Yanmar 4jh3-dte won’t run

[VandKoala]

Hey everyone!

I hope you’re all doing well! I could really use some help with my Yanmar 4JH3-DTE diesel engine. We just bought a sailboat, and here’s the situation: the engine starts up, but then it dies after just a couple of seconds. The first time we started it, it ran for about 30 seconds before stopping.

We discovered that it’s not sucking enough fuel. We’ve checked the entire fuel system and even fed it directly from a clean jar into the pump. If we use an extra electric pump to force feed it, the engine runs and revs up nicely. But as soon as we stop the extra feed, it stops again.

Do you think there’s something in the pump itself that I can check? It feels like there might be a clog or something. Any advice would be greatly appreciated!

The engine is from 2010 and has 1100 hours on it.

Thanks a bunch!

 

[ChromeDome]

When running, are all cylinders firing evenly?

When feeding it from a jar, where did you disconnect the hose from?

Is the return line free (blow with a pump or your mouth and listen for bubbles in the tank)?

Have the (pre- and engine) filters been checked for water or replaced?

Is there any chance of air to be sucked into the feed line?

 

[Beneteau381]

Hey everyone!

I hope you’re all doing well! I could really use some help with my Yanmar 4JH3-DTE diesel engine. We just bought a sailboat, and here’s the situation: the engine starts up, but then it dies after just a couple of seconds. The first time we started it, it ran for about 30 seconds before stopping.

We discovered that it’s not sucking enough fuel. We’ve checked the entire fuel system and even fed it directly from a clean jar into the pump. If we use an extra electric pump to force feed it, the engine runs and revs up nicely. But as soon as we stop the extra feed, it stops again.

Do you think there’s something in the pump itself that I can check? It feels like there might be a clog or something. Any advice would be greatly appreciated!

The engine is from 2010 and has 1100 hours on it.

Thanks a bunch!

You’ve diagnosed it yourself, the electric fuel pump is failing? But if you are feeding it directly and it work’s then there could be a blockage in line from the tank. Maybe the stack pipe in the tank is blocked with bug

 

[VandKoala]

You’ve diagnosed it yourself, the electric fuel pump is failing? But if you are feeding it directly and it work’s then there could be a blockage in line from the tank. Maybe the stack pipe in the tank is blocked with bug

When I feed it with an electric pump it is working but not reaching full revs and if I back throttle to “neutral” it dies immediatelly even with the pump. And it can’t suck the diesel itself at all

 

[VandKoala]

When running, are all cylinders firing evenly?

When feeding it from a jar, where did you disconnect the hose from?

Is the return line free (blow with a pump or your mouth and listen for bubbles in the tank)?

Have the (pre- and engine) filters been checked for water or replaced?

Is there any chance of air to be sucked into the feed line?

It works very smoothly and quietly when running.
I disconnected the hose very close to the engine/pump. There is still one 15cm hose left, probably should also check that one.

Return is free, bubbling in the tank.

New filters and we went around them with a jar of diesel to eliminate any suspicion.

Probably the last possible air suction spot could be that last hose before pump. Will check that.

 

[Beneteau381]

It works very smoothly and quietly when running.
I disconnected the hose very close to the engine/pump. There is still one 15cm hose left, probably should also check that one.

Return is free, bubbling in the tank.

New filters and we went around them with a jar of diesel to eliminate any suspicion.

Probably the last possible air suction spot could be that last hose before pump. Will check that.

The stack pipe in the tank?

 

[ChromeDome]

Fuel is sucked from the tank by the feed pump which means that the whole system is under vacuum. Hence you'll never see a leak, but the risk air getting sucked in can't be ignored.

Even the slightest amount of air in the fuel will make the engine starve. You need to take a systematic approach by first loosening the fuel air bleed screw at the filter, then work the primer pump until all air is gone from the filter. Tighten the bleed screw. Then loosen the fuel line at the filter feed pump (built into the injector pump) and pump the primer pump again. It may take quite some pumping but you must keep on until absolutely no more air comes out. Tighten the fuel line.

If air appear in the fuel line again, you have a leak. If not and it still starves, a blocked fuel supply must be the culprit.

If you do not have it already, a service manual can be downloaded here

 

[black mercury]

I believe your engine fuel filter has a hand priming pump on the top of it. If the primer is sucked down when engine is running you have a fuel blockage before it. Not sure where you fed the injection pump but if you feed the injection pump directly from a clean container with the return going back into the container and you still have the symptoms after running for a few minutes then the fault is within the injection pump, probably the vanes of the lift pump being seized.

 

[Beneteau381]

Fuel is sucked from the tank by the feed pump which means that the whole system is under vacuum. Hence you'll never see a leak, but the risk air getting sucked in can't be ignored.

Even the slightest amount of air in the fuel will make the engine starve. You need to take a systematic approach by first loosening the fuel air bleed screw at the filter, then work the primer pump until all air is gone from the filter. Tighten the bleed screw. Then loosen the fuel line at the filter feed pump (built into the injector pump) and pump the primer pump again. It may take quite some pumping but you must keep on until absolutely no more air comes out. Tighten the fuel line.

If air appear in the fuel line again, you have a leak. If not and it still starves, a blocked fuel supply must be the culprit.

If you do not have it already, a service manual can be downloaded here

They usually have an electric lift pump so no hand pumping. Having said that some have pump on top of filter.If it has an electric pump it’s the same as a car usually. Switch on and it pumps the fuel through. So assuming I am correct then there must a blockage on the suction side OR a bad fuel pump.

 

[VandKoala]

Fuel is sucked from the tank by the feed pump which means that the whole system is under vacuum. Hence you'll never see a leak, but the risk air getting sucked in can't be ignored.

Even the slightest amount of air in the fuel will make the engine starve. You need to take a systematic approach by first loosening the fuel air bleed screw at the filter, then work the primer pump until all air is gone from the filter. Tighten the bleed screw. Then loosen the fuel line at the filter feed pump (built into the injector pump) and pump the primer pump again. It may take quite some pumping but you must keep on until absolutely no more air comes out. Tighten the fuel line.

If air appear in the fuel line again, you have a leak. If not and it still starves, a blocked fuel supply must be the culprit.

If you do not have it already, a service manual can be downloaded here

I think I have gone through this today, but I might have missed something. Will go again tomorrow morning.

 

[VandKoala]

I believe your engine fuel filter has a hand priming pump on the top of it. If the primer is sucked down when engine is running you have a fuel blockage before it. Not sure where you fed the injection pump but if you feed the injection pump directly from a clean container with the return going back into the container and you still have the symptoms after running for a few minutes then the fault is within the injection pump, probably the vanes of the lift pump being seized.

I have connected the electric pump here, but there is another 15-20cm of the hose left, that might be sucking air. On the other hand, I did not see any bubles in the return line…

 

[VandKoala]

They usually have an electric lift pump so no hand pumping. If it has an electric pump it’s the same as a car usually. Switch on and it pumps the fuel through. So assuming I am correct then there must a blockage on the suction side OR a bad fuel pump.

No mate, there is no common rail system or an electric pump. I have a manual pump and a bleeding pipe before the diesel gets into one of the two (selectable) filters.

 

[Beneteau381]

No mate, there is no common rail system or an electric pump. I have a manual pump and a bleeding pipe before the diesel gets into one of the two (selectable) filters.

An electric lift pump is used on direct injection engines as well. I know it’s not common rail. The system on yours looks quite grotty and those hose clip connections don’t fill me with confidence. Take the manual lift pump out of the system/equation and replace it with the electric pump to experiment whether it solves the problem. If it does then you know the lift pump is bad. If it doesn’t then you have a blockage on the suction side. Bug/black sludge hits the suction stack pipe in the tank first so that’s where blockages start.

 

[ChromeDome]

Note: When putting an electric pump into the feed line, the vacuum from that point to the engine will change to a pressure.

Should be able to push fuel/air forward to bleed at the engine feed pump.

 

[Beneteau381]

Note: When putting an electric pump into the feed line, the vacuum from that point to the engine will change to a pressure.

Should be able to push fuel/air forward to bleed at the engine feed pump.

Replace it like for like as I said and the pressures in the system are the same as before

 

[VandKoala]

Small update…
Now the question is if some of that shit os also in the pump/injectors.

Will clean it all and see.

Cheers everyone for ideas and help!

 

[ChromeDome]

Looks like brown sugar Did you taste it (tip of tongue)?

What part of the fuel line did you find it in?

Your filter should have catched it.

 

[VandKoala]

Looks like brown sugar Did you taste it (tip of tongue)?

What part of the fuel line did you find it in?

Your filter should have catched it.

That is the “funny” part - it is just past filters in the lowest point of the fuel line. The water separator is built in the filters. But this hose was lower than that. Probably in the 2-3 years the boat was standing in a garage - that what was the result. There is no secondary filter (that I can see) before the pump. I will install one as I am all in diesel anyways…