Another electrical question from me.

[Newf]

I have a 3 cylinder Volvo Penta diesel (D1-30) in my boat and want to install a standalone pushbutton to energize the glow plugs when or if the need arises. For anyone familiar with this engine, you may be aware of a known issue with the "MDI Black Box" (Mechanical Diesel Interface). This box can fail at any time and leave you stranded and unable to start your engine. As a solution, many have installed an emergency bypass to restart the engine. I have already installed the bypass for the starter but I need to install one to the glow plugs.

My question is can I just run an appropriate sized wire from the battery to a push button and from the other pole on the push button to the bar connecting the 3 glow plugs and if I can, should it be fused? I was told I can run a wire from the existing preheat post on the MDI Box but I'd rather not touch the box if I don't have too.

Please keep it simple. These bypasses would be for emergency use only, should the MDI fail.

Thanks

 

[ship happens]

Hey @Newf, the only challenge I see is getting a push button rated for that kind of amperage. Not really a huge challenge. I'm sure with some searching you can find something. I don't know anything off the top of my head. I would assume 8 to 10 amps per glow plug. That would be in your favor only dealing with 3. That being said I would also always no matter what try and get 30 percent headroom on whatever electrical system your putting in place. Can squeeze that a little bit on somthing like a glow plug because it's momentary, but I would still aim for a 50 amp momentary switch or higher. Maybe look at Cole Hersee stuff? If anyone in the marine side has somthing like that they would be the first place I looked.

 

[InterMechanico]

These are OK...

Product - 9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch

9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch - The Heavy Duty Push Button/ Horn is designed to provide a reliable and secure connection with the vehicle's electrical system and work with 6V or 12V electrical systems.

picocanada.com

But if you look at the wiring schematic, you'll likely find that the control module energizes a relay or high current solenoid which in turn powers the glow plugs.

The best way would be to wire the momentary switch to energize that same relay. This way you are using most of the existing system without the electronic module.

 

[noluck]

you want a relay that will handle 80 amp, glow plugs are a direct short to ground

 

[Newf]

Thanks guys. There is an electrical engineer that has looked extensively into these failures on the MDI box. Volvo Penta has gone through multiple revision of it and my understanding is that the issue has still not been totally solved. Many have failed at less than 100 hrs. Fortunately I must have gotten a good one as it’s still hanging in there since 2014. From what I have read it would be about a 30 amp draw. I have a 50 amp push button switch that I was going to use. I did not want to go through the MDI box unless I had too. Would wiring it direct like I first described not work for the 10 to 12 seconds that it would be engaged? Very limited knowledge here with electrical so just trying to understand it.
Thanks again for your comments.

 

[ship happens]

@Newf I dont see why you cant run those 3 little plugs through a high amperage switch. As long as its a really good switch with Yes a solenoid makes more sense and if you had more glow plugs to deal with it would be the only option imo

A direct short to ground has zero resistance. Glow plugs have a resistance.

Block heaters are something to consider as well. They actually solve more problems in the end.

 

[seachicken]

These are OK...

Product - 9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch

9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch - The Heavy Duty Push Button/ Horn is designed to provide a reliable and secure connection with the vehicle's electrical system and work with 6V or 12V electrical systems.

picocanada.com

But if you look at the wiring schematic, you'll likely find that the control module energizes a relay or high current solenoid which in turn powers the glow plugs.

The best way would be to wire the momentary switch to energize that same relay. This way you are using most of the existing system without the electronic module.

View attachment 101567

This is the ticket, keeps it simple and less modification.

 

[noluck]

This is the ticket, keeps it simple and less modification.

great option if you are mounting it on or near the engine and not bye the helm

 

[Newf]

These are OK...

Product - 9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch

9452-11 - 60A 12V Mom On-Off Push Button/Horn Switch - The Heavy Duty Push Button/ Horn is designed to provide a reliable and secure connection with the vehicle's electrical system and work with 6V or 12V electrical systems.

picocanada.com

But if you look at the wiring schematic, you'll likely find that the control module energizes a relay or high current solenoid which in turn powers the glow plugs.

The best way would be to wire the momentary switch to energize that same relay. This way you are using most of the existing system without the electronic module.

View attachment 101567

A couple of responses seem to suggest this would be the way to go. I will be installing the switch tomorrow so one more question. From the info that I can find there are two relays inside of this little MDI box. If the issue is failure of the MDI module why would I want to connect to it?
There are 3 terminal post in the outside of the MDI, Battery, Start and Preheat as shown on the Photos. So are you suggesting to run a wire from the Preheat terminal post to the switch and the other wire from the switch to the bar connecting the 3 glow plugs? If the box fails will the glow plugs still energize with the switch? Not opposed to doing this, just want to make sure this will work if the module fails. I know that a wire from battery to switch to glow plugs will work but will do as you suggest if it’s a better/safer way.

Yes to the question if I will be installing the switch close to the engine. It will be no more that a 2ft run of wire on either side of the switch. Will 10gauge wire be big enough for this?
Again, thanks for the comments. I appreciate the input.
Marcel

 

[Newf]

Talked to a guy at Trotac yesterday and explained what I was doing and for what I wanted “emergency start” he saw no issue and also said that the 10 gauge was more than sufficient . Hooked it up today and replaced the 40amp switch that I was using for the start switch with a new 50 amp so both are the same. Gave a 10-sec hold on the pre-heat and it started on the first revolution. Quite pleased given that it was probably as cold today as any day that I will be fishing. Just need to tidy up the wiring with a few zip ties and good to go.

Thanks again.