Apparent rise in oil level.

[Graham and Jo]

Hiya everyone, Dotterel has an Isuzu 4 cylinder 38 Hp engine. The Oil level seems to have risen since I last checked it. Since checking it all I have done is gone to the winding hole just behind our mooring turned round and come back. It took about 30 mins. (Longer than it should as someone had moored two breasted boats opposite the hole). 

 

I reckon it has about a pint or perhaps two too much. I have drained some out and can confirm no water. I worry about diesel. 

 

The system has an electric self contained fuel pump so I am left thinking about injectors. 

 

Anyone know if injectors can leak fuel into the sump?

 

Cheers Graham

 

Supplemental, the oil warning light ii off but it has no pressure guage. A ten minute run has seen no rise in oil. Other possibility is some bozzo i.e me hasn't been shoving the dip stick in far enough. 

 

Edited June 21, 2024 by Graham and Jo
Typo

[Tony Brooks]

Fuel from a dribbling injector might find its way past the piston into the sump, but unless it was leaking when the engine was stationary I would think most, if not all would get burned off. I don't know for sure, but I would expect the injector pump(s) to have delivery valves in their outlet, so a dribbling injector would be unlikely to leak when the engine  is stationary.

 

I think at least some Isuzu engines have individual injector pumps inserted into the crankcase, so if one of those sprung a leak it could get into the sump, but I would not worry about it for now. keep an eye on it and only worry about the pump(s) if it keeps rising.

 

[Graham and Jo]

Thanks, I have run it some more with no change. We will head off on a short trip and check again. Cheers Graham 

[PeterF]

I found the stop on the top of my dipstick on my old boat had come loose and moved perhaps 6 to 8mm up resulting in the dipstick going in further giving higher readings. From memory the stop was a hard rubber moulding. The correct position was confirmed from the painted/ unpainted interface above the stop.

[Arthur Marshall]

I've always wondered how much the change in the trim might change the level on the dipstick. If I'm full of diesel and low on water there's a considerably change of angle of the boat.

[Graham and Jo]

9 minutes ago, PeterF said:

I found the stop on the top of my dipstick on my old boat had come loose and moved perhaps 6 to 8mm up resulting in the dipstick going in further giving higher readings. From memory the stop was a hard rubber moulding. The correct position was confirmed from the painted/ unpainted interface above the stop.

I had a look at that and don't think it has moved. I do think it is quite easy not to push it home when taking the oil level. Cheers Graham 

 

Ps under way now with SWIMBO driving I will report back. 

4 minutes ago, Arthur Marshall said:

I've always wondered how much the change in the trim might change the level on the dipstick. If I'm full of diesel and low on water there's a considerably change of angle of the boat.

We certainly have more water than when I changed the oil. 

[DShK]

I had rising oil levels. I had suspected my injectors might be dodgy for a while (just the odd misfire). Luckily my engine you can test spray them easily enough. One didn't seem like a good spray pattern, so I sent them off. Sure enough, one injector needed sorting.

 

I've only put 100 or so hours on the engine since then, but the oil level doesn't appear to be rising.

 

Dribbling injectors can definitely cause rising oil levels. 

[Graham and Jo]

15 minutes ago, DShK said:

I had rising oil levels. I had suspected my injectors might be dodgy for a while (just the odd misfire). Luckily my engine you can test spray them easily enough. One didn't seem like a good spray pattern, so I sent them off. Sure enough, one injector needed sorting.

 

I've only put 100 or so hours on the engine since then, but the oil level doesn't appear to be rising.

 

Dribbling injectors can definitely cause rising oil levels. 

Oh dear! I will find out soon! Cheers Graham

[blackrose]

Are you sure you haven't been checking it cold and later checking it hot (expanded) so you're not comparing like for like? 

Edited June 21, 2024 by blackrose

[DShK]

22 minutes ago, Graham and Jo said:

Oh dear! I will find out soon! Cheers Graham

Someone with experience might be able to feel/smell diesel in it for you. I personally couldn't tell.

 

The good news is that it isn't a big job to sort. You should in theory be able to pull the injectors yourself and send them off to someone to refurb them. Cost me about £100 for mine.

[Graham and Jo]

I compared the oil I took out to fresh oil and it felt the same! We are about 20 mins from mooring so will have a look at the oil levels then. 

 

Glad it isn't too expensive.

 

Cheers Graham 

Well we have cruised 4 miles which took 1hr 20mins. I have just checked the oil level and there has been no change. So at the moment it is being put down to operator error when changing the oil. I will be checking it every day. Mind you I do that anyway. We have left Calcutt and are heading for Coventry. Cheers Graham

[Graham and Jo]

This morning's oil level was fine. I do wonder if the leaking injector could be the right answer. Perhaps something stuck in it and over a week it leaked. I guess it could have dripped into the cylinder and then past the rings. 

 

I never turn off the diesel when away from the boat, perhaps I should? I turn off everything else. 

 

Plan is for a precautionary oil change, switch off diesel when not using engine.

 

The engine runs very smoothly so I don't think there is a general issue with the injectors.

 

Cheers Graham 

[Peugeot 106]

Don’t forget that if you you have a return line that dips  into the top of the tank the diesel can syphon back from there so you may have to isolate the return line as well as the supply line. Some terminate at the top of the tank I think but many, and mine, dip down into the bottom of the tank. I hang my keys on the return line isolation valve to remind me not to start it with it isolated. I’m not an expert so if this doesn’t apply to your engine maybe someone can shout out

[Graham and Jo]

1 minute ago, Peugeot 106 said:

Don’t forget that if you you have a return line that dips  into the top of the tank the diesel can syphon back from there so you may have to isolate the return line as well as the supply line. Some terminate at the top of the tank I think but many, and mine, dip down into the bottom of the tank. I hang my keys on the return line isolation valve to remind me not to start it with it isolated. I’m not an expert so if this doesn’t apply to your engine maybe someone can shout out

Thanks for that, I turned off both. I don't know which is which without tracing them through all the odds and ends I keep in the engine bay. I also don't know what the pipes do inside the tank! 

 

Cheers Graham 

[Graham and Jo]

I have been investigating this effect further. The oil level definitely rises when the engine is stationary and the fuel is switched on. When we took the boat to Birmingham the oil level did not rise. (The fuel was switched off when the engine wasn't running). To me this suggests a leak through an injector as the other possible cause of an injector pump leak ought to get worse when the engine is running. 

 

Can anyone tell me what the injectors are? I am either going to replace them or service them. 

 

Cheers Graham 

 

[Tony Brooks]

Personally, I would take the injectors to a fuel injection specialist for testing and overhaul. Even if you buy "new" ones that will probably be just refurbished, and for injectors there is nothing wrong with that, as long as they were competently done.

 

Remember that you have four separate injector pumps, all set into the engine, so a leak from one of the pumps could result in a rise in engine oil level. How likely this is will depend upon engine running hours. I don't necessarily buy the logic that a pump leak should get worse with the engine running. Fuel pressure with the engine running may well cause a lip seal to seal, and it may well distort O rings enough to make them seal as well.

 

 

[Graham and Jo]

Thanks Tony, I am in touch with 4 fuel injector service people at the moment - all going to ring me back! If there is an leak from the pumps that's probably beyond me! I did talk to Calcutt but they couldn't confirm that they could do the job. Current plan is to do the easy bit first - the injectors then see what happens. 

 

Cheers Graham 

[Tony Brooks]

4 minutes ago, Graham and Jo said:

Thanks Tony, I am in touch with 4 fuel injector service people at the moment - all going to ring me back! If there is an leak from the pumps that's probably beyond me! I did talk to Calcutt but they couldn't confirm that they could do the job. Current plan is to do the easy bit first - the injectors then see what happens. 

 

Cheers Graham 

 

I am not surprised Calcutt may be being a bit hesitant about doing the pumps. It all depends upon how they link to the rack/control rod. If they have pins or some such that just drop into holes/slots in the rack then it should be an easy job, but if it is like older Listers where the rack parts need individual adjustment it may be far more complex. I would not tackle the job without a decent manual to explain what needs to be done. Maybe talk to Engines Direct to find a local agent who should be experienced with such jobs. I hope another member who knows will enlarge on this.and

[Graham and Jo]

I found a local injector company who took one look at the tip of one injector and said yes they have a problem. I am picking them up on Monday next week and we will see what happens. I did have a look at removing the injector pumps as apparently replacing the seals is quite easy. Getting the engine at top dead centre and preserving the alignment of the body and the mount to keep the timing right is a bit harder. 

 

Cheers Graham 

[BEngo]

Scribe a line on the body and the mount.  If you dont have an engineers scriber handy a masonry nail can be sharpened up on an oilstone or a sheet of fairly coarse (say 150 grit) wet and dry or some emery tape.  At a real pinch a Stanley knife blade will do one scribe per tip.

[Graham and Jo]

41 minutes ago, BEngo said:

Scribe a line on the body and the mount.  If you dont have an engineers scriber handy a masonry nail can be sharpened up on an oilstone or a sheet of fairly coarse (say 150 grit) wet and dry or some emery tape.  At a real pinch a Stanley knife blade will do one scribe per tip.

I have done that sort of thing before having spent way too many years maintaining classic cars. But sometimes I just feel a bit tired! 

[David Mack]

Out of interest, what is the mechanism by which a leaking injector can allow a significant quantity of fuel into the cylinder, and then into the sump when the engine is not running?

The injector pump pressurises the fuel in the pipe from pump to injector, and in a leak-free system some pressure would presumably remain once the engine is stopped. And if the valve in the injector leaks, then a quantity of fuel could leak into the cylinder. But as the fuel is effectively incompressible, and the injector pipes are thick walled and therefore not very elastic, it would only take a miniscule amount of leakage for the pressure in the injector pipe to dissipate entirely, and thereafter no more fuel would leak out of the injector. Some of that small quantity of fuel might run down the cylinder walls and past the piston rings to end up in the sump, but some would surely remain on the cylinder walls or the top of the piston, to be burned when the engine next runs.

I find it hard to believe that leaking injectors can be the cause of measurable sump oil dilution by fuel. I would have though that leakage from the injector pumps, if housed within the engine, or through a leaking diaphragm on an engine-mounted mechanical lift pump would be much more likely causes.

[Tony Brooks]

6 minutes ago, David Mack said:

Out of interest, what is the mechanism by which a leaking injector can allow a significant quantity of fuel into the cylinder, and then into the sump when the engine is not running?

The injector pump pressurises the fuel in the pipe from pump to injector, and in a leak-free system some pressure would presumably remain once the engine is stopped. And if the valve in the injector leaks, then a quantity of fuel could leak into the cylinder. But as the fuel is effectively incompressible, and the injector pipes are thick walled and therefore not very elastic, it would only take a miniscule amount of leakage for the pressure in the injector pipe to dissipate entirely, and thereafter no more fuel would leak out of the injector. Some of that small quantity of fuel might run down the cylinder walls and past the piston rings to end up in the sump, but some would surely remain on the cylinder walls or the top of the piston, to be burned when the engine next runs.

I find it hard to believe that leaking injectors can be the cause of measurable sump oil dilution by fuel. I would have though that leakage from the injector pumps, if housed within the engine, or through a leaking diaphragm on an engine-mounted mechanical lift pump would be much more likely causes.

 

There may be a path via backflow through the leak off line into the injector, and then past a leaking nozzle seating. Remember, the leak off flow basically comes from leakage from the centre of the injector. For this to happen, it would need the leak off pipe to be dipped into the fuel in the tank, rather than just exit into the top. There are no seals in injectors, and the nozzle to body seating is just face to face.

 

Apart from the fact the OP said the level did not rise during running, if the nozzles were jetting fuel onto the cylinder wall it may well not all burn off, allowing some to leak past the rings into the sump. 

Edited 2 hours ago by Tony Brooks

[Graham and Jo]

Interesting thought about the leak off pipe. I have no idea what it goes in the tank other than it goes in next to the main fuel pipe. I had wondered about the fuel getting past the lift pump and injector pumps but if the leak of pipe is under the fuel level in the tank  then it could provide a path. So perhaps it doesn't leak when the engine is running because the fuel level has dropped. The last time it rose I had just filled the tank which is definitely above the leak off pipe. Who knows. I am picking up the refurbished injectors on Monday next week and we will see what happens. Graham 

[magnetman]

I would be investigating the lift pump. 

ETA read first post !

Edited 2 hours ago by magnetman