Megasquirt Support Forum (MSEXTRA)

Hi all,


Engine ran fine a couple of months ago. It's got colder here — but I don't think that's entirely it.

It just doesn't catch — I get the odd backfire when I switch the ignition off.

Attached are the MSQ and MSLs from today.


James

Something's wrong with the crank sensor input. Can you get a tooth log of an attempted start?

Hi Matt,


See attached.


James

It's missing a lot more teeth than the missing teeth. Try a tighter sensor gap, or adjusting the VR trim pots.

HI Matt,


For sure something was up with the sensor and the connector. The crimps on the connector weren't so good, and the plastic on the sensor had gone soft over time so was a bit wobbly. (read — bad crank sensor mount design) So I replaced those, hoping it would be the issue.

Looking at TunerStudio whilst it's cranking it's still not syncing right.

The tooth logger on screen looked much better — but still no starting. I've attached the logs.


James

Looking at the logs — could it be that the voltage is dropping off and causing the sync error 2?

It goes down to 7V or so.

The battery turns over the engine reasonably ok — but all this attempting to start has had a bit of a toll.

There's still a few points where it fails to read a real tooth. More cranking voltage would boost cranking speed, and if this is a VR sensor, more cranking speed gives a stronger signal.

I gotta admit: I didn't look at the MSL last night, only the CSVs. Your cranking rpm is only about 130, not what I would call "reasonable". Get a good battery in there before looking for other problems. Were you activating the throttle wildly during some of those crankings, or is that TP action logged a separate symptom?

Matt Cramer wrote:There's still a few points where it fails to read a real tooth. More cranking voltage would boost cranking speed, and if this is a VR sensor, more cranking speed gives a stronger signal.

Yep it's a VR sensor. I'll connect up a jump battery to give it some more juice.

billr wrote:I gotta admit: I didn't look at the MSL last night, only the CSVs. Your cranking rpm is only about 130, not what I would call "reasonable". Get a good battery in there before looking for other problems. Were you activating the throttle wildly during some of those crankings, or is that TP action logged a separate symptom?

I'll sort the battery and try again. I did have my foot on the throttle — no idea why! Out of frustration probably

So, used jump leads — engine turns over much better now.

Still seem to be getting a sync error.

And the tooth logs

Just a thought - is there any chance that when I wired up the sensor to “fix” it that I’ve now wired it up backwards?

James

James wrote:Just a thought - is there any chance that when I wired up the sensor to “fix” it that I’ve now wired it up backwards?

James

Don't think so.
There is something wrong in latest toothlogs.
Loking at the logs and starting whit the long missing tooth there should be 35 tooth before the next Long missing tooth.
Sometimes it is 34 or more than 35.

Did you replace the sensor or just reconnected it ?

I replaced the sensor and also replaced the connector as the crimping was a bit iffy.

LAV1000 wrote:

James wrote:Just a thought - is there any chance that when I wired up the sensor to “fix” it that I’ve now wired it up backwards?

James

Don't think so.
There is something wrong in latest toothlogs.
Loking at the logs and starting whit the long missing tooth there should be 35 tooth before the next Long missing tooth.
Sometimes it is 34 or more than 35.

Did you replace the sensor or just reconnected it ?

Matt Cramer wrote:It's missing a lot more teeth than the missing teeth. Try a tighter sensor gap, or adjusting the VR trim pots.

Did you try this whit the replaced sensor ?

No, that is a good point!

Hi all,


I thought this had gone away — and have erroneously been chasing weird timing issues.

From what I can see with the tooth log - it seems to be counting teeth ok? This log was taken with the injectors and coil disconnected as they are backfiring badly when connected. There's also a log from today which shows the sync error.

I have also attached a log from it partially running yesterday.

Is there something I am missing?


James

The tooth log was doing fine right up until the very last page...
Fairly minor noise issue, but more likely to cause a loss of sync than a backfire. If you're getting fairly continuous backfires, make sure the timing is OK.

Thanks, Matt.

Does the megasquirt "recover" from that kind of oddity? Does it filter over it or is it troublesome?

My car has 3 x ignitors inside the MS box — running to a wasted spark coil pack. (it's a 6 cyl)

Have spent more time on the car and pointing the strobe at it. Coils 2 and 3 are working fine and firing around TDC... but coil 1 seems to be firing totally out — by almost 180 degrees.


James