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> HOW TO: run the fuel pump for carb conversions, the easy solution!
SirAndy
post Feb 25 2005, 06:41 PM
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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 ...
(IMG:style_emoticons/default/smash.gif) Andy

(IMG:http://www.914world.com/bbs2/uploads/post-11-1109378319.jpg)

(IMG:http://www.914world.com/bbs2/uploads/post-11-1109378417.jpg)
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Jonathan Livesay
post Apr 5 2018, 01:24 PM
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QUOTE(SirAndy @ Feb 25 2005, 05:41 PM) *

HOW TO: Run the fuel pump for carb conversions

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)
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SirAndy
post Apr 5 2018, 02:05 PM
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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)

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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.
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Posts in this topic
SirAndy   HOW TO: run the fuel pump for carb conversions   Feb 25 2005, 06:41 PM
nebreitling   nice one!! straight to classics!...   Feb 25 2005, 06:48 PM
redshift   LOL Do you have more pics? Other angles? Can a pe...   Feb 25 2005, 06:51 PM
MarkV   Thanks, I am riunning mine off the coil. Whats up...   Feb 25 2005, 06:51 PM
914GT   Hey Andy... wouldn't a good German use a brown...   Feb 25 2005, 07:01 PM
rgalla9146   Hey Andy... wouldn't a good German use a brow...   Apr 5 2018, 06:01 PM
rhodyguy   super andy. http://www.914world...   Feb 25 2005, 07:10 PM
SirAndy   ...   Feb 25 2005, 07:31 PM
scott thacher   heres a minor twist to this system, on a 1.8 the f...   Feb 25 2005, 09:13 PM
914rat   I did this conversion and it didn't work.Where...   Nov 3 2011, 10:54 AM
McMark   Third position...   Nov 3 2011, 11:09 AM
Elliot Cannon   I powered my pump from this pin.   Nov 3 2011, 12:20 PM
anderssj   Another "twist" to this approach . . . ....   Nov 3 2011, 12:26 PM
ClayPerrine   Another "twist" to this approach . . . ...   Feb 7 2015, 04:28 PM
Elliot Cannon   Now everyone knows to trip the switch to disable ...   Feb 8 2015, 10:37 PM
Steve Pratel   Hmmm, anyone know how this would apply to the 912E...   Feb 8 2015, 03:05 PM
patssle   The awesome side-effect of this is you can easily ...   Feb 8 2015, 03:10 PM
Steve Pratel   So I've been researching how this applies to t...   Aug 27 2015, 09:50 PM
SKL1   Just got two of those inertia fuel cut off switche...   Aug 29 2015, 09:47 PM
Jonathan Livesay   HOW TO: Run the fuel pump for carb conversions I...   Apr 5 2018, 01:24 PM
SirAndy   I tried this on my '74 with carbs which had be...   Apr 5 2018, 02:05 PM
Jonathan Livesay   I tried this on my '74 with carbs which had b...   Apr 5 2018, 02:47 PM
SirAndy   Yes sir. I even put all 4 relays and both fuses in...   Apr 5 2018, 03:20 PM
Jonathan Livesay   Yes sir. I even put all 4 relays and both fuses i...   Apr 5 2018, 04:21 PM
SirAndy   Oops sorry the other tab, the "last ditch...   Apr 5 2018, 04:30 PM
Jonathan Livesay   Oops sorry the other tab, the "last ditch...   Apr 5 2018, 08:15 PM
SirAndy   So if all else fails I could run off the 12V side ...   Apr 5 2018, 08:20 PM
Jonathan Livesay   So if all else fails I could run off the 12V side...   Apr 5 2018, 09:50 PM
MarkV   Both relays need to be in place and working.   Apr 5 2018, 02:07 PM
porschetub   I had to do that "hack" because the corr...   Apr 5 2018, 07:07 PM
Noonan   So what's the correct fuse size for the fuel p...   Apr 6 2018, 09:27 AM
SirAndy   So what's the correct fuse size for the fuel ...   Apr 6 2018, 10:27 AM
Noonan   Oh yeah, there it is, had to zoom way in. Thank...   Apr 6 2018, 11:10 AM
Mark Henry   If you're like me, /6 conversion with no relay...   Apr 6 2018, 11:02 AM
mtndawg   Hi, resurrecting a classic. I have a 1975 and the ...   Apr 15 2019, 11:20 AM
Pdr1787   Hi everyone, Long story short, someone cut my mai...   Jun 5 2020, 07:05 PM


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