Willys43

[1project2many]

New Question. This link shows #1 cyl fires is 90*. I thought TDC #1 was 0*. Truly odd fire. What am I missing?

The author started counting "0" at #2 TDC. It's unconventional but I believe the point was to illustrate that pistons on a common crank throw are 90 degrees apart. If you subtract 90 degrees from the numbers he used they'll match what I posted.

If two ecms were receiving this signal could the base initial spark advance be set to 0* and to 90* to create 2 ECMs firing 90* offset from each another?

Good question. I think you can get the ecms to offset timing using only one crank sensor although the number should be closer to 30 degrees. You wouldn't get nice, even injector pulses between the banks but with TBI that probably wouldn't matter. But I think you might have a problem starting the engine. How are you going to deliver correct spark to all six cylinders before the ecm takes over?

FYI this is very similar to a discussion about how to create 8 cylinder DIS from (two) four cylinder DIS modules each using its own crank sensor with 90 degrees between the two. The answer was to either use two ecms each running 1/2 of the injectors or to use an additional component to split the outgoing spark pulses to the correct DIS module. Without the means to design and build electronic circuits one is limited to using two ecm's.

[Willys43]

I just pulled the plug wires on the odd bank, no fire at all, put them back and pulled the even bank. Started about normal for 30* weather.
Put all wires back on and started it, even bank still not firing but it runs anyway. Not even hardly noticeable at idle. I think the
"best" application will be to remove the odd fire pickup coil, put two pickup coils in the distributer at 45*or75*(distributor *) spacing in order to fire the 90 /150 crank timing, using two ECMs

[Willys43]

Does anyone know what output is required from a pickup coil?

[1project2many]

I just pulled the plug wires on the odd bank, no fire at all, put them back and pulled the even bank. Started about normal for 30* weather.

I love it! You can set the rpm at which the ECM takes over. It's usually around 400 rpm but it can be lowered.

The voltage from the pickup coil varies with shaft speed. It's been a long time since I checked one but I seem to remember 5-8V A/C during cranking. I can try and dig out some old manuals tonight and get an actual value.

[Willys43]

You may be able to set the ECM takeover to a lower RPM but you might get in to trouble depending on the pulse voltage needed by the ECM and what the output pulse voltage of the pickup coil. I suspect that is why there isn't computer controlled timing below 400+/- RPMs, not enough juice. How would you real time tune dual ECMS? Read one then burn and replace two chips?

[1project2many]

Hey, now... You're the guy starting the engine on three cylinders. ;)

In my experience a quality control module will provide sparks and a reference pulse at extremely slow speeds. Think about how slowly a weak battery will crank the engine. GM often has very conservative values, which I understand, but that doesn't mean we can't make changes to see what the results are. One thing to keep in mind is that the old Delco starters required more current than current permanent magnet types and would reduce the voltage available to other components very quickly. If there's a PMG type starter that will fit the Willys I'd swap on general principle. Today's vehicles are designed so the ecm has full timing control immediately with no bypass mode.

Real time tuning... I'd start by trying to monitor each ecm independently and mirroring the tune from one in the other. At least until I saw a need to adjust them differently. I think two different windows open with monitoring software running and getting readings from two different cables might be possible. Emulating might be more of a trick but it's not impossible.

[lionelhutz]

During cranking, if the coil didn't send a good enough signal to be able to send the ignition reference pulses to the ECM then the engine would never start since the injectors would never be fired. The pickup coil doesn't power the module or create the power for the signal sent to the ECM. The module has battery power applied to it for that.

I would first try the single pickup driving both ECM's with the initial spark advance in one ECM set to 90*. I'm pretty sure you could combine the two ECS signals back to the module either just by connecting them together by using signal diodes worst case. At 400rpm, the second ECM would likely start producing spark pulses while the engine is still cranking.

[1project2many]

I've checked with an old GM repair manual, "Engine Performance Testing" copyright 1987, to obtain correct voltage values for a good pickup coil during cranking. From the manual:

The resistance of a pole piece should be 500-1500 ohms. This does not mean the pole piece is good if the resistance falls within this range. The true test of a pick-up assembly is whether it produces an increasing voltage with RPM, and produce at least 300 mV (AC voltage) during cranking above 150 engine RPM.

In another section an illustration appears to show the 300 mv trigger level voltage for a 7 pin module.

[Willys43]

If I can use just one pickup, its an easy modification to the factory pickup coil. My intake is single plane, which would be better fueling Two ECMS with 1 injector each(odd fueling) or 1 ECM with 2 injectors (even fueling)
?

[1project2many]

hard to say. I think I would use two injectors, one ecm each. Otherwise only one injector will fire with every other ignition pulse. You could run both from one ecm and set the calibration with asynchronous fueling like most of the 4.3 engines but that really doesn't seem to run as well. Have you picked an ecm? You want a calibration that will let you enter the number of cylinders properly.

[Willys43]

1227747, I'll probably try both ways and see what the differences are.

[Willys43]

What causes an odd fire to run on cylinders 1,3,5 only? Answer-Some dumb ass put incorrect plugs in Cyl 2,4,6 and they all quit approximately at the same time (PO). Worked my butt off trying to find that out? Needless to say since the whole bank wouldn't run I never would have believed that all three plugs would have been bad.

[1project2many]

Wow. That would have been a tough one. As we say, "Whoda thunkit?"

It's hard to find parts or brands to put trust in these days.

[Willys43]

The plugs had a flat bottom with a hole in it. I'd never even seen a plug like it before. I've been driving diesels too long. I swapped out the points in the middle of trying to diagnose the no fire issue. I actually found my tach and dwell meter I haven't used in at least ten years. Set the dwell and then checked the RPMs. this thing idles at 300 RPM. I didn't think that was possible. No wonder it's weak when letting out the clutch without the throttle, sure thumps good.

[1project2many]

Did they look like this?


Or this?


Or maybe this?


The top two designs are "surface gap" plugs which are fairly cold but are supposed to be difficult to foul. The bottom design was sold by J C Whitney for many years.

Then there's the old "anti-fouler:"