MDI (Mechanical Diesel Interface) Failure

[Captain Nice]

MDI failed mid-cruise (engine stalled, wouldn’t re-start) on Volvo Penta D1-30 (R21-EC). Knowing the potential for failure, I had a spare (new) unit on board. Swapped the old with the new and was back underway in ten minutes. Apparently, a new MDI also resets the running hours value back to zero in the tachometer window (freshens-up the engine!). The accumulating hours ARE being registered, however, the digits are extremely faint and almost impossible to see; quite different from pre-failure. Anyone else have this happen, or have a clue as to why and how to correct?? Thanks for reading.

Bill

 

[Captain Nice]

Immediately after posting this diatribe, I looked in the Operator’s Manual(!), and apparently there is a way to adjust the tachometer window backlighting at the Stop/Start panel. Not sure why a new MDI would have changed the backlighting, but worth a try!

 

[MassTug]

Hey. Sorry to hear that you had the dreaded MDI failure. Luckily you had probably been reading the post here and know that this is a well-known and common issue with those engines. You were very smart to have a spare one with you. They are not cheap. We had an MDI failure at the dock and ended up replacing it with initially one of the outdated modules. When that didn’t work, we actually bought an updated one from Volvo penta. You’re correct it resets the engine hours. I don’t know any workaround for that. We didn’t have any issues with the backlighting on the display afterwards so that might be a unique problem to you. There are plenty of chats and blogs about the MDI failure in that engine online. You may find some good research in terms of getting a backlighting better. This is the one thing that bugs me the most about the Volvo engine. It’s an expensive replacement and after arguing with Volvo, they were unwilling to budge on replacing it or giving us a discount. Enjoy the boat. Jonathan littleredtug.com

 

[Newf]

Can't help with your question but I was wondering about your replacement MDI. Is it the latest revision and if so what is the serial number? Also are you aware of failures with their latest revision or does it look like they have figured it out? Mine is 10 years old and I should look at getting a spare. I have installed an emergency bypass for start and glow plugs so will not be stuck if it fails.

 

[Thatguy]

Many say that the failure is a result of voltage spikes, and that the latest versions are better equipped to handle this. As Jonathan said, there are post on multiple websites regarding this if you have the time to dig around a little. I did find a listing of serial numbers and dates of manufacture-if buying a replacement or spare be wary that there are still vendors out there selling very early versions (as we found out).
One thing for sure, it is known that shutting the computer off without first hitting the “stop” button can cause a damaging voltage spike. It may not kill the unit immediately, but will certainly shorter the lifespan (at least according to electrical engineers).
JP

 

[Captain Nice]

Thanks all for the thoughtful responses. The reason I had the spare MDI was because when my engine was replaced (the emissions thing) it didn't come with the most recent version, based on part number (#22458451). Because of this Forum, I knew there was potential for a problem. I fussed at VP and they sent me a current part, #22594274-P at no cost, and just kept it on the boat. I ran the original one from 2017 until now (285 hrs). Not sure if I should buy another spare or just do the bypass thing!
On the matter of backlighting, the Alarm/Dim button on the control panel did the trick. Read Your Manual, as they say. What was throwing me was the Volvo Penta logo that first appears in the tach window upon energizing was perfectly legible while the Hours digits were not. We learn by doing.

Thanks again very much,
Bill (Captain Nice)

 

[Newf]

Hi Bill,
With respect to buying another spare. If it were me, I would option to install the bypass. I've installed both the start and preheat and it's easy and cheap compared to the price of the box. You new MDI box may fail tomorrow but it may never fail. I still have the original one (2014) on mine with 3300 hrs on the engine. It may fail tomorrow as well but if it does I will just lift the hatch, push the button and I'm back in business in 10-20 seconds. I would then get a new box at my leisure. Just my 2 cents. Thanks for your info on the current part #'s.

Marcel