sefi question

Reply Subscribe

Thread Tools

Search this Thread

May 22, 2004 | 08:03 AM

92beast

Thread Starter

New User

Joined: Nov 2003

Posts: 7

Likes: 0

sefi question

Ok, I have a question for all you efi guru's. I am about to order the fms mass air kit for my 1992 f 150 w/ 302. After that is complete I will be swapping out the 302 for a 351. My question is, in what order do the injectors fire when changed to sefi with the fms kit? Do they fire in the same order as the igniton? I know I will need to change the ignition firing order to the 302ho/351. But what about the injector wiring? Any help would be appreciated.

May 22, 2004 | 09:33 PM

HardScrabble

Temporarily Deactivated

Joined: Aug 2003

Posts: 1,859

Likes: 2

I'm bumping you back up to the top of the page, since you got not replies. Search for sefi and MAF conversion, there are some good threads on this topic.

May 22, 2004 | 11:16 PM

tripndrag

Tuned

Joined: Nov 2002

Posts: 395

Likes: 11

You will be fine, leave the injector wiring like the kit says to install it. All you have to do is make sure to get the plug wires on correctly with the new firing order when you do the engine swap. Even though the kits are made to work with the truck firing order the HO firing order will work fine also. The cars had a little more strict emmisions regulations, that is why they went sequential. Wiring the injectors like the truck kit says to, you will have less miss firing injectors than you did with the speed density, that is why it states you will have better idle quality. My speed density system never had any idle trouble, I can't tell an idle difference with the Mustang shortblock I installed in my truck with the FMS truck mass air conversion kit, it runs great.

May 23, 2004 | 01:45 PM

MustangGT221

Post Fiend

Joined: Nov 2001

Posts: 14,947

Likes: 6

From: Topsfield, MA

Theres the regular 5.0 spark order, then the mustang 5.0H0/5.8 firing order. The FMS kit's firing order will work for either firing order, but if you're swapping to the 5.8, get the FMS kit that has that firing order. It'll still run the 5.0 though, just won't be 100% sequential. Leave the spark plug wires where they are on the 5.0.

May 23, 2004 | 01:59 PM

92beast

Thread Starter

New User

Joined: Nov 2003

Posts: 7

Likes: 0

Thanks for the input, I really appreciate it. But do any of you guy's know the order that the injectors fire? I would assume it is the same order that the ignition fires, but I don't know.

May 24, 2004 | 04:45 PM

EPNCSU2006

Lead Driver

Joined: Nov 2002

Posts: 9,555

Likes: 40

From: Concord, NC

The injector order should match the ignition order. 351/302HO is 1-3-7-2-6-5-4-8 and the stock 302 should be 1-5-4-2-6-3-7-8. It will run with SEFI in the wrong order, but you are defeating the whole purpose of SEFI. The main kit Ford sells for the trucks is wired for the stock 302 firing order. When you switch to a 351, you will have to run the plug wires in the 351 order, and it's best to change the injector sequence to match.

May 24, 2004 | 10:29 PM

tripndrag

Tuned

Joined: Nov 2002

Posts: 395

Likes: 11

What EPNCSU2006 said is correct but, the main purpose of the mass air kit is to allow the computer to know exact measurements of air into the motor and adjust the fuel/air ratio to make it run correctly even with lots of engine modifications. The SEFI is only good up to 3k RPM's, at that point the RPM's are to fast for the CPU to keep up the sequential firing. You won't be able to tell a difference if you change your harness, I have tried it both ways. Ford puts epoxy on the computer connector so you have to cut the wires and splice or build your own injector harness.