Volvo Penta MDI (Black Box) failures

[Alfred423]

Originally Posted by Challo

After 5 MDIs (I paid for the labor and several of the units), we spent the off-season eliminating it. A perfectly good engine should not be limited by a piece of electronics.

S/V Challo

What parts did you use for the tachometer and the flywheel sender?

[CarinaPDX]

Originally Posted by Alfred423

What parts did you use for the tachometer and the flywheel sender?

Any tach that takes an alternator input ("W" terminal) should work if it has the desired RPM range.

Greg

[Alfred423]

OK. So you ditched the fly wheel sensor and went to the Alternator. That works though I would like to stay with the fly wheel. Thank you for the response.

[CarinaPDX]

Originally Posted by Alfred423

OK. So you ditched the fly wheel sensor and went to the Alternator. That works though I would like to stay with the fly wheel. Thank you for the response.

No, I haven't changed anything. I just recommended that as a simple way to go. There is a "W" terminal on the stock Mitsubishi alternator so easy to do. This should work: https://www.summitracing.com/parts/rra-68358p

Alternatively you could use the existing inductive pickup. This looks like it might work: https://www.amazon.com/Sierra-Intern...VOU/ref=sr_1_1 . You would need to make sure the teeth count is within 90-180, and you might call Sierra for electrical compatibility.

For a lot more money, VDO makes both alternator and magnetic pickup for flywheel versions.

Greg

[foxinsox8]

I seem to have missed it but How does your system trigger the alternator to switch on?
Thanks Tim

[aberglas]

Attaching to the W alternator will measure the alternator RPM which would be a few times the engine RPM. How does that work? Do tachos or alternators have a way to divide them down?

[foxinsox8]

Wizo, did you sort the oil gauge. Is an oil filter sandwich plate the possible solution to relocate sensors? cheers Tim

[SV_FlyingTigress]

This might be in the thread, but I used the pats list and wiring schematic from this YouTube

https://m.youtube.com/watch?v=wHR5P4...RpIGRvb21zZGF5

[Samwise]

End of last year, I was also hit by the infamous MDI problem.

In warm waters with an outside temperature of around 40°C, the engine had been running for a few hours in the morning and could be switched off without any problems.

Later in the afternoon, the panel would not switch back on. There was no response from the MDI box.


So I took the thing home and, together with someone who routinely analyses automotive ECUs, we examined the MDI box. There were none of the typical external causes, such as

e.g.

- Short circuit in the starter motor circuit, glow plug circuit or a blown stop solenoid

- Water ingress in the panel

- Voltage spikes due to a loose battery connection

Nothing was burnt on the PCB. The power supply and all regulators were OK.


However, we found a combination of oddities that I have not seen described before.


To confirm these findings we would like to find more boxes that have the same problems:

We are looking for MDI boxes that have silently quit their service and for which the fault can NOT be traced back to external causes.


We have simply become curious: If the same problem occurs more frequently and it turns out to have the same cause, then we can show a way to fix it and the affected MDI boxes won't just become a worthless paperweight.

[toddtimes]

Originally Posted by Samwise

To confirm these findings we would like to find more boxes that have the same problems:

We are looking for MDI boxes that have silently quit their service and for which the fault can NOT be traced back to external causes.

Pretty sure I've got one like this lightly taken apart. Do you want it?

[Samwise]

Originally Posted by toddtimes

Pretty sure I've got one like this lightly taken apart. Do you want it?

It would be great to get our hands on one, although shipping USA->Europe may be expensive of course.

I'll send you a PM if that's OK.