Black oil like stuff from exhaust

[Ian45]

After getting some very helpful answers after posting about my electrical problem during our first proper cruise on the Thames last week I am now hoping someone might put my mind at rest at a more worrying issue that also became apparent during our cruise.

Our boat is a Sealine 218 with a Volvo Penta 205A 6 cylinder petrol engine. During our cruise the engine ran well apart from a rather worrying scenario that happened about five times. After the engine had been running for a few hours and the engine was warm, I had occasions when the engine was started after being turned off (going though a lock) that it wouldn't fire on the turn of the key without some considerable throttle at which point it would gurgle into life and deposit a black substance into the river along with some smoke, then struggle to idle until it was put into gear and given some throttle to make our way again at which point it return to normal!

Our Marina said that a service may help or at the very least help indicate the problem. My main concern was that it was oil being spat out but if that was the case wouldn't it show up all the time?

Just concerned something major is wrong? Part from the above it will start from cold with no problem and for the most part start from warm with just a turn of the key.

 

[vyv_cox]

It sounds like the choke might be closing when the engine stops, not recognising that the engine is warm when you restart. I suggest you check how it is controlled, maybe a temperature sensor isn't working. The black might be unburnt fuel and some carbon.

 

[Ian45]

It sounds like the choke might be closing when the engine stops, not recognising that the engine is warm when you restart. I suggest you check how it is controlled, maybe a temperature sensor isn't working. The black might be unburnt fuel and some carbon.

Thank you for the quick reply. I'm happy that there is a possibility it could be carbon/fuel and not oil, I had visions of facing MASSIVE repair bills.

Am I right in thinking that if it was oil getting into the engine and being spat out that it would A: stop the engine running properly and B: have constant smoke from the exhaust or oil whenever I started and not just occasionally?

 

[vyv_cox]

Thank you for the quick reply. I'm happy that there is a possibility it could be carbon/fuel and not oil, I had visions of facing MASSIVE repair bills.

Am I right in thinking that if it was oil getting into the engine and being spat out that it would A: stop the engine running properly and B: have constant smoke from the exhaust or oil whenever I started and not just occasionally?

I'm struggling to think of a mechanism that would drop significant oil into the combustion chamber when the engine was stopped but not come through when it was running. Difficult to think of one. I would look at the choke first, it's far easier!

 

[Ian45]

Many thanks again. Looking like I have to get acquainted with engines AND electrics with boat!

Oh the joy.....

 

[TQA]

I'm struggling to think of a mechanism that would drop significant oil into the combustion chamber when the engine was stopped but not come through when it was running. Difficult to think of one. I would look at the choke first, it's far easier!

Valve stem oil seals? Usually worst on start up from cold and acceleration after a long idle but??

 

[Ian45]

Valve stem oil seals? Usually worst on start up from cold and acceleration after a long idle but??

Absolutely fine from cold start up and also fine most of the time when warm, it's just now and then without any rhyme or reason, well now I have a possible reason thanks to the help from the forum.

 

[omega2]

overfueling, change the spark plugs or at least check the gaps, also the ignition leads, and distributer cap.

 

[Ian45]

Can anyone recommend a mobile Volvo engineer that covers the Thames area? I tried VolvoPaul but it's out of his reach and he is booked for two months already!

My marina can't do anything for about three weeks before they can give me a date so wondering if another option was available?

I will try to take a look regarding the choke but until I know more about the workings of the engine I am more worried about spending good money after bad if I adjust/change/buy the wrong bits not too mention at this stage I wouldn't know how to check said parts anyway.

I realise I am going to have to get to grips with familiarising myself with the workings of the boat to not only save money but also benefit if we break down on the river but I would like to be on the river asap rather than spending hours with my head in the engine bay or waiting for the Marina. We only got her late last year and are all keen to get out on the Thames as much as possible.

 

[oGaryo]

understand what you're saying but there are basic checks you can make that won't take too long.... first look at the symptoms.. it's not happening every time when warm which suggests something is loose or sticking.. first thing I would do is check for bad earths, ht leads secure, sticking choke, etc if you get lucky you'll find it straight away and be on your way.

what was this electrical problem you had earlier?

basics: you need air, fuel and an ignition source to make the bang that moves the pistons so if this is unburnt fuel being deposited, I wouldn't necessarily suspect a fuel flow issue.. if the engine's being starved of air (choke, flame arrestor blockage and the like) or it's not getting a spark... at least, those would be my inital thoughts as the most obvious causes.

your biggest challenge is reproducing the fault so you can test for the cause at that time

 

[Ian45]

what was this electrical problem you had earlier?

Found out our leisure battery isn't getting charged but the starter battery is. The boat has what could be an original split charge relay unit so possibly that is the culprit.

I would love to take a look and find the problem but it's the 'not knowing' how to check and what, with all the wires going here there and everywhere I may be making a decision on something that is perfectly OK!

My urgency is just the quickest way to get back to normal, last thing I want is to throw money at it just for the sake of it. The novelty of having a boat again after twenty years is still with me, kid in a sweet shop scenario lol.

I'll be back at the boat on Saturday so will get that engine hatch up and take a bloomin' good look around.

Many thanks for the help.

 

[oGaryo]

Found out our leisure battery isn't getting charged but the starter battery is. The boat has what could be an original split charge relay unit so possibly that is the culprit.

I would love to take a look and find the problem but it's the 'not knowing' how to check and what, with all the wires going here there and everywhere I may be making a decision on something that is perfectly OK!

My urgency is just the quickest way to get back to normal, last thing I want is to throw money at it just for the sake of it. The novelty of having a boat again after twenty years is still with me, kid in a sweet shop scenario lol.

I'll be back at the boat on Saturday so will get that engine hatch up and take a bloomin' good look around.

Many thanks for the help.

Ian, I'm not familiar with the Volvo engines but have done a fair amount of work fixing stuff on my Mercruiser engines... where on the thames are you, I'm going past Oxford and Abingdon if she's moored there... happy to pop my head in the hatch if you're moored in that region on route to Southamapton via the A34... assuming these engines are similar I may get lucky and spot something for you

 

[Ian45]

Ian, I'm not familiar with the Volvo engines but have done a fair amount of work fixing stuff on my Mercruiser engines... where on the thames are you, I'm going past Oxford and Abingdon if she's moored there... happy to pop my head in the hatch if you're moored in that region on route to Southamapton via the A34... assuming these engines are similar I may get lucky and spot something for you

It's at Marlow (Harleyford). That is an extremely kind offer that I would welcome if it can be arranged without putting you out? Just having someone with more knowledge than I to at least point at bits and say "that's your engine" would be a big help.

I'll send you a PM

 

[pentane]

Sounds like either the choke - probably bi-metallic, either heated electrically in which case check the circuit to it or it might be in a little housing on the inlet manifold and attached to the choke flap with a metal rod a la mercruiser.

Or could be sticking float in the carb, I've had exact same symptoms. Try a carb re-build kit or at the least strip the carb and clean with carb cleaner (doh!) - maybe the float chamber is gummed up. Best get a kit though as you wil have all the seals. Keypart etc should be able to help.

Try not to drop anything into the inlet manifold once the carb is removed, somewhat awkward to get out again

Oh, and usual warnings about petrol vapour in combined spaces etc...

 

[Ian45]

Sounds like either the choke - probably bi-metallic, either heated electrically in which case check the circuit to it or it might be in a little housing on the inlet manifold and attached to the choke flap with a metal rod a la mercruiser.

Or could be sticking float in the carb, I've had exact same symptoms. Try a carb re-build kit or at the least strip the carb and clean with carb cleaner (doh!) - maybe the float chamber is gummed up. Best get a kit though as you wil have all the seals. Keypart etc should be able to help.

Try not to drop anything into the inlet manifold once the carb is removed, somewhat awkward to get out again

Oh, and usual warnings about petrol vapour in combined spaces etc...

Lots of good information from extremely helpful forumites. Once it finally gets sorted I will post an explanation in the hope it may help someone in the same situation.

Many thanks.

 

[Bilgediver]

I'm struggling to think of a mechanism that would drop significant oil into the combustion chamber when the engine was stopped but not come through when it was running. Difficult to think of one. I would look at the choke first, it's far easier!

Knackered valve guides and seals with poor drainage from rocker space?

 

[vyv_cox]

Knackered valve guides and seals with poor drainage from rocker space?

The test I always used for valve guides was to let the engine tick over for a while, then open the throttle. Copious smoke if it's the valve guides, whereas far less if it's rings. OP says there is no smoke, if I remember correctly?

Automatic choke problem still seems most likely to me. Not the same one, but here's an example. Air-cooled VWs have a small electric element in the choke housing, heating a bimetallic strip attached to the choke butterfly. As soon as the engine is running the choke begins to open, fine in normal running. I live on top a hill 2 miles long with a cross-roads at the bottom. The engine would always stall at the cross-roads because the engine was still cool but the choke was now wide open. If the wire is off, or the element burns out, the choke never opens. Engine runs rough and uses lots of fuel.

Sounds like this problem is not quite the same, probably a different mechanism. Choke closes when the engine stops, maybe a solenoid? If a temperature probe detects that the engine is warm it opens fully when the engine is restarted but if the probe is faulty, connection loose, etc. it doesn't happen.

 

[Ian45]

Engine runs rough and uses lots of fuel.

This bit about using a lot of fuel rings true. I know the 205 is quite a big lump of an engine but cruising at Thames speeds it still seems incredibly thirsty.

 

[vyv_cox]

This bit about using a lot of fuel rings true. I know the 205 is quite a big lump of an engine but cruising at Thames speeds it still seems incredibly thirsty.

If it is that type it's easy to check and to test. On the side of the carburettor with this type of choke you will see a ceramic cup held on by a ring with three screws. The heating element is inside this. it looks like this http://www.machine7.com/product.php?xProd=11068&xSec=2498

Take the air cleaner off to see if the choke butterfly is parallel with the air flow when the engine is warm and immediately after running. If not, rotate the ceramic cup after loosening the three screws, until it is. The butterfly should remain in the same place, gradually closing over quite a few minutes. If the heater has failed the butterfly will be closed and won't open but you can open it when the engine is warm to prevent the problem.

 

[rafiki_]

This bit about using a lot of fuel rings true. I know the 205 is quite a big lump of an engine but cruising at Thames speeds it still seems incredibly thirsty.

I think the engine is running too rich, which is why it is struggling to start when hot. This is also your black deposit, unburnt fuel. Sounds like a good service is in order, changing air filter, checking/changing points/plugs, and re-set the carb. The base engine should be similar to Gary's previous Mercs. When sorted, you should be burning about 1 gallon per hour at river speeds.