fuel cut off solenoid and hidden switch

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=113681
Printed Date: April 28, 2024 at 12:14 AM

Topic: fuel cut off solenoid and hidden switch

Posted By: electrickery
Subject: fuel cut off solenoid and hidden switch
Date Posted: May 08, 2009 at 6:28 AM

Hello everyone,

I'm new and haven't posted here before so my apologies if this question has been answered before.

I am installing a fuel cut off solenoid for both saftey and security reasons on a very old vehicle. The idea is that if the ignition is switched off, fuel doesn't flow and mitigates the effect of a fire in an engine bay.

I want to incorporate a hidden switch so I can also use it for security. If that switch is broken and someone tries to drive the vehicle away, they won't get very far if they don't know about the solenoid and the hidden switch.

Here's the bit I don't know how to do.

When I break the circuit with the hidden switch, I would like an LED to blink on the dashboard to remind me that the switch is off and also fake an enabled car alarm.

How can a get power to flow to the LED when a switch is off?

Many thanks

Replies:

Posted By: Big Dog
Date Posted: May 08, 2009 at 10:59 AM

Here's a quick diagram....sorry about the quality.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Posted By: electrickery
Date Posted: May 08, 2009 at 11:12 AM

Wow Big Dog, thank you very much for replying. Your picture was great quality compared to mine.

Unfortunately my old vehicle has a mechanical fuel pump. I had come up with a similar idea using a relay.

posted_image

I was a little concerned that with this method pin 87 is live when I have the car running. Is that OK?

Also, since posting, I've had a crash course on electrics and I've discovered DPDT switches and thought about this instead. Would that work with a 10A toggle switch from Maplin?

posted_image

Posted By: electrickery
Date Posted: May 08, 2009 at 11:15 AM

Ah, well those images didn't work. Maybe they were too big.

Posted By: electrickery
Date Posted: May 08, 2009 at 11:23 AM

I think the images were in a format that this forum can't handle. Hopefully this will work.

posted_image

Posted By: Big Dog
Date Posted: May 08, 2009 at 12:33 PM

Your second diagram would work but not the first.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Posted By: electrickery
Date Posted: May 08, 2009 at 12:43 PM

Thanks. I'll get some bits tomorrow and try to make it work. posted_image

Posted By: howie ll
Date Posted: May 08, 2009 at 5:18 PM

Wait, I know it's a mechanical fuel pump but surely if the engine stops turning, the fuel pump ceases?

Posted By: ckeeler
Date Posted: May 08, 2009 at 5:43 PM

howie ll wrote:

Wait, I know it's a mechanical fuel pump but surely if the engine stops turning, the fuel pump ceases?

bingo!!