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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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Bulldog9
post Aug 27 2015, 09:50 PM
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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.

Attached Image

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!
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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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