help with Volvo engine problem

[IanC]

Can anyone give me a list of things I should look at to try and solve a problem with one of my Volvo AQ140 petrol engines. Here's the situation: - it starts OK and will rev when not in gear. When in gear and cruising it will do OK at slowish speeds, but when you open her up the engine dies back - it's like it looses all power and will even stall when you are accelerating. You can then start it again without too much difficulty. When this problem happens - you can 'punch' the accelerator and can get the revs up and she will do OK. There is nothing around the Prop - the temperature gauge shows normal - there's plenty of petrol in the tank - what could it be? Any ideas of a hit-list to look at would be really welcome.

thanks so much

Ian C.

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[VicS]

I believe this engine is based on the B21 engine fitted in Volvo 240 series cars.

I had a similar problem many years ago with the car when the diaphragm in the carburettor failed.

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[h4nym]

Ian

Certainly smacks of fuel starvation somewhere - the other engine, I take it, is fine? If that's the case, then u can eliminate all the fuel supply process that's shared eg fuel filter, pump etc. Trace through from the first point at which fuel becomes supplied to that individual engine.

Best

H

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[IanC]

Yes - the other engine is running fine. I have only had the boat since November '02 - I have not changed the petrol filter - is that where I should start - and do I get them from Volvo?

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[gonfishing]

this sounds very similar to my current problems, firstly try and gain access to the fuel tank and make sure there is no crap etc floating around,you can remove the fuel pick up pipe and shine a torch in , then check your breather pipe, as it is possible that there is a blockage or something in the line which will cause the same problem. make sure all fuel line connections are secure and not leaking or,again this will cause problems also check inline seperator and strainer make sure all is clean make sure all fuel lines are in good order ang not kinked or bent sometimes on rubber hoses the inside starts to degrade and you end up with a flap of rubber moving around which will also cause problems, so far this has not cost anything except time and effort!!! next strip fuel pump and check to see if diaphram is ok no cracking or brittleness and that inlet valve and outlet valve must be in perfect order no sign of wear /damage permissable if it is showing signs of wear go to your local motor factors or contact BarryH on mobo forum, then check the diaphrams on the top of the carbs any sign or damage/ wear then replace them about £1.00 ea from motor factors if this doesn't cure the problem you like myself will have to seek expert opinion and get check book out!!!!

hope this helps
julian

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[BarryH]

The AQ140 doesn't use CD carbs as the likes of the Strombergs. It'll have solex downdraughts PAI44's with accelerator pumps to aid acceleration, believe it or not.
Sounds as if the carbs are running out of balance a little. If it was starvation the thing wouldn't open up when the throttles was "punched". Could be running weak though. Is the engine temp ok. The basic setting for the Air volume screw, on the back of the body near the bottom, is 1 1/4 turns off of seated.

Timing. It needs to be set properly on these engines as theres no vacum advance on the dizzy. Advance is taken care of by the centrifugal wieghts only. Next time the engine dies, check to see if there is petrol in them by operating the throttles. If the pumps squirt fuel into the ventri's then its not petrol starvation. I'd check that the things are balanced and set up properly. Bit of a pain of a job but these engines are prone to rough running if the carbs aren't set up properly. How old is it and what sort of hours run. The spindles in the throttle bodies wear and let air in leaning out the mixture and causing rough running and uneven tickover.

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[IanC]

Thanks - the engine hours (according to the hour meter about 470 hours) although it's some 20 years old. The boat has only been used on rivers - and has had little use over the past few years. We've only had her since November 02 and she has been doing good - the other engine is doing fine. The - the temperature gauge is showing normal. I'm not the greatest engineer - although I am a careful DIY'er - so are the things you are suggesting possible - or do I need to go to a boat-yard (with my wallet)

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[BarryH]

Re: Idiots guide to balancing the carbs

Right first off. Disconnect the throttle cable. Then slacken off the spindle clamps. Back off both throttle stop screws then adjust until the just meet the the throttle body stops. Next make sure the lugs are in the middle of the forks on the spindle clamps. Carefully tighten up the spindle clamps making sure you don't move anything. That will syncronise the carbs. Just to make sure they operate together. The accelerator pumps are a fair indication of this. They should both squirt fuel at the same time.

Next. screw in the air volume screws until the just seat. Then back them off 1 1/2 turns. This will give you your intial settings. Now start the engine and let it warm up. It won't tick over by itself yet, but get it warm. Shut off the engine and give each throttle stop screw half a turn. Now restart the engine. It should idle all be it a bit low. Now the trick bit. Get yourself a gunsons vacum gauge and a catering size coffee tin. Cut a 2 1/2 inch dia hole in the bottom. place this on the carb and put the ventri fitting of the vacum gauge in the hole you cut. Check each carb and see how they are pulling. The carb reading the lowest amount, turn the air volume screw OUT until you get some where near the same reading as the other one.....got that! Make sure they are both pulling evenly. Now reset the tickover with the throttle stop screws until you get the right rpm, about 900-950 will be about right so it wont stall when you put it in gear.

If you haven't got a vacum gauge, you can use a bit of rubber half inch tube to listen to the carb pulling. Place it next to the ventri and listen to the "tune" that it gives. The carb pulling at a higher rate will give a higher note when put next to your ear. IE tuning the carbs!!

Right now reconnect the throttle cable and refit the flame traps and air box, not forgetting the crank breather tube. That as they say should be it. Others will say its wrong, but its the best way that I've found of doing it. Make sure the ignition is in good order. Common fault is the rotor arm giving out. Its the same as the car one and has a capasitor/ resistor embedded in it, or something like that.

If you need anything else, give me a PM. Hope you get it sorted. Don't go to your local boat mechanic, friend of mine called the local mobile car chappy and got his volvo sorted at half the cost, I wasn't about!

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[IanC]

Re: Idiots guide to balancing the carbs

Thanks - I'll have a go

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