Kubota B20 with D950 Diesel Freshly Rebuilt Won’t Start

[Mark15]

I have been working on restoring an old B20 that has been out of service for a long time. When I got it, the previous owner had parked it after it had overheated and lost usable power. It had then sat outside for about 10 years in the weather.

It had a seized engine (from sitting), and I’ve discovered later it also had a cracked head and t-stat housing, so it probably ran without coolant causing the overheat problems. #2 cyl was also very eroded, so I re-sleeved that one, while the others seemed to clean up nice with a hone.

Replaced pistons, rings, rod and crank bearings, seals etc. Also, replaced the head with a brand new one made by Kumar Bros that included new valves. I think I have posted everything I can think might be relevant for diagnosing the current issue, but I do have a long build thread on my blog of the entire project if interested: https://www.modernsurvivalists.com/...-utility-tractor-and-putting-it-back-to-work/

I adjusted valves to .007” - .008”. Before installing injectors, I tested compression at 300-325psi for all 3 cylinders. This is slightly lower than what the manual says is acceptable, but I assume that could be due to the new rings not yet seated to the sleeves, or the new valves not worn in fully either?

I think I have all three injectors bled of air, and it sounds like it wants to start, possibly firing on 1-2 cylinders, but that’s all I can get. I am worried about repeatedly attempting too much for fear of washing out the new rings with diesel.

Here is a video of how it sounds when I am trying to start it up:
https://www.youtube.com/watch?v=w75a1ikIoB8&feature=youtu.be


Any suggestions of what I should try next?

 

[beckmurph]

White exhaust is unburned fuel, I think.
Sounds to me like it is turning over to slow.
Are you sure your glowplugs are heating up properly?



Sent from my iPhone using Tapatalk

 

[Mark15]

The glow plugs should be working. They tested for the correct resistance on my DMM, and they seem to be pulling a fair bit of current when I connect the wire to the battery.

I wondered too about the starter crank speed. I wasn't sure how fast these engines typically crank over. Battery is healthy and the connections are solid. If the starter motors were less expensive, I would get a new one just to try, and keep it for a spare if not the issue. But at $321 that's an expensive item to replace without knowing!

 

[North Idaho Wolfman]

Sounds like a fuel delivery issue to me?

Pull the lines off the injection pump and make sure you are getting consistent fountains of fuel out of each port of the injection pump.
Also make sure it's not sucking in air on the fuel system, when in doubt pull the feed line from the lift pump to the injection pump and replace it with a clear hose.

 

[Mark15]

Thanks for the suggestions!

I installed a clear hose between the lift pump and injection pump. Decided to flip the high pressure lines and mount the injectors where I could see them pop. I had the injectors rebuilt at a shop, but decided it was worth verifying how they are working.

After bleeding the air, the #1 and #3 injector seem to be popping and getting some atomization / mist. I am not certain what they *should* look like, but they look to me like they should at least be enough to fire that cylinder. #2 however is just pissing and squirting a small stream, so I suspect that one is bad.

I filmed this test so you guys can see if you would agree: https://www.youtube.com/watch?v=PJ-XFagb7z4

Does it make more sense to just order a new one from Messicks, or should I look for a less expensive one that was rebuilt or pulled from a good working motor?

 

[Tooljunkie]

Move injector to the other line, see if spray changes, if it does not then replace it.

My opinion is you running that starter way too long. Even unloaded with no compression it will overheat starter.

 

[North Idaho Wolfman]

Do as Tooljunkie said and swap injectors, but it looks to me as all three are not flowing right.

Not tying to be a salesman, but I have 3 new injectors from oregon fuel injection for that engine, still wrapped and in the boxes.
http://www.orangetractortalks.com/forums/showpost.php?p=212465&postcount=1

 

[Mark15]

Move injector to the other line, see if spray changes, if it does not then replace it.

My opinion is you running that starter way too long. Even unloaded with no compression it will overheat starter.

Yeah I agree. It didn't seem like I was cranking it nearly as long at the time, but watching the video that was all I could keep thinking too.

 

[Mark15]

Do as Tooljunkie said and swap injectors, but it looks to me as all three are not flowing right.

Not tying to be a salesman, but I have 3 new injectors from oregon fuel injection for that engine, still wrapped and in the boxes.
http://www.orangetractortalks.com/forums/showpost.php?p=212465&postcount=1

Sorry I didn't see your message Wolfman before I ordered a new one from Messicks, or I would have bought yours!

Installed the new injector outside the engine alongside the other two just like before. The spray pattern on the new one seemed similar to the other two, so I installed them and bled the lines.

Sadly, engine still will not start. I must be missing something and it is getting frustrating. It seems even closer now, the higher speed cranking sound is more consistent, like all 3 cyls. are trying now, but it just wont catch. I also tried misting diesel from a spray bottle into the intake manifold, but no change.

So with compression above 300 psi, and fuel being present, all I can think is maybe there is a timing issue somehow. But if the valve timing was off, we wouldn't get compression would we? And shouldn't the spray bottle test make it fire even if injection timing is off?

Additional thoughts from the tear down that may be related
When I tore the motor down, the timing gear was aligned oddly, like it was installed not using the alignment marks, however it seemed to be off a consistent number of teeth form each corresponding gear, so I assumed it worked out the same. When I reinstalled it, I aligned all the marks like the manual specified. I did not pull the injection pump, so I assumed it shouldn't need adjusted, or at least not off far enough to not run. But I did perform the injection timing test in the manual and noticed it starts fuel injection 3 flywheel teeth after the #1 FI mark.

 

[Mark15]

Here is a picture of the timing gears from tear down showing the timing marks being off.

The marks on the center gear punch marks are off by 6 teeth for both the valve cam gear and the fuel cam gear. Unfortunately I had already removed the crankshaft gear before I discovered they were off. But since I know the engine ran well before it overheated, I assume it must have been off by 6 teeth as well. Why it would have been assembled this way I have no clue!

And I have also attached a pic of how I re-assembled it, with all punch marks lining up. I assumed it should be the same, and would prefer to have them all line up. Am I overlooking anything here?

 

[100 td]

To me, the timing marks look good, they will be out of whack once the engine is rotated due to the different ratios of the gears and will come into line again after "X" rotations.

I would remove the glow plug rail and plugs and check each individual glow plug across 12 volts to ensure a nice quick glow at each plug, may as well get these proven now so it starts easy in the winter.

You could then also use a booster cable directly from the battery positive to the glow plug rail, wait ten seconds, then crank, and disconnect when it fires up or you stop cranking. This reduces any voltage drop through switches etc. and ensures full voltage to the plugs.
YMMV

 

[North Idaho Wolfman]

Timing marks only align every 138 revolutions on that motor.

Now for the news that your not going to like, your PSI is too low to fire effectively.
Lower limit is 325 PSI, and yes 25 PSI makes a huge difference.
Standard is 450 PSI.

Now if you had it running before you changed the head, the valves are probably not seating, If it was a Kumar Bros head I would count on it, as I've seen several that are like that.

 

[Mark15]

Okay thanks guys.

I will double check the glow plugs for a nice glow when I get them back out. They tested for the correct resistance on a DMM, so they should be working fine, but no harm in checking them visually too! I already have them directly wired to battery while I have been testing, but thanks for checking on that too!

Yeah, it is a Kumar Bros head, and every valve dribbled a small amount of fuel when I set it on its side and filled the ports with diesel. I considered contacting them to see about getting it exchanged, but I figured if very valve on this one is leaking somewhat, I imagine its the process they use, and any replacement from them would be the same way also. I am wondering if I am better off just finding a machine shop to give it a proper valve job. I also did some reading on various forums online and it sounded like many builders these days advise against any lapping at all, and that the valves will typically "hammer in" as the engine breaks in and the seal will improve.

The compression is currently 325psi on two cylinders, and 350psi on the other. I assumed it would be lower initially, since the rings have not worn in / properly mated with liners yet. But what compression is typical for a fresh rebuilt / never fired cylinder?

Is this really low enough that the engine won't even start? In a way I am hoping so, just because I have no idea what else could be the problem at this point.

 

[Mark15]

Wanted to post a follow up on this. Thanks for all the help guys. Leaking valves from the brand new "ready to go" Kumar Bros head was indeed the issue!

Here she is firing up for the second time. Music to my ears! Didn't get the first fire up on film. I couldn't run it long as I don't have the radiator hooked up yet.

https://www.youtube.com/watch?v=Pmi-xAKwk1M

This was my first diesel rebuild. Do any of you seasoned guys think everything sounds okay in the video above?

Short known history on this engine -
Previous owner ran engine without coolant due to cracked t-stat housing until it overheated and wasn't running right. Parked it outside and it sat untouched for nine years. I got it and engine was seized with rain water / pitting in #2 cyl. Full rebuild by myself, re-sleeved #2, new pistons / rings in all three. New Crank / rod bearings, etc.

Wouldn't start, then discovered original head was cracked. New KB head, still wouldn't start, due to leaking valve seats in new head. Fixed that using old valves and a drill to grind seats uniform.

My plan to so get cooling system plumbed up, run it in for 30 minutes, re-torque head bolts and then finish assembly, and drag a back blade around for a few hours to load it for a good piston ring break in.

 

[North Idaho Wolfman]

Sounds good, might need a set of injectors if it keeps up with the hard black smoke starts.