Yanmar IGM10 Slowing down and dying.

[lexi]

My Yanmar can start up and run 5minutes and sometimes to an hour, then engine note changes and slowly dies. If I open bleed on injector pump, it picks up and can then repeat the same symptoms, until I open again. My first thoughts are air coming in at CAV 296 separator. Not a sign of leakage there though. I also have one of these plastic Vetus tanks with the push on fittings.
An Old Salt in the bay with same engine thinks it is the return line. He reckons that the route back to tank is too long and uphill. For the same symptoms as I have had, he diverted the leak off the a catch tank. My CAV 296 has been refurbed with new gaskets done by the book , as has the whole fuel system with new fuel etc etc. It is all clean after a full rebuild. It is a fully rebuilt 16ft clinker launch.
I will try the catch tank trick, put some clear hose in before. IP and look for bubbbles, then maybe jury rig a gallon tank up.
Any thoughts on any of these moves appreciated.

 

[ghostlymoron]

Is this a new problem or has it always behaved this way?
Certainly sounds like a small air leak which is difficult to track down. If it was a leak in the return line I'd think you'd be able to see fuel leaking out.

 

[andsarkit]

I have the same engine and used to have a Vetus tank mounted higher than the engine. There was never a problem with the return fuel line.
It sounds more like an air leak somewhere. You need to check or bypass all possible fuel junctions for leaks.
Have you also checked the fuel filter on the engine for cleanliness or leaks?
You could also check the exhaust elbow and exhaust hose for blockage although this doesn't seem likely from the symptoms.

 

[Porthandbuoy]

It sounds very much like air getting drawn in on the suction side of the lift pump. It doesn’t take much for the symptoms you describe. Check the bolt and bleed screw on top of the CAV filter; replace the O-rings. If the compression fittings have been made and remade a few times air might be getting in there. As a temporary fix try wrapping the fittings in self-amalgamating tape or painting them with ‘liquid whipping’ (stuff you dip rope ends in to stop them fraying).

 

[Sumara of Weymouth]

Just a thought, have you checked the tank breather. I found mine was blocked with a blob of varnish!

 

[lexi]

Thanks guys. All fuel lines are new and the system all has be put together again this season with clean clean everywhere.
Before boat rebuild, all the engine and tank etc were in the same positions. Previous owner, had no issues with anything he says.
I can't see how the leak off back to tank can be the problem? But my Old Salt friend is a PRO engineer and is convinced that this gives problems because the pressure is not sufficient to to get spill off back along length of boat and up into tank.
I think air draw more likely.

 

[DownWest]

Thanks guys. All fuel lines are new and the system all has be put together again this season with clean clean everywhere.
Before boat rebuild, all the engine and tank etc were in the same positions. Previous owner, had no issues with anything he says.
I can't see how the leak off back to tank can be the problem? But my Old Salt friend is a PRO engineer and is convinced that this gives problems because the pressure is not sufficient to to get spill off back along length of boat and up into tank.
I think air draw more likely.

Doubt it is the spill off, as that is 'leaking' from the 170 bar injector, so capable of quite a head.
Def sounds like an air leak. How about putting in a bulb pump before the engine filters and pressurising the system?

 

[lexi]

Doubt it is the spill off, as that is 'leaking' from the 170 bar injector, so capable of quite a head.
Def sounds like an air leak. How about putting in a bulb pump before the engine filters and pressurising the system?

Thanks DW. Primer bulb is on the list too.

 

[Boater Sam]

Lift pump diaphragm?

 

[ghostlymoron]

If prev owner says no previous problems it must be something that you have changed since taking ownership or he's lying! Assuming he's honest, I'm sure that you'll find the problem lies in the O-rings
on the fuel filter. I've had one of these and never had any problems but some people do. The main things to watch are that the two small rings are easy to put in the wrong place ie swapped over. Also don't overtighten the through bolt which can also cause it to leak. I'm assuming you didn't dismantle any fuel pipe connections, but if you did it would be worth nipping them up a tad.
The 296 filter head I had was the one with a built-in priming pump which I found very useful and sooo much more workman like than the squeezy bulb type.
Like this but you can get them cheaper off eBay BOSCH DIESEL FUEL FILTER OE QUALITY HOUSING PRIMER LIFT HAND FEED PUMP CAV 8MM | eBay
Check and check again I'm sure you'll find the problem. The problem is, as the leaks air getting in, there's nothing to see on the outside. Good luck.

 

[Tranona]

Check the seal on fuel filter on the back of the engine. This can distort when tightening up and not seal properly.

 

[lexi]

If prev owner says no previous problems it must be something that you have changed since taking ownership or he's lying! Assuming he's honest, I'm sure that you'll find the problem lies in the O-rings
on the fuel filter. I've had one of these and never had any problems but some people do. The main things to watch are that the two small rings are easy to put in the wrong place ie swapped over. Also don't overtighten the through bolt which can also cause it to leak. I'm assuming you didn't dismantle any fuel pipe connections, but if you did it would be worth nipping them up a tad.
The 296 filter head I had was the one with a built-in priming pump which I found very useful and sooo much more workman like than the squeezy bulb type.
Like this but you can get them cheaper off eBay BOSCH DIESEL FUEL FILTER OE QUALITY HOUSING PRIMER LIFT HAND FEED PUMP CAV 8MM | eBay
Check and check again I'm sure you'll find the problem. The problem is, as the leaks air getting in, there's nothing to see on the outside. Good luck.

I stripped that cav unit and put a new kit on. Read up on the guide concerning misplaced o rings etc. New olives and new copper pipes as well. All new proper fuel hose. Engine ran in boat at home and thought it good, The engine was a consistent runner with PO as he was out every day I was and I never saw or heard a whisper.
Yes. all my own work this and is always a chance when you change things I suppose.
Thanks for all the suggestions from everyone.

 

[vas]

my bet on the awful lift pumps. Take it apart, check the diaphragm and reseal. Had endless issues with it, ended up removing plugging it and replacing it with an electric lift pump.
you mention a CAV, do you still have the onboard yanmar one? check for stripped bleed screw copper washers there as well.
I'd remove the CAV for testing with the main onboard filter to make sure it's not the problem

 

[ghostlymoron]

I'm not quite sure where we stand on this - have you solved the problem and what was it. (Excuse me if I'm being thick)

 

[lexi]

my bet on the awful lift pumps. Take it apart, check the diaphragm and reseal. Had endless issues with it, ended up removing plugging it and replacing it with an electric lift pump.
you mention a CAV, do you still have the onboard yanmar one? check for stripped bleed screw copper washers there as well.
I'd remove the CAV for testing with the main onboard filter to make sure it's not the problem

Noted and have considered this . Thanks
Do you mean just run the engine with Yanmar fine filter straight from the tank?

 

[lexi]

I'm not quite sure where we stand on this - have you solved the problem and what was it. (Excuse me if I'm being thick)

Boat is 30 miles from me, so gathering a few bits for jury rig and testing etc. May get back to it tomorrow.
Just to reiterate. Am I correct that assuming it is well bled initially or it would not start and run for nearly an hour?
I did not have to bleed the injector or leak off to get it going. Would that have made any difference? When it is slowing to stall, loosening the bleed screw on fuel pump, speeds it up and gets it going again ,when the fuel comes out of screw. Need to have a look and see where my return is going as I copied the PO set up. People have a multitude of ideas where that return goes to.
Thanks for your interest.

 

[vas]

Noted and have considered this . Thanks
Do you mean just run the engine with Yanmar fine filter straight from the tank?

exactly, my generator engine is running with the yanmar only filter for 15+ yrs and 1000+ h. Tried adding a CAV copysomething was so annoyed ripped it off.
there are quite a few things that could be leaking CAVs have such a reputation, so removing one by one the possible causes will give a result quicker (imho)

mind, return from a yanmar 1/2GM idling is v.little, so difficult to see where that gets in the issues you're having.
Undoing the bleed screw with engine running pushes air out so engine runs on it's diesel, haven't tried it with engine running would expect lots of diesel to burst all over tbh.
so would look from yanmar filter and back for the leak

V.

 

[lexi]

exactly, my generator engine is running with the yanmar only filter for 15+ yrs and 1000+ h. Tried adding a CAV copysomething was so annoyed ripped it off.
there are quite a few things that could be leaking CAVs have such a reputation, so removing one by one the possible causes will give a result quicker (imho)

mind, return from a yanmar 1/2GM idling is v.little, so difficult to see where that gets in the issues you're having.
Undoing the bleed screw with engine running pushes air out so engine runs on it's diesel, haven't tried it with engine running would expect lots of diesel to burst all over tbh.
so would look from yanmar filter and back for the leak

V.

It's a crazy old game because I rebuilt an old Landy with Lucas pump CAV filter/separator and the same type ancient lever diaphragm pump and had no issues over many years. Implementation and position of components may have been better of course.
Strange that you cannot buy a membrane replacement for the Yanmar lift pump?

 

[vas]

if you take it apart you'll see the membrane is not (easily) removable.
new liftpump is around 50quid (if not more)
mine had the "plate" holding the two tiny valves slightly bent which meant the pressure/volume wasn't quite right.
also needed resealing (used red instant gasket many will freak out on the thought ) but it wasn't quite right after all that tinkering...

 

[DownWest]

Parts4engines have well priced lift pumps. Had similar trouble with a 1GM10. But your symptoms don't sound like the prob we had.