Yanmar 1GM10 problem

[QBhoy]

QBhoy thanks for your input after nearly four months of working on the engine I think I'm starting to lose the plot?

No worries. If you have compression and fuel…only a few things can stop her running.
just thinking around that new muffler and exhaust. Any possible issues restricting here breathing ? Likely not..you’d suspect it’s more likely around the fuel or compression holding perhaps.

 

[LittleSister]

Low compression? Never mind oil in the air intake, try Easy Start.

It will help establish whether it is not firing because something (like compression) is not quite right - in which case it will likely fire anyway with Easy Start) - or there is still something more fundamental amiss.

(Also I noticed you responded to the suggestion that the exhaust might be blocked by saying you'd replaced 'the exhaust', and disconnected the hose, but an exhaust blockage is most likely to be in the elbow, before the exhaust hose.)

 

[martincharlesbrooks@gmail]

Thanks for your input we tried easy start as well before we done all the work on the engine it was difficult to start but would with a bit of easy start . I've checked the exhaust elbow and also connected a hose sticking out the hatch plenty of pressure but no starting my friend is checking his timing on his 1 gm10 to compare with mine

 

[Birdseye]

Diesel engines are really simple. If you have fuel, air and compression it will fire. Sounds as if you have checked the fuel ( have you turned the engie over with the injector out of the head so you can see the spray pattern?). Highly unlikely you wont have air. So most likely it comes down to compression. 200 psi is at the absolute bottom of diesel engine compression ratio ( about 14:1) so the fuel air mixture wont get hot enough. In diesels with this low a compression ratio there is a glow plug to help with the ignition - the 1GM 10 does not have one so it has a compression ratio of 25:1 or a pressure nearer 350 psi.

If the injection timing / camshaft is way out it could be that the fuel is being input on the exhaust stroke with the valves open which will make compression even worse. As would the decompression lever if activated

An easy test. Fit the starting handle to the front of the engine. If you can turn it by hand you have a compression problem - I used to be able to stand on mine without it moving.

 

[martincharlesbrooks@gmail]

Thanks for your help we have a good spray pattern on the injector I can just about turn the engine by hand so I know I'm down on compression it was running before I fitted new rings now it won't fire at all warming the air intake/oil in the bore to increase compression etc no sign of firing .when I first had a problem with the engine it started to sound rough so I decrease the revs on putting into neutral it cut out and hasn't started since .l will check the injection timing again thanks for your help.

 

[vas]

has the high pressure pump been checked/overhauled?
I'm asking as my gm2 had a recurring issue with air in fuel and at some point redoing the copper pipe from the hp pump to the injector on the hp pump side I overdid it the nut and the lower nut moved as well. After that it was just hell... (and was only on the one of the two pots!)
had to remove the hp pump take it to a specialist who took it apart and reset things (don't ask, wasn't there!)
started straight away after that.

 

[martincharlesbrooks@gmail]

Thanks I took the high pressure pump /and the injector to a specialist for a check and service

 

[mpk]

Hey fellas,
I have the same problem. When I got the Yanmar 1gm it was run hot and piston was sized in the bore.
I disassembled the engine and inspected it. I sent the head out to a reputable machine shop for a valve job, checked the bottom end and got a new con rod and bearings, also got a new piston (it came with the rings installed), machined the cylinder, set the valve timing, bled it a million times. When I crank it over, water comes out the exhaust and I can smell exhaust, but it just won't fire up?
Any suggestions, thanks

 

[earlybird]

Is the compression good? Is the injection timing correct? Is fuel definitely reaching the injector? (probably if you can smell the fumes). Re water; from where is it being introduced? If the boat is afloat, then shut the cooling water seacock during prolonged cranking and don't connect a hose to the system if you're ashore. Hopefully it's not getting in the cylinder, otherwise you'll have trouble.

 

[mpk]

Yes, compression is good, timing marks are on the money, valve lash is correct... I suspect my fuel lift pump is bad because after one manual pump I don't see any fuel running thru my temporary fuel line and I have poor pressure throughout the system.

 

[LiftyK]

Have you made any changes to the alternator? The original has a smaller than usual pulley to reduce load on startup. Perhaps try starting with the alternator disconnected.

 

[Boater Sam]

If its injecting when cranked you will get white smoke from the exhaust. Even at 200psi it should smoke.
No smoke = no fuel being injected.

if all else fails and it is injecting fuel and not water, stick a blowlamp up the inlet whilst cranking.

 

[earlybird]

If the lift pump might be dodgy you could rig up a temporary tank to feed by gravity to the injection pump. Also bear in mind that GM engines aren't very good starters in cold weather. (but I'm not recommending "Easy-Start").