pulsewidth zero during log, normal?

[808state]

msii, smd 3.57
firmware 2.687
no mods, bought preassembled.
controlling fuel only

my car seems to be running ok at this point. however, when i'm doing my logs, i notice that at points in my log, my pulsewidth goes to zero, duty cycle is 0, and afr is 21.9, crank goes "y". mind you it seems only for a split second. i don't notice anything when driving at this point (though only a couple times i did in this thread viewtopic.php?f=31&t=33610 ).

attached are my logs and msq file. would anyone know what could be triggering the above parameters?

[TPI 85 Blazer]

Does that mean the ECU is resetting?

[Matt Cramer]

Not a reset - that looks like it briefly lost the tach signal. This is not normal; you'll want to make sure you are not filtering out too much in the tach signal source.

[808state]

matt-

can you explain what you meant by

not filtering out too much in the tach signal source.

is this something in megasquirt or mgl? or something you do physically.

i'm picking up my tach signal via the negative of the coil using the inner/white wire of the coax shielded wire. then, at the ecu end, connecting the inner white wire to the relay board, and connecting the outer sheath of the coax shielding to the chassis ground. you can see what i did in the pic below with the area squared in red.

[Matt Cramer]

Filtering depends on what you are doing for the input. In your case, do you have any resistors or similar things in line with the wire?

[808state]

matt-

no resistors inline. white wire inside of the coax/shielded wire goes directly from the negative of the coil to the relay board.

[Matt Cramer]

The negative terminal of the coil can be a noisy place. You might want to try a 1K to 10K resistor inline with it just to see if that changes anything. It may have had a patch of noise slip through that the ECU didn't know how to interpret.

[808state]

matt-

i got a bunch of 2 watt resistors ranging from 1k, 2k, 3k, 5k, 7.4k, and 10k. being that this is an intermittent problem, can't make it appear on demand in all conditions. the 5k made the car a little hard to start. 10k car won't even start/stay running. of the all the resistors, maybe the 1k maybe made alittle to no change than what i had originally. i also changed out the coil from the msd2 blaster to a summit one with no change. i have a feeling it's the toyota ignitor for my 80 corolla that's giving an odd signal that megasquirt can't recognize.

at this point i'm already planning on changing to a pertronix ignitor i (1641) and pertrnoix flame thrower 3 ohm coil. my car is already an elctronic type ignitions, so i have to get an older points style distributor to make this work. hopefully this will give megasquirt a cleaner tach signal to work with and will give the added bonus of timing control. thanks for all the advice.

[808state]

ok, i switched my 20+ year old toyota electronic ignitor and pickup to a brand new electronic pertonix ignitor i and pertronix coil. unfortunately, i'm still getting a pw, rpm to 0 ever so often just as before. usually around the 3k range.

what should i do next to get a clean tach signal? should i:

1) change out the wire from the coil- to the relay board?
2) upgrade the firmware from 2.68 to something more recent?
3) use my megasquirt direct driver bip373 to control the pertronix i and coil and wired up like this viewtopic.php?f=89&t=33796&p=206419#p206419
4) get a msd 6a unit and use the tach output to connect up the the megasquirt for the tach signal? though this post showed a similar problem i'm exhibiting i think viewtopic.php?f=89&t=34563.

thanks for any suggestions.

one more thing of note, on my 3.57 smd board, the tach jumpering is as follows although all i'm doing is feeding the megasquirt the negative off the coil. note sure if it makes a difference based on what i'm doing now.

# Tach input selection jumper JP1 is across 1 and 2.
* Placing a jumper across positions 1 and 2 enables the variable reluctance (VR) circuit.
* Placing a jumper across positions 2 and 3 enables opto-isolator ("Hall") tach input.

# Tach selection jumper J1 across 1 and 2.
* A jumper on pins 1 - 2 enables the opto-isolator.
* A jumper on pins 3 - 4 enables VR (variable reluctor) operation (non-inverted).
* A jumper on pins 5 - 6 is for an inverted VR signal.

[Matt Cramer]

Jp1 should be in the 2-3 position for coil negative triggering, not 1-2. Just checking to be sure that wasn't a typo; I'd be very surprised if it ran if you had JP1 and J1 both in the 1-2 position.

[808state]

good catch matt. jp1 was jumpered across 2 and 3.

would i have a better chance getting a reliable tach signal (without the 0 or jumps around 3k) from going the direct coil route or the msd output route?

[Matt Cramer]

Usually the MSD output is cleaner and easier to trigger from. The post you mentioned was about the only time I've seen it being a problem.

[808state]

installed new msd 6a ignition and new msd blaster 2 ignition coil (epoxy) along with pertronix ignitor (existing). connected megasquirt tach signal to msd 6a tach output. also, had to install new autometer 3700 tach because previous tach didn't work with the msd 6a. megasquirt isn't controlling the timing but is picking up the tach signal from the msd6a instead of the "-" off the coil.

did some logs and so far no tach spikes or drops. yeah!!! car revs smoothly without hesitation. took it up to 6K no problems.

tach output from msd6a solved the problem. thanks matt!