Yanmar SB8 injection regulator

[Compass790]

Originally Posted by rockin411

So glad I found this discussion. I have an SB12 and mistakenly took the fuel pump apart when I think all I needed to do was properly bleed the line - I missed the loosen the delivery valve step.

I'm a little confused how far to tighten the regulator spindle. There is a spring on the end that would push the needle closed so I wouldn't think you would tighten so far to compress the spring all the way? I'm a complete newbie to this diesel stuff but so far the SE12 service manual has been pretty good.

Also, when the needle is closed, is that full throttle or does that shut off the fuel supply?

Thanks

Was going to suggest to PM Wotname but he is onto it.
He will walk you through the steps of that model injection pump as he is The CF guru for them. Worth the wait for him to have the time to help you as i guess you aren't in a hurry in winter. If you cannot understand his instructions you will need to give up on DIY as he's better than the manual or IMO most, so called "yanmar techs".
I will follow with interest. Good luck

[Bilgediver]

Originally Posted by rockin411

So glad I found this discussion. I have an SB12 and mistakenly took the fuel pump apart when I think all I needed to do was properly bleed the line - I missed the loosen the delivery valve step.

I'm a little confused how far to tighten the regulator spindle. There is a spring on the end that would push the needle closed so I wouldn't think you would tighten so far to compress the spring all the way? I'm a complete newbie to this diesel stuff but so far the SE12 service manual has been pretty good.

Also, when the needle is closed, is that full throttle or does that shut off the fuel supply?

Thanks

When the needle is closed 100% of fuel delivery goes to the injector . As the needle valve opens fuel is bypassed from the injector till when open far enough the engine stops running

[Wotname]

Originally Posted by rockin411

So glad I found this discussion. I have an SB12 and mistakenly took the fuel pump apart when I think all I needed to do was properly bleed the line - I missed the loosen the delivery valve step.

I'm a little confused how far to tighten the regulator spindle. There is a spring on the end that would push the needle closed so I wouldn't think you would tighten so far to compress the spring all the way? I'm a complete newbie to this diesel stuff but so far the SE12 service manual has been pretty good.

Also, when the needle is closed, is that full throttle or does that shut off the fuel supply?

Thanks

Bilgediver has stated it correctly.

To expand the explanation a bit as you are a self identified newbie, this injector pump is an old design and is very basic in operation.

The camshaft has a lobe that causes the pump to operate once every rotation and remember the camshaft only rotates at half the crankshaft rpm. That is, the pump operates at every second cycle of the crankshaft.

To vary the rpm of the engine, the amount of fuel injected needs to be altered - max fuel for max rpm and min fuel for idle.

However in the injector pump, the plunger pumps a constant amount of fuel towards the injector each time it operates. To decrease the fuel to the injector, some of the fuel in the high pressure side of the pump is bleed off back to the low pressure side of the pump via the regulator needle / spindle .

Thus when the regulator needle is CLOSED, all the fuel is delivered to the engine. This is full throttle (Wide Open Throttle - WOT) and is max rpm.

As the regulator needle is OPENED (slightly), some fuel is allowed back into the low pressure side of the pump and therefore less is delivered to the engine - reducing the rpm.

[Wotname]

Originally Posted by rockin411

So glad I found this discussion. I have an SB12 and mistakenly took the fuel pump apart when I think all I needed to do was properly bleed the line - I missed the loosen the delivery valve step.

I'm a little confused how far to tighten the regulator spindle. There is a spring on the end that would push the needle closed so I wouldn't think you would tighten so far to compress the spring all the way? I'm a complete newbie to this diesel stuff but so far the SE12 service manual has been pretty good.
........

As you have moved the regulator spindle somewhat, you need to follow the steps in the red box rather than the first three steps.

And perhaps re-read this post.

Originally Posted by Wotname

When the clamp (#2 & #8) is loose, the spindle #7 should turn fairly easily although there is a o ring inside that provides some resistance to turning it. The idea is that when it is turned CW to tighten it, you MUST NOT tighten it down hard. The other end of the spindle is a needle type valve and can be damaged by turning it too far. You tighten it until you just feel it stop and hold it by hand while the clamp is secured.

If you get it right, the arm (#1) is holding the spindle (#7) fully closed when the speed control is set to full power. If it isn't, then you haven't adjusted it correctly.

Note, there is only a few degrees of rotation of the spindle (#7) between stop and full power so it is easy to get it wrong the first time.

[Wotname]

Originally Posted by rockin411

......
I'm a little confused how far to tighten the regulator spindle. There is a spring on the end that would push the needle closed so I wouldn't think you would tighten so far to compress the spring all the way? ....

Yes, you need to tighten it and fully compress the spring, this ensures the needle is fully seated (i.e. CLOSED). However you must not tighten it so far as to cause damage to the needle (or it's seat). Don't try to ram it down .

It is unlikely you can feel the spring compressing, there is too much resistance in the O ring seal to notice the spring compression - at least to my fingers anyway.

Finger tight works!!!! Lightly grip the spindle and wind it down until you feel resistance, then stop.

Also re-read this post

Originally Posted by Wotname

Also remember that you might have to bleed the injector pump after adjustment.

You can tell when everything is correct by listening for the injector "squeak". Set full power on the throttle, decompress the cylinder and crank the engine a couple of times - you should hear a squeak as the injector operates. If not, then there is either air in the system or the regulator arm/spindle is not adjusted correctly.

Please let us know how it works out.

Disclaimer - I am not a diesel mechanic or Yanmar engineer however I have some DIY experience on this injector pump.

[Wotname]

@rockin411, after you get it right and the engine running nicely, sometime in the future, the regulator needle will wear. The first sign of this is the lack of a squeak when rotating the engine with the throttle set at full power (WOT).

The squeak is the injector pump / injector operating. This is when you carry out the adjustment in red below.

[Wotname]

Originally Posted by Compass790

Was going to suggest to PM Wotname but he is onto it.
He will walk you through the steps of that model injection pump as he is The CF guru for them. Worth the wait for him to have the time to help you as i guess you aren't in a hurry in winter. If you cannot understand his instructions you will need to give up on DIY as he's better than the manual or IMO most, so called "yanmar techs".
I will follow with interest. Good luck

Crikey Cobber, no pressure

At this rate, I'll need a larger hat for 2020

But thanks for the kind words anyhow

[rockin411]

Thanks so much Wotname! That was an excellent explanation and totally makes sense. I'm heading to the boat now to hopefully get it running again.

One last question/confusion: The cable that connects to the regulator is what I use to kill the engine(a push/pull switch). So the regulator is either open(off) or closed(engine running). There is another cable for the throttle that is attached somewhere else. What is actually controlling the speed of the engine since I only have 2 positions for the regulator - open/closed? What is varying the amount of fuel to the engine and how does the throttle play into the equation?

Thanks again for the time and as you said in an earlier post, have another virtual rum on me. Cheers!

[copaco]

Happy New Year Wotname.

[rockin411]

Your instructions worked perfectly... Cranked the first time. Thanks again for your help!

Now to deal with the white/blue smoke. I'll start a new thread for that.

[Compass790]

Thought Wotname could sort you out no worries.
I'll move to your white/blue smoke thread when you post it as have some experience with that .
Good that you got a win. Heard of many "mechanics" that struggle with those injector pumps.

Here is a link that you may well find interesting & informative:
http://www.cruisersforum.com/forums/...il-207584.html

[Wotname]

Originally Posted by rockin411

Thanks so much Wotname! That was an excellent explanation and totally makes sense. I'm heading to the boat now to hopefully get it running again.

One last question/confusion: The cable that connects to the regulator is what I use to kill the engine(a push/pull switch). So the regulator is either open(off) or closed(engine running). There is another cable for the throttle that is attached somewhere else. What is actually controlling the speed of the engine since I only have 2 positions for the regulator - open/closed? What is varying the amount of fuel to the engine and how does the throttle play into the equation?

Thanks again for the time and as you said in an earlier post, have another virtual rum on me. Cheers!

OK to be clear, I have never seen an SB8/12 in the flesh and the no manual that I have seen details the throttle and stop cable functions. From what I has ascertained from the internet and from what I have with with my YSE8 and others YSE8s & 12s, the throttle and stop functions and combined in one cable. However it is quite possible for it to be separated into two cables and I THINK the YSM does that. Compass 790 could confirm that or otherwise.

I do know however that the engine rpm is determined by the engine governor and the throttle cable. The throttle cable has to be connected to the governor arm - possibly indirectly (via a spring). A stop cable (when used on this injector pump) would usually allow the governor arm to move further past the idle position. Put another way, the throttle cable allows the governor arm to operate anywhere between idle and full power and the stop cable allows the governor arm to move further past idle to engine cut off.

Of course, the governor arm controls the regulator spindle and it is the regulator needle valve that determines how much fuel goes into the engine.

To repeat, at full power (WOT), the regulator needle is closed allowing all the fuel to go to the engine. As the regulator needle is opened slightly (by action of the governor arm), the engine will get less fuel and rpm will decrease. This action continues until the engines reaches idle rpm. If the regular needle is opened further, the engine simply stops due to lack of fuel.

Perhaps post #9 in this thread may be helpful (or not )
http://www.cruisersforum.com/forums/...ol-220737.html


This should not be confused with a stop cable that acts on the decompression lever should such a cable be fitted. In such instances, the stop cable operates the decompression lever with prevents the exhaust valve from fully closing and therefore removes compression from the cylinder.

[Wotname]

Originally Posted by copaco

Happy New Year Wotname.

Thanks mate, happy new year to you!

[Wotname]

Originally Posted by rockin411

.....
One last question/confusion: The cable that connects to the regulator is what I use to kill the engine(a push/pull switch). So the regulator is either open(off) or closed(engine running). There is another cable for the throttle that is attached somewhere else. .....

Could you post some photos of where both cables are connected at the engine?

I could learn something new about throttle cables and stop cables for this injection pump.

[Compass790]

Wotname is right the YSM does have a separate stop cable but it is a different injection pump. I suspect, but don't know, that the SB would have the same setup cablewise as the YSE.
If you need further help rockin411 re cable setup I suggest to PM Homer Shannon from the thread I mentioned in post#26. I'm sure he would be happy to supply pics of his throttle/stop cable setup as he also has the SB12 Yammer