Problem with Volvo Penta 250 not reving under load

[PaulJ6152]

Can anybody help on the following problem, sorry its a bit lengthy but wanted give as much info as possible.

I have twin VP 250’s (the old Volvo 2 ltr single OHC engine) At the end of last year I got water in the fuel tank- leaking seal on filler cap. Both engines wouldn’t start water had got into carbs and engine.

So I removed fuel changed fuel filters stripped all four carbs (Solex 44 PAI’s), changed points, plugs, checked timing (also the advance) dwell and balanced carbs , even checked compression in cylinders.

Both engines now start fine and will run perfectly throttling easily and as I am on the river we don’t normally open the engines up and they run fine. However I wanted to see all was OK so opened up and one engine is fine but the other will not rev properly, its OK till about 2500 and then It seems to be labouring as though not enough fuel getting to it.

I have rechecked the carbs and all seems clear, accelerator pump works fine and the fuel pump is pumping fuel. I don’t seem to have any air leaks.

The carbs only have the idle speed and idle jet adjustment so no much to adjust and assume the normal mixture is set.

One other thing I noticed was, if I opened the idle mixture screw while under load the engine opened up a bit better. So assume the richer mixture from the idle jet was helping so it seems to point to carburettor problem.

Any ideas would be much appreciated as I think I have run out of them.

 

[Stemar]

There are a few possibilities, but I reckon the most likely is a bit of crud in the main jet that's restricting the flow.

If you can get the engine to point where it's struggling then stop it it might be instructive to check the level of fuel in the float chamber. If it's low, then that would also give the symptoms you're getting, and would indicate a restriction in the fuel supply. Quite a lot of carbs have a mesh strainer in the fuel inlet, which oftewn gets missed in the cleaning process. Other possibilities are: filter, tap, crimped fuel pipe, etc. I once had a car with an electric petrol pump that couldn't keep up with the demands made on it by the rather nicely sorted engine and kept cutting out at sustained speeds of over 95. It took me ages to figure that one out!

 

[PaulJ6152]

Thanks for the pointers. You are right it does have mesh strainers which were dirty but cleaned them I suppose could have got clogged again.

The level in float chamber is interesting when I got back to the marina I ran the engine for a while and removed the cover to float bowl and level was low in both carbs compared to the other engine. However ran it again and checked and level OK. I have checked needle valve and thats OK as well.

Certainly have pressure there as loosening fuel pipe fuel squirts out. when engine not running.

Only thoughts I have are to try swopping fuel pump with other engine and swop carbs.

One of the advantages of having 2 engines ?!