B7100 is a NO-GO

[steve]

My son and I just purchased a B7100HST. The former owner replaced the rings, "lightly" honed the cylinders and lapped the valves because there was blue smoke at idle. When he got it back to gether he couldn't get it started. He gave up and sold it to us for cheap. We got it home and tried to get it started but its a no-go so far. We put in new glow plugs, fuel and blead the injector lines and now we get a little white smoke when we crank it but still no start. We pulled the injector return line off the fuel tank to see if fuel was getting there but it is dry. I can't tell if he was into the injectors or the injection pump but they might have been messed with. So where do we go from here. My thought was to pull the injectors and see what kind of spray/drip we are getting as I think this is a fuel problem. Help

 

[bruceatlam]

I would:

1. check compression
2. make sure that the valves are set correctly
3. check head bolt torques
4. then work on fuel

 

[steve]

Thanks Bruceatlam! We'll check those things and report back.
Steve

 

[Kubota Newbie]

check with the previous owner, make sure that they didn't monkey with the injector pump or camshaft timing, and that if they did they KNEW it was all timed correctly when they reassembled it. You can screw with fuel, compression and all that other stuff till the cows come home and if he's got the cam or pump out of time it will probably never start.

 

[Stumpy]

Yep agreed. Check the compression first, that'll tell you whether he messed something up in the cylinders or valves or whether it's an injection issue. Go from there.

 

[Kubota Newbie]

Well... actually, the compression test tells you nothing IF the cam is out of time. You really need to know how much they took apart. If they did an in the tractor hone and re-ring then you could reasonably assume the timing is correct since they wouldn't have taken the cam out. BUT, if they took it clear apart you need to know for sure the cam timing is correct. Otherwise, the valve overlap, opening and closing could be off and make the compression test numbers meaningless.

 

[steve]

Good news, well at least some news. The timing gear case has not been opened, and the injectors and pump have not been messed with either so we're headed for the rocker arm adjustment next and then compression test. Keep you posted on our progress.
Steve

 

[Stumpy]

Sure it does. If it's one tooth back your intake is closing too late and you'll see weak compression and a diesel probably wouldn't even light except on a hot summer day.

If it was one tooth forward then compression probably wouldn't tell you the story. The exhaust opening/closing early would cut off the power stroke and give it poor scavenging. You might see full compression but if it would run it would smoke like crazy and have no power. Anyway if the valve timing is off you've got bigger things to worry about (like valves hitting pistons).

But since you've eliminated timing of the valves or injectors you've got three possibilities. 1-He botched the honing and the rings can't hold enough pressure to run. If that's the case you'll see low compression, do a leak down test (pump compressed air into the cylinder at TDC on the compression stroke and listen for where the hiss is coming from) to confirm. 2-The adjusters are loose and you've got no valve lift in which case go back and take his tools away from him. 3-You're not getting fuel at all for some reason. Perhaps he pinched the line when removing the injectors? Test this one carefully, those injectors are strong enough to hypodermically inject fuel into your skin from a few inches away. That would be bad.

Let us know and good luck!

Matt

 

[B7100]

Try disconecting the decompression cable just in case its lifting the valves.

dave

 

[birddogger]

The former owner replaced the rings, "lightly" honed the cylinders and lapped the valves because there was blue smoke at idle. When he got it back to gether he couldn't get it started.

I think this is the problem. It just wasn't done the correct way. Cylinders don't wear round, no problem because the rings wear to conform to the out-of-round. Now put in new rings that are round, in an oval hole. How's that gonna work? You may get by with that in a spark-ignition engine.
It was running, he tried to fix it, it stopped running. What does that say about the fix?

 

[fj40dave]

Is the fuel valve opened?

Timing correct?

It's gotta be something simple....while I'm no xpert, I would think these motors would start and blow a lot of smoke if the cylinders were oval and the new rings were round, or the valves were lapped a little too much and the start-up would be noisy as all heck.....but to not fire off, must be a sequential thing, or something missing from the sequence.

 

[Kubota Newbie]

Assuming it is getting fuel, the leak-down/blow-by test will tell him a lot.

Be careful while trying to hold it a TDC while doing the leak-down test.

 

[Stumpy]

Yes as in don't. I did that with my motorcycle and nearly snapped my wrist off. As long as you're within a few degrees of TDC on the compression stroke it won't go anywhere.

 

[steve]

B7100 is a GO!!! We re-torqued the head. Each bolt took a quarter to an eighth of a turn to get torqued to spec. The valves were way out. Exhaust was gapped at about a sixteenth of an inch and the intakes were so tight that they never closed completly. The rocked shaft was just slightly thighter than finger tight. No wounder it didn't start! All is set to spec now. We glowed it up and cranked it over and it started right up. It doesn't take much to make these engines happy! Next thing is to tighten all the injectors as we noticed bubbles in the pool of fuel left over from the bleeding them. Also drop the pan to check the torque on the connecting rods. I don't dare to run it long if he has those finger tight too. Thanks to all the advice.

 

[GWD]

B7100 is a GO!!! We re-torqued the head. Each bolt took a quarter to an eighth of a turn to get torqued to spec. The valves were way out. Exhaust was gapped at about a sixteenth of an inch and the intakes were so tight that they never closed completly. The rocked shaft was just slightly thighter than finger tight. All is set to spec now. We glowed it up and cranked it over and it started right up. It doesn't take much to make these engines happy! Next thing is to tighten all the injectors as we noticed bubbles in the pool of fuel left over from the bleeding them. Also drop the pan to check the torque on the connecting rods. I don't dare to run it long if he has those finger tight too. Thanks to all the advice.

Now that's some good news! Thanks for reporting back.