carb swap fuel presure to high

I'll spare you the usual rude comments I make about EFI to carb conversions and tell you simply - Do it the right way .

Most of the poorly done carb conversions use the stock EFI electric fuel pump. They drop the 40+ PSI down to the 4-6 PSI needed for the carb with a shunt return regulator. That is not the proper way to do it. If the shunt regulator fails, it will flood the engine and wash all the oil from the cylinder walls causing the pistons and rings to score the cylinder walls.

The proper way to do it is with a pickup that replaces the EFI pump and a electric fuel pump designed for carbs. You will have the 4-6 PSI you need to make the carb work correctly and will not flood if it fails.

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 an external electric fuel pump unless you change the timing cover for one with the mechanical fuel pump mount on it. Rip all the EFI wiring out, and the computer controlled fuel pump won't work. You will need to add a relay & switch and wire in the existing inertia switch for an external low pressure electric fuel pump. Do not try to wire the fuel pump without the relay. The 15-20 amps the pump pulls will overload the circuit. This will take power away from other items on the same circuit or cause the fuse or fuse link to blow.



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 Amazon Hose - Rubber, Hydraulic and Industrial Hose - since 1919 for more information.

For some help fabricating your own stainless steel hose assemblies, see
www.TurbineFun.com

For stainless steel braided hose and fittings for automotive use:

See Search Results for stainless steel hose - SummitRacing.com
Search Results for stainless steel hose - SummitRacing.com

stainless steel hose - JEGS High Performance

See http://www.aeroquip.com/pages/performance.html for more information on High performance automotive hose products

AN fittings require a 37 degree flaring tool. A standard automotive or household plumbing tool is 45 degrees and cannot be used with AN flare fittings. If you do, the flare is subjected to too much stress when the fitting is tightened, and is likely to fail or leak.

See MSC Industrial Supply Co. , McMaster-Carr or for the flaring tool you will need . Prices start at $85 and go up

MSC Industrial Supply Co.


McMaster-Carr


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 Crane Cams | Automotive Home Page for more information. Cost is about $400, which makes the 85 Mustang reman units look really appealing.

Tools needed:
Crimp tool for connector pins $9-$30 AutoZone, NAPA, Advance Auto Parts or other store
100-150 watt soldering gun (recommend WELLER 8200PK soldering gun kit 100/140W) $30 at Lowes or $40 at Home Depot
3/32”-1/8” rosin core electrical solder, 1/4 lb roll $6 at Ace Hardware, Home Depot or Lowes
Assorted sizes of heat shrink tubing. Buy long pieces and cut length to fit. It is cheaper that way. Parts-Express.com - Heat Shrink Index: 2:1 Ratio, 3:1 Ratio, Heat Shrink Kits
Hot air gun to shrink the tubing ($30-$40) Home Depot
Jeweler’s screwdriver kit $5 at Ace Hardware
Assorted automotive wire, 18-16 gauge 10’-20’ foot spools in different colors. $5 a roll at Advance Auto Parts.
Ford connector pins AutoZone, NAPA or other store $5-$10 for a kit of 10-12 assorted pins

You will have $110-$150 in materials and tools if you don't already have them.

The water temp and oil pressure signals feed from the sender to the main harness through the 10 pin EFI engine harness. To utilize these senders, you need to identify the wires and find a way to reconnect them to the main harness after the EFI engine harness is removed. You need a weatherproof quick connector to join the sender wiring to the main harness.


You will need to construct a wiring harness from the ‘85 carb distributor to the Duraspark box if you go Duraspark, or other distributor to coil wiring.
The voltmeter picks up its signal from the switched voltage present on the instrument panel, so you don’t need to worry about that.

The fuel tank gauge is also independent of the computer wiring.

AutoZone wiring diagrams can be found if you are willing to dig through the self help repair section of their website. Repair Info | AutoZone.com

How to solder like a pro - Ford Fuel Injection » How To Solder Like a Pro a must read for any automotive wiring job.

Soldering pigtails onto existing pins is road kill quality work as far as I am concerned. Take some time to study the way the Ford connectors are assembled and you will find that a small jeweler’s screwdriver will release the pins from the connector shell. New pins and a crimping tool are available from the Standard Motor Parts or Bendix Electrical parts line that the NAPA & Bumper to Bumper Auto Parts stores carry. Ask any auto parts store about Standard Motor Products or Bendix Electrical wiring parts. Those that carry them will be able to get the parts you need. AutoZone has a cheap kit with 10 pins for about $5. Just enough pins to leave you short when assembling a connector.

One of the interesting things about the Ford OEM wiring diagrams is that the connector shape on the drawing matches the connector shape in the car. That makes it easier to identify connectors and circuits. OEM Ford diagrams are available at for an 85 Mustang at Helm Incorporated: Search Results or can be found in the Chilton series of auto repair manuals for Mustangs.

The following is an excellent idea from a fellow Stangnetter who tackled the wiring plan the right way. He obtained the wiring diagrams from an 85 carb'd V8 Mustang and laid them out side by side with the diagrams from his car. He then traced out each circuit and the wire colors and connectors associated with them. After tracing the circuit and connectors for a circuit, he laid out the changes he needed to make. One circuit at a time made a difficult big job into many smaller easy to manage jobs.

Double post, ISP hicupped...

My 93 is now carb'd but I used NONE of the EFI parts to make it work...
Fuel pump is a holley blue with regulator, down to 7 psi, a holley vacuum secondaries 650cfm, with a bit of a lean idle. It works very well with this setup. I didn't use the stock fuel pump relay either, I used my own, and ran it to a switch I control on the ash tray door cover. Using any efi leftovers and then asking about it here will only get you tons of smartass answers from some "holier than thou" members....

The blue Holley is ur best bet. It comes with a regulator. U just need a gauge mounted somewhere. My pump is bolted to spare tire well under the car right ahead of the differential. Noisy, but it works. My fuel tank is dumped so the pump gets fuel from the lowest part of the tank.

on some of the pre 92 they use the connectors next to the booster to feed the guages inside and the fuel pump but on the 92-93 they only have one connector next to the booster. is that connector feeding the guages and coil?

93project said:

My 93 is now carb'd but I used NONE of the EFI parts to make it work...
Fuel pump is a holley blue with regulator, down to 7 psi, a holley vacuum secondaries 650cfm, with a bit of a lean idle. It works very well with this setup. I didn't use the stock fuel pump relay either, I used my own, and ran it to a switch I control on the ash tray door cover. Using any efi leftovers and then asking about it here will only get you tons of smartass answers from some "holier than thou" members....

Click to expand...

From one of the "holier than thou members" you got the electric fuel pump puzzle 75% right. Using a switch to control the electric fuel pump isn't the recommended procedure. A search would have turned up the electric fuel pump diagram I posted above. It shows the right way to use a relay to control the electric fuel pump.


My opinion: putting a carb on a car originally equipped with EFI is like putting a mustache on Leonardo Di Vinci's Mona Lisa. It just isn't right. It shows a lack of education, understanding and appreciation. Carbs have their place on NASCAR and racetrack only applications, but a street driven car that originally had EFI isn't one of those places. The 5.0 Mustang's EFI system is simple to work on, efficient and reliable. In the 19+ years & 275,000+ miles I have been driving and fixing 5.0 Mustangs, the EFI has never been a problem. Fuel pumps and an ignition coil have been the only headaches in the engine management area.

Joe R.

Well, no offense. I've always appreciated the info you've posted.and have used some of it. My switched relay set up works juuust fine. And as for using carbs where there was efi.... I did this because I grew tired of soldering my severely damaged harness. It had burn damage, melted o2 connectors, etc. Just didn't seem worth it for a hobby car....

i must be uneducated, non understanding or appreciative or im just tired of watching my bank account drain trying to get the kinks worked out of my efi. i just want to drive the damn thing and if i went carb from the beginning and did not buy every part to the efi (everything was gone) i would have it tagged and on the road a long time ago and for a grand or so less in cash. im going to go at the efi one more hard time and if i cant get the tune right im going to the carb also.

1bad67sbf said:

i must be uneducated, non understanding or appreciative or im just tired of watching my bank account drain trying to get the kinks worked out of my efi. i just want to drive the damn thing and if i went carb from the beginning and did not buy every part to the efi (everything was gone) i would have it tagged and on the road a long time ago and for a grand or so less in cash. im going to go at the efi one more hard time and if i cant get the tune right im going to the carb also.

Click to expand...

Post your EFI problems and I will do my best to help you.

Opinions are like noses: everybody has one. When you post on Stangnet, you open the hood of your virtual car and invite everyone to poke their nose in your business. Be prepared to hear some things you don't like. Some of those things are right, some of the are wrong - just don't get your nose out of joint because of them.

Quality, quality, quality…
Some of the motivation of my negative comments about carb to EFI has to do with the quality of workmanship. A lot of the “repairs” that I have seen on the road and while prowling in the junkyards looks like road kill.

If you are one of those few people who do excellent work, please disregard my negative comments. They are not intended for you.

i undertand what you are saying and i would rather have efi, thats why i have been trying for so long. i think my main issue is to many used ebay parts. they are ok if your fixing a repair but building one up from the ground i should have got more new parts/sensors to not have the fight i now have. i will let you know if i need advice, thanks