easy fuel pump wiring question...

I'm hookin' up a holley blue to my 67, and i'm not sure how to hook in a kill switch for it. Also, how do i get it to just fill the line and only run the pump when i need gas? I had it hooked up all cruddy as a test to get some ideas, but when I turned the key in the on position, the fuel pump didn't stop running.

Just to be more clear, my friend's '93 will turn the pump on when the key is in the on position, and then stop. Obviously, there are alot of differences between my carbed '67 and his, but I need some recommendations guys. Even the basics, down to relays and fuses! Thanks!

Things that may be important:

MSD 6al
msd dist.
msd coil
oil pump safety switch



<font size=-1>[ This Message was edited by: cward8 on 10/18/02 9:31am ]</font>

Well, the 93.. Th comp controls the fuel pump mostly. It will turn on for 1-3seconds, and then turn off unless the engine is cranking. You wouldn't be able to do that easily on your non-computer controlled car.

I usually see electric pumps hooked up like this.

1 30amp Relay, (of course you can wire it properly, i won't go into that)
1 oil pressure shut off switch (opens ground when oil pressure drops to a pre-determined pressure, usually 1.5psi or so)

Wired te relay into a circut that is only powered when in "run" position.. So when the car is running, and theres (hopefully!) oil pressure, it just keeps the relay powered.. No problems there.. If for some reason the engine stalls, theres no oil pressure, and the switch opens the ground, the fuel pump turns off. I would think that most people have a manual bypass to activate the f/p when they want to (I know I would).. Such as the first time you start the car, might no be any fuel in the bowls..

You can get the o/p switch from summit/jegs and the likes..

I second that.

You want to run +12(RUN ONLY)---pressure switch---fuel pump. Ground is ground.

But as the previous post says you have to get around the pressure switch.

You can have the coil (POS) feed a relay that feeds you +12V run. Know how to hook that up?

You could always bypass the oil press switch while you're under the hood on those rare days when there's no fuel in the bowls.

Auto shutoff is a computer function. I have a small switch wired in series with a late model intertia shutoff switch connected to a 30amp relay's coil terminal. You don't have any choice really - when the ignition is on, the pump runs unless you wire in a near-the-dash kill switch which you then control. Wire in the intertia switch (they are in the rear/trunk of about all fuel injected Fords) so that when you get thumped the pump will stop. The oil presssure switch is good, but can be a real pain in a street/strip car. I like to switch my pump off and run out the carb before I pull it for tuning or letting the car sit for a while. If you wire in an oil pressure switch, you'll need to wire an override switch for "carb empty" situations. I can run the motor about 2 minutes with the pump off, so I see little use for an oil pressure shutoff switch.
[addsig]

for a bypass switch use a spring loaded one that you have to hold on. That way you would accidently leave it on. Otherwise it'll override your pressure switch safety feature

Whoo! Thanks for the replies everyone. I'm such a noob to electrical stuff, some of this is very difficult for me to visualize. I was already planning on maybe bypassing the oil pump safety switch because it doesn't seem like it helps much. If I'm cruisin' and lose oil pressure, the motor is still gonna run until the bowl is empty?! However, if hooking it will still work with what I'm doing, that's great. I mentioned before that I wired it up really poorly to see what would happen. I made a diagram here, and it's really really embarrassing. Please do not laugh! hehehehehe [img]/phpBB/images/smiles/icon_lol.gif[/img] I can see melted wires and blown fuses with this setup! Not to mention the switch doesn't work!

http://users.superford.org/cward8/fpwire.jpg

Anyway, what kind of damage can occur if the key was just left in the on position and the fuel pump just kept running? The way it was originally wired in, was it ran from the pump to the solenoid, then to the msd6al (?) and would only run when I was cranking or the car was running. It stopped working right though and only worked when I was cranking. Thanks again all. (BTW - Anyone know a place to see a diagram about wiring in a relay?)

<font size=-1>[ This Message was edited by: cward8 on 10/19/02 1:07am ]</font>

http://www.designtech-intl.com/conte..._04_111_02.pdf
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Depends on the setup. If you have a deadhead regulator (tank--pump---reg---carb), then the pump justs beats itself to death against the regulator. As long as the regulator is set to deliver pressure below what it takes to knock the carb needle off it's seat (usually &lt;6.5 PSI), nothing else will happen except noise (LOTs of noise with a Holley Blue). If you run a return setup (tank--pump--carb--reg--tank), then the fuel just recirculates; the warning about pressure at the carb still applies. The regulator pressure should be set with the engine running.

Based on Larry's supplied diagram, here's a potential wiring setup:

Switched + ignition -->85 (terminal on relay)
Ground --------------->86
Battery feed --------->30
Fuel pump + ---------->87
Fuel pump - ---------->frame ground

Note: You put your kill switch and intertia switch in the wire between ground and pin 86. Breaking this wire opens the relay and stops the pump. USE A FUSE ON ALL POWER FEEDS. About 2 amp on the ignition leg and 20 amp on the pump feed from the battery, depending on the pump current rating.

[addsig]

I cannot thank you all enough for the great help, as soon as I get a chance I'm gonna start wiring it up! I'm sure I'll have more questions when doing it, but we'll see what happens!

Ok guys, got everything I need to wire this up, and been reading a bit to get a clearer idea of everything. I think I have a good understanding now of the way this must be wired up, but I was wondering...

The way I plan on wiring it up now, is to forget about the oil pump safety switch altogether. I'm going to wire in a toggle switch and relay as a good theft deterrent and a great way to make sure the bowls of the carb are empty when I need to pull them off. My question is, does this make the oil pump safety switch completely useless to me? Obviously it will no longer kill fuel when pressure reaches a certain psi, but is there another way I can wire it up so that an idiot light goes off? Or maybe I can wire to the MSD box so it cuts spark?

Right now, the fuel pump lead is going to the solenoid, and then straight to the MSD box. Only one wire from the MSD box is running to the oil pump safety switch. However there are 3 prongs on the switch. Holley's site doesn't help me much, and I checked out the MSD site also, with little help. My problem is that the fuel would work when cranking, but not when running. Could this be because of a low oil pressure situation? Maybe the wiring was ok before (I'm going to change it anyway), but it quit because the safety switch was killing the pump after cranking? Why is the wiring running through the MSD box?

Sorry for so many questions in one post, but this is driving me mad. Also, I find all of this electrical stuff very interesting. [img]/phpBB/images/smiles/icon_cool.gif[/img]