fuel pump idiot light set up

[jvandyke]

My dash has a mini rocker switch and a seperate little light cut into the dash panel. I think they may have once been used for a car alarm. I'd like to make these functional, just because I'm anal I guess.
Was thinking of hooking up the rocker to power my electric fuel pump. That's easy enough but in the past, whenever I turn off the fuel pump I seem to ALWAYS forget to turn it back on when I take off, not too cool. So I'd like to rig the switch so that the separate little idiot light comes on when the fuel pump is off. I'm thinking on/off/on rocker (current one seems to be on/off/momentary on) but the only ones I've found so far are not automotive (125v vs. 12v) Would that still work? Not ideal as it leaves a "neutral" position (the off) where there would be no light and no pump but whatever. Unless there's a better way?

[namba209]

Depending on the switch configuration, you could use the switch to either break the circuit from power to the lite or the ground to the lite. You need to determine that, then put up a diagram on the site and I or one of the other members could give you a simple schematic. HTH.

[jvandyke]

This (like many things I guess) is not my forte. I assume most switches simply complete a circuit so to have one switch turn one thing on while turning another off requires a special switch. Ideally it would be a mini rocker with two positions, down: pump on light off, up: pump off light on. Don't know enough to know what to look for in such a switch. Probably easier to get the on/off/on type (available right next door to me in 125v format).

[OriginalOpelGTOwner]

The voltage rating on any switch is just a measurement of the electrical insulation properties across the contacts when they are open (separated). Any 125 Volt switch will work just fine in a 12 volt application. You never want to use a 12 volt rated switch in a 125 volt circuit. Radio Shack has a nice selection of switches you can pick from. I like your idea "fuel pump off red light on". You could also wire in a green LED for power to pump on.

[namba209]

Give me a couple of minutes to draw up a schematic for your "new" switch. It would probably be easier to do that instead of trying to figure out what kind of switch you already have, or you may have one that will work. What I envision is an on-off switch with 3 or 6 terminals on the back. Either one will work. I'm gonna draw it up in a "Word" document, my scanner isn't compatible with my new computer. For a start, I'll presume you have a switched power source to the fuel pump switch, which means the key has to be on for it to work, and I'll go from there. BRB.

Here's hoping you can see this and it uploaded o.k.

[jvandyke]

Originally Posted by OriginalOpelGTOwner The voltage rating on any switch is just a measurement of the electrical insulation properties across the contacts when they are open (separated). Any 125 Volt switch will work just fine in a 12 volt application. You never want to use a 12 volt rated switch in a 125 volt circuit. Radio Shack has a nice selection of switches you can pick from. I like your idea "fuel pump off red light on". You could also wire in a green LED for power to pump on.

Confirms my suspicions on switch voltage, thanks. I was at Radio Shack earlier today and didn't see the perfect switch, got a 12v light though.
Yes, an idiot light for fuel pump is nice for idiots who forget to turn their pump back on (ALL THE TIME; ask my daughter, she'll confirm how many times I've done this in the year I've had the car, it's sad, especially when you're trouble shooting stuff and suddenly your car won't run for a completely different reason!)
Not sure I want a "green on" all the time though.
Maybe an illuminated switch that is lit red when off (pump off=light indicating that) but not lit when on (pump on=no light).
But I don't think that's a very common switch design either.
But, I've got two holes in my dash so I'd just as soon have a separate light anyway.

[newman27]

OK, I'll ask a stupid question (your signature line used to say that was OK ). Why doesn't the electric fuel pump come on with the key in the start position and shut off when the car is turned off? In other words, why the manual operation? I would label the switch "Ejection Seat" and tell your kids they better behave... Then again, I enjoy tormenting my kids...

Matt

[namba209]

Matt, I can't answer that specifically, but the GT in question has a carb, so all you need to do is turn on the pump for about 5-10 seconds to fill up the float chamber prior to starting and not be needed during the start cycle.

[jvandyke]

Originally Posted by newman27 OK, I'll ask a stupid question (your signature line used to say that was OK ). Why doesn't the electric fuel pump come on with the key in the start position and shut off when the car is turned off? In other words, why the manual operation? I would label the switch "Ejection Seat" and tell your kids they better behave... Then again, I enjoy tormenting my kids... Matt

Yes, I could just wire the pump to a switched source but it's nice to able to turn it off, there is no ACC position so when I'm working on the car or sitting waiting to pick up a kid or something I like to listen to the radio without the pump running.
Holes are already in the dash so better use them for something I guess.
I picked up an on/off/on mini rocker switch and I'll go with that.

[hrcollinsjr]

Originally Posted by jvandyke ...so when I'm working on the car or sitting waiting to pick up a kid or something I like to listen to the radio without the pump running.

How about just wiring your radio direct? You'll have to turn it off each time you turn the key off or use the new switch to turn the radio on/off instead of worrying about the pump. I would think that there is a greater draw on your battery with it in the run position.

Harold

[oldopelguy]

You could also hook up a very small indicator light between the ignition switch and the wire going to the fuel pump from the switch. If the indicator light is small, it won't pass a lot of current, not enough to actually run anything off of anyway. Thing is, when the fuel pump switch is off, the wire going to the fuel pump drops to ground voltage. Similarly, when the ignition switch is off the wires it sends to the coil and such drop to ground voltage. If you wire a small light between them it will illuminate whenever one of the switches is on and the other is off. That means:
-car on + fuel pump on = light off
-car off + fuel pump off = light off
-car on +fuel pump off = light on
-car off + fuel pump on = light on

So the light would be off under all "normal" conditions, and on during those abnormal ones when you need a reminder to do something with the switch.

[namba209]

A couple of things here, first I put a switch schematic in my earlier post in this thread. Second, according to my DESTEC schematic, the radio is supposed to be wired in to one of the 4 studs, specifically, the one with the buss bar that powers the clock, dome lite and cigarette lighter, so it always has power to it and is not powered by the ignition switch.

[jvandyke]

Thanks for the input. Good idea to wire the radio to always hot (but if I'm so forgetful to turn on my fuel pump, will I also leave the radio on? hmmmmm another idiot light!!)

[jeff denton]

I like Stephen's idea. It's that simple.
You do have a "no oil pressure" cutoff relay in the system, right?

[markandson]

If your current switch is momentary then use it to power up a latching relay circuit. The normally closed contacts of the relay could be used to power your pump off light and the normally open contacts would be used to power the pump. It's a pretty simple circuit.

[jvandyke]

Originally Posted by jeff denton I like Stephen's idea. It's that simple. You do have a "no oil pressure" cutoff relay in the system, right?

Not yet but it's on the list.

[jeff denton]

Where I meant to head with that was to point out that with the relay which we all previously once agreed was a critical safety feature (and mandated in our racing rules), whenever the engine isn't turning the fuel pump is not energized. Thus how could the fuel pump be accidently left on?
The momentary rocker could be used to "prime" the carb, it just bypasses the relay's function. On my Opel I do this with the starter switch, which is a SPDT momentary toggle. Pull it towards you to prime the carb. Push it away to crank the engine. To make it quit doing what you're using it for just let go of it.
If you need real electrical safety you want to put a battery switch in your car. Another racing rule. Shutting it off is the same as disconnecting your battery. What could go wrong then?
In boats with said battery switch they will wire two circuits around the cutoff. The bilge pump and the stereo memory. Otherwise the boat is electrically dead.

[jvandyke]

Well I went with plan A for now anyway. Ending up making my own light from parts of two, so it was small and flush. On/off/on mini rocker works as intended: down=pump on light off, up=pump off light on (only downside is there is a neutral where neither is on but even I can remember to push the rocker all the way up or down and not leave it inbetween). So PO's added dash holes are functional and I might spare myself some aborted take offs! It's all good. Thanks for the input! Got a first drive in the GT in a couple months with a sudden record warm up. Tempted to commute in it tomorrow but the speedo isn't working for some reason.

[jvandyke]

Picture of rocker and light can be seen here . (to left of stereo)
Light looks good when lit. Not too obnoxious sticking out of the dash like the old LED one did.

[heimue]

You can have it all, all you have to do is use one of the 3-position switches. The top position (referring to the drawing) would switch your pump (and light if you want) on (for priming), the center position sets it to automatic (pump on when ignition is on), the lower position is pump off (for maintenance or whatever).
The same switch and principle also comes in handy to switch your car stereo on/auto/off.

Dieter

[Dennis Texas]

How about having a relay activate the fuel pump that seals itself in when you turn key to start and stay energized until key is off that way you can listen to radio or anything else with key on and fuel pump wiill not be on until the car is actually put is the start position. If you desire a light it could be added to the contact for the seal in on relay. Just another opinion.

[jvandyke]

All good and interesting ideas. My original intent was to use the holes in the dash added by the PO for something other than nothing. Mission accomplished with the added bonus that I may be able to avoid trying to run my car without a fuel pump which doesn't work very well for very long
Hooking up the radio power supply to a non-switched hot is also easy and obvious, I just used the PO's wires when I put it in last spring. Should be easy to hunt down that hot and move it.

[jvandyke]

For some reason I've been blowing the fuse on the circuit my fuel pump runs through. Thought it was the switch so I just disconnected it and ran straight off one of the unused male spades on the fuse box. Blew another. Started rewiring the pump and a few questions.
What gauge wire would be appropriate to run back to the pump? What effect would too small a gauge have? Too light a gauge draw too many amps and blow fuses?
Also not sure my ground is good enough but would a flakey ground cause an intermittent fuse blow? Right now it's grounded to one of the pump mounting screws.

[namba209]

I would suggest a minimum of 14 gage wire. Too small a gage would act like a fusible link, meaning the wire would get hot and burn out, opening the circuit. The same thing would also happen with a flaky ground, intermittent circuit operation. If you have a sheet metal screw going in to the frame work or body, mounting the pump, it should create a good ground. I still think a 15 amp in line fuse will fix the problem.

[markandson]

The best way to know what to do is to know the amperage drawn by the pump. Either check the specs on the pump if they are available or put an ammeter in series with the positive lead to the pump, a good volt meter should also have ammeter capability. After you know what you need to supply then you can size the wires and fuse properly. Too small a wire can cause a fire and also starve the pump motor for amperage which could cause the pump to fail.