how does eec iv know piston #1?

Hi, i can't figure out how eec iv know piston #1 for vehicles with tfi ignition. But it must know in order to drive the fuel injectors in a proper order right? But how does it know?

Its a batch fire system, totally normal for no position sensor.

It goes off of the sensor in the distributor, not too complicated

Not for him, no order-not sequential-batch fired FI, no sensor.

i'm aware of the hall effect sensor inside the distributor creating on/off signals from the rotation of windows and vanes, but how does eec distinguish from these pulses which ones are #1? unless one of the windows is a different size but aren't they all the same for tfi systems?

It doesn't, no cylinder sensor, like engines driven by cap and rotor points systems #1 is determined by which way the rotor points.

Your ECU also only has two fuel injector circuits and more than two cylinders. No need or possible use for crank position/cam position sensors.

yes, no crank position sensor. but isn't there a PIP signal in the tfi connector and does that get generated by hall effect?

so what cues eec to open injector #1?

Your EEC doesn't know when #1 intake valve is opening, and it is not needed.

With TFI system the TFI module just sends the PIP(Profile ignition pickup) signal to the computer(EEC), this signal is from the sensor in the distributor and tells the TFI when rotor is pointed at a spark plug wire on the cap, there is no special pulse for #1 TDC on power stroke, like you have with a Crank Position(CKP) sensor or a Cam Position sensor(CPS), the TFI module just fires the coil, and spark goes where rotor is pointed.

The EEC(on a V6) will open 3 fuel injectors on each PIP, well just before the next PIP when intake valve is open.
Injectors 1, 3, 5, and then 2, 4, 6 will alternate for each PIP, this keeps the lower intake full of air/fuel mix that can be pulled in by any cylinder on it's intake stroke.

So EEC doesn't need to know when #1 is at TDC power stroke, neither does the TFI module, the rotor needs to point at #1 spark plug wire at that time but that is set manually by the owner, along with base spark timing

This is called Batch Fire injection as others have said, opening multiple injectors at the same time, this was the first step in fuel injection, one step up from a carb.
A carb kept intake full of air/fuel mix all the time, Batch Fire is similar but just the lower intake and because of Feedback from O2 sensors less fuel could be used.

Sequential injection was used to lower emissions and increase MPG, there is no real performance gain, and if EEC on sequential system "gets lost" it will switch to Batch Fire to keep engine running.

My 4.0l uses EDIS so has a CKP sensor and knows when #1 intake valve will be open, but it still uses Batch Fire, because it has the EEC-IV(pre-'95) which were generally setup to be batch fire only, although some Mustang EEC-IV computers did have the 4, 6 or 8 fuel injection wires/connections required to operate each injector independently.

If you look at your fuel injection wiring you will see all have a red wire, that's the 12volt power they get when key is turned on.
Injectors are opened by the EEC Grounding them.
If you see that each injector has a different colored 2nd wire(ground wire) then you have sequential injection, if you see only 2 different colored 2nd wires shared by the 6 injectors then you have Batch Fire, your EEC only has 2 grounds to control 6 injectors.

Despite all that is still needs to know when it sees cylinder 1 come around. It just doesn't care about which stroke it's on.

Cylinder 1 is identified to the computer by it's window on the vane wheel in the distributor being larger than the others.

On newer engines that use a crank sensor they do the same thing. The trigger wheel on the crank has 35 teeth and a spot where one is missing. The missing spot being lined up with the sensor corresponds to cyl 1 being at TDC.

adsm08 said:

Cylinder 1 is identified to the computer by it's window on the vane wheel in the distributor being larger than the others.

Click to expand...

that being the case doesn't it mean i have to match my #1 spark plug cable to the #1 window in the vane wheel? But I never had to do this.. That's where I am very confused..

whitebroncoii87 said:

that being the case doesn't it mean i have to match my #1 spark plug cable to the #1 window in the vane wheel? But I never had to do this.. That's where I am very confused..

Click to expand...

That is why I avoided that part...............

The distributor shaft is machined so rotor will only go on one way, the sensor wheel will also only go on one way, so they are matched, yes the sensor wheel/vane/tone ring does have a #1, and it is matched to the rotor.

When you time the distributor so rotor is pointed at #1 spark plug wire when engine is at TDC #1 power stroke, everything is good to go.

whitebroncoii87 said:

that being the case doesn't it mean i have to match my #1 spark plug cable to the #1 window in the vane wheel? But I never had to do this.. That's where I am very confused..

Click to expand...

Sorta, kinda, yeah-ish.

The proper procedure for spiking the distributor is to have the engine with cyl 1 at TDC on compression stroke before putting the dis down, and to have the rotor pointed at the #1 position when the dis is fully down. If you do that then you have matched the wheel to the plug wire like you said, you just don't think about it that way when you do it.

As Ron pointed out, the rotor only fits on the shaft one way, so getting that screwed up should be a non-issue. Basically if you can manage to put that rotor on backwards, you can probably shoot yourself with a bow and arrow.

ok, so rotor and #1 window are structurally pointing the same way and cannot be altered so i don't have to think about it. got it thanks!

so tfi is batch fire, cylinders at a time? i haven't checked if mine has shared return wires like ron said, but if injectors #1,3,5 opened and only #1 sparked, what happens to the gas that got sprayed into 3 and 5? never got used? how does this make sense?

Yes, if you shoot yourself with a bow and arrow...I want pictures...

Sounds like you've got it down now...when I started doing the timing on my 2.3 I was totally confused about how it all worked...but it is as simple as the rotor only goes on the shaft one way...the shaft of the distributor at that end is cut almost in half right at the top so plopping the rotor on can only be done one way...unless you've got the wrong part to start with...that can confound you even more...

It's all simple...but...there is one thing you need to watch out for...and that is the spiral twist of the rotor when you insert it into the hole where it belongs. This takes a few tries to get right but it can be done. The key to doing it all is marking where the #1 piston is in relation to the distributor...mark it on the intake so you know that when you insert the distributor and it twists into place, it will point at that mark...and, of course, this is making sure that the #1 piston is TDC and ON THE COMPRESSION STROKE...

That's really all there is to it...

whitebroncoii87 said:

so tfi is batch fire, 3 cylinders at a time? i haven't checked if mine has shared return wires like ron said, but if injectors #1,3,5 opened and only #1 sparked, what happens to the gas that got sprayed into 3 and 5? never got used? how does this make sense?

Click to expand...

Your's has shared return wires. All 2.9s were batch fire. To do sequential fire you need a crank and a cam sensor so it can judge the compression stroke, you only have a crank sensor.

The fuel sprayed to cylinders 3 and 5 will get used eventually. Those valves have to open at some point.

If you are worried about it being wasted, or getting worse fuel economy for having batch fire, don't. The 4.0 used both methods and the earlier batch fire engines consistently get better mileage than the sequential fire ones.