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ihcfan · 04-12-2016, 16:46

Background:

Hunter 27. Originally had SB8, replaced with YSB12 after some cabin modification. YSB12 seller said engine ran. Became suspicious of sellers claim months later upon discovering there was no injector nozzle.

To Date:

Pulled and cleaned the high pressure fuel pump. Clean injector and reassembled complete injector from both the SB8 and YSB12 parts. Injector 'chirps' when pumping fuel (I think this is normal, it's likely the sound of the check ball acting against the spring as the plunger pushes the fuel to the injector). Injector (after reassembling out of the two) 'pops' at about the same time the pump chirps. With the injector out of the head it seems to make an 'okay' spray pattern. It doesn't seem very atomized, but I'm not sure how atomized diesel spray from an injector is supposed to look. I pulled the starter and checked the injection timing, it appears to be almost exactly at 10 degrees before TDC. I pulled the valve cover and checked the valve lash, and it appears to be correct (about 0.2mm).

Problem:

It won't start...and doesn't really seem to be 'close' either. When I use the starter with the throttle open I get white smoke from the exhaust. Using WD-40 to assist, I get more white smoke. Never does it seem like it is about to catch. When I use a blow dryer and WD-40 I get even more white smoke, but again it doesn't even seem close to catching. I have tried running the starter with the compression release level open for a few turns and then allowing it to close and still only get smoke.

When hand cranking, I cannot turn the crank all the way through the compression stroke quickly without the compression release engaged. Thus, I feel like I have pretty good compression, though I haven't measured it.

I also have bled the fuel system (actually quite a few times). Because I've pulled the injector out and hand cranked it for quite a while, I'm pretty confident there are no air bubbles in the fuel line. There are no noticeable fuel leaks.

It also had old fuel when I started. Figuring it was the fuel, I used the lift pump to take all of the old fuel. I replaced it with 5 gallons of fresh fuel before doing any of the above tests.

So, short of pulling the head and working the valves, I'm running out of ideas. Thoughts?

Thanks,

Keith

jimbunyard · 04-12-2016, 18:07

First make sure you have a fully charged battery, good connections, positive and negative, and good cables and solenoid wires to ensure proper starting speed.

Then try this. It sounds like you have plenty of fuel, so, holding the injector pump in 'no fuel' mode, with the decompression lever engaged, spin the engine over for about 10 or 12 seconds. Do this about 4 or 5 times, but be careful not to overheat the starter. Be sure that the injector pump stays in the 'no fuel' mode while doing this. Then have a go with WD-40, or starting fluid (just a little squirt) and maybe the blow dryer, and see if she tries to start.

If it does fire, trying with the throttle in differing positions may get it going eventually, it may be a little ragged running at first but might even out as it warms up.

Injector nozzles really need to be operating at spec for the engine to run cleanly and efficiently, and for that they have to be taken to a shop that has the proper testing and calibration equipment. The cost is reasonable if you stay way from boat dealers and mechanics. Take them to an injection shop that caters to farm equipment owners...

ihcfan · 04-12-2016, 18:20

Thanks! I will try it this coming weekend. I did just purchase a new injector as I'm still not confident that the injector is popping at the right pressure. So hopefully I can put the new injector in and run your test this weekend. Again, thanks!

P.S. I also decided to grab a head gasket, valves and springs in case, as well as the copper washer that goes below my injector (which was missing, and I discovered looking in the shop manual this evening should actually be there).

boatbod · 05-12-2016, 16:00

Most diesels need about 400psi compression in order to fire. If it's a bit less (approx 330), you should be able to make it run with a hot air preheat, but any less than that and you'll probably be out of luck.

pmagistro · 20-12-2016, 17:32

Side question: is the YSB the same as the SB12? If so, what shop manual have you been using? I'd like to find a better one for my 1978 SB12.

ihcfan · 25-12-2016, 20:36

It's the sb12 with the head moved to the side so the cylinder is horizontal rather than vertical. Lower profile but wider. Very much the same motor.

ihcfan · 25-12-2016, 20:37

See sailingthanksdad.com for the best manuals I've found.

Steven UK · 26-12-2016, 04:56

That engine looks like a single so the timing could be 360deg off (720deg between ignition events) everything else sounds ok. White smoke is unburndt fuel, sounds like you have compression... Good luck

westwinds · 26-12-2016, 09:46

Worn cam lobes? Way too much valve lash? Do a compression test, but not the leak down type as you want to check more than valves and rings. Also check rocker arm movement. Leak down compression test is best for rings and valve problem detection.

boatbod · 27-12-2016, 17:06

Quote:

Originally Posted by Steven UK

That engine looks like a single so the timing could be 360deg off (720deg between ignition events) everything else sounds ok. White smoke is unburndt fuel, sounds like you have compression... Good luck

White smoke just means you got the fuel warm enough to smoke but not hot enough to burn. Commonly I've seen that on cold days when cranking a diesel with marginal compression and no preheat. Runs fine once you get it going, but a b!tch to start.

You could try warming the intake air with a heat gun to see if you can give it enough encouragement to fire up, otherwise you have to consider other avenues. (Compression test, ether,...)

Steven UK · 27-12-2016, 18:21

Quote:

Originally Posted by boatbod

White smoke just means you got the fuel warm enough to smoke but not hot enough to burn. Commonly I've seen that on cold days when cranking a diesel with marginal compression and no preheat. Runs fine once you get it going, but a b!tch to start.

You could try warming the intake air with a heat gun to see if you can give it enough encouragement to fire up, otherwise you have to consider other avenues. (Compression test, ether,...)

True, last time I had this issue on an old tractor (friends) it was down to not turning over quite fast enough. Starter, cables, battery e.t.c.

boatbod · 27-12-2016, 19:25

Quote:

Originally Posted by Steven UK

True, last time I had this issue on an old tractor (friends) it was down to not turning over quite fast enough. Starter, cables, battery e.t.c.

Yup, cranking too slow will definitely do it too.
If you have compression release levers, opening them, cranking and closing them one cylinder at a time well sometimes get you going. It's worked for me on a 3GM a time or two.

westwinds · 02-01-2017, 09:50

We have many good suggestions. Next thing to do is some trouble shooting so we can pick through those suggestions. Do a compression test first. Then check starter wiring for voltage drop. Crank engine while using multimeter on one volt range. An analog meter (with a needle) works best. The third thing is use clamp on amp meter to see how much amps the starter is using, or remove starter and take it in for testing. The fourth thing is use a hydrometer to check battery for bad cell.

Steven UK · 02-01-2017, 13:21

With the older engines with compressed air leaking past the rings the faster it turnes the more pressure will be generated (less leakage), once it fires no more issues the engine will run fine.

The engine will slowly wear out and you have to make a decision on when to rebuild. Personally I tend to leave it later than most but that's just me.

Also very low compression will lead to the engine turning over faster at start up. But this is generally more serious than just worn rings.

Good luck, let us know what you find.