Bill,

I was looking at your wiring diagram. I see a potential for a ground loop on Pin 14 which is the shield for your knock system. These are grounded on both the engine and the case side.

I would personally move the grounds to the chassis rather than the engine. But that should not matter as you indicated that they are all at the same point.

Do you have a high torque starter? These can be noisy and are in close proximity to your crank sensors. The fact that the load is increased on the starter when the plugs are in place and you have a cyclic noise in your pickup might indicate a ground issue of the starter feeding back into the MS ECU. Can you move the grounds to the chassis, left side of engine bay, and test for the noise?

You have a noise problem. Now we just have to figure out where its coming from.

How are the jumpers configured on the Board? V3.0 or V3.57?

The 5v coils don't like noise... I haven't had a chance to look yet but there is a simple setting in earlier ms for cranking to be time based for the next trigger event. This setting solves starter circuit noise problems while cranking. The only test to see if that is your problem is to wire the starter motor to a separate battery(dedicated electrical system for starter cranking only)or to push start and log/observe.

The knock sensors are wired up but disabled in TS, so hopefully they shouldn't be causing any problems, however I will look into that wiring.

I installed a HiTorque starter because the original Bosch starter really struggled to turn the engine over against compression. It might be worth trying the Bosch starter again. Maybe the engine has loosened up a bit with all the cranking! A PITA job but least it's all clean under there.

It is relatively easy to move the ground from the engine to the lug behind the fuel filter, so I can try that before I dive into anything more labour intensive.

Not sure what you mean about jumper config. It is whatever it came with.
Is there something specific I should check?

That sounds like fun! But do-able. I am just visualising how that might work because the power to my engine bay relay panel originates from the starter connection (via the alternator wire).
I'd have to remove the battery cable and alternator wires from the starter, bolt them together, then run a separate battery cable and ground to the starter from the second battery. I guess a remote starter button might be best as well.

I tried a few changes this afternoon to try and identify the source of noise with no real progress.
1. Moved the main ground from engine to chassis ... no improvement
2. Wired starter 12v direct to a separate battery ... no improvement
3. Wired starter and solenoid to separate battery ... no improvement

By "no improvement" I mean that the log still looks the same with large spikes (B) every 35 teeth and smaller ones (A) still visible at about 51 like this ...

http://forums.pelicanparts.com/uploa...1402226558.jpg

Actually, there is s change, the large spikes are much larger than they were on previous logs!
Is it possible for the starter to create noise in the crank sensor circuit even though it is electrically separate? If so, I will try the original Bosch starter for the next test session.
Also forgot to try cranking up R56. Maybe tomorrow.

Have you tried switching your input capture edge?

Looks like the signal is now ~3 times as strong so we are likely headed in the right direction. What goes with this is the noise also travels through all circuits not just the crank sensor. The trigger circuit for the coils is also impacted with noise preventing the coil from experiencing a trigger event.

You can further reduce noise returning all sensor grounds to the ECU.

We can also tweak the noise filtration setting in the software... I need to open your msq I suppose.

No Steve, I haven't revisited that. I think I had to switch it to the current setting (falling edge) very early on because the coils were getting very hot. Then again, I may be confusing this with Spark Output which I changed from "going low" to "going high". It is quite a while ago and I wasn't taking notes of the changes at that stage but I will look into it.
However, I still don't see how a change to this setting would overcome what looks to be a noise problem in the tooth log.

What spark plugs are you running? If they don't have resistors, stop the show and get resistor plugs in there.

I will look into the relocation of the grounds but this doesn't sound simple. All the ground pins in the ECU connectors are joined (soldered) together in the harness just out of the ECU and then run as two heavy wires through the harness to the ground at the engine. I moved this ground point to the body today with no effect.

The ground wire from the crank sensor goes to MS3 pin 7 as per MS diagrams. I presume it is grounded internally somewhere or routed out via one of the six ground pins on the MS3 connector. The sensor shield is connected to the common ground in the harness before connecting to the engine (or body).

Are you saying that the grounds should be to the case of the ECU? That doesn't make sense to me as the case isn't actually connected to any of the cards or the ground wires.

Apart from the hardware adjustment of R56 and R52, I am not aware of any software settings related to noise filtering so I will look into that as well.

None of the recent tooth logs I posted have been taken with power to the coils so plugs have no effect. Fuses for injectors and ignition are out. As far as I am aware, the tooth log is looking at the crank sensor output only.

The plugs I have now are NGK R Iriway 8, which are standard plugs for a 3.6 I think. Can anyone confirm whether these are resistor type or not? If not, what plugs do I need?

Hi Bill,

Yes, they should be separated ideally on the DB37. Collect the sensor grounds at the engine together onto one line and run that to Pin 7. The line does not need to be huge... one sensor wire is adequate. That DB37 pin 7 is an old diagram I mentioned earlier...

Pins 19 through 14 should remain bundled on an adequately sized ground wire to the engine block.

Crank position sensor should be pins 1/2 on the DB37 which are geographically as far separated from the ECU processor grounds that are noisy (pins 14 through 19).

We have a few changes to makes by the sounds of it but they are relatively minor if you are have a single wire of capacity running to the engine to accept those sensor grounds.

http://www.msextra.com/doc/ms3/Gener.../v3-wiring.png

Megasquirt 3 - V3.0 board schematics

I would also confirm the spark plugs - might be more than one problem combined here and it's nice to change then test and repeat until you kill the problem dead. :)

Thanks for your perseverance, it is much appreciated, but I have to call it quits for now. It's late at night at I have a 6am start tomorrow.
I understand what you are saying with regard to the ground wiring and I'll work through it tomorrow. Fortunately I had the foresight to put two or three spare wires in the harness, so they may come in handy.
Goodnight :)

Bill. The crank sensor negative lead should ground through pin 1 on the MS board per the standard wiring diagrams.

http://msextra.com/doc/ms3/General_Pix/v3-wiring.png

I think Pin 7 should be OK but Pin1 is isolated on the board. . The shield should also be grounded at the ECU through Pin 2. You have it at the chassis/engine ground. This might be the ground loop that is picking up the noise in the trigger.

(edit) Looks like we are all pointing to the same ground issue.

This plug cross references to NGK 2668; old stock #BKR8EIX. This plug does have a resistor. I think we're back to harness changes and noise isolation other than the plugs... would have been too easy if it were the plugs. ;)

Features & Benefits

Laser-welded iridium center electrode; extremely durable to heat, corrosion, and electrical wear; tapered ground electrode minimizes quenching; and outstanding acceleration, high fuel efficiency, and durability
Product Details

<table id="prodspecs" cellpadding="0" cellspacing="0"><colgroup><col class="first-childtd"> </colgroup><tbody><tr> <td>Part Number:</td> <td>2668</td> </tr> <tr> <td>Weight:</td> <td>0.108 lbs</td> </tr> <tr> <td>Resistor:</td> <td>Yes</td> </tr> <tr> <td>Heat Range:</td> <td>8</td> </tr> <tr> <td>Center Electrode Material:</td> <td>Iridium</td> </tr> <tr> <td>Number of Electrodes:</td> <td>1</td> </tr> <tr> <td>Ground Electrode:</td> <td>Nickel alloy</td> </tr> <tr> <td>Insulator Type:</td> <td>Ceramic</td> </tr> <tr> <td>Thread Size:</td> <td>14 mm.</td> </tr> <tr> <td>Reach:</td> <td>3/4 in.</td> </tr> <tr> <td>Seat Style:</td> <td>gasket</td></tr></tbody></table>
"NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking. NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.
They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.
In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion."

I meant the input capture from the crank sensor not the coil signal output. It may make a difference.

I found this in the megamanual. MegaSquirt-II - Advanced Electronic Fuel Injection Computer by Bowling & Grippo ©2005

http://forums.pelicanparts.com/uploa...1402255933.gif

Thanks Jamie. Pisses me off a bit because the version of this diagram I worked from is different to the one you posted. To avoid confusion I won't post it here, but it shows crank sensor connection to pin 24 and ground to pin 8. Not sure why I used pin 7 instead of 8 but they are common grounds. In the old diagram pin 1 is used for CHT ground.
Looking at my wiring diagram, I will make the following changes in the harness at the MS3 connector:
- crank sensor shield to pin 2 (was grounded at G1)
- crank sensor ground to pin 1 (was 7)
- CHT ground to pin 7 (was 1)
- IAT sensor ground to pin 7 (was 2)

Yes, there are multiple versions of wiring diagrams. Documentation is a challenge.

We all just want to see this project working. Let's hope the wiring changes work to reduce the noise.

I went through this exact exercise... only reason I knew of these changes. Be sure to move tps and o2 grounds as well. Good luck.