Yanmar Ysb8 not starting, injector pump doesn’t seem to be pumping

[lydude]

Hi all, can’t get a Ysb8 to start. New fuel, electric primary pump works. I get a big stream from the injector pump when I loosen the delivery valve and injector pump is bleed very well.....I believe. I turn engine over and nothing from delivery valve? I took injector pump apart and everything looks clean and nothing seems worn. Not sure I could tell but nothing obvious. Should I just put a new injector pump in? Do they just go bad and nothing pumps out? Any help or insight would be great.
Thanks
Liam

[dkenny64]

what happens if you spray WD40 in the intake.. does it fire?
could the decompression lever be stuck and not working?
do you get diesel at the injector is you crack open the line while its cranking?


-dkenny64

[lydude]

Yes fires when I sprayed some started fluid in.
No diesel when cranking, I’ve taken off high pressure metal line and cranked and no fuel spurting out at all? I’m pretty sure decompression lever works fine.

[a64pilot]

I am completely unfamiliar with that motor, but are you certain that the fuel shut off isn’t shut off?

[lydude]

Fuel is in flowing freely with the electric primary pump.

[Halifax Sailor]

May sound dumb, but same happened to me last year. Planned on changing both filters before launch but didnt and then engine would not start. Electric fuel pump couldn't get any fuel thru primary and secondary was totally empty (engine ran it dry). Felt pretty stupid but glad that's all it was. Changed out both, bled lines and vroom.

[Compass790]

Originally Posted by lydude

Hi all, can’t get a Ysb8 to start. New fuel, electric primary pump works. I get a big stream from the injector pump when I loosen the delivery valve and injector pump is bleed very well.....I believe. I turn engine over and nothing from delivery valve? I took injector pump apart and everything looks clean and nothing seems worn. Not sure I could tell but nothing obvious. Should I just put a new injector pump in? Do they just go bad and nothing pumps out? Any help or insight would be great.
Thanks
Liam

A few of questions for you.
Have you been working on the fuel system before it failed to start?
Was it a good starter before this problem occurred?
Do you have a copy of the service manual? Check the CF library for a copy
I wouldn't replace the injection pump just yet if there are no obvious faults like scoring or rust.
They don't usually just go bad unless dirt or air is in them. Once you answer the questions it may give us a clue.
Wotname knows more about those IP's I'll alert him to your post
Here is a link to a video you might like.

https://www.youtube.com/watch?v=kougXR9Rfnc&t=264s

[dkenny64]

the electric pump only get the fuel to the injector pump.. not past
do you have fuel at the injector is you crack open the line.


my first boat had the YSE8 yanmar...
does spraying WD40 in the intake make it fire..no.. check the compression release...yes...back to the first question


-dkenny64

[lydude]

Thanks
Just changed all fuel in tank
Starter turns engine over quickly
Electric pump fills up injector pump when bleeding. Get major stream of fuel when I unscrew delivery valve. But when I tighten it up again and turn over engine nothing will spurt out of delivery valve. I know fuel is in IP has bleeder screw on banjo fitting suppling it. How nothing comes out baffles me. Don’t know how any air could be in there? Pretty sure I have the air venting figured out.

[Compass790]

Originally Posted by lydude

Thanks
Just changed all fuel in tank
Starter turns engine over quickly
Electric pump fills up injector pump when bleeding. Get major stream of fuel when I unscrew delivery valve. But when I tighten it up again and turn over engine nothing will spurt out of delivery valve. I know fuel is in IP has bleeder screw on banjo fitting suppling it. How nothing comes out baffles me. Don’t know how any air could be in there? Pretty sure I have the air venting figured out.

Ok is the throttle wide open when you are cranking it? Is the governor linkage ok?
Did the problem occur suddenly?

[Wotname]

Originally Posted by lydude

Hi all, can’t get a Ysb8 to start. New fuel, electric primary pump works. I get a big stream from the injector pump when I loosen the delivery valve and injector pump is bleed very well.....I believe. I turn engine over and nothing from delivery valve? I took injector pump apart and everything looks clean and nothing seems worn. Not sure I could tell but nothing obvious. Should I just put a new injector pump in? Do they just go bad and nothing pumps out? Any help or insight would be great.
Thanks
Liam

Some points to consider.

The injector pump (IP) is very simple but somewhat different to latter style IPs.

You will only see a very very small amount of fuel from the delivery valve and only if the regulator lever is in the full power position..

The best way to tell if fuel is being injected is to set the throttle fully open (WOT), decompress the engine, turn it over rapidly by hand and listen for the injection squeak. If it is injecting fuel, there will be a distinct squeak at the injection moment. If no squeak (or very weak squeak), there is no fuel being injected. Note - the throttle must be wide open (i.e. regulator lever fully operated and regulation valve fully closed) for this test.

The operation manual gives full details on how to adjust the regulator valve if you have disassembled it. It must be followed exactly but it isn't difficult.

It also must be adjusted periodically as the regular valve wears. By periodically, I mean say every 1000 hours - anytime the squeak becomes weak!

This IP doesn't usually fail without warning and last time I checked, parts where still available (2 years ago). There are only three parts needed. The plunger and barrel assembly (sold as a matched pair), the regulator needle and the delivery valve.

Do you have the operators manual or a service manual? You need them if you want to work on or replace the the IP.

[Wotname]

Originally Posted by lydude

Thanks
Just changed all fuel in tank
Starter turns engine over quickly
Electric pump fills up injector pump when bleeding. Get major stream of fuel when I unscrew delivery valve. But when I tighten it up again and turn over engine nothing will spurt out of delivery valve. I know fuel is in IP has bleeder screw on banjo fitting suppling it. How nothing comes out baffles me. Don’t know how any air could be in there? Pretty sure I have the air venting figured out.

The way the the YSB IP regulates fuel quantity being delivered is sort of the opposite of most other IPs.

It regulates the amount of fuel delivered to the injector by bleeding off the high pressure side of the pump back to the low pressure side. At full power, no (or very little) high pressure fuel is diverted back to the low pressure side. At idle, most of the high pressure fuel is divert back to the low pressure side. This all happens internally in the IP.

EDIT: When you crack the delivery valve, you no longer have a high pressure side as you have opened that side to the atmosphere.

[Wotname]

BTW, that is an excellent video posted by Compass790 upthread and describes the IP very well. The squeak can be heard at 3.21 and 4 minute marks.

Unfortunately it doesn't describe the regulator adjustment after re-assembley. This is a critical step.

[Pegu Club]

An outside chance but,... is your engine stop button solenoid sticking in the off position? Ask me why I ask this...

Fair winds,

[lydude]

Thanks Wotname, that all gives me a bit of insight. I’m not sure I’ve adjusted the regulator properly, I did try as I had removed it all. I did order a new regulator valve but haven’t gotten yet. I did have the throttle wide open, not sure if reg was correct. Sounds like it needs to be fully closed “screwed down” when throttle is all the way down. I’ll check that next weekend. Great video thanks! I’ll study up the regulator adjustment. Based on video not much fuel gets pushed out. It’s hard to crank my engine by hand as my fiberglass covers the engine and my homemade hand crank is about 12” long so hard getting it going, thus use starter.
Thanks again look forward to trying your tips next weekend!