Volvo TAMD41A exhausts

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petrolhead63

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Hi, I have been trying for some time to get some guidance on how the exhaust limiting flaps work and when. On our "new" boat it seems to work on port but not on starboard. Oddly the solenoid seems jammed in...short operating rod. I can push the exhaust flap back against the spring pressure so the flap is not seized.

The working one operates when ignition is switch on and as the engine is revved the flap pulls back against it. This being the case I am unsure why it even needs the solenoid because the flaps are close I think at low revs or stationary?

Any help appreciated
 
The exhaust pressure flaps are there to help reduce smoke on cold starts and are closed below a set temperature but will open if and when the engines revs reach a certain point.

Solenoids are expensive at around £300.
 
OK many thanks, so there is a thermo switch somewhere controlling the solenoid or is it a bimetallic spring of some kind?

Where I get baffled is as follows. The flaps as I see it are closed with ignition off, they are not seized because I can manually push/pull the rod which is hooked to the solenoid backwards which I assume then opens the flaps in the same way exhaust pressure would do.

If I energise the ignition on a cold engine (the working solenoid!) I can see the solenoid click forwards, which does nothing to the exhaust flap because it is closed any way? the flap actuating arm is set so it can be pulled by the solenoid but can manually pull back and slide on the solenoid. Does this then stop the exhaust flap opening under pressure at lower revs because the solenoid offers a physical hold back?

On the side which appears to have a seized solenoid it is stuck in I think, the rubber bellows compressed but I can still pull the rod back by hand therefore opening the flap? is that correct.

I assume on the side that is currently duff I would be best advised to disconnect the flap off the rod and wire it open against the spring pressure?

Thanks ever so much for you interest.
 
AFAIK based on my 31As, the flap will be open by default and is pulled closed by the solenoid (against a spring in the solenoid) when the engine has power ("ignition") and the throttle at idle. There is a microswitch on the throttle (engine end) that activates on idle which energises the solenoid. There seems some circuitry that stops the solenoid operating in paid succession. There is nothing temperature related about this.

On your "duff" side, try disconnecting the solenoid to make sure it simply isn't permanently powered (albeit unlikely). Assuming it isn't, something sounds like it is stuck and/or the spring in the solenoid has failed.

Good luck!
 
thanks Viscount, I have looked and the duff side solenoid does not seem permanantly energized and also the black plastic end cover on the electrical end is blown with looks like rusty runs out of it! It is pulling the flap closed permanently I think being stuck in retracted position.
I do seem to be able to push the lever backwards and I think therefore open the flap....will exhaust pressure do this, or should I disconnect/fasten the flap open until I sort it fully.
It is difficult seeing this dodgy engine one, other is easy and looks suspiciously new ;0) but I think the flap is open if the rod is pushed back fully extended.
My research shows the solenoid is no longer available and a replacement is a stop solenoid off a 61 engine with more wires? does anybody know.
 
hi Tall Tim, thanks for your interest. I have now established the usual after market/Volvo suppliers do the new 3 wire solenoid conversion kit at £225 plus VAT, needing a conversion wiring harness at another £24 plus vat. The original 2 wire solenoid not available any longer.

I need to establish now what is on ours, the port one looks very new, shiny and no green paint! the starboard one looks similar but maybe older.

A 3 wire solenoid from my car knowledge has a strong coild to pull and a weaker one to hold in after actuation and therefore prevent overheating, if this is the case I suspect maybe the 3 wire is permanently on the strong pull coil if it is wired into a boat circuit only catering for the two wire version.

I know the conversion has a micro switch and plate to fit on the fuel pump aread and set up so the flaps close at circa 1100rmp, does anybody know how the original solenoid gets its message to close?
 
Well for those interested.
The duff solenoid is off, and the plunger/spring had gone off line in the cylinder and jammed solid. This I think caused an overload on the pull coil which maybe did not turn off because the plunger did not fully retract. The back end of the plastic cover/cables etc were fried!
The boat had had replacements before, they are both newer style three wire ones.
I think it is the same as a bigger 61 motor stop solenoid but am not sure, if it is there are better priced compatible solenoids available.
 
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