MS board power backfeed

General support questions and announcements for MS3. See also MS3 manuals.

Moderators: jsmcortina, muythaibxr

SvenCS
Helpful MS/Extra'er
Posts: 113
Joined: Mon Feb 08, 2010 10:33 pm
Location: Seattle

Re: MS board power backfeed

Post by SvenCS »

Matt - I Checked the voltage at L2 today. 5.00 volts on both legs of L2 before and during the voltage spikes. With key on or engine running.

I have been suspecting that this is heat related. The ECU board was around 60°F when we started. I let the car run for 20 minutes and no problems. So I then used a hair dryer to blow some warm air into the box that contains the ECU. After just a moment of this the voltage starting going up and down (see screen shot). It behaved differently, in that it was oscillating up and down and not just rising to 22 volts like before. We then blew just cool air at the ECU box and it stopped within 10 seconds, back to normal 13.5 volts steady.

Does this info help?

Thanks,
BatVUpDn.png
2015-04-09 VaryingBatVolt.msl
1972 BMW 3.0 CS, v3.0 board, MS3 + MS3X, external MAP, VR-sensor, 60-2 crank, CAM gear tooth sensor, wasted spark, sequential
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: MS board power backfeed

Post by Matt Cramer »

Interesting. The MS3-Pro can normally take a lot of heat; I once ran one about 12" from an exhaust manifold. Is there any additional circuitry in the box?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
SvenCS
Helpful MS/Extra'er
Posts: 113
Joined: Mon Feb 08, 2010 10:33 pm
Location: Seattle

Re: MS board power backfeed

Post by SvenCS »

Yes. Only two additional small circuits. I have the 55 pin Bosch adaptor board DIYA provides installed at one end of the ECU box. At one end one this board is the MXP4250 MAP sensor and a resistor (both of which I replaced), and at the other end there is a BIP373 ignition driver circuit and resistor. See attached diagram.
BIP373MPX4250.jpg
The ECU is located in the glove box so does not see much engine heat. Again, with the hairdryer test there was not much heat needed. Could an individual component be faulty that just a 10-20 degrees of heat would cause it to fail?
1972 BMW 3.0 CS, v3.0 board, MS3 + MS3X, external MAP, VR-sensor, 60-2 crank, CAM gear tooth sensor, wasted spark, sequential
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: MS board power backfeed

Post by Matt Cramer »

It's possible. Let me know what happens to the voltage on L2 when you try out the hair drier.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
SvenCS
Helpful MS/Extra'er
Posts: 113
Joined: Mon Feb 08, 2010 10:33 pm
Location: Seattle

Re: MS board power backfeed

Post by SvenCS »

I did that earlier with the hair drier test. It stayed at 5 v.
1972 BMW 3.0 CS, v3.0 board, MS3 + MS3X, external MAP, VR-sensor, 60-2 crank, CAM gear tooth sensor, wasted spark, sequential
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: MS board power backfeed

Post by Matt Cramer »

How about the VREF voltage? MS3-Pros actually have a separate VREF power supply that tracks the main 5V plane. If just that is affected, there's a much smaller list of parts that can be the problem.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
SvenCS
Helpful MS/Extra'er
Posts: 113
Joined: Mon Feb 08, 2010 10:33 pm
Location: Seattle

Re: MS board power backfeed

Post by SvenCS »

I am pretty sure that held steady at 5 v as well. I didn't measure it when I used the hair drier, but did earlier when the problem was occurring. Also, the BARO log stays steady throughout when the 12v line is fluctuating (101.0-101.1 with the occasional blip to 100.9 or 101.2). Wouldn't those readings change more dramatically if the 5 volt vref input varied?
1972 BMW 3.0 CS, v3.0 board, MS3 + MS3X, external MAP, VR-sensor, 60-2 crank, CAM gear tooth sensor, wasted spark, sequential
phoenix3d
Experienced MS/Extra'er
Posts: 183
Joined: Wed Mar 19, 2008 2:12 pm
Location: South Africa

Re: MS board power backfeed

Post by phoenix3d »

Hi Matt. Apologies for hijacking this thread..

But Having the same problems with my MS3-Pro module setup here..

When cold we get approx 11.9 volt reading on TS reasonably steady until it's been running for a while.
Then i get bouncing voltages up to around 22.6v down to 16v...
then randomly settles back to a low 11.9 - 12.2v range for a couple of seconds and then back up to High readings again.. Regardless to say messes with Voltage correction on the injectors and coil Dwell.

Measuring on the Voltage Supply line to the ECU with Fluke Multimeter - Rock steady 13.6v all the time.

Please help me out with this as it's a clients car and needs to be sorted asap.

I can take a datalog if you require.

No Additional Add-on circuitry on board.

Gordon.
SvenCS
Helpful MS/Extra'er
Posts: 113
Joined: Mon Feb 08, 2010 10:33 pm
Location: Seattle

Re: MS board power backfeed

Post by SvenCS »

My problems ended up being a tiny blip of solder on the board, even though I carefully searched for this many times. I am not sure if your situation is the same. good luck.
1972 BMW 3.0 CS, v3.0 board, MS3 + MS3X, external MAP, VR-sensor, 60-2 crank, CAM gear tooth sensor, wasted spark, sequential
phoenix3d
Experienced MS/Extra'er
Posts: 183
Joined: Wed Mar 19, 2008 2:12 pm
Location: South Africa

Re: MS board power backfeed

Post by phoenix3d »

Oh MAN!!...

Thanks SvenCS..

That means having to pull everything apart and check with microscope.. (I'm practically blind.. getting old :shock: )

I've also noticed that I'm having aberrant behavior on the Digital Hi Speed frequency inputs. When the ECU is cold Dig 1, Dig2 & Dig3 dont work at all (no input - regardless of signal present on the lines at the nodule) but as it runs a while they start to come "on-line" starting with Dig3 then Dig2 and finally Dig1.

I wonder if this isn't a Duff Module. (Being that it was already sent back for not having Boot monitor installed... :? ) Can't afford to send Up & down all the time (here in South Africa, stuff is Frigging expensive)

Random Stuff keeps happening every-time I try get things working properly.

Gordon.
Post Reply