Volvo AQ140a cutting out

[dfleminguk]

Crane in at the weekend and the start of the new boating season! Good! but having engine problems /forums/images/graemlins/frown.gif
I have a AQ140a volvo penta petrol engine (1979ish) on a 280 sterndrive.
At the end of the last season I was having trouble with the engine cutting out at low revs or idle, after it had been warmed up and had been for a decent run. Sometimes it doesnt stall but just sounds laim, like its getting too much fuel through. Its then really difficult to restart and is appearing to flood.
The engine always starts first time from cold and runs great at higher revs. However if you were to start the engine from cold and leave it ticking over (say to charge the betteries) it will cut out and flood after around half an hour.
A volvo engineer suggested it wasn't a carb problem (which surprised me) and suggested that the coil could be breaking down which has now been replaced. I then looked at the distributor, leads, plugs, condensor ect

Anyone any other ideas???

Thanks Dave

 

[oldgit]

hi dave and welcome to forum,there are a couple of folks on here who my well be able to help,but you are probably going to get help faster if you also pop over to Practical Boat owner forum on this one.

 

[BarryH]

Welcome to the forum. For everything Vilevo look at http://www.arweb.co.uk/volpen/usergroup

Ok so you've got a flooding prob? On your engine you've more than likely got downdraft solex's. Simple carbs to work on once you have the knack. If it it a flooding prob then check the float levels in the carbs. Altho it sounds as if they're running rich to me. What model solex's are fitted to your lump?

A look at the plugs will give a good eyeball indication as to how things are burning. Is the engine idling smoothly or lumpy. Is there a bit of a lag when you open the throttles? Bit more info and we'll have this cracked.

 

[dfleminguk]

Thanks both of you. The carbs are solex downdraft and I think they are SOLEX 44 PHN-3. The carbs had been set up by a marine engineer but could do with avoiding the cost of marine engineer fees again being a poor student and all! Since they had been set up and running fine for abit, I wasnt sure if the actual carb settings would need altering from this??
However, Appologise if ignorant here......., wondered myself if they were running rich, I opened up the air adjustment half a turn on both then a full turn on both but didnt really seem to make any difference. There anything im missing which I should be doing as well?

The engine runs smoothly at idle if started from cold, however if you leave it running at idle as it warms up it becomes progressively lumpier, and then cuts out after around 20 mins to half an hour. As you mention, when it is running lumpy when warm, there is a lag when you try to open up the throttle. Throttle picks up fine from cold however.
The other strange thing is that during a weekend away or a week away of intensive use the problem doesnt go away but it does seem to get better. For example took part in a sail past which meant running on tickover for nearly an hour and it ran fine! Maybe this was just a fluke lol

The plugs look ok I think they are ever so slightly carboned up but they arnt totally black or anything.

Would blocked air filters achieve any of the above symptoms???

Thanks for the advice though mate, hopefully I know where to start looking now!

 

[BarryH]

Hmm ok. Right. turn the fuel/air volume screw in util it just seats. Then back it out by 1 1/2 turns. Thats your basic setting. Make sure both carbs are in sync. ie opening at the same time. you can adjust this on the linkages betwixt the carbs. Make sure both throttle levers are in the middle of the forks. That should be the carbs back to basic settings.

If the flame arreseters were clogged it would make the lump run rich anyhow. By the sounds of the plug colour it doesn't seem that your running rich.

What plugs have you got fitted. Are they the right heat range? One thing to check is the return/vent hose on the front carb It goes back to the fuel pump. You'll only find this on later engines.

Might be worth checking the spindles for wear. They can let in air leaning out the mix. An engine running lean tends to run hot. Hows the temp? If,in your original post, the coil were to be breaking down then I don't think you'd be able to restart easily. I've had one go on me and the only cure was to replace it. Have you checked for a spark when the engine dies?

Its fairly hard to diagnose probs on here without actually looking at the thing running or not. I would work through things logically on both fuel and ignition systems until you find the fault or am I teaching granny to suck eggs!

 

[dfleminguk]

Cheers! yeah i guess it isnt the best way to diagnose it on here lol but I have a few more ideas about what to look at now. Thanks for getting back mate will let you know how I get on!

 

[spannerman]

It sounds like you have given us our biggest clue when you say it starts easily, this is a sure sign that its probably running too rich as these engines can be pigs to start from cold if you don't get the throttle in just the right position. So as the others say check the carb adjustments and poss the float levels. Also in view of the age is there any crankcase pressure from worn pistons\cylinders, I have had at least two of these engines where the blowby gases which are fed into the airfilter box suffocated the engine at idle when it was warmed up, if you pull out the rubber hose from the airfilter and it runs more smoothly there is your problem. Solution without rebuilding the engine was to route the engine breather hose out through the transom.