Megasquirt Support Forum (MSEXTRA)

Hi there. A little background first.
Datsun 280ZXT engine. MS3X full sequential fuel & COP. Distributor has DIYAuto Crank & Cam trigger wheel. Engine running OK for about 2 years with my hand made MS & MSX wire harness. I purchased new MS & MSX harness from DOYauto and just installed. I had IAC valve concern and injector cutting out at high boost-you may have read my post. No solution for that.
Now new harnesses installed- Engine would not fire at all. I discovered I wired my distributor plug wrong. I had crank, cam & ground mixed up. Power wire was good. MS Pin #1 not connected at all per email from Matt Cramer. Wired like I had previuosly
It will start with throttle featuring but sounds like only 3 cylinders firing then dies.Timing appears in ballpark but running so bad its hard to say. IAC valve disconnected.
what do I check??
msq of short run attached
Tooth log of cranking attached
composite log of cranking attched
Ito be honest I don't what I'm looking at on these logs.
Hope I attached the right ones. let me know if something is not right. I will make another log.

Test mode--all 6 injector and COP's worked good. So does Fan & fuel pump relays.
Both temp sensor function. A/F wide ban appears to be fine. Throttle position calibration good.
MAP seems high when cranking.
Using same msq as before my rewire job. I do have timing set fixed 16 degrees. I will change to 10 degrees. I had the distributor out while rewiring.

Post the MSQ, too.

my current tune

Try it on "wasted COP", get wonderment about the cam signal out of the picture. Another trick I find useful is to disable all but one cylinder at a time. It probably won't run as a 1-cylinder engine, but it will quickly become obvious which cylinders are actually working.

Hey Bill
Thanks for a couple good ideas.
Wasted COP made no difference. Still sounded like 3 cylinders hitting-poorly.
The I tried starting with one coil & matching injector at a time. Still in wasted COP mode. 1,2,3 fired 4,5,6 did not.
I then double checked testmode output on cylinder #5 coil & injector. Both functioned.
Should I have 5v on MS wire 24 crank & MSX 2 cam. With connector pulled off distributor I get 5v on Cam signal wire and 12v on Crank signal wire.
I said previously I crossed wired Cam, Crank & ground-can't say what combination. Could this have damaged the distributor or ECU

Please keep thinking!
Dave

As I thought about the test. I think the fuel pressure diminished as I tested each cylinder.
I checked again with fuel pressure. #5 fired. so that means 1,2 3, 5 fires.

I took another composite log. I though I cranked longer but!!
I had injectors off.

What am I looking at on this log? What does it tell us?
Megalogviewer says needs needs registered to read large files. I don't know what I see anyway:)
I don't see a register path or link for megalog

That comp log shows that the cam pulse is right at the same time as the crank missing-tooth gap. I think that is the one place where it (cam pulse) cannot be.

The lost sync marks (red lines) may be because of the bogus cam signal, if ignition settings are still set for dual-wheel. Maybe try setting for single (missing-tooth) crank wheel. Also, post the current MSQ.

Use a timing light to check every cylinder. I recommend using a simple (non dial-back) light, but that isn't a big concern in this case. Right now, you are just looking for spark to be consistent and at the same time on all cylinders. Same for the injectors, use a meter to read AC voltage between the two wires on each injector when the engine is running. It is hard to tell what exact voltage you should be seeing (and it will be low), but all should be close to the same.

I changed ignition setting to single wheel missing tooth. Wasted spark. Fixed timing at 10 degrees. msq attached at this stage.
While cranking it popped and complained like timing way off. Would not start. I took a data log of this cranking-attached. wow some awsome rpm's oall overver 20,000

I need my helper to crank while checking timing in cylinders. I checked timing last night while making that composite log and timing bounced all over.

oops Sorry. here is the msq

about 4 posts ago I asked about voltage on cam wire & crank wire. Does anyone know what it should be and maybe why if it's incorrect. or solution. 5v on cam 12v on crank.

I don't see enough info posted to tell you what those voltages should be. You say it is a DIY crank/cam wheel in the dizzy, but what kind of sensors? Hall for both, I'm guessing, but what are they pulled up (or down) to? 5V or 12V? Note that the pull-up resistor could be in the MS (MS3X board has one built-in), or in the sensors, or in the harness, or perhaps in multiple places. A sensor could have pull-ups to both 5V and 12V. It will work, but will confuse the issue even more.

What wires did you do wrong in the crank/cam sensors? Swapping the crank/cam signal wires does not usually do damage. Connecting the signal to ground shouldn't be a problem, as long as the sensor ground was still connected to ground, But any combination of swapping those sensor wires is "iffy". I would expect damage, if any, would be to the sensor(s) and not the MS.

The trigger wheel is sold by DIYAUTOTUNE.com for a Datsun 280ZXT distributor to replace the stock trigger wheel. The distributor utilizes an optical sensor.
The engine and MS combination ran for a couple years, so I know it will work again. I will take a few days/week and locate a replacement optical sensor and hopefully the entire circuit board in the dizzy. I'll give that a try. Sounds like many Nissan VG30/33 engines used this sensor and hopefully circuit board.
thanks for your help Bill. I'm hoping it's not MS as you say.
I'll report back.

OK, optical sensors, got it. Those are similar to Hall, an electronic circuit triggered by a light beam instead of a magnetic field. Point is, the electronics may be quite sensitive to wrong voltage polarity, same as Hall. I still see hope that the MS is fine.

Back again. Sorry for so long posting.
Installed new CAS. Engine started better. TS dash shows CAM fault but Composite log looks good. Cylinder #6 &4 is my problem.
The engine will idle now on 4 cylinders---this is a straight 6 L28ET
Test mode shows injectors & COP work fine. I moved both injectors and COP to other cylinders and problem does not follow. Cylinder compression is fine.
#6 plug is black. #4 not as bad but is dark. Brand new plugs.
It acts like timing is off on these 2 cylinders. This is not possible is it? firing order confirmed.
new composite log & msq
getting desperate
Dave

sorry I didn't attach log & msq.

RPM's are little high in the data log. 80k-100k
what causes this?

In MLV, check in the "options" tab to see if you have "RPM x 100" turned on.

Have you used a timing light on 4 and 6 to verify what timing on those is?