what kind of fuel pump to use on efi to carb switch?
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If this is a 93 or earlier model mustang your job will not be too hard. The 94 and later model cars intergrate the computer control into more systems and do not lend themselves to carb conversion unless you are very good in the electrical department. The electrical complexity of the EFI system is what most guys don't understand and is the motivation to switch to a carb'd engine.
A low pressure pump with 7-12 PSI output is what is recommeded for carb use. Plan on using a pressure regulator near the carb for the final pressure setting of 5-7 PSI. Do not use the EFI computer to control either the fuel pump or ignition system. There are correct ways of doing these chores, and using the old computer isn't one of them.
Use the red/green wire on the coil to provide a trigger for the new fuel pump relay. Run a 14 gauge wire from the battery or fuse panel to the power side of the relay and fuse it with a 15 amp fuse. Run a 14 gauge wire to the fuel pump and from the fuel pump to ground. Check with the fuel pump manufacturer for the current requirements for the pump you select. A pump that draws more current will require a larger wire size and fuse. Do not under or overfuse the wiring unless you are looking for trouble.
AutoZone wiring diagrams
http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs
Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.
Do not attempt to leave the EFI in place in an attempt to control either the electric fuel pump or ignition. Doing so qualifies you for the “Road Kill Mechanics Award”.
If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.
You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See http://www.amazonhose.com for more information.
While you are at the electrical part, you'll need a Durspark or similar ignition system. The 85 Mustang GT 5 speed has a suitable Duraspark distributor with a steel gear compatible with the roller camshaft. The EFI ignition depends on the EFI sensors to advance the spark. Rip out the TPS and MAP/Baro sensors and the computer will have no idea of the proper ignition timing for best performance. Running a fixed timing setting is only for test purposes or for a race track only car. Don't try it on the street: the results will not be nearly as good as a properly setup Durspark or equal. Crane makes a really nice distributor for non-EFI applications. . See http://www.cranecams.com/index.php?show=browseParts&lvl=4&prt=127 for more information.
A low pressure pump with 7-12 PSI output is what is recommeded for carb use. Plan on using a pressure regulator near the carb for the final pressure setting of 5-7 PSI. Do not use the EFI computer to control either the fuel pump or ignition system. There are correct ways of doing these chores, and using the old computer isn't one of them.
Use the red/green wire on the coil to provide a trigger for the new fuel pump relay. Run a 14 gauge wire from the battery or fuse panel to the power side of the relay and fuse it with a 15 amp fuse. Run a 14 gauge wire to the fuel pump and from the fuel pump to ground. Check with the fuel pump manufacturer for the current requirements for the pump you select. A pump that draws more current will require a larger wire size and fuse. Do not under or overfuse the wiring unless you are looking for trouble.
AutoZone wiring diagrams
http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs
Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.
Do not attempt to leave the EFI in place in an attempt to control either the electric fuel pump or ignition. Doing so qualifies you for the “Road Kill Mechanics Award”.
If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.
You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See http://www.amazonhose.com for more information.
While you are at the electrical part, you'll need a Durspark or similar ignition system. The 85 Mustang GT 5 speed has a suitable Duraspark distributor with a steel gear compatible with the roller camshaft. The EFI ignition depends on the EFI sensors to advance the spark. Rip out the TPS and MAP/Baro sensors and the computer will have no idea of the proper ignition timing for best performance. Running a fixed timing setting is only for test purposes or for a race track only car. Don't try it on the street: the results will not be nearly as good as a properly setup Durspark or equal. Crane makes a really nice distributor for non-EFI applications. . See http://www.cranecams.com/index.php?show=browseParts&lvl=4&prt=127 for more information.
Try www.holley.com they will have a pump and regulator that you can use. They helped me get mine running.
z2o_what
Member
i found it to be alot cheaper to change the timing cover and run a mech. pump.
and, of course you will have to replace the stock pump with a piece of hose or get a carb pick-up.
and, of course you will have to replace the stock pump with a piece of hose or get a carb pick-up.
81maroonhatch
New Member
i plan on doing this to my mustang heres my question when i get a duraspark ignition where does the negitive end of the coil come from
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