Yanmar Issues Still

[sailorchic34]

Ok I have issues.... Well that is I'm still having starting issues with my 3gm30F. Its hard starting, hot or cold. Acts exactly the same. I have to have the throttle at about 30% to get it started. One cylinder catches right away, the other two lag behind many seconds 5-10 seconds. Once the other two cylinders fire, life is good. This with 60 ish degree F days.

No smoke at startup, hot or cold. Once started and running on all cylinders it runs fine. It has what I think is high crankcase pressure. But it runs at speed fine (once warmed up) in gear up to 3500 RPM under load.

Turn it off and wait 15 seconds or a minute and its hard starting again, with the same delay firing on 2 cylinders....

I have checked the valves (good), replaced the racor filter and cleaned the air filter.

Coolant and oil are fine, no leaks, no water in oil etc. Oil pressure is perfect and it does not run hot at all.

I'm thinking it might be either sticking/back leaking injectors (IE not sealing tight) or the lift pump is failing. It sort of sounds like leaky injectors. It acts like its not getting fuel to the two cylinders right away. Throttle response is fine once they are firing. No major smoking at startup, which to me means the fuel is not getting to the cylinders on two cylinders.

If it was low compression, I would think I would expect lots of smoke once the cylinders started firing. But no smoke on startup

About 1000 hours on the engine.

I'm thinking of pulling the discharge line of the lift pump off tomorrow and seeing if it pumps.

While it could be low compression, I would think it would be easier to start once it was warmed up. But it acts exactly the same hot or cold. This has only been a problem since this winter started or sometime after. Maybe in the last month or two...

In other forums it seems others have this same problem / issue with the GM's and this seems normal. But this engine use to start up fine hot and was only a little cold nature below 50-55 degrees F.

[bobconnie]

Still sounds like a fuel delivery prob to me !! sounds like your on the right track!!just keep ckn the fuel system, one place at a time it will show up. Good Luck. (from your past posts, im sure you will get it handled!!)

[Lancerbye]

As Bobconnie stated it is most likely a fuel delivery problem. If you had a leaky injector you would see a lot of smoke on start up. I would suspect more an injector pump that is having a hard time getting the fuel pressure to the injectors high enough fast enough. Sometimes lack of lubrication in the injector pump prevents it from delivering the pressure required to trip the injectors and your engine starves for fuel until those pressures can be reached. Or you may have some worn parts in the pump. It sounds more like a case of fuel starvation than anything else. A small intake leak to the pump can cause the same thing.

[bill good]

Have you checked the owners handbook? I think it is the same for 1,2 &3GMS & after a number of years, I found where it stated use full throttle for starting.

[djmarchand]

Your symptoms sound exactly like a fuel delivery problem: no smoke on startup is the main clue and it takes throttle advance (which lets the injector pump push more fuel through to clear the injector lines until it starts).

[NoTies]

I would be taking a long look at the lift pump. It sounds to me like the valves may be not sealing and allowing fuel to back flow. This is actually a hard problem to diagnose without a spare lift pump or good vacuum/pressure gauges.

[sailorchic34]

Well, I pulled the fuel pump and tested it. Pumps fine and no back leak. The fuel hose was loose on the banjo bolt. But after tightening it there was no change.

I also blew through the fuel line and could hear bubbles in the tank.. Hum should I be able to hear bubbles????

Also checked the return line and it was clear too, though hose clamp was loose there too...

So next on the list will be to pull the injectors, and testing the spray pattern while cranking the engine. Fun fun....not.... That will be thursday ish....

[phantomracer]

when was the last time the injectors were replaced?

I took a Mack Boring class and it was discussed they should be rebuilt time to time. Usually they can just be swapped out for rebuilt units to reduce downtime. Unsure what the interval is..(1000-1500 hours maybe)

I assume the stop lever is not engaged.

The previous owner of our boat installed an electric lift pump. It really helps in bleeding the system...which I assumed you did.

Also assume the decompression levers are not engaged!

Hopefully its simple.

But it can only be fuel. It has compression (spark) and air, so the only thing left is fuel.

[Badsanta]

I have to use full throttle on mine and if the battery is down any it will not crank as fast and that has caused me starting problems also on my 3gm30

[roverhi]

My 3GM starts instantly even down to 50 degree temperatures. Swap out the injectors to see if you can move the problem from cylinder to cylinder. Might want to buy an extra injector that you can use for trouble shooting and/or a spare if needed.

[Badsanta]

don't forget to get a bunch of the copper crush washers also

[phantomracer]

Originally Posted by roverhi

My 3GM starts instantly even down to 50 degree temperatures. Swap out the injectors to see if you can move the problem from cylinder to cylinder. Might want to buy an extra injector that you can use for trouble shooting and/or a spare if needed.

ditto. coldish and low battery..doesn't seem to care, starts virtually instantly (also have 3gm30)

[FSMike]

sailorchic -

Having read many of your posts I would not presume to offer you any technical advice. I will, however, raise a glass of red to the diesel gods (while facing west), and make an offering in the name of you and your Yanmar.

Good luck,
Mike

[phantomracer]

might want to contact Mack Boring for advice on their rebuild/exchange service or for troubleshooting

Mack Boring & Parts Company - Reliable Power. Everywhere.

[Ziggy]

Originally Posted by sailorchic34

So next on the list will be to pull the injectors, and testing the spray pattern while cranking the engine. Fun fun....not.... That will be thursday ish....

Has the starting problem appeared suddenly or developed gradually? If it developed gradually it could be worn injectors (but then I would expect the engine to run rough all the time, not just when starting.) If it was sudden, I suppose it could be an air leak in the fuel lines. Are there any visible fuel leaks around the lift pump? If so, that could allow air to get in.

It could also be as simple as incorrect injector pressure setting, although I have no idea how that could happen unless they were recently serviced and incorrectly adjusted.

As Phantom racer points out, injectors should be periodically serviced. Yanmar recommends every 1000 hours or 4 years, whichever comes first. If you're close to that interval, you might as well take them out and bring them to an injector service shop to have them checked out.