efi to carb: neeed to ask a few things

I re-read your previous post "HELP: '87 runs super rich and dies if it idles lower then 1,900 rpms" and it seems that you left a lot undone in the diagnostic/discovery process. No code 11 and the computer has problems. It sounds like your wiring is a hack job, Mustangs never came with a push button for the starter.

87fromMI said:

while i was looking at the wiring diagram, I looked at the black/white 46. The first thing it passes through is the neutral gear switch. mine is broken. they just took a piece of speaker wire and jumped the starter solenoid and connected it to a push button to start it, its kinda rigged up but works. if that switch doesn't work, will it inhibit the flow of electricity through the system. the car doesn't start by turning the key. you have to turn the key to give everything power then hit the button to turn the motor over, if the car isn't in neutral or the clutch isn't pushed in and you hit the button the car will role forward because of the starter

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That may affect how the starter works, but it will not affect the computer in the manner your post describes, making the engine run rich and not idle. What will happen is that you may not be able to dump the engine running codes.

It is possible that the O2 sensor wiring harness is damaged or missing, seeing that some of the starter circuit wiring has been tampered with.

Diagram courtesy of Tmoss & Stang&2birds



The Mass Air conversion requires moving wiring pins in the existing computer wiring harness, adding some pins and wiring for the MAF, or replacing the computer wiring harness with one from a 89 or later 5.0 Mustang. The Mass air harness is not compatible with the Speed Density computer. You cannot swap computer back and forth without changing the wiring and pins to match the computer. I did not get the impression that you had done that when you switched computers.

87fromMI said:

Well my '87 lx had a really bad electrical problem, so I had a carb and intake in the barn I put on it. im 17 and dont have help with it, so im trying to make shure i do this righ and dont rig it up, or buy parts that are good enough or wont work. Heres the parts i have"

• oem 85 distrutor w/ steel gear
• holley 600
• edelbrock 289 performer intake

1. Now I need to find a fuel pump. the local parts store carrys the MR. Gasket 12S fuel pump that puts out 7psi and 35gph. would that be good enough? also what kind of regulator should i run with it?
2. next is i have the oem cardone replacement distributor for a '85. I believe i have to change the ignition system to work. I have a msd 6al box and coil, would that work?
3. And with the changing of fuel pumps, I need to get a different sump in the tank. is there any cars i could take one out of that would work, or make one, or buy one.

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1. Stay the hell away from those pumps. Do it right and either get an electric pump designed for a carb setup along with a proper fuel pressure regulator, or swap out the timing cover and install a mechanical pump and eccentric and run it like stock. Don't eff around with fuel management.

2. Your MSD should work, but the wiring/installation is different.

3. You can swap the whole tank for an '85 or older tank.

Gearbanger 101 said:

Carb = bad
EFI = good

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