Fuel return pipe on Yanmar 1GM10

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ianwoods

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Hi, I continue to have cold start problems on engine. I nowwonder if the fuel return pipe that leads from the injector to the tank could be the problem. It is a rubber hose 15 years old with jubilee clips. The run from the injector is nearly horizontal befor a steep descent to the top of the tank which lies lower than the engine. Do I need any U bends in this pipe to prevent airlocks? What is the best alignement of the pipe?
I hope to eventually get to the bottom of this annoying problem. Many thanks for constructive advice.
 
I know how frustrating these things can be! it's a very simple engine but the scope for baffling problems seems infinite. Perhaps no worse than any other engine ...
Anyway: can you give a detailed description of the symptoms?
For instance: does it turn over briskly when you press the starter button? If not there's a whole raft of possible reasons why not. But assuming it does:
when you do get it started, does it run well? is the exhaust smoky and does this persist after the engine has been running for a while? how is the fuel consumption? you imply that it's OK when warm, is this correct? is the fuel supply clean, without water or bugs? are the fuel and air filters clean?
I doubt that it has anything to do with the fuel return but nothing would surprise me.
Yes, could be compression. Amongst other things.
Have you checked the injector?
 
Poor starting has always been a feature of this engine which is in contrast to one on a previous boat. I have a new75ah battery with a high cold cranking capacity that spins the engine reasonably fast - no faster than when both ships batteries are in parallel. The fuel filters have been changed and there are no diesel weeps in the fuel lines. The engine appears in mint condition. I had the starter motor stripped down and the auto electrician said it too had had very little use. Its load test was perfect. I had the fuel injector cleaned and tested - OK. Earth lead on engine is clean and tight. Air filter has been cleaned. I took off the exhaust elbow and its fine. Engine takes about 30-45 seconds of cranking to start - then its hunting for about 10 before firing up. After that it it will start all day even after sitting for many hours. I motored for 12 hours one day and the next day it was still a beggar to start. I also reset the valves. Everything in mint condition beneath the cover. I am uncertain about engine hours but it runs beautifully without smoke and plenty of poke. So I search for that simple thing.
 
BetaMarine installations require the pipe to dip below the level of the bottom of the tank before entering the top.
Quote from manual:' The overflow/leakoff pipe must loop down below the fuel filter level and back up again so that drain down is avoided. This can cause poor starting.'
It does make a big difference, I neglected to do this and after a few days the engine required more cranking before starting, after a few weeks a lot more or use of the hand primer.
May be the same on a Yanmar.
 
From what you are saying I would think there is a slow leak wich is allowing air in on the sucking side of the fuel circuit.Have you tried to rig a gravity fed supply directly to the injection pump?This would eliminate a lot of connections.On my previous boat I fitted a new 1GM10 and connected the return line to the top of the fuel filter housing.That's because the old Yanmar that was there before(can't remember the model) had the same set up.It worked fine for 9 years.
 
Hi, I continue to have cold start problems on engine
..............................................................................

You mention in your next mail that the engine continues to hunt for a while after starting then runs fine. This is a symptom of an air leak in the diesel line.

Do you have a promary fuel filter such as the CAV jobbie with about three sections all bolted together with one bolt which compresses 3 joint rings.

This bolt is engineered so as not to over compress things,ie it has just the right amount of thread and can in some isntances become thread bound and appear tight before enough compression is given to all seals. If the top seal allows air into the filter this is not apparent and the results are as you describe. A small leak may take several days to allow air in when the engine is stopped but not enough to leak during stops for tea etc. If this leak is level with the fuel level in the tank then there will be no fuel leakage out.

This sort of leakage can also appear where alternative parts are used in Volvo filters which look the same .
 
The return pipe on my 1GM dips below the tank as it goes underneath the cockpit to the tank in the stern. Entry to the Vetus tank is through the top which is actually higher than the engine - so don't think thats your problem. Mine has always started instantly except in very cold weather when it benefits from being turned over for 10 seconds or so with the decrompressor lifted. This also helps the oil circulate before it fires.

As to other causes - you have checked the elbow for coking up, but what about the rest of the exhaust sytem. excess back pressure a common cause of poor starting.
 
Long shot but my 1GM10 normally a good starter did the same after a winter lay up, we tried all the usual things with no luck,once it had started it ran perfectly eventually in desperation we removed the injection pump from the engine and discovered that a link from the pump inside the engine that was spring loaded had stuck as soon as we prodded it it sprang back as it should have been in the engine off position. That solved my problem and it has been a good starter since then (3 years)

As far as I can tell this link tells the pump to inject more fuel for starting, when the crankshaft is spinning fast enough (when the engine starts) the governor pulls this link against the spring pressure and reduces the extra fuel until you stop the engine and the spring comes back into effect.

At least this is how I think it works. the good news is that by removing the oil filler cap and poking around with your finger in there you can feel the lever below the pump OBVIOUSLY WITH THE ENGINE NOT RUNNING.
hope this helps
pete
 
Im having similar problems at the moment. According to one of the posts on the yanmarhelp site is the need to replace the governor springs. Cannot give you any more details at the moment but will try to post a link later.
 
Yes, you can get at the governor lever thru the filler cap. It is a fork that operates the fuel control rack in the injector. It has a spring on the shaft that controls it from the governor on the crankshaft. It is also connected by two springs to the regulator (throttle) control.

You can make sure the governor lever is working because you can see it thru the fuller cap hole. However, if you want to check the mechanism fully (and replace springs) you have to take the whole front cover off. Sounds daunting but actually quite straightforward - will also allow you to check the water pump at the same time!

If you have a 1GM and want to DIY invest £25 in the official workshop manual. Very clear and informative - even gives you the specification of the springs! I managed to take the cover off, strip it down completely because the casting was corroded, repair the casting, have it powder coated then put all the fuel control mechanism back together. Reassembled the whole thing, put it back in the boat and started first time.
 
I replaced the return pipe on Monday taking it down to a U bend below the tank and back up and into the tank. Regretably the engine took forever to start this morning. One thing less now.
 
Thanks for the possible link. I am now thinking governor. The cold starting is the problem when perhaps something happens in the governor spring mechanism. As I said when started it will run allday and even stop and start without any bother -BUT leave it overnight so it ends up totally cold then its the devil itself to start and then in a hunting motion till it gathers itself up. Thanks . Hope to here from you again.
 
Thanks for the idea. It seems to be the route I ll have to follow. I bled the whole system again today but very poor starting.
Could you oblige with the full details of the manual and where I could purchase it from?
Does the engine need to come out?
I have access only from the top of the engine (thro the cockpit sole) with about 1 foot of space at the front of the engine. With this constraint would it still be possible to do the Job? Many thanks in anticipation.
 
Thanks for the information Pete. I think I am about to follow the same route, hopefully without removing the engine.
Any tips on doing the job would be well received. Many thanks.
 
I poked my finger in the oil filler hole and felt the forked lever which I could push rearward. It then moved forward as if gently spring loaded. Could it be that the forked lever has become detatched from the rack pin on the fuel injection pump? If so would I be able to reconnect it by taking out the pump from its orifice? Hoping Im geeting to the solution of this cold starting? Thanks
 
Ian
No, the engine would not run if the fork was not connected to the rack. It is just a little pin sticking out of the side of the injector. If you have downloaded the manual Page 4-1 has an exploded diagram of the whole mechanism. (I ordered mine thru my local dealer)
Have you tried turning over with the decompression lever up with throttle half open and then dropping the lever. This is what I do in the depths of winter (boat is afloat) and has not been started for a coupls of weeks. Never fails.

As to taking the front cover off, I would not do this in situ as you need a puller to get the crank pulley off, and there are loads of bits some of which will almost certainly end up in the bilges. The engine is light enough to lift by hand. You can use the mainsheet to lift it out. This assumes you have access to the half coupling and engine mountings.

Getting back to the basic problem, not convinced it is a fuelling problem otherwise the engine would not run so well otherwise. Worth checking the exhaust run. Do you have a water trap, a silencer and a nice big loop to the outlet. I was advised against fitting a silencer on mine because of potential back pressure problems. Hose can also delaminate over time which causes an internal restriction not obvious from the outside. Checking this is definitely better than pulling the engine apart.
 
Tranona thanks for the info. Today I was discussing prob with colleagues and one who is a retired mechanic had a look.
Suggested that control lever inside oil filler was not receding far enough. We noticed that the sealing wire had been removed by a previous owner. Tampered? He released Fuel Injection Limiter lock screw a fraction - and yes it fired up from cold in a couple of seconds. However exhaust very smoky and the engine conked after a couple of minutes. Turned screw in a touch to reduce fuel and started and runs ok but a little smoky under load. I hope it starts again tomorrow from cold. Obviously a previous owner has had a poke at this governor adjustment and there was insufficient fuel getting through because the rack couldnt move forward far enough - hence the cold start and hunting problem. I am not sure about further adjustment of this screw. I suppose trials of cold starting and less smokey runs over the next few days may give me the elusive solution. Any thougths?
 
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