B7100 Overhauled now trying to seize up

[D2Cat]

If need be, I can provide you a picture of a Kubota F2302 in which the injection lines are not the same length. Why would differing lengths affect timing?

Post up your pictures and we can talk about it! All the loops and bends are there for a purpose, and it's not to make sure mechanics don't get them switched!

 

[North Idaho Wolfman]

I just got done doing a rebuild on a D950, very similar to your D750.

When were were setting it up one of us got the math wrong and installed to many shims under the injection pump, and that along with sealer was too much and did exactly what you are saying is happening to your engine.

How many shims do you have under the pump now?
Did you use any sealer on the shims?

Simple things to know, compression, temp at the head when it runs.

 

[L.C. Gray]

If need be, I can provide you a picture of a Kubota F2302 in which the injection lines are not the same length. Why would differing lengths affect timing?

Injection lines on a mechanical pumped system have to be the same length or timing will be different from one cylinder to another. Compression ignition engine timing has to be pretty much right on the mark to run properly. Spark ignitions aren't as critical on timing so you can get away with more variance in timing. Spark plug wires don't need to be the same length to preserve uniform timing like injection lines do. The reason is that the electrical energy travels through the wire at near light speed (670,616,629 mph) while the pressure wave in the injector line travels roughly at the speed of sound(767 mph). At the speed the spark gets from point break to plug gap theres negligible difference in time between a 12" wire vs a 36" wire. The same isn't true with the diesel, different length lines can make them run unbalanced.

 

[DVoss]

Longer line=delay in timing. Thats why sometimes you see 2 or 3 extra loops, in a line...

I will post a picture tonight after work.

Question for the masses.....are fluids compressible?

 

[Grouse Feathers]

If you run the numbers:
The speed of sound in diesel fuel = 1250 meters/sec = 49212 inches/sec
2400 rpm = 40 rev/sec = .025 sec/rev = 0.00007 sec/degree of rev
49212 inches/sec X 0.00007 sec/degree of rev = 3.4 inches /degree of rev
If one injector line is 3.4 inches longer the pulse will arrive 1 degree later.
And this isn’t the whole problem. There are 20 pulses/sec at 2400 rpm, this will create waves in the injector lines. The location of the wave peaks and valleys are affected by the length and geometry of the injector lines. So to keep the pressure the same at the injectors the length of the lines must be the same.
This was really interesting; I didn’t know any of this before I read this thread. The calculations were easy and the wave and geometry information I got from “The Handbook of Diesel Engines” on Google Books:
https://books.google.com/books?id=1...n line length effect on diesel timing&f=false

 

[bucktail]

I will post a picture tonight after work.

Question for the masses.....are fluids compressible?

Liquids are not compressible.

 

[BAP]

Get back on track Guys. He didn't hand make injector lines from scratch so that is not his problem. Fighting over injector line length is a topic for another thread. OP problems are on his rebuild.

 

[DVoss]

My apologies...

 

[BAP]

Sanddog, have you made any progress with your tractor?

 

[sanddog]

UPDATE

My new infrared temp gauge finally arrived so I was able to actually measure the temperature after running the tractor. Started it up and it ran for right at 2 minutes before bogging down and dying while emitting a small amount of black smoke. I took measurements of the top of the head:
front 156 F
middle 170 F
back 156 F.

I started it again and it ran for about one minute and 20 seconds before dying again. I tried to keep it running by speeding up the motor and it did briefly speed up before dying with even more black smoke. I does not appear to be starving for fuel. After this run, the temps were as follows:
front 161
middle 186
back 173.

The radiator core showed 157 near the top. It does not really appear to be overheating and I am going back to the machine shop recommendation to looks "down stream."

While running the tractor, I moved the three point hitch lever for the first time that I can recall every giving it a try. The hitch raised up just fine, would stop and hold (based on hand pressure) and would lower back down under hand pressure. When engaging to lift, there was a slight sound of gears meshing. I ran it to the top, moved position lever to neutral, and tried to move the lever to the up position again and heard a definite sound of gearing trying to mesh but could not get it to "engage." I did not force it, as it obviously did not want to engage under these conditions. Is this normal behavior or should it allow you to move the lever into the lift position and allow pressure to bleed off since the lever is already up???

I still need to recheck the injection timing, as I don't think I had the fuel lever all the way to wide open throttle when I last checked it and adjusted the shims. I have not used any sealer on the shims. I cannot now remember exactly how many are in place and they differ thickness anyway. I still have the original stack that came out ready to go back in based on checking again with WOT.

After the last assembly, I did run the motor on an engine stand before mating it back up to the transmission. Unfortunately, I did not have my timer running but it certainly seemed like it ran for longer than the two minutes max that I get with it on the tractor. It did die, as now, but I do not recall if it had any black smoke?

 

[HealeyBN7]

It sounds as if you might be starving it for fuel after it starts.

Still sounds like fuel starvation to me. I replaced my original fuel pump with an ebay special that looked the same, but didn't work. After it ran for a few minutes, it would stop. They original pump would also do this occasionally. The difference is the old pump allows the fuel to continue to flow after it stops running. The Chinese pump would cut off the flow.

 

[CountryBumkin]

Do you have a clear filter you can install in the rubber line at the "inlet" side to the injection pump? Then you can see if you are running out of fuel (at least the tank to injection pump side of the fuel system).

 

[North Idaho Wolfman]

From what you are explaining now it sounds like you are deadheading the hydraulics.

Does the motor bog down before it dies?

 

[sanddog]

Still sounds like fuel starvation to me. I replaced my original fuel pump with an ebay special that looked the same, but didn't work. After it ran for a few minutes, it would stop. They original pump would also do this occasionally. The difference is the old pump allows the fuel to continue to flow after it stops running. The Chinese pump would cut off the flow.

I checked the fuel pressure from the lift pump earlier and it was pretty close to what is expected. I also had a clear line from the lift pump to injection pump for a bit and no signs of running out of fuel or air in line.

 

[sanddog]

Do you have a clear filter you can install in the rubber line at the "inlet" side to the injection pump? Then you can see if you are running out of fuel (at least the tank to injection pump side of the fuel system).

I did install a clear line between the lift pump and injection pump and no signs of air bubbles or otherwise running out of fuel.

 

[sanddog]

From what you are explaining now it sounds like you are deadheading the hydraulics.

Does the motor bog down before it dies?

Yes, the motor does clearly indicate (at least to me) it is bogging down before it dies. this is the reason I took it all back apart and back to machine shop. However, there were no signs of any wear on any of the parts and all tolerances were good.

It also emits a little black smoke as it begins to bog down, just like you would expect when the motor comes under load. At least that is what I have experienced with my other diesel tractors.

Confused -- that pretty much sums it up. The three point lift is not working like any other I can recall. As I stated above, it will go up and down, but feels like you are shift a manual transmissions when moving to lift position and then does not want to go into "gear" at all when the arms are already up and you try to move the lever into the lift position. This does not seem right to me, but I need to find something that lays out the fluid flow/valves to get an idea as to how this works.

 

[North Idaho Wolfman]

I had a problem with mine when the feedback rod was bent and sticking,
causing the control to work chaotically.

Does it have a loader on it?

 

[Tooljunkie]

Heres a point to ponder, valve adjustment correct? Valves heating up, compression starts to go away what seems to me the two cooler cylinders.

If its siezing up there should have been some evidence, aluminum deposits on cylinder walls or scored bearings. Tough one to see is a bad cam bearing.

As wolfman said hydraulic pump deadheading?
The bobcat i had a deadheading issue with locked up in seconds. Engine had no time to spool up.

 

[L.C. Gray]

If the injector pump is hydraulically governed using the fuel as the hydraulic medium, the rpms will try to go up, not down in a fuel starvation situation. With a lack of fuel pressure the governor will wrongly sense the rpms are dropping and try to correct it. The classic symptom of this is the rpms racing up and down as the governor seeks equilibrium before finally getting air bubbles in the injector lines ending fuel delivery to the injectors and the engine dying off.

The OP's comment regarding black smoke would tend to rule fuel starvation out as the black smoke would indicate an over fueling, not under fueling, situation.

As to the suggestion that the valve clearances are changing as the engine heats up causing a loss of compression, that would be accompanied by grey or white smoke from "cold fire" and incomplete combustion of the fuel.

 

[North Idaho Wolfman]

If the injector pump is hydraulically governed.

It's not, Kubota engines are a flywheel governed.