Pesky fuel leak!

[robertt]

Had a diesel leak from my Yanmar 2GM20 since last year, following a rough night on a mooring. The next morning the contents of the entire fuel tank were under the engine. You would think that something as dramatic as that would have a really obvious cause. But no...

Still getting diesel under the engine whenever it is running.

No obvious drips from banjo bolts, fuel pipes/hoses, either of the fuel filters, bleed screws or injectors

I did notice a bit of sludge running down from the lift pump and the little membrane/gasket felt wet to touch

After a year of trying this that and the other I had a mechanic working on the engine last night

He replaced the lift pump, retapped a suspect bleed screw and replaced a part of the fuel return hose.

And still there is a drip from somewhere right at the back of the engine where, apart from fuel return pipe, I can't understand why there would be anywhere for fuel to leak from. Can't see where it is originating, but by climbing right inside my cockpit locker I can see drips landing in the locker sole between the gearbox and engine only when it's running. Due to difficulty getting to rear of engine the mechanic removed the alternator and air filter to try to get a look at the rear of the engine but he is a big bloke and couldnt really manage to get in to this area. Drips every few seconds so fairly significant leak. So why can't I find the source?! Really frustrating. Fuel hose from tank to engine is sound.

Has anyone had a similar problem or able to suggest source?

Short of taking the engine out I don't know if I can get any better access to this area.

Anyone want to buy a yacht?

 

[capnsensible]

Had a diesel leak from my Yanmar 2GM20 since last year, following a rough night on a mooring. The next morning the contents of the entire fuel tank were under the engine. You would think that something as dramatic as that would have a really obvious cause. But no...

Still getting diesel under the engine whenever it is running.

No obvious drips from banjo bolts, fuel pipes/hoses, either of the fuel filters, bleed screws or injectors

I did notice a bit of sludge running down from the lift pump and the little membrane/gasket felt wet to touch

After a year of trying this that and the other I had a mechanic working on the engine last night

He replaced the lift pump, retapped a suspect bleed screw and replaced a part of the fuel return hose.

And still there is a drip from somewhere right at the back of the engine where, apart from fuel return pipe, I can't understand why there would be anywhere for fuel to leak from. Can't see where it is originating, but by climbing right inside my cockpit locker I can see drips landing in the locker sole between the gearbox and engine only when it's running. Due to difficulty getting to rear of engine the mechanic removed the alternator and air filter to try to get a look at the rear of the engine but he is a big bloke and couldnt really manage to get in to this area. Drips every few seconds so fairly significant leak. So why can't I find the source?! Really frustrating. Fuel hose from tank to engine is sound.

Has anyone had a similar problem or able to suggest source?

Short of taking the engine out I don't know if I can get any better access to this area.

Anyone want to buy a yacht?

You may wish to reconsider your sales pitch......

Good luck with the leak seeking!

 

[dave_gibsea]

Hi Robert, I have had an anoying fuel leak from the fuel filter bleed screw for some time. I've tried various cures including new copper wahers, fiber wahser but still there is a small leak. I have heard that the rubber seals can be a problem too. I suggest you place some sturdy paper towles in strategic places to try and locate the exact location. Yanmar fuel filter units are (for once) not stupidly expensive.
Good luck! Dave

 

[Spyro]

On the side of the engine with air filter and alternator is the Injectors and as you say fuel return pipe. There is nothing below these that have fuel. As it's only a leak when running I would suspect a leak beyond the fuel injector pump where the fuel is under pressure. Try drying everything off around the injectors. and then stuff some coloured paper towelling around them. start up and watch for leaks. Access is pretty good to the injectors and fuel lines to them so a leak there should be easy enough to see. A leak from the secondary filter can find it's way down to the lift pump via the pipes and appear to come from the lift pump. I've had this happen.

 

[robertt]

On the side of the engine with air filter and alternator is the Injectors and as you say fuel return pipe. There is nothing below these that have fuel. As it's only a leak when running I would suspect a leak beyond the fuel injector pump where the fuel is under pressure. Try drying everything off around the injectors. and then stuff some coloured paper towelling around them. start up and watch for leaks. Access is pretty good to the injectors and fuel lines to them so a leak there should be easy enough to see. A leak from the secondary filter can find it's way down to the lift pump via the pipes and appear to come from the lift pump. I've had this happen.

Thanks Spyro, that sounds like a good strategy.

As regards the secondary filter, there was a leak from this area previously, but there is no longer any sign of fuel running from the filter housing down the fuel pipes. From the amount I can see dripping into the sole I would expect to be seeing some very obvious seepage from whatever is the source and can't see any. That's what's so frustrating.

 

[haydude]

Had a diesel leak from my Yanmar 2GM20 since last year, following a rough night on a mooring. The next morning the contents of the entire fuel tank were under the engine. You would think that something as dramatic as that would have a really obvious cause. But no...

Still getting diesel under the engine whenever it is running.

No obvious drips from banjo bolts, fuel pipes/hoses, either of the fuel filters, bleed screws or injectors

I did notice a bit of sludge running down from the lift pump and the little membrane/gasket felt wet to touch

After a year of trying this that and the other I had a mechanic working on the engine last night

He replaced the lift pump, retapped a suspect bleed screw and replaced a part of the fuel return hose.

And still there is a drip from somewhere right at the back of the engine where, apart from fuel return pipe, I can't understand why there would be anywhere for fuel to leak from. Can't see where it is originating, but by climbing right inside my cockpit locker I can see drips landing in the locker sole between the gearbox and engine only when it's running. Due to difficulty getting to rear of engine the mechanic removed the alternator and air filter to try to get a look at the rear of the engine but he is a big bloke and couldnt really manage to get in to this area. Drips every few seconds so fairly significant leak. So why can't I find the source?! Really frustrating. Fuel hose from tank to engine is sound.

Has anyone had a similar problem or able to suggest source?

Short of taking the engine out I don't know if I can get any better access to this area.

Anyone want to buy a yacht?

I wonder if in cases like this and after having exhausted all investigations and professional repairs, one could make a claim to the insurer to have the engine replaced because the risk of fire it causes!

 

[Mrnotming]

A spray leak can cause Diesel engine runaway,i.e the engine runs on the vapour in the engine box.I had a high pressure feed pipe (metal) on the Volvo 7A do this and it made a right old mess. Keep looking as runaway engine is more likely than fire, or as likely.
Mind your eyes especially, wear goggles and no loose clothing if poking about with the engine running.
Hope it is something simple say in the return line.A dental mirror with telescopic handle might be a good purchase or one of those Lidl cameras on a stick!

 

[RichardS]

I haven't got your engine or the space problems but if it only leaks when the engine is running and the leak is from somewhere not alongside the engine/pump/filter/injectors and therefore easily visible then surely it must be coming from the return hose somewhere?

Can you disconnect the hose as close as possible to the injectors and temporarily run a short length of new hose from the injectors to an empty polykeg. The start the engine keeping an eye on the level in the polykeg. If there is now no dripping you know where it was coming from.

Richard

 

[robertt]

I haven't got your engine or the space problems but if it only leaks when the engine is running and the leak is from somewhere not alongside the engine/pump/filter/injectors and therefore easily visible then surely it must be coming from the return hose somewhere?

Can you disconnect the hose as close as possible to the injectors and temporarily run a short length of new hose from the injectors to an empty polykeg. The start the engine keeping an eye on the level in the polykeg. If there is now no dripping you know where it was coming from.

Richard

That sounds like a good idea, I'm going to try this

 

[ronsurf]

I wonder if in cases like this and after having exhausted all investigations and professional repairs, one could make a claim to the insurer to have the engine replaced because the risk of fire it causes!

I didn't think diesel was flammable as a liquid. It would need to be very hot before it even thinks about burning.

I've traced drips before that were a long way from their source. A drip doesn't happen until it reaches a low point or sharp edge. There also may be a fine spray onto a hose, that then runs along the outside, eventually dripping when it gets to a bend. If the high pressure lines are fractured, chafed or dislodged, you can get a fine spray that is invisible to the eye.

Good luck

 

[Lon nan Gruagach]

One drip is about 1/10th millilitre, so 10,000 drips per litre. 1 drip per second is about 1/3rd litre per hour, so an empty tank overnight would need more than a drip every few seconds.

 

[Strolls]

Due to difficulty getting to rear of engine the mechanic removed the alternator and air filter to try to get a look at the rear of the engine but he is a big bloke and couldnt really manage to get in to this area. …

Short of taking the engine out I don't know if I can get any better access to this area.

If you're having trouble seeing where it is, you can get a USB inspection camera on Amazon or eBay for less than £10.

http://search.ebay.co.uk/search/search.dll?query=usb+Endoscope

 

[robertt]

If you're having trouble seeing where it is, you can get a USB inspection camera on Amazon or eBay for less than £10.

http://search.ebay.co.uk/search/search.dll?query=usb+Endoscope

Wow! Can't believe how cheap this is. Just bought one.

 

[robertt]

Found the leak at last (then discovered another easily fixed one)!

It was a weeping from one of the injectors

Thanks for all helpful comments, particularly in relation to the fact that as the leak was only apparent with engine running it had to be coming from the high pressure side (I hadn't worked this out, but it was spot on).

Looking forward to a less smelly boat from now on!