 HOW TO: run the fuel pump for carb conversions, the easy solution! |
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| SirAndy |
  Feb 25 2005, 06:41 PM
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#1
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Resident German  Group: Admin Posts: 42,366 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California  |
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 |
Apr 5 2018, 01:24 PM
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#2
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Senior Member Group: Members Posts: 746 Joined: 13-March 10 From: La Canada CA Member No.: 11,461 Region Association: None 
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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 |
Apr 5 2018, 02:05 PM
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#3
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Resident German Group: Admin Posts: 42,366 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
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 |
Apr 5 2018, 02:47 PM
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#4
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Senior Member Group: Members Posts: 746 Joined: 13-March 10 From: La Canada CA Member No.: 11,461 Region Association: None
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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 |
Apr 5 2018, 03:20 PM
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#5
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Resident German Group: Admin Posts: 42,366 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
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 |
Apr 5 2018, 04:21 PM
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#6
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Senior Member Group: Members Posts: 746 Joined: 13-March 10 From: La Canada CA Member No.: 11,461 Region Association: None
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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 |
Apr 5 2018, 04:30 PM
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#7
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Resident German Group: Admin Posts: 42,366 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
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) |
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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
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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