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JinnyMint
JinnyMint

Posted: Sun Mar 27, 2016 1:13pm

Post Subject: Lost Revs

I have a 34ft narrow boat powered by a Vetus M3.10 The engine starts well and runs on tick over for an hour ok, thirty mins into cruising I loose revs, the engine drops down to tick over speed. It doesn't stop but I have to push the throttle lever right forward and after a few seconds the revs pick up. This happens at ten to thirty mins intervals, any suggestions please ?

Tony-B
Tony-B

Posted: Sun Mar 27, 2016 5:32pm

Post Subject: Lost Revs

Tony-B
Tony-B

Posted: Sun Mar 27, 2016 5:41pm

Post Subject: Lost Revs

In the autumn I would suggest that it could be fallen leaves around the prop but not in the spring. Make sure there is nothing around the prop by FEELING down through the weed hatch. After running a while check that the stern gland is no more than slightly warm. If it is a packed gland may be over tight or the engine alignment may need resetting. Also make sure the engine is not overheating. I doubt it is because you have not mentioned clouds of steam/smoke. If all that is OK I am afraid that only leaves the fuel system. Vetus do/have fitted electric lift pumps with a filter in one end under a bayonet twist off cap. make sure this is clean if you have one. Then you need to check the bottom of the fuel tank for water build up and signs of bug (discoloured fuel & slime). Finally replace the fuel filters making sure that they are fitted correctly and cut the old ones open so you can see what they have caught - slime means bug. Then come back and tell me what you have found.

JinnyMint
JinnyMint

Posted: Sun Mar 27, 2016 6:11pm

Post Subject: Lost Revs

Thank you, will do.

JinnyMint
JinnyMint

Posted: Mon Mar 28, 2016 1:45pm

Post Subject: Lost Revs

Dear Mr Brooks, Following your advice I have lifted the weed hatch and the prop and shaft are all clear. I have drained and checked the sedimentor, no discernable water and no slime or sediment. I have drained and removed the main fuel filter and pulled it apart, no slime or anything untoward i can detect. I have checked the stern gland and i can turn the shaft by hand quite easily. I will check for heat when i replace the fuel filter and take a cruise next weekend. I will keep you informed. Thank you for your help. Regards Brian Clensy

Tony-B
Tony-B

Posted: Tue Mar 29, 2016 7:22am

Post Subject: Lost Revs

Thanks Brian, that rules out a lot of things so we look at the less probably but I noticed that you did not specifically say you check the filter in the end of the electric lift pump or confirm that your engine has a mechanical lift pump. When the engine is playing up check the exhaust smoke. If it is blacker than normal check the air cleaner is clear and that there is at least the equivalent of a 3 sq.in. vent allowing air into the engine bay. Make sure the gearbox has enough oil in it, especially if its a Technodrive. I understand that letting them run but out of gear for long periods can cause internal damage. This only applies to a Technodrive box. If none of the above effect a cure then I have heard of another Vetus suffering like this but never got told the cause so maybe it would be time to consult a Vetus agent.

JinnyMint
JinnyMint

Posted: Tue Mar 29, 2016 9:37am

Post Subject: Lost Revs

Thank you for the advice, weather permitting I will go through all the things you recommend and report back. Much obliged. Brian Clensy

Tony-B
Tony-B

Posted: Wed Mar 30, 2016 7:32am

Post Subject: Lost Revs

A further thought. Make sure the return pipes to the fuel tank are clear. On the Vetus I think you have to small hoses joining the main return pipe. One small pipe from the injector pump or filter and the other from the injector leak off. If the pipe is blocked or badly restricted air could build up in the filter or injector pump and then the engine would misfire, lose power, or even stop. If it stayed running and purged the air itself it would run properly again. Try cracking the injector pump bleed screw open a little when it is playing up.

JinnyMint
JinnyMint

Posted: Fri Apr 01, 2016 4:20pm

Post Subject: Lost Revs

Dear Mr Brooks, sorry i didn't read your last post till just now, will have a look at that tomorrow. In the meantime i have replaced the fuel filter and checked the filter at the end of the lift pump, which i believe to be mechanical, the filter was clear and as it should be.I have changed the engine oil and filter, it needed it anyway and i checked the gearbox (Hurth HBW) oil it was a little low so topped it up. My engine is indirect cooled through an heat exchanger and the exhuast gets passed out with the water, there is no smoking apart from when starting from cold and then only for a second or two. Today I took the boat out for a four hour cruise from Napton bottom lock to just past bridge 101 and back. Sad to say the problem still persists in fact a little worse as this time the engine died on two occasions, sometimes it would regain revs on its own after about ten seconds other times moving the throttle forward did the trick. In that four hour trip this must have happened a dozen times in various intervals, five mins to three quaters of an hour. Sorry to have gone on at such length. Thank you for your continued support. Regards Brian Clensy

Tony-B
Tony-B

Posted: Fri Apr 01, 2016 5:41pm

Post Subject: Lost Revs

Your last reply raises another question. If it is mechanical fuel pump then as far as I am aware there is no filter in it. If you found a filter in the end of the fuel pump then it should be an electric pump. They are usually cylindrical, about 1.5" in diameter and may be 5" long. They may have an earth (negative) wires screwed onto an end cap and will have a positive going into the middle of the pump body from the top. Electric pumps do eventually get unreliable and electrical circuits develop loose/dirty connections. Apart from the leak off pipe you have checked everything else and it all sounds OK, yet it still sounds like a fuel problem. Before messing with the leak off/return pipes check all the electrical connections relating to the lift pump. if all look sound try to rig up a gravity feed fuel tank to the main engine filter and see if the problem goes away. If it does then you its probably a lift pump problem. If you want to send a photo of your lift pump to Tony@tb-training.co.uk after Saturday night I will be back from Bruges so will be able to receive it and confirm if its mechanical or electrical.

JinnyMint
JinnyMint

Posted: Fri Apr 01, 2016 6:28pm

Post Subject: Lost Revs

Thank you, The fuel pump and primer pump is situated at the bottom front of the engine below the alternator and water impeller housing. I enclose a photo from the vetus handbook. I could not find any electical connections to mine though accessibility is very limited so might have missed them. Thanks Brian Clensy ps enjoy your trip.

Lost Revs
Tony-B
Tony-B

Posted: Sat Apr 02, 2016 4:29pm

Post Subject: Lost Revs

Thanks, from your description of its position and what I can see of the photo it is all but certainly a mechanical pump. The reason I asked that you email the photo to me rather than put it on the forum is because the forum reduces images to an unusable size - have a look and see. It even looks as if it may have a strainer under a cap but I can not be sure about that from the photo. Forget anything I said about electrical fuel pumps, it will not apply.

JinnyMint
JinnyMint

Posted: Sun Apr 03, 2016 7:27am

Post Subject: Lost Revs

Dear Mr Brooks. My apologies for not sending to right address, have been unable to get to the boat until hopefully today. Yes there is a gauze filter under the dome cap which I have checked and it is clear. Do you still require photos or shall I proceed to check the return pipes? Thanks once again for your continued assistance. Regards B Clensy

Tony-B
Tony-B

Posted: Sun Apr 03, 2016 7:46am

Post Subject: Lost Revs

Yes, check the return pipes. Probably two at the engine end going into one back to the tank. If there is no problem there I am stumped so consult a Vetus dealer or a well recommended engineer who will be able to actually inspect the boat. As all your filters and that pump strainer were clean I doubt it is water or dirt/bug in the tank. As it sometimes clears itself I doubt it is a split or blocked pump pick-up pipe in the tank. It could be an air leak into the fuel system and a faulty rubber seal on a filter or the top of the lift pump could be the problem but I would not expect any of those to allow the fault to clear itself. I think that Vetus fit an electric stop solenoid so it is not likely to be the stop "valve" partially redu8cing the fuel supply. Sorry.

JinnyMint
JinnyMint

Posted: Sun Apr 03, 2016 2:30pm

Post Subject: Lost Revs

Dear Mr Brooks, thank you for your kind assistance, I will do as you suggest and I will advise you of the outcome. Regards Brian Clensy

Tony-B
Tony-B

Posted: Wed Apr 06, 2016 10:16am

Post Subject: Lost Revs

As you have done all the usual things and the problem is still there I have been giving it further thought. It could still be a slight air leak into the fuel system but if so it will be a beast to find. It could also be a valve or injector sticking open for a while and then freeing. It would be good to check all the valves have some clearance when you rock the rockers (you will need to use the technique for setting valve clearances to get each rocker into the position you can move it) and check if any are stiffer to move or have a larger clearance than the rest. If the exhaust starts smoking when the engine plays up I think it would be worth getting the injectors overhauled, especially as I suspect this is an older engine because it has a mechanical lift pump. When the engine is running you should be able to feel the pressure pulses in the injector pipe by lightly gripping each one in turn between thumb and figure. If you find you cannot feel pulses on one injector pipe when it is playing up then that injector is possibly faulty.

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