TAMD 74p engine revs (or lack of) problem

[crazy4557]

I have the standard Volvo EDC on my engines. Starboard engine runs and revs out of gear fine. Port engine runs and sounds fine in neutral but is very lazy when you open the throttle and doesn't want to 'rev up' when you blip the throttle in neutral. When under way at idle speed if you open port throttle on it's own you get very slow acceleration/response. Open both throttles equally and port engine behave's fine. Both are similar max revs at WOT. No extra smoke and temperatures are rock steady.
Does anyone have any clues as to the issue here? This happened last year but seemed to go away after a while when the boat was used frequently but with hardly any use this year the issue is back.
I'd like to know that it's not a potential big problem as we're off for a 3 week jaunt next week.
If anyone has any clues as to what it might be I'd be very grateful.

 

[bvickers]

I had a similar problem with my 74P's a few years ago. Sounds like it may be the boost pressure sensor - there's a pipe that leads to it that fills with condensation - it could be that. Not sure I understand why when you open both throttles they're ok though - are you sure that is the case? Anyway best of luck with getting it fixed.

 

[nicho]

Both our 74P's had to have the boost pressure sensors changed - a common occurance we were told. The port engine would often not rev when opening the throttle. Sometimes, after much manipulation of the throttle, it would suddenly pick up as normal. Both sensors were changed as a precaution, and no further problems for three years, when we sold the boat on. I gather the sensors were redesigned to alleviate the problem of condensation.

 

[crazy4557]

Both our 74P's had to have the boost pressure sensors changed - a common occurance we were told. The port engine would often not rev when opening the throttle. Sometimes, after much manipulation of the throttle, it would suddenly pick up as normal. Both sensors were changed as a precaution, and no further problems for three years, when we sold the boat on. I gather the sensors were redesigned to alleviate the problem of condensation.

Thanks for your help Nicho and BVickers, I'll give them a go.

 

[nicho]

Thanks for your help Nicho and BVickers, I'll give them a go.

I would get some advice from a Volvo engineer first, just in case it's not what we suggest. Great engines though aren't they.

 

[scubaman]

...

 

[scubaman]

I had a similar problem with my 74P's a few years ago. Sounds like it may be the boost pressure sensor - there's a pipe that leads to it that fills with condensation - it could be that. Not sure I understand why when you open both throttles they're ok though - are you sure that is the case? Anyway best of luck with getting it fixed.

There is a cap, shape of a bolt, at the end of the said pipe, just below the edc unit. Crazy, try opening it and let the condensation drain out. Leave it open overnight or a couple of days if time allows. i'll see if I can find a pic of it.

 

[crazy4557]

There is a cap, shape of a bolt, at the end of the said pipe, just below the edc unit. Crazy, try opening it and let the condensation drain out. Leave it open overnight or a couple of days if time allows. i'll see if I can find a pic of it.

I think I know what you're talking about but a picture would be helpful..

Spoke to the VP agent today who seems to think it could be a sticky potentiometer, they suggested using the boat and it'll probably free up to which I asked if they could make the wind beggar off and I'll go and play

 

[scubaman]

Just a sec, i'll take a new photo...

 

[scubaman]

This is the forward end of the engine, port side

In this close-up you can see the pipe and cap in question.

Undo the bolt on the right and the condensation drains out.

 

[crazy4557]

Very kind Scubaman...I'll take a look in the morning and report back.

 

[hector]

Excellent work....... This is what this forum is all about. I've the same engines so will check mine too.

 

[crazy4557]

Scubaman...Removed the nuts as suggested and plenty of water came out and left for a while. Made no difference to throttle response unfortunately, thanks anyway.

Went out yesterday and boat performs exactly as it should and accelerates up to planing speeds without hesitation, just when you use port engine only it decides not to play.
I'll keep using as suggested elsewhere and see if that helps. Not right though so needs to be 'fixed' sooner or later.

 

[scubaman]

What happens if you turn the rev sync off?

 

[crazy4557]

Not exactly sure what how to do that so can you please explain :encouragement:

 

[scubaman]

Not exactly sure what how to do that so can you please explain :encouragement:

It's the 'equals'-button on the edc-panel. Depress that to de-activate the rev sync (the iirc blue ligh goes off). By default, the system keeps the revs in sync while under way, so one doen't need to fine tune the throttles to achieve the same. Again iirc, it shouldn't be active on the lower revs, but it would be interesting to see if turning it on/off has any affect on things. If it does, it might point to the pot being the problem. This in case the rev sync-function by default follows the throttle that is ahead, if you know what i mean.

 

[IDAMAY]

We had exactly this problem with TAMD 74P in a Sealine T47 some years ago. Clearing the water out of the vacuum pipe didn't solve the problem because the diaphragm switch at the ECU end had rusted. An engineer managed somehow to clean the switch and dry things out which effected a temporary repair but eventually we needed a replacement switch. The switch was, as you might guess, rather expensive at over £100 (iirc) around 2008. Mind you that was the least of the cost because diagnosis cost £100s as we were in Denmark where there was little experience of electronically controlled engines. We subsequently changed the switch on the other engine as a precaution and then regularly drained the vacuum tube. Hope you get it sorted for your cruise.

 

[nicho]

We had exactly this problem with TAMD 74P in a Sealine T47 some years ago. Clearing the water out of the vacuum pipe didn't solve the problem because the diaphragm switch at the ECU end had rusted. An engineer managed somehow to clean the switch and dry things out which effected a temporary repair but eventually we needed a replacement switch. The switch was, as you might guess, rather expensive at over £100 (iirc) around 2008. Mind you that was the least of the cost because diagnosis cost £100s as we were in Denmark where there was little experience of electronically controlled engines. We subsequently changed the switch on the other engine as a precaution and then regularly drained the vacuum tube. Hope you get it sorted for your cruise.

Yep, corrosion on ours meant they both had to be changed too.