Emergency fuel tank

[B58]

I think your issue is down the tank, if you have the slightest air leak fuel will run back into the tank. Check the lift pump valves for debris it could hold the valve open. you could fit an outboard style hand primer which would assist the little lift pump, it also has a one way valve installed.

What i would do, is to use a remote tank, and directly feed into the fuel injection pump, by-passing the fuel filter and lift pump.

Run your engine until to temperature, and leave it overnight, check again in the morning.

Yanmar intended for the engine to use a gravity fuel tank of 30 liters due to the engines tiny fuel consumption of around 0.2l/hr.

These tanks are like hens teeth, however, if you could have a 10 l fuel tank fabricated and use that as a day tank.

 

[TernVI]

Thanks B58

The engine will run for about 10mins before shutting down so I guess it must be further back in the system. Also if I run the engine regularly it seems to be ok but when left for a week or two it then does the above.

The current tank is located low down (below engine) on the port side and when full does cause a slight list to port, locker with all the c**p is that side also. I do have a lazarette and have thought about putting a outboard style tank in there before. This is much higher than the engine and I guess would make the engine gravity fed.

If you're not very lucky at making fuel joints leakproof, it would make the bilge gravity fed....

I'm wondering if your problem might be the fuel draining back, drawing air in through the return pipe?

 

[stevd]

From my experience, air getting in from the return side of the fuel system would not cause an engine to cut out after ten minutes. It would be caused by air getting in from the "suction side" (before the fuel pump). An air leak from the return side would only cause the fuel to drain back to the tank when the pump wasn't running and would happen after a period of not being run, for example starting the engine the next day - making the engine difficult to start, or need the fuel bleeding through the system again.

Has it been confirmed that it is definitely air getting into the system, as your symptom of cutting out after a period of time could also be caused from a blocked fuel tank breather pipe creating a vacuum in the tank, and causing the fuel pump to be unable to draw fuel - running the engine without the fuel filler cap on would be a check for this.

There could also be debris in the tank blocking the pick up pipe.

It does sound most likely to be air getting into the system, but as said above it could be something different.

I wouldn't be looking for air leaks after the suction side (ie return side) of the system though.

 

[Gixer]

Thanks stev, I think it’s around the cav filter I’m getting the problem. I’ve got a guy coming down to look at it and hope he’ll see something I've missed.

 

[stevd]

Thanks stev, I think it’s around the cav filter I’m getting the problem. I’ve got a guy coming down to look at it and hope he’ll see something I've missed.

They can be troublesome - I had the same issue - and I completely understand your frustration with it! Do you have clear fuel lines to and from the CAV housing? These can be useful as you can usually see if there was air in them, and see if it was before or after the CAV filter.

If the guy doesn't get to the bottom of it, I would definitely try some hylomar (its about a fiver a tube) on the threads of the hose tail fittings on the cav filter, or as previously mentioned some loctite but it is pretty expensive compared to the hylomar.

 

[AntarcticPilot]

How much fuel gets returned varies a lot between different engines.
In my experience, it's not much on Yanmar GMs. Just what leaks past the injectors.
Other engines are different AIUI, they seriously circulate fuel.

One thing you can do temporarily is put a clear filter after the lift pump. then you will see the air and collect it, preventing it reaching the injector pump.

The jubilee clip you intend to undo to change tanks is prime suspect for the cause of the problem!

It's substantial on Volvo 200x engines - you can hear it running back into the tank if you put your ear next to the tank.

 

[TernVI]

It's substantial on Volvo 200x engines - you can hear it running back into the tank if you put your ear next to the tank.

Indeed, but the Op doesn't have a Volvo....

 

[BobnLesley]

...Only issue I can think of is the return which would go back to the main tank therefor the emergency can would drain faster than normal...The engine is only a 1gm10...

Anyone else have this kind of set up for emergencies?

We rigged exactly this and in similar circumstances.
I've noted the warnings that you've received suggesting it'd drain in just a few minutes' but would suggest that you test/try it out; our engine was a Yanmar too (3GM30F) and I was pleasantly surprised by how little fuel was returned to the main tank, when I mentioned this at the time it was suggested that Yanmar engines feed far less diesel to the injectors than most other engines, so less fuel return; I've no idea if this is true, but it bore out our findings, we ran the engine (albeit not hard) for the best part of an hour on a 10 litre jerry can and it was still well over half full still when we shut it down. We were so pleased with the outcome that we built a platform and strap system at the forward end of a cockpit locker to securely hold a spare 20 litre jerry can and stowed beside it was a spare cap with a small hole and a 7' length of fuel hose with banjo fitting, banjo bolt, copper washers and a correctly sized (13 or 17mm?) spanner. In extremis we could rig a gravity feed of clean fuel to the lift pump at the engine in <5 minutes.

As an aside, our problem too was an air leak which we struggled to track down. eventually tracing it to an original Yanmar hose with the banjo union crimped to the end; the air leak was on that crimped connection but the rate at which it leaked (anywhere from 10 minutes to 5-6 hours after being bled before stopping) was what confused us; this leak-rate being dictated by the precise route/bend/twist on the flexible hose and. I foolishly assumed that it couldn't possibly be that joint, so, if you can't trace the leak, then buy a length of good quality flexible hose, jubilee clips and copper washers, also renew or salvage the old banjos from the Yanmar hoses and rebuild the lot.

good Luck

 

[Stemar]

I think it’s around the cav filter I’m getting the problem.

Chuck it out and fit a screw-on filter from a car breaker. You could get a "proper" marine one at marine prices; the diesel won't know the difference, but your wallet will.

Better still, fit a pair in parallel, with taps to switch between 'em. I did that 15 years ago and have changed the filters just once since, because they were getting rustier than I liked. I run on one and the other's primed and ready to go. It takes seconds to switch.

 

[Gixer]

So I got an experienced marine engineer to go though my fuel system on Thursday. The checked everything, replaced copper washers and tested the engine, everything's fine.

Went down today and guess what, the engine stalled after 10mins, aaarrrggghhhh........

 

[mrangry]

I had to do this when caught out in rough weather as the diesel bug gunk had been stirred up and the engine died. I thought I was being clever rigging up the tank for the diesel heater. Only issue was it consumed all 15 litres within a few minutes as I had forgot to feed the return back to the emergency tank. Its a Yanmar by the way.

 

[TernVI]

I had to do this when caught out in rough weather as the diesel bug gunk had been stirred up and the engine died. I thought I was being clever rigging up the tank for the diesel heater. Only issue was it consumed all 15 litres within a few minutes as I had forgot to feed the return back to the emergency tank. Its a Yanmar by the way.

Model of Yanmar?

I once thought it a neat wheeze to divert the return from my 3gm into a can, to get some clean filtered diesel. Unfortunately not much came out!

 

[mrangry]

Model of Yanmar?

I once thought it a neat wheeze to divert the return from my 3gm into a can, to get some clean filtered diesel. Unfortunately not much came out!

Yanmar 4JH2E

 

[fisherman]

Yes, know several who have got home on a syphon from a can hung above the engine, but you must collect or divert the return. I always carried enough fuel in cans to get home, (50 litres).
For an emergency supply try an outboard tank, it even has a squeezy bulb for easy bleeding. (but also remember the return, even if you collect it and pour into the tank. An old Ford processes many times the fuel it burns)

 

[Gixer]

So I got an experienced marine engineer to go though my fuel system on Thursday. The checked everything, replaced copper washers and tested the engine, everything's fine.

Went down today and guess what, the engine stalled after 10mins, aaarrrggghhhh........

I've quoted my message above to let you guys know where I am with this and to see if you have any advice on what I have planned.

Ok, I've got the royal hump with my diesel fuel system and the whole lot is coming out! Its been in there since the boat was built and the tank, pipes, etc are over 30 years old. Instead of spending money on sorting a emergency fuel supply why don't I just 100% sort out what I've got?

The current tank (25L) is situated low down and on the port side which means when full gives my boat a slight list to port which I've never liked. Also as its low down the engine (1GM10) has to pump it upwards which isn't clever.

On my boat I have a lazaette which shares the same floor height as the cockpit which is a good foot above the engine. This is also on the center line of the boat so would stop the listing. From this point I will fit new tank, possibly Tek-tank with new A1 rubber hoses to and from the engine though a brand new CAV filter.

Any thoughts on this?

 

[mrangry]

Have you checked the o ring seals on the diesel water trap primary filter? Try bypassing this unit to check maybe?

 

[Gixer]

Have you checked the o ring seals on the diesel water trap primary filter? Try bypassing this unit to check maybe?

Hi, thanks for the input, yes this has been changed. I haven't bypassed the filter yet but will see if I can rig something.

 

[TernVI]

Not sure I'd fit a brand new CAV filter, unless like me you have a stock of filter elements to use up....

 

[fisherman]

The great thing about having the tank higher is the fuel leaks out rather than air leaks in....at least you can see it. Also, in many FVs I've seen the pick up pipe in the top changed for a drain out pipe in the bottom, usually after much frustration with air coming in the joints. KISS!
There is mention above of by-passing the lift pump: some engines need the positive pressure at the injector pump, in mine it would have needed 16 feet of gravity.

 

[Kelpie]

When we were very new to sailing we found out the hard way that our engine had two filters. I had dilligently changed the fine engine mounted one at the start of the season, but the upstream coarse filter was left unchanged and inevitably blocked when we were sat on a buoy off a lee shore in Loch Nevis. Continuing my cluelessness I ended up running the (Beta 14) engine from a jerry can, and after maybe half an hour noticed that we had used maybe half of it. That was when I learned about fuel return lines. Fortunately by that point we were able to continue under sail, saving the remaining fuel in the can for entering harbour at the other end.

If I were to fancy a fuel supply project, it would be a twin filter and vacuum gauge system. You can buy them off the shelf at great cost but I think you could put one together for much less from the parts.