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> HOW TO: run the fuel pump for carb conversions, the easy solution!
MarkV
post Apr 5 2018, 02:07 PM
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Both relays need to be in place and working.
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Jonathan Livesay
post Apr 5 2018, 02:47 PM
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QUOTE(SirAndy @ Apr 5 2018, 01:05 PM) *

QUOTE(Jonathan Livesay @ Apr 5 2018, 12:24 PM) *
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. (IMG:style_emoticons/default/idea.gif)

Are all the relays in place and working properly?
(IMG:style_emoticons/default/idea.gif)

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?
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SirAndy
post Apr 5 2018, 03:20 PM
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QUOTE(Jonathan Livesay @ Apr 5 2018, 01:47 PM) *
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.
(IMG:style_emoticons/default/rolleyes.gif)
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Jonathan Livesay
post Apr 5 2018, 04:21 PM
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QUOTE(SirAndy @ Apr 5 2018, 02:20 PM) *

QUOTE(Jonathan Livesay @ Apr 5 2018, 01:47 PM) *
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.
(IMG:style_emoticons/default/rolleyes.gif)

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?
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SirAndy
post Apr 5 2018, 04:30 PM
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QUOTE(Jonathan Livesay @ Apr 5 2018, 03:21 PM) *
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".
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rgalla9146
post Apr 5 2018, 06:01 PM
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QUOTE(914GT @ Feb 25 2005, 09:01 PM) *

Hey Andy... wouldn't a good German use a brown wire? <!-- emo&:) -->(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)<!-- endemo -->


I agree (IMG:style_emoticons/default/smile.gif)
But a great write up.
An easy and correct way to avoid a
sketchy arrangement !
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porschetub
post Apr 5 2018, 07:07 PM
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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 (IMG:style_emoticons/default/headbang.gif)
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.
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Jonathan Livesay
post Apr 5 2018, 08:15 PM
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QUOTE(SirAndy @ Apr 5 2018, 03:30 PM) *

QUOTE(Jonathan Livesay @ Apr 5 2018, 03:21 PM) *
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".
(IMG:style_emoticons/default/shades.gif)

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? (IMG:style_emoticons/default/smile.gif)
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SirAndy
post Apr 5 2018, 08:20 PM
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QUOTE(Jonathan Livesay @ Apr 5 2018, 07:15 PM) *
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? (IMG:style_emoticons/default/smile.gif)

Yes and yes ...
(IMG:style_emoticons/default/biggrin.gif)
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Jonathan Livesay
post Apr 5 2018, 09:50 PM
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QUOTE(SirAndy @ Apr 5 2018, 07:20 PM) *

QUOTE(Jonathan Livesay @ Apr 5 2018, 07:15 PM) *
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? (IMG:style_emoticons/default/smile.gif)

Yes and yes ...
(IMG:style_emoticons/default/biggrin.gif)

(IMG:style_emoticons/default/biggrin.gif)
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Noonan
post Apr 6 2018, 09:27 AM
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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

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SirAndy
post Apr 6 2018, 10:27 AM
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QUOTE(Noonan @ Apr 6 2018, 08:27 AM) *

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

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.
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Mark Henry
post Apr 6 2018, 11:02 AM
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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.
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Noonan
post Apr 6 2018, 11:10 AM
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QUOTE
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.
(IMG:style_emoticons/default/shades.gif)


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

Thanks!
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mtndawg
post Apr 15 2019, 11:20 AM
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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?
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Pdr1787
post Jun 5 2020, 07:05 PM
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Hi everyone,

Long story short, someone cut my main harness to rig up my car to work. The relay board was toosed as well (IMG:style_emoticons/default/headbang.gif) .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
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