Incorrect Tach Reading in TunerStudio when Cranking

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F100guy
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Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

I've been struggling to troubleshoot why TunerStudio is showing ~12000 RPM when cranking.

I'm using a MSII V3.0 with firmware MS2Extra comms342a2. The system is installed on an old F100 with a 240 straight 6 and a Duraspark II system retrofitted.

For my initial setup, I'm not trying to control spark timing and am pulling the tach input signal directly from the negative terminal on the coil and terminating on Pin 15 on the Relay Board.

I've checked my cranking RPM's with an old Tach & Dwell meter and found that it's cranking at 350-400 RPM.

I'm not sure if I have something jacked up in my msq or if I'm having noise issues.

Any help is appreciated.
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2017-09-02_22.19.40.msq
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kjones6039
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by kjones6039 »

Can you post a log to go with that msq?

Ken
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
MS2 v3 w/extra 3.4.2 Release
36-1, Delphi LS2/7 coils in wasted spark, driven by v2.0 logic board from JBPerformance
Spartan Lambda Sensor from 14point7
TinyIOX from JBPerformance
F100guy
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

Short log from last crank cycle attached. Thanks for taking a look.
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kjones6039
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by kjones6039 »

Not what I was hoping for...... Do you have an msl made during cranking?

Ken
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
MS2 v3 w/extra 3.4.2 Release
36-1, Delphi LS2/7 coils in wasted spark, driven by v2.0 logic board from JBPerformance
Spartan Lambda Sensor from 14point7
TinyIOX from JBPerformance
F100guy
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Posts: 8
Joined: Sun Oct 08, 2017 7:12 am
Location: Savannah, GA

Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

Bear with me. I figured out how to data log to create the .msl file. Try this.
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2017-10-08_16.18.47.msl
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rickb794
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by rickb794 »

Have you tried "basic trigger" instead of "fuel only" in the ignition tab
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
F100guy
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

@rickb794 -- Gave it a shot but same results (i.e. high displayed RPM on crank and no start).

In trying to minimize system noise, I did a little re-engineering on my grounds to get them more in line with recommendations. I also changed over the spark plugs this evening to a set that I know are resistor plugs. The displayed RPM's are now at 9000 to 13000 versus ~20000 that were showing yesterday. Prior to yesterday, I've seen the displayed RPM's at 12000, so I don't think I've made anything noticeably better but at least I know I'm more in line with the recommendations for minimizing noise.
F100guy
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

Any additional ideas? I've been traveling for the past week and haven't had a chance to do any more troubleshooting.
rickb794
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by rickb794 »

Have you followed the instructions to the letter in Section 5.2.1 of the hardware manual?

http://www.msextra.com/forums/viewtopic ... 01&t=65757
Go through all the issues presented in that topic thoroughly.

Relay board must be grounded with a heavy multiconductor wire (I prefer monster cable) to the motor.
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
F100guy
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Location: Savannah, GA

Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

I wanted to provide an update on what changes I've made, the results, and my further research.

I have re-engineered all the grounds so the engine ground from the relay board goes to the front of the engine where the negative terminal of the battery attaches, the aft ground from the back of the engine to the firewall now has no other grounds associated with it, and the chassis ground from my Duraspark II and the signal grounds from the relay board share a ground point on the firewall. I've ensured that there is metal-to-metal contact for both firewall ground points.

I've also moved the coil to the lifter gallery cover under the #6 spark plug. This allows my wiring for the coil and the TACH signal wire for the relay board to run directly from the firewall to the coil with sufficient separation from any spark plug wires. I have the TACH signal wire connected directly to the negative terminal on the coil.

After doing the above re-work, I tried starting the engine again and the RPM's still went high somewhere between 14000 and 20000.

So, I went back to the Megasquirt II Assembly manual and found a short note under step 51.b that states

If you find that the tach signal sometimes jumps too high (20000 rpm or more) you can either replace the D2 Zener with one having a higher voltage rating (28, 32 or 36 Volts), or add one or more 5.6 Volt or higher Zener diodes in series into the tach input wire to DB37 pin #24 (the banded end of the diode(s) should be closest to the negative coil terminal).

So, I'm purchasing to 5.6V zener diodes to see if this will solve the problem.
F100guy
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

Time for an update with where I'm currently at in this saga.

I received the two 5.6V zener diodes last week and installed them in series in the tach signal wire -- cut the signal wire, soldered the two diodes together in the same orientation, soldered the diode pair to either free end of the tach wire (diode bands closer to the coil).

Then, tried to start the engine only to find the same results as before -- cranking RPM's too high (13K to 21K).

So, after exhausting my ideas of what to do external to the MSII, I decided to go back and double check my build of the ignition section of the MSII board. Here I found that I had accidentally left out the C31 capacitor and my R13 resistor appears to be a factor of 10 to large -- yellow-violet-orange (47-kohms) instead of yellow-violet-red (4.7-kohms). Unfortunately, I can't find where I may have switched resistors between two locations. So, I ordered another 4.7-kohm resistor.

In the meantime, I connected the MSII back to the truck and yielded the same results as before.

I'm not quite believing that a factor of 10 reduction in the resistor will yield a factor of 50 reduction in my registered cranking RPM's.

The saga continues.
F100guy
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by F100guy »

No good news from testing this weekend.

I made the change to the R13 resistor, but no real change in the displayed RPM's.

I'm out of ideas other than going over the board, component by component, looking for build errors. The only other thing I can think of is to give up on getting the tach signal from the coil and get the hardware to to install a crank trigger with pickup. But, that approach violates my approach of starting simple, getting that working, and then going to more complicated.

Suggestions?
rickb794
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by rickb794 »

It seems to me that would be more simple than the path you have been on.

There is no reason I see to hold back from crank triggering and many in favor of it.

Don't let the FUD hold you back.
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
DaveEFI
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by DaveEFI »

The normal place to ground everything is to the engine block. Since that already has to have a good ground for the heavy starter current. Grounding to the firewall may not be ideal.

It's something where a 'scope is useful. To see the actual signal MS is getting. Normally, triggering from the coil negative is the easiest way of getting a decent tach signal.
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rickb794
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by rickb794 »

Grounding - section 3.2 of the manual

Core wiring - Section 3.3 of the manual follow it.
Power from the battery not the vehicle harness.
Wideband controller (very noisy) powered off the Fuel pump
5 ground wires (15-19) direct to the motor.

Read and follow the Do's and Dont's at the top of the forum

Resistor plugs (absolutely)

No Low resistance spark plug wires (ignore the marketing terms associated with these wires)
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
DaveEFI
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by DaveEFI »

It's also where the basic Stim is very useful. That should prove if the tach input is working correctly. Think also the relay board makes things more difficult these days. It's OK for the relays and fuses, but I'd wire everything else direct to the DB37 on the MS. Especially all the grounds - and just run one back to the relay board for the main relay coil etc ground.
Rover SD1 3.5 EFI
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Tech Edge O2
London UK.
rickb794
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Re: Incorrect Tach Reading in TunerStudio when Cranking

Post by rickb794 »

Too many installs using the relay board and having problems.

I think the issue lies with the interconnect cable as well as the relay board itself.
The long run of light gauge wire in very close proximity is not the best.
I don't think it honors the new grounding strategy well if at all.
It makes the wire runs longer and more parallel than needed on most any install.
Breaking out wires from the harness pretty much defeats the whole purpose and idea behind it.
Even if you just break out the main ground leads 15-19, you create a potential ground loop at the relay board which still needs it's own ground to operate.
Correctly identify your MS ecu here
Read the Do's and Don'ts to avoid the common pitfalls before starting your install or asking for help
Use only these manuals other manuals may cause brain damage or worse.
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