Back by popular demand, Sir Andy's "HOW TO" series presents:

HOW TO: Run the fuel pump for carb conversions

There are numerous tech. articles out there that cover this issue.
When you switch from the stock FI to carburetors, you have to install a low pressure carb fuel-pump.
But, since the FI fuel pump is controlled by the FI brain, removing the brain means the wires to the fuel pump won't give you 12V ...

There are a lot of "band-aid" solutions out there, some people remove the pump relay and add a jumper there, others even run the pump off the coil!
While all those solutions work (more or less) they all lack one thing, you're now running the pump without a relay! (and in case of the coil, without fuse as well)

The best (and also easiest!) solution is to trick the relayboard into believing that the FI-Brain is still connected ...

And it's as simple as connecting one wire from the 4-prong FI connector to ground.
You keep the stock fuel pump relay and fuse and you use the stock wires to power the new fuel pump.
Below you'll see 2 pictures showing how to attach the wire. on the pump side, simple make 2 more extension wires with "male" connectors on one end and plug them into the stock (roundish) plug for the stock fuel pump.
No need to hack into the original harness!!!

This install is clean and simple! (and cheap!)

In the pics below the thick red wired replaces the FI-Brain ...
Andy

nice one!! straight to classics!!!

LOL

Do you have more pics? Other angles? Can a person with a wire, and two crimpy ends do this in less than a minute?

Who took that picture?


M

Thanks, I am riunning mine off the coil.

Whats up with the green wire pulled out of the harness in photo #2 ?

Hey Andy... wouldn't a good German use a brown wire?

super andy. . straight to classic. i will be changing to this method.

k

yes ...


yes ...


me, myself and i ...


the engine harness is from my old 1.8L which had the green wire for the heater blower in the engine harness. my car now has a '74 (?) main harness and the wires (green/brown) for the heater blower are spliced off the the main harness instead.
i didn't want to cut the hard plastic protection of my engine harness to remove the wire but i had to take it out of the connector as the layout of the prongs changed between '70 and '74 ...


yes, but i didn't have any handy besides the red one. some day, i'll change it to brown.
not on top of my list right now ...

Andy

heres a minor twist to this system, on a 1.8 the fuel pump relay is in the relay pack, so no relay there. what i did is to put a realy in the fuel relay spot as a spare, and i had a short wire from the screw that hold the realy board in place with a connector on it, when ever the fuel pump was needed or the relay pack was acting funny i just pluged it in.

now on the suby harness i an using the suby fuel pump relay to ground the stock fuel pump relay out through that pin , that way the suby brain still sees the suby relay in its wiring and it does its job

I did this conversion and it didn't work.Where is the relay so I can see if it's still good.Had to go back to running it off the coil.

Third position...

I powered my pump from this pin.

Another "twist" to this approach . . . .

Because the pump will run as long as the key is in the "on" position, I wired a fuel pump inertial switch (from a Ford ) into the wire running from the 4-prong FI connector to ground (the "red" wire in Andy's pictures). That way if the car is in an accident, the ground is "interrupted" and the fuel pump stops (NOTE: this is a little different from Ford's approach, which puts the switch on the hot side of the pump instead of the ground).

Here's a picture of the switch:

Click to view attachment

The switch costs 25-30 new at your FLAPS; I got a couple of used ones at the local pick-n-pull for a couple of bucks each.

These switches have been known to go bad once in a while, but mine has been good for a couple of years.

Here's a link to a site that provides some good info on the switch:

http://www.therangerstation.com/tech_libra...rtiaSwitch.html

Instructions for installing the Smart Racing Products (SRP) version of the switch are here:

http://www.smartracingproducts.com/pdfdocs...fuelshutoff.pdf

My switch is currently mounted near the ground post just forward of the relay board cover. I'm thinking of putting it in the + side like Ford did--and as recommended in the SRP instructions. Then I should be able to mount the switch somewhere in the passenger footwell.

Hope this helps!

Now everyone knows to trip the switch to disable your car.

I did that back in 89 while Christmas shopping at the mall. I was driving an old Dodge Aspen, and was waiting for a parking space. The person in the space backed out toward me, and a "Female Dog" in a Lincoln Town car cut right in front of the car backing out and quickly pulled into the space. She jumped from the car and took off into the mall. So I just pulled up and bumped her car with the old Dodge.

Later I came out to put some packages in the trunk of the Dodge, just to hear her grinding away on the starter till the battery died. I went back in the mall and when I came out again, the wrecker was pulling the Town Car out of the parking space.

I so wanted to tell her what happened after the car was on the flatbed on it's way to the shop, but I didn't get the chance.

Hmmm, anyone know how this would apply to the 912E? I wasnt thinking about this at all, I assumed the fuel pump relay was powered on and off with ignition

The awesome side-effect of this is you can easily disable the fuel pump when you want to leave the key on if you're working on the car. No need to have the fuel pump on. Just disconnect the cable!

Also even if you're not using the other 2 or 3 relays...keep one on the board for a backup.

Disabling some ones car because they parked like a dick, pretty makes you a DICK!

So I've been researching how this applies to the 912E, and have come up with a couple options. Someone on the 912E board suggested to wire it directly with an oil pump cut off switch, and I found this website

http://www.how-to-build-hotrods.com/electric-fuel-pump.html

It seems like a good way to do this. Has anyone tried this? Makes sense to me, especially as it retains the pump while crank ability. Here is a schematic for the oil pressure switch.

Click to view attachment

The 912E has a double relay for the fuel pump. One side is connected to a wire harness that runs to the vehicle, the other half ran to the brain. I've managed to do most of my modifications leaving most of the stock wiring and such in tact, so I'd like to keep doing that and just jump the other side of the relay through an oil pressure switch. I'm thinking to find the pin that grounds the relay in the run position (like the jumper in this thread) run it through the OP switch and call it done. This would keep the run while starting function and the on while running with oil pressure feature, and in the case of a stall, key left on, etc. Fuel pump will not run.

But some good news, I put 5 gallons of fuel in the tank tonight and pumped about 2 quarts into a glass jar, with no filter to clean out any debris or crap in the lines and it came out clean as a whistle. After letting it sit for a few days will do it again to see if fuel in the lind=es loosened up any crud. I even poured it through a paper filter back into the gas can and there was little to no debris in the paper. Looks like I got a great tank!

Just got two of those inertia fuel cut off switches from Summit Racing- supposed for a Ford and look a little different than the ones in this thread. This was discussed on a thread a couple weeks ago I haven't been able to relocate on the search function.

They came with no instructions but I put the switch in the front trunk near the pump next to the spare tire on my '73. I luckily mounted it vertically (as instructed in the switch on this thread) and "assume" that is correct. I have sent a question to customer service at Summit to confirm.

Need to install it on my '71 but will wait to confirm that this model is also supposed to be mounted vertically.

Will be some piece of mind, though I must admit I've been driving the '71 with carbs without the switch for over 15 years! Luckily no issues but I don't drive it a lot...

I tried this on my '74 with carbs which had been running the fuel pump off the coil. No luck, checked the black/red wire at pin 13 for continuity to the original fuel pump plug and that was good , double checked that my ground on the 4 tab connector was good, but still nothing. I traced the black/red wire from pin 12 which used to go to the aux. air regulator in the FI harness but was now cut off near the distributor, and had continuity all the way back to the fuel pump plug. Get everything but volts when I turn on the key. Fuel pump turns on with key when I plug it into the other tab on the 4 tab connector. Any ideas what I am missing here? Or what else I can try? Any guidance would be greatly appreciated.

Are all the relays in place and working properly?

Both relays need to be in place and working.

Yes sir. I even put all 4 relays and both fuses in and tried the relays in every conceivable variation in case one was bad. I realize that some of the relays don't do anything, but just in case I misunderstood which were the power and fuel pump relays. The 12 volts to the tab on the 4 tab connector comes through the power relay doesn't it?

The *ground* wire on the 4-tab connector grounds the relay so it can provide 12V to the fuel pump.
Normally, that ground switching is done by the FI brain.

In hindsight, i probably should not have used a red wire for ground.

Oops sorry the other tab, the "last ditch" nonfused power for fuel pump tab (the one opposite the ground tab. The one that Elliot Cannon pictured in post 11 on this thread. I am just wondering if the fact that that one runs the pump means that the power relay is OK. Could my relay board have an issue?

Yes, yes and yes.

That one comes off the power relay and should have 12V .
And yes, the relay board can certainly be kaputt, the solder connections can come lose. Have you checked the underside?


The whole reason i did this writeup was to show people that you can use all the existing wiring and relays to run your carb fuel-pump without any hacks.

And yes, i consider pumping 12V from a different relay into the fuel pump feed wire a "hack".

I agree
But a great write up.
An easy and correct way to avoid a
sketchy arrangement !

I had to do that "hack" because the correct feed had no power even after trying several relays ,ennoying as I cleaned up the board and resealed the base without testing
Ran it through an redundant relay and put inline fuse in ,have a replacement board to go in soon.
I'am checking into a hidden switch to shut the pump off also have a few idea's.

So if all else fails I could run off the 12V side of the 4 tab connector through an in line fuse under the relay board cover to the fuel pump and no one but me (and you I guess) would ever know. Would that still be a hack?

Yes and yes ...

So what's the correct fuse size for the fuel pump?

SirAndy has an 8amp, Elliot has a 16amp, the wiring diagram shows a 25amp and I have a 16amp (which may make sense as I don't have rear defrost)




On the same note, what's the upper fuse position for? It's blank in the wiring diagram

Click to view attachment

If you look again, you can see that i have a blue fuse in there, the white one is in the top slot, which if i recall correctly is for the optional rear window heater.

If you're like me, /6 conversion with no relay board you can run a VW 321 906 059C relay.
It uses the tach signal (lack of) to cut power. Faster action than a relay using the oil pressure switch.

Only drawback is no power till it sees a tach signal, not an issue on start-up with carbs with full float bowls. You would have to jump the relay if they were empty, like in first engine start or after carb service.

Oh yeah, there it is, had to zoom way in.

Thanks!

Hi, resurrecting a classic. I have a 1975 and the previous owner did not have the car set up to shut off the fuel pump when the engine is off. I’ve made a short wire to ground from the tab on the relay board, just like the red wire in the photo. Under my fuel tank in the front, the original wires are powering a pierburg pump. I’m not clear what I need to change in the wiring connectected to the pump to make this work?

Hi everyone,

Long story short, someone cut my main harness to rig up my car to work. The relay board was toosed as well .Now I have rewired and fixed the main wiring harness. bought a relay board and ignition harness (I have a carb set-up now). I do not see any wiring leading to the fuel pump. How do I go about this?? Thanks in advance