Yanmar yse8

[Stevemattingly]

Hi guys, I recently sold a Hurley 24 to a lovely couple. I had run the engine for an hour with them. They took there first trip and she started fine and ran for an hour and they then stopped for an hour. Restarted and punched the tide back. At some point the engine petered out. I have been working on the engine for the to try and resolve the issue. The injector has been checked and is working perfectly although advised it is set at the higher psi (60 over 48 I think). I have stripped the injector pump and all is clean. The injector sprays a nice mist outside of the engine. I have adjusted the IP screw to 90 degrees from stop but also tried many other adjustments in-between. I have also set up separate fuel feed and still no joy. The governor appears to be moving as it should.
Compression can't really have just dropped off as it still appears to have plenty.
Air intake is clear as is exhaust elbow. Batteries are excellent.
What am I missing. HELP! Many thanks Steve

[mcpusc]

> I have adjusted the IP screw to 90 degrees from stop but also tried many other adjustments in-between.


follow the instructions for the governor adjustment in the manual to the letter — are you getting the injector "squeak" as described? if not repeat adjustment & bleeding until you do

[Wotname]

^^ what mcpusc said!!!!

Governor / regulator arm adjustment is critical and you must get it 100% right.
No squeak, no go. It is easy once you know how to do it but it can be tricky the first time.

[Stevemattingly]

Many thanks for prompt replies guys. I have tested outside of the engine many times to get the squeak. I have the IP off again now and it wasn't pumping fuel again. I have removed the ball and spring and it now is pumping and squirting as she should. So are the springs too strong(I bought a second pump) or can you over tighten the gland to put to much pressure on the spring. Both spring assemblies are doing the same! Can I run it without a spring?
Sure I am getting closer!
Cheers Steve

[Stevemattingly]

Ps, the second pump I purchased is actually from a yse12. They look identical but the piston is larger therefore pumping more fuel. Everything else is identical. Will it still run with the bigger fuel pump piston? I was hoping to build one good pump from the two.

[mcpusc]

I have removed the ball and spring and it now is pumping and squirting as she should. So are the springs too strong(I bought a second pump) or can you over tighten the gland to put to much pressure on the spring.

IME you have to get absolutely *all* the air out of the injection pump before it will pump any fuel at all past the delivery valve. with a completely dry pump I had to bleed at the injection pump inlet, at the bypass lever gland, at the delivery valve gland, and then finally at the injector, all while turning the engine to work the pump. i've had to manipulate the bypass lever while bleeding as well to get a tiny bubble out of the pump.

Can I run it without a spring?

nope, you need the delivery valve for it to work properly.

Ps, the second pump I purchased is actually from a yse12. They look identical but the piston is larger therefore pumping more fuel.

Will it still run with the bigger fuel pump piston?

careful, like you said the plunger size is how yanmar controls full-throttle fuel volume on these engines — with the throttle at full, the entire volume of the plunger is injected, so that will be nearly 50% more fuel than it was designed for! personally i'd be real worried about an overspeed, i don't believe there is any other feature of the pump that will control max speed like on more modern diesels...

FWIW you can still buy new injection pumps and parts for these engines, both from yanmar and from third-party suppliers. I replaced my YSB8's injection pump with a new third-party one off alibaba last year for about 25% of the yanmar dealer quote; its been working great for about 50 hours so far.

[Stevemattingly]

Many thanks again!
So on a IP bench test the fuel pumps nicely with the delivery valve gland slightly loose. If I tighten the fuel stops while manually working the piston is this correct? Does it build up pressure to get past the spring pressure when in the engine? Now thinking try the yse12 piston! Cheers guys

[Wotname]

The way the regulator needle valve works is sort of the opposite to what many initially think. Its job is to divert fuel from the high pressure side back to the low pressure side. When it is closed (fully CW), all the high pressure fuel is delivered to the cylinder via the delivery valve. When the regulator needle valve is slightly open (spindle rotated CCW), some of the fuel from high pressure (outlet) side is allowed to pass back (inside the body of the pump) into the low pressure (inlet) side. The range of movement of the spindle from closed to slightly open is only a few degrees.

So with the regulator spindle closed (fully CW) all the fuel goes into the cylinder.
As the spindle moves slightly CCW, less fuel is delivered to the cylinder.
When the spindle is moved further CCW, no fuel is delivered to the cylinder; it is diverted back to the inlet side of the pump.

The plunger (piston) always pumps the same volume of fuel each stroke. With the
regulator needle valve closed, it all goes to the cylinder. With the regulator needle valve open, it all goes back to the inlet (low pressure) side.

The speed of the engine is controlled by the very small movement from closed to just slightly open.

Operating the plunger (piston) by hand, you probably can't develop enough pressure to push past the delivery valve when the regulator needle vacate is closed (CW). As this needle valve is opened and fuel is allowed back to low pressure side, it becomes easier to manually pump the plunger.

[Stevemattingly]

Excellent response again for which I am very thankful. I do understand the principles of how it all works which leads to the question of why do we set the fuel adjustment screw 90 degrees from closed as surely it can never deliver max fuel?

[Wotname]

You don't set it 90 degrees from closed - if you do, it will never work.

I'll post the adjustment instruction shortly.

[Wotname]

If the IP has been apart, you have to adjust it after re-fitting by following the steps in the GREEN section, taking particular note of where to set the punch mark (green arrow).

The red section is ONLY for making an adjustment as the needle valve wears. It simply rotates the eccentric pin 90 degrees which makes a very minor adjustment.

If the green section is followed exactly, the needle valve will be closed when the governor wants max fuel.

[Stevemattingly]

Speed control lever to full I assumed is throttle control in cockpit.
Punch mark I assumed is the slot in the adjusting screw(although this gives the possibility of two settings)
Set it all up and bled through again.
She didn't start so added easy start and got her running for a short test.
Left it a while and tried again without easy start and no joy.
Will run her again tonight when the tide is in for a good run and test her out.
Many thanks for this awesome service!

[Wotname]

Originally Posted by Stevemattingly

Speed control lever to full I assumed is throttle control in cockpit.
Yes

Punch mark I assumed is the slot in the adjusting screw(although this gives the possibility of two settings)
NO
........!

The punch mark is a tiny indent as would be made by using a centre punch and hammer. It may be painted over or hidden by rust but it will be there on item 3.

Note that the pin on item 3 which engages with item 1 is eccentric. The punch mark allows for the eccentric pin to be set in the correct position.

When you set the punch mark as per step 3 in the green box, the item 3 pin will keep the regulator needle valve fully CW (closed - full power) when throttle is set to full.

As the needle valve wears, it will no longer be fully closed when fully CW. When this happens (no injector squeak), you use the RED box instructions which is rotating item 3 through 90 degrees CCW. Because of the eccentric nature of the pin on item 3, item 1 is moved ever so slightly CW thus ensuring the needle valve is again fully closed.

The red steps are a one shot adjustment and further wear requires going back to the green steps.

Hope this makes sense, it becomes obvious once you have done it a couple of times. The trick is to find the punch mark and look how it relates to the eccentricity of the pin on item 3.

[Stevemattingly]

Wow, it must be painted over as I did look! Will give it a good clean and reset up again. Hopefully another step closer. Will report back tomorrow. Many many thanks again!

[Wotname]

Going from memory - I think it will be in line with (or at 90 degrees) to the offset nature of the eccentric pin on item 3.