volvo aqd40 'ignition boost' key?

[symondo]

Almost at a point of getting our boat into the water.. but this 1still stumps me!

I would imagine on turning the engines on, let the glow plugs warm, turn over and good to go, as I'd expect from any diesel.

So why is there an ignition boost key? Anyone else heard of this? I've tried tracing the wires but I cant see where they go.

 

[superheat6k]

Possibly a cross connect between battery banks perhaps.

 

[oldgit]

Almost at a point of getting our boat into the water.. but this 1still stumps me!

I would imagine on turning the engines on, let the glow plugs warm, turn over and good to go, as I'd expect from any diesel.

So why is there an ignition boost key? Anyone else heard of this? I've tried tracing the wires but I cant see where they go.

As far as I can remember you turned the key to the preheat position.counted to 10 or 15 whatever and then started engine.
Never bothered or needed it in the 5 years of owning a pair od AQD40As.If you cranked long enough sooner or later they started even with well over 4000 hours on the clock.
Engines were all OK and apart from servicing were untouched apart from alternators and starter motors.
If only the same could be said for the @#$%&* ***drives.

 

[symondo]

So it should give a few extra amps to the glow plugs on turnover then? I've never seen a 'boost' key before hence asking.

 

[VicS]

Almost at a point of getting our boat into the water.. but this 1still stumps me!

I would imagine on turning the engines on, let the glow plugs warm, turn over and good to go, as I'd expect from any diesel.

So why is there an ignition boost key? Anyone else heard of this? I've tried tracing the wires but I cant see where they go.

There is no mention of this in the operators manaul, presumably some feature that a previous owner has added.

Very possibly, as suggested, a switch to remotely parallel two battery banks if necessary for starting but does the boat have two battery banks? If not then that's not the answer!

 

[superheat6k]

Didn't realise this was on the starter sequence of main key.

On a petrol engine the ignition coils are commonly 6v with a ballast resistor in series to split the 12 v supply. When the starter operates the voltage plummets, so the boost restores the 6v to the coil by temporarily bypassing the ballast resistor, which means you keep a nice fat spark during the start.

Therefore possible the same key switch was also used for petrol engines.

 

[symondo]

Didn't realise this was on the starter sequence of main key.

On a petrol engine the ignition coils are commonly 6v with a ballast resistor in series to split the 12 v supply. When the starter operates the voltage plummets, so the boost restores the 6v to the coil by temporarily bypassing the ballast resistor, which means you keep a nice fat spark during the start.

Therefore possible the same key switch was also used for petrol engines.

It is a completely separate key, nothing to do with the ignition keys that I can see.

There are 2 battery banks currently but we are replacing this next week with a complete set of new batteries with a better cca and amp hour rating per unit. We are also increasing the bank by 2 batts.

 

[superheat6k]

It is a completely separate key, nothing to do with the ignition keys that I can see.

There are 2 battery banks currently but we are replacing this next week with a complete set of new batteries with a better cca and amp hour rating per unit. We are also increasing the bank by 2 batts.

Sounds like a cross connect. On mine there is a starter style solenoid that connects both banks +VE, allowing one bank to start the opposite engine if the batteries go a bit flat, but mine is a simple button (Fairline).