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

[lydude]

Hi Pegu club
Not sure I have a stop button solenoid. I just back off throttle and engine stops. Do you have one on your Yanmar Ysb8 ?

[a64pilot]

Originally Posted by lydude

Fuel is in flowing freely with the electric primary pump.

I’m talking about the fuel cut off at the HP pump. They way you shut down the motor, I assume you pull a cable?

[Wotname]

There is no stop button on a YSB8. To stop the engine, the throttle is simply fully retarded.

[Wotname]

Originally Posted by a64pilot

I’m talking about the fuel cut off at the HP pump. They way y9u **** down the motor, I assume you pull a cable?

There isn't even a fuel cutoff at the HP pump.

The throttle setting goes from stop to idle to full power by moving only one lever. With this HP pump, it is called the regulator lever. It is very basic but it works .

[Wotname]

Yanmar did improve the cut off function later on the SB8 where the throttle cable could only move the lever to the idle position and a second cable (engine stop cable) allowed the same lever to move further which allowed all the high side of the HP pump to compteley redirected back to the low side.

EDIT: I have only seen this on some SB8's, maybe it wasn't a Yanmar thing after all.

It doesn't show up in my SB parts book.

[Pegu Club]

Originally Posted by lydude

Hi Pegu club
Not sure I have a stop button solenoid. I just back off throttle and engine stops. Do you have one on your Yanmar Ysb8 ?

On my old Yanmar SB 12 there was a stop button, on my Beta 16 there is a stop button as well that operates a solenoid that does the actual stopping, it was miss aligned and was hanging up making starting troublesome, a mere realignment by Jim the genius mechanic at Deatons yacht service in Oriental NC did the trick starts right up perfectly

Fair winds,

[Halifax Sailor]

Same thread different question. I have a ysb8. Until this year, it would start within 10 seconds no matter how long it had sat. Even first start after winter layup. Si I did the original start up, read all the manuals to set the valve clearances (prob never been done), engine is now hard to start when cold. Have checked clearances several times, they are set to .2 mm as per the manual I have. I have changed both fuel filters and all fuel lines just in case I had a leak. It does start a little easier but that does not give me great confidence. Once started and warm, runs like a top. After changing the filters, had to bleed the fuel lines and got great stream at the HP? fuel pump just before the injector. Starting to really scratch my head now. I put a can of Sea Foam in today to see if by chance injector is clogged. Here's my thoughts:
1) Fuel line from electric in-line fuel pump is a loop about 4" above engine. same as before but wondering if maybe air gets in there? But I just changed this line with all the other rubber ones.
2) Injector dirty? will running the engine with Sea Foam clean it out? wait and see I guess.
3) Batteries are good, so far starting with shore power attached so plenty of juice.
4) Bad fuel? Didn't use hardly any last year because of covid. Did put a stabilizer in the fall. When I pulled the bowl off the primary filter, the fuel was very cloudy. New filter, new fuel from same tank, its very clear but engine still starts hard.
5) Only thing I didn't check if electric fuel pump connection is good at start switch. Maybe intermittent when first starting?

Any advice or help would be great.

[Halifax Sailor]

Me again with a ysb8 question. Sounds like at least 2 of us have somewhat the same issue. Mine is hard starting for the first time ever. I have changed the filters, all fuel lines and today added can of Sea Foam. Had to bleed the lines after filter change but that was quick and got fuel in 10 secs. Still starts hard (30 secs or so) when cold but starts in 5 secs or less when warm. Hoping the Sea Foam will work as I just dont know what else. I did check the valve settings and they are set to spec. New exhaust elbow and all new exhaust hose. I did not buy any fuel last summer so am now wondering if I may have a bad fuel issue. I did put some stabilizer in last fall and engine runs great when started and warm so scratching my head here............................

[Compass790]

Originally Posted by Halifax Sailor

Same thread different question. I have a ysb8. Until this year, it would start within 10 seconds no matter how long it had sat. Even first start after winter layup. Si I did the original start up, read all the manuals to set the valve clearances (prob never been done), engine is now hard to start when cold. Have checked clearances several times, they are set to .2 mm as per the manual I have. I have changed both fuel filters and all fuel lines just in case I had a leak. It does start a little easier but that does not give me great confidence. Once started and warm, runs like a top. After changing the filters, had to bleed the fuel lines and got great stream at the HP? fuel pump just before the injector. Starting to really scratch my head now. I put a can of Sea Foam in today to see if by chance injector is clogged. Here's my thoughts:
1) Fuel line from electric in-line fuel pump is a loop about 4" above engine. same as before but wondering if maybe air gets in there? But I just changed this line with all the other rubber ones.
2) Injector dirty? will running the engine with Sea Foam clean it out? wait and see I guess.
3) Batteries are good, so far starting with shore power attached so plenty of juice.
4) Bad fuel? Didn't use hardly any last year because of covid. Did put a stabilizer in the fall. When I pulled the bowl off the primary filter, the fuel was very cloudy. New filter, new fuel from same tank, its very clear but engine still starts hard.
5) Only thing I didn't check if electric fuel pump connection is good at start switch. Maybe intermittent when first starting?

Any advice or help would be great.

1) have you adjusted injector pump as described upthread by Wotname? It's described in the service manual.

2) have you checked injector spray pattern as described in service manual?
3) if lift pump is spurting fuel at the injector pump with no bubbles you can be reasonably confident supply up to that point is not the issue. As you know they use very little fuel.
4) Are you sure the compression is good?

[Halifax Sailor]

Originally Posted by Compass790

1) have you adjusted injector pump as described upthread by Wotname? It's described in the service manual.

2) have you checked injector spray pattern as described in service manual?
3) if lift pump is spurting fuel at the injector pump with no bubbles you can be reasonably confident supply up to that point is not the issue. As you know they use very little fuel.
4) Are you sure the compression is good?

OK, here's my level of understanding. As far as I know compression is good as this only started after I adjusted the valve clearance, Moved it too close as I read the manual wrong. Engine started real hard so asked some questions and reset it to manual. I am going to check the spray pattern next, just wondering if I am overlooking something?

[Wotname]

Originally Posted by Halifax Sailor

OK, here's my level of understanding. As far as I know compression is good as this only started after I adjusted the valve clearance, Moved it too close as I read the manual wrong. Engine started real hard so asked some questions and reset it to manual. I am going to check the spray pattern next, just wondering if I am overlooking something?

Yes, you are overlooking something.

Please allow me to be blunt in spirit of helping you sort your cold starting problem.

1. The valve clearance will not be the problem now that you have reset it to 0.2mm (between the valve stem and the rocker arm - i.e not between the pushrod and rocker arm).

2. The problem (whatever it is) did not just happen but apparently it has gotten worse since last season. How do I know this? Easy, 10 seconds for starting is way too long for this engine; way way too long. Sure it might have 'always' been this long since you have had it but it wasn't anywhere near this long when it was new. So whatever is causing the hard start has deteriorated to the point it needs fixing.

So it can only be one of three things; fuel/compression/air. Lets look at each in turn.

Fuel - is clean diesel getting delivered to the injection pump without any air? For this engine, the simplest way to determine if the injector pump is primed and delivering fuel is to listen for the injector 'squeak'.

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.

This can be heard on the video upthread. If you aren't not getting the squeak when tested as described, you are not getting fuel into the cylinder or you are deaf. If you are getting the squeak, then you are getting fuel and your hearing is OK.

Of course, checking the spray pattern at the injector will achieve the same result.

Compression - if you are experiencing hard starting and you have fuel and air, then by definition the compression is low. What causes low compression on this engine? Valve seats, head gasket, ring sealing or low starter motor rpm.

Let's start with the easy one first - low starter motor RPM. You have stated elsewhere you battery is good and is connected to shore power but is it really good and are all the cables and terminations good. Easy to check, clip your voltmeter leads between the big cable on the starter solenoid and the engine block. Measure the volts while turning the engine over through compression. It is below say 9V, you have a problem with the battery or cable or terminations or corrosion. Now check spinning the engine over decompressed. The volts should be at least 1 or 2 volts higher. If it is, then try starting the engine using the decompression lever in the same manner as you would if hand starting. If it starts when using the decompression lever as a starting aid, then you have an electrical problem.

Ring sealing - easy way to check if the rings aren't sealing is to add a very small amount of engine oil into the cylinder by way of the air intake. Only use a very small amount, no more than a teaspoon (5ml). Add the oil while turning the engine over decompressed in order to get the oil distributed onto the cylinder wall. Now try starting, if it starts easier after adding the oil, the rings aren't sealing well enough.

To check the head gasket and the valve seats requires the head to be removed. Once the head is removed, you will need a new head gasket anyway.


Air - you have stated the air intake is OK and you have replaced the exhaust mixing elbow (water injection point). If so, then the air is most likely OK unless you have a complete exhaust blockage further along the exhaust hose. To confirm, you can disconnect the exhaust at the engine and try starting. Of course you can't run it with the exhaust disconnected but it doesn't hurt to try starting it to see if that makes an improvement.


Get the fuel/compression/air OK and the engine will cold start easily.


My guess is either...

the injection pump regulator needs adjustment as described earlier in this thread (and in several others) as on this engine it does wear and does need the occasional adjustment in order to hear the injection squeak. That is why the adjustment procedure is included in the owners handbook. However don't touch it if the squeak can be heard.

or


the compression has got too low for a reliable easy cold start. If compression, most likely electrical (too slow starter motor rpm) or ring sealing. This engine does get corrosion (rust) on the lower cylinder wall when laid up for long periods if moisture gets into the cylinder. Being an horizontal cylinder, the water seats on the cylinder wall near the piston and creates some rust there each year so slowly the compression goes down over the years.


Please report back .

[Compass790]

Ya excelled yourself with that post Wottie the King!
Couldnt have put it nearly as well myself. If Halifax sailor can't sort his starting out with that tutorial it's definitely time to call in the mechanic who, if he is any good, will just follow your tutorial.

[Wotname]

Further to this thread.

Difficult cold staring is often a compression issue especially on engines that don't have glow plugs or other warming devices.

However one aspect of compression (with reference to difficult cold starting) which is often overlooked is low starter motor rpm during the start phase i.e. an electrical problem.

You can have good rings, good valve seats and good compression numbers but if the starter motor rpm is low, you can have problems with a cold start.

Decompression levers (if fitted) can be used to good effect to prove or disprove potential starter motor electrical issues. Using the starter motor, spin the cold engine over decompressed for a few seconds until it is spinning rapidly and then re-engage compression on one cylinder (keeping the starter motor engaged). If it fires up right away, you have confirmed there is an electrical issue with the starter motor circuit when used normally.

[parachute]

There two other things can stop engine starting a loose Solenoid and a small hole that lets dieel out and air in. Put kitchen roll around the fuel pump, fllters and the the fuel lines. Turn engine over and if there is a leak you will see it.

[Wotname]

As a case in point to demonstrate low starter motor rpm causing hard cold starting.

New owner with a 250 cubic inch, 40 year old diesel engine taking about 30 seconds of turning over before starting when cold. Starts within a few seconds when warm. Vendor says it has been like that for years, its just an old starter motor but not to worry, there is a new starter motor is the spares that come with the boat.

New owner fits new starter motor but it makes no difference so he gets a new battery but again it makes no difference so he begins to consider a compression test etc.

I said it sounds too slow.

After cleaning some terminations and replacing a dodgy battery switch, it started within 10 seconds.

Great, it is fixed they said.

I said, no it isn't, it's better but it is still too long and still sounds too slow.

So more work carried out on the electrical aspects and now the engine starts within 2 to 3 seconds when cold and instantly when warm.

My guess is a head rebuild would make it slightly better but essentially the main problem was low starter motor rpm.

Note - the engine didn't have decompression levers; they would have the diagnosis much easier.