Yanmar 1GM10 Fuel Leak

[nednaic]

Hi,

New to the forum. Was hoping someone could shed some light on this.

Have a Yanmar 1GM10 in a 26' cruiser. For the last while, it has been leaking diesel constantly, but slowly. We can't seem to figure out where it's coming from. Only seems to happen either during or after the engine has been running. It never leaks while the boat is on land.

Has anyone had this sort of problem before? It really is getting annoying at this stage.

I'd appreciate any help.

[Tellie]

Perhaps you could be more specific on where the leak is on the engine. Does it puddle somewhere constantly?

[nednaic]

It all goes into the bilge, so could really be coming form anywhere on the engine. Just wondering if anyone has had this problem before. We don't know where to start.

[Charlie]

are you sure it is coming from the engine? Could be from the return line or the fuel line. You have to trace the path of the fuel from the fuel tank to the filters, thru the lift pump, thru the injection pump and then back thru the return line. The reason I think it might be the return line is b/c you haven't said anything about the engine dying.

[nednaic]

Never had a problem with the engine dying. Often have trouble starting it though. But once it's running, everything is fine, until the diesel runs out from the leak...

Thanks for the replies so far. I'll check that the next time I go down. Tricky bit is the fact that the engine is so low down and surrounded by bulkheads. Better bring a torch and a mirror.

[shakey doug]

Try sprinkerling baby powder around all fuel fittings and likerly areas hopfully a snail trail will show up.

[lockie]

My 2GM had a leak on the top of the fuel filter. There are 2 bleed screws there: the aft one is the inlet, the forard one is the outlet. The inlet one has a small nylon washer which wears after many bleeds and thus is known to leak. The outlet one isn't normally bled, but mine leaked anyway, and a new fibre washer fixed it.

Cheers, lockie

[Spirit28]

The 2GM20 in my old boat used to have a leak as described by Lokie (probably still does!!). Another guy in my marine had the same problem and used to catch the leak with an old detergent bottle cut to size so it slides under the filter. Had a bit of paper towel there to soak it up and was replaced every few months.

No more smelly bilges....

Could always replace the crush washer to fix as well..

[troppo]

Nednaic, probably by now you have fixed the leak but anyway here is my limited experience . . . .

My new boat has a 1GM10 and it had several fuel leaks. I smelt fuel and could see some drips in the bilge. To find the leaks was difficult. Easy enough to find fuel but where exactly was it coming from. I used a torch with a strong beam and spent time checking the motor from various angles after running the motor. Sometimes the new angle made it clearer where the fuel was leaking from. I then used bits of toilet paper, unused and dry, to touch the areas, such as the fuel bleed screws, and then looked at to see if it had absorbed any fuel. With one leak, I could see the drip hanging on the bottom of the fuel piping so tracing up from there I wrapped toilet paper carefully around some screws then checked them to see which one had fuel on it.

I traced the problems down to (1) one bleed screw on fuel filter had been stripped by PO and replaced with some grey goo glue, (2) another bleed screw on filter just was not sealing properly, possibly the washer, (3) bleed screw on injector not quite tightened enough but possibly I will need to change the pipe as I suspect the threads have been stretched (4) on fuel filter the incoming and outgoing fuel pipes rely on copper washers, mine leaks there, and in the manual it says over time they don't seal as well as when new and need replacing so I am doing that.

[Tranquillity]

I would like to add some questions. I have just completed the installation of a new 1GM10 into my 25' yaght.
I had installed a Yanmar primary filter just above the top of the motor, and was drawing fuel from a tank whose top line was level with the air filter. The fuel was being extracted from the tank via a dip tube.
I exercised the lift pump, and bled air from the secondary filter bleed screw.
All went well to begin with, and the motor started up on the first swing.
I ran the motor for about 10 minutes, then decided to launch for a 'sea trial' - and I had it idling at 1300 ppm for about another 5 minutes when the motor slowly decreased rpm then cut out all together. Thinking that it was a 'fuel issue' i.e air in the fuel circuit, I noted after disconnection that the fuel line from the tank was dry. I by-passed the primary filter with a direct line, then bled air from the bleed on the secondary filter, and managed to start the engine again. ( I now suspect that the early success in starting was due to presence residual fuel in the bowl of the secondary filter. )
Anxious to isolate the source of the air, I ventured to disconnect the tank, so I rigged a drum of diesel above the motor and routed a fuel line from it the the lift pump inlet. I was able to start the motor after priming as before - and I noted that the siphon effect of fuel pressure was adding positive ( instead of -ve ) pressure to the fuel delivery. After 10 minutes I stopped the motor and now observed that diesel had ben leaking into the bilge. I presumed that the leak was coming from the same source of the air when the fuel was under suction. I tightened the bleed screw on the secondary filter - but noted that it was beginning to be difficult to seal . The sealing is via a copper crush washer.
I have since found a bleed screw on the inlet to secondary high pressure pump - the screw looks purpose built as it has a soft washer - so I assume that I should be using this screw instead of the bleed screw on the secondary filter which is the more vulnerable to repeated use ) .
I now had worked out by cracking open the tubing gland on this pump outlet, I can remove air on the high pressure side as well ( cranking the engine in this case ).
So the last venture saw me start and run the engine for 10 minutes, when it again got air in and slowly decreased rpm till it huffed and puffed and stopped again
I still have the primary filter by-passed until such time as I can solve this problem.
I now am again wondering just where the air is getting in.
Does a faulty ( seal ) crush washer let air in on the seconday fuel filter bleed screw - such that over 10 minutes it slowly lets air in. That pre-supposes that the fuel supply is under -ve pressure - something I find difficult to believe.

The other possible source is a faulty dip tube .

I have a supplentary question regards the purging of air - if one purges the low pressure side, then moved to the high pressure side if the high pressure pump and removes air there as well - is there a need to go on to the injector and purge air there as well. I would have thought that any remaining air in the high pressure line would be expelled out through the injector.

Any clues please !

[lockie]

I've never had to bleed at the injectors - just at the filter and the injector pump outlet.

Mind you, I discovered a second bleed on the filter outlet and had to bleed that last time, never a problem previously.

lockie

[troppo]

Originally Posted by Tranquillity

. . . if one purges the low pressure side, then moved to the high pressure side if the high pressure pump and removes air there as well - is there a need to go on to the injector and purge air there as well. I would have thought that any remaining air in the high pressure line would be expelled out through the injector.

Any clues please !

Not sure if I can help but here is my experience. The copper crush washers become "work hardened" and so replacing them is a good option for getting the things to seal better. Usually the high pressure side does not need bleeding. One manual I read said purge from the low pressure side and try to start the motor. If no go, then bleed the high pressure side. It has worked for me just doing the low pressure side.

[capngeo]

mine is a bastard to bleed... but it is old and suffers from low compression.

[Tranquillity]

Thanks folks for suggestions.

I think I have now worked out a promising strategy.

1. Testing the fuel delivery to the lift pump
As I said before, I am getting air entrained into the fuel circuit even after I have bled it, and then have managed to restart the engine - then after 5-10 minutes, the engine stops due to the re-emergance of air. In my case I cannot access the dip tube due to lack of head space above the tank.
This is my plan of action now.
First - test the integrity of the dip tube. This can be done by creating a siphon out of the fuel tank and engaging the dip tip in the process. By setting up a flexilble fuel line - which connects at one end to the dip tube outside the tank , and the other end to a squeeze bulb, with say 12" of clear tube on the down side of the bulb - then have have this tube ending at the bottom of a clear plastic bottle ( eg. a meths container ) locacted at a level lower than the tank - then squeeze away at the bulb until one gets the diesel flowing into the bottle, filling it from the bottom up. If the fuel delivery sysytem including the dip tube is free of leaks, then diesel will eventually flow and continue to flow, into the bottle, and there should be no air bubbles.
Next, pinch off the flow down stream of the squeeze bulb and allow the passage of time ( say 5 minutes or more ! ). Then release the 'pinch' and diesel should start to flow automatically. Alternatively if you fail to hold the pinch, you can re-squeeze the bulb, and flow starts again - the key observation to make here, is to note if air has re-appeared. If so, it would indicate a mini leak somewhere between the squeeze bulb and the fuel source in the tank.
2. Test the fuel delivery downstream of the lift pump
As I said before, I suspect the copper crush washer on the secondary fuel filter not sealing properly. I am to take new washers, plus will try this.
In doing some extra reading on copper crush washers. they have a reputation for hardening up through repeated use - so one should either just simply replace them, or otherwise - anneal the washer. This renders the copper back to a state of malleability and improves its ability to again seal. To anneal, apparently you heat the copper washer up until just cherry red, the quench it. All this I plan to do, then air bleed the pressure system, starting at this filter location, then moving to the bleed screw on the inlet of the injector pump, then next move to the high pressure side to the inlet connection nut on the pipe at the injector, loosen it, then bleed by cranking the engine.

Hopefully all this will achieve a positive result - and will report again afterwards.

Regards

[Tranquillity]

Its me again reporting on progress in tracking source of air in fuel.
As mentioned in last report, I finally established now that there was an air leak in the hose adaptor on the top of the tank at the dip tube socket.
Strange as it seems, having a leak here does not result in fuel leaking out. Because , the internal pressure at this fitting is either atmospheric pressure ( whilst motor not running ! ), or a negative suction pressure whilst the motor is running. I managed to find this leak by use of the squeeze bulb applying a positive pressure by reversing its direction , then using soapy water over the area of the leak, and observing the bubbles.
Being in a very difficult to access position, I removed the dip tube entry fitting an re-taped the thread ( 1/4" BSPT ) as best I could , and managed to get a much better seal. I thought I had nailed the problem, and managed to run the engine for about 45 minutes this time, whereupon it again stopped due to air. Then re-purged the air , tried again, and same result - it lasted about 45 minutes.
I deduce that a small air leak will allow air to slowly accumulate in the lift pump up until the pump loses its prime.
I then rigged a jury fuel tank - being a 10 litre drum located at a level above the motor - with the feed line to the lift pump descending downhill - and relying on a siphon effect to feed fuel in to the lift pump. This worked fine without any air ever getting into the system.
So now its back to getting that dip tube fitting resealed. I am tempted to use a sealing compound rather than the teflon tape - but I note the warnings in other threads against using thread seal compounds on diesel lines.

Regarding the other issue with copper crush washer - I annealed it as suggested and this time it sealed much better. I have since acquired spare crush washers. For the record - the bleed screw washer on the secondary fuel filter ( on a #1GM10 ) is OD = 14mm, ID = 8mm. and thickness = 1 mm
Also for the record, the spanners needed to air bleed this motor are,
1. Secondary fuel filter bleed screw = Metric 10mm
2. Injector pump inlet bleed screw = Metric 12mm
3. Injector pump outlet tube line fitting hex nuts = Metric 17mm
After repeated purging, I now have developed some dexterity at purging air, so have had these three spanners mounted and located handy and ready foir use in the engine cavity.
The use of the squeeze bulb has been invaluable for fault finding. I had contemplated installing an electric line pump as a ready fix for my problem - but have reservations that it would have been a fix. If air is getting in in the first place via a suction leak at the top of the dip tube on the fuel tank, air is going to accumulate in the lift pump, despite the presence of the this upstream pump. I appreciate that this squeeze bulb is not designed for diesel service, and soon will degrade - so its use in my case will be temporary.
Thats it for now.
Rgds - Tony T