and I'd get a stumble...

Others do for various reasons. If I was running a stock setup or a single 32/34 or 34/36 I'd still run the mech pump.. and I like the factory setup with the manual prime lever under it.

 

[Bill Blue]

Why do people switch to an electric fuel pump?
Do other alterations make an electric fuel necessary?
Andrew

Needed high pressure fuel for EFI. I think a lot of electric fuel pumps are installed during a long battle with a mysterious miss, hesitation or hard starting. I would guess that 90% of them do not solve the problem.
Bill

 

[Tim R]

Having been to car accidents where people have been burned alive because of the fuel pump not switching off and spraying them with burning petrol I install an inertia switch with an electric fuel pump. The switch sits of the bulkhead behind the glove box in our Alpine. It is a very simple set up, a ball bearing that sits in a cup with a spring beneath it under a rubber cap. If the switch is banged hard the ball bearing is dislodged and the spring lifts it up and stops electric contact and the pump stops pumping. The inertia switch is the black unit on the left of the photo. I install it on the bulkhead so that if ever it is activated incorrectly (if I should bounce down a kerb hard or something like that) it is easy to reach up and reset it. I've never needed to do this yet. Some Rover cars used to have the inertia switch installed near the front of the car behind a headlight and pranksters would thump the bonnet of the car and make it activate...... then when you try to start the car it won't go!
Tim R

 

[husky drvr]

Or...I have option D.

Pump is wired so it only works if the motor is running. This is a PITA if the car has been sitting ages as if it doesn't start data you have to jump the pump to fill the bowls.

Just curious, was there an issue for you to have not wired a bypass to the pressure switch to operate the pump with starter engagement?

 

[alpine_64]

Just curious, was there an issue for you to have not wired a bypass to the pressure switch to operate the pump with starter engagement?

My friend did the wiring for me ( I don't mix well with current) and we didn't have an inertia switch so he wired it to operate only when the motor was running... I've just left it that way

 

[sunbeamowner]

Why do people switch to an electric fuel pump?
Do other alterations make an electric fuel necessary?
Andrew

Biggest reason I think is 'Fuel vapor locks' on a hot day. The mechanical pump needs continual cranking to pump the fuel up to the carby/s. The electric pump just needs the ignition turned on to pump.

 

[Tim R]

Don, after a car crash the engine often continues to run that is why you want an inertia switch fitted.
Tim R