Volvo AD31P - Won't rev beyond 2000 rpm

[petermills]

I have a Sealine 240 with a single Volvo AD31P engine. She was Ok last year but on starting up recently I could'nt get more than 2000 rpm out of her either in gear or in neutral so nothing to do with props etc.. The engine sounded less smooth than previously so I'm wondering what could be wrong. Oil press and temperature guages are both reading normal so any advice or words from anyone who has had a similar experience would be much appreciated.

 

[TRH]

Hi You may have your Turbo stuck,That was my trouble on same engine.

 

[Portland Billy]

I gather you've looked at the fuel filters ?

 

[oldgit]

advice or words from anyone who has had a similar experience would be much appreciated


Can you remove duct tube between turbo and filter.Pop your finger in and feel if vanes freely turn,if so turbo is prob OK,think it may be permissable to apply gentle pressure with finger to free ,with out causing any damage.
This is of course done with engine off and cold.

 

[ulyden]

You dont need any boost to get it up in speed in neutral! Chek your wire to the fuel pump! Or twist it manualy to maximum! Air in the system can fool you also! Just let the engine heat up before you try it!

 

[Drifter]

If you've just started the engine after the winter break it could be the primary fuel filter.
If the diesel tank is of metalic construction and has been emptyish over the winter it may have suffered from internal condensation and the moisture could now be sitting in the primary filter.

 

[RAI]

If it sounded rough, was it firing on all cylinders? (A blocked injector?)

 

[aquatom]

Could be a valve or two seized!

 

[maverickofpoole]

Turbo boost pressure switch telling the ecu that it aint working thereby switching to limp me home mode?

 

[aquatom]

No ecu on an ad31!

 

[Viscount]

Fuel / air blockage or not operating on all cylinders is my view. Other issues would only be relevant under power IMHO.

 

[maverickofpoole]

No ecu on an ad31!

Well it aint that then

 

[CX54WEK]

Dirty/blocked up air filter?

 

[spannerman]

Most likely the turbo, if it worked last time it won't be the throttle cable.
Take off the aircleaner and see if the turbo spins, if not, them remove the exhaust bend as this is where the problem will be, it may have rusted around the turbine, so carefully scrape away any rust that is fouling the blades until it spins freely.
Had this on a D4 less than a year old!
If the turbo is OK then you need to go through the fuel system, replace all filters and clean any sediment bowls, and blow through the lines.

 

[Jegs]

Turbo Problem

Thanks. Spannerman, another piece of helpful advice that I shall try to store in what's left of my grey cells.

John G

 

[petermills]

Volvo AD31P not revving beyond 2000 rpm

Thanks to everyone for your input.
Turbo vanes spin easily and air filter is clean. Fuel tank was filled at end of last season so not a condensation problem. However i just checked the fuel lines from tank to fuel cock and fuel cock to filter. These are braided armour type but they have kinks in several places which is probably restricting fuel flow. No problems last season so I'm wondering whether the extreme cold has got to them and closed them up where they are bent. If this is the case, would this be the cause of the low revving????

 

[ulyden]

If you can idle the return fuel is heating up the tank. A diesel like this ad some hundres watt in the fuel! Chek that it flows in the return line!

Strange that you reach 2000 rpm in neutral end the same with the propeller running!

You are sure the hp pump is getting its demand? Is the feed pump ok?

You dont need much air or fuel to spin at hot engine up to rated speed!

Is there any smoke? Color? If you have white smoke it might be air in the fuel hp lines or the pump!

 

[dingdongs]

if u look on;www.iboats.com under forums and then mercruiser/volvo a guy has exact same problem so may get some info on that site too.on todays posting and yesterdays.

 

[spannerman]

Now we have eliminated the turbo, you could try using a 5 gal can of diesel connected with a couple of hoses direct to the lift pump and return fitting on the injection pump, if it works you know its the plumbing in the boat, if its the same then its on the engine, as mentioned it could be the lift pump.

 

[petermills]

Problem Solved!!!
One of the two flexible,armoured fuel lines fitted by a previous owner I assume, was too long. In order to get it in the space available it had been bent/kinked into position. There were kinks in three places and when the pipe was removed it was almost impossible to blow through it. Although this was an armoured pipe, the internal pipe is very thin and susceptible to kinking. I guess that over the winter the kinks had become more impacted by freezing. The pipes in question are to the required ISO standard and are covered in a bright yellow sleeve. The only letters that might indicate the manufacturer are 'GCE'. I'd recommend boaters to be wary of these pipes in the future.
Once the replacements were fitted the engine revved quite freely to 4000 plus.
Thanks again!!