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Shibaura S753 Not Running Good

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
I'm trying to get this Generac 8KW with a Shibaura S753 diesel engine up and running after sitting for 10 years in the desert.

I have flushed the fuel tank, replaced the electric fuel pump, replaced all filters, anti-freeze, fuel shut off solenoid, fan belt, battery, Main Circuit Board and returned some botched wiring back to factory.

It starts up and immediately goes into a very high rev, the fault light comes on then it slows down and runs very rough. It is spewing black smoke during this whole process. No adjustment on the governor has any effect, even if I manually move it.

I have to squeeze the fuel line off to get it to shut down.
 

Birken Vogt

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Fuel, air, timing. This is not an electronic problem.

The black smoke makes little sense if it continues when the engine is no longer running fast. Inspect the intake from the air filter to the cylinder head (valve cover in this case). Remove the valve cover/manifold and do a sanity check on valve lash and look into the cylinders through the intakes (can do that on this engine IIRC).

Next pull the shutdown solenoid from the back of the injection pump. It just unscrews. The pin should be sticking out several inches with force. It retracts when energized. Put a thin screwdriver in its hole and you should feel the rack push closed and spring back freely.

There is also a shutdown lever on the other end of the injection pump. This should also pull the rack down and it should spring back on its own.

It sounds like it might be stuck full on but why the engine would run away and then slow down needs to be investigated.

Don't start it any more without a positive way to shut off intake air to keep it from being damaged.
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
Thanks, I will check those things tonight.

This unit apparently got it's injector pump rebuilt then the customer didn't have the funds to pay for the work. That is why it has been sitting all these years.
 

Birken Vogt

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You might want to remove the injection lines and undo the 4 bolts that hold the pump down and see that the linkage is connected correctly then. There is a little steel arm from the governor in front that moves a pin that slides the rack back and forth. Held in by a tiny cotter key. Or maybe the injection pump is messed up and nobody identified a problem until now because they never tested it or something. Or maybe it is just gunked up.
 

dalmatiangirl61

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Last Subscription Date
07/10/2019
Shibaura, yeah, thats the little 3 cyl diesel in my que of projects to work on. Sorry no help on your problems, but I'll be watching this thread in case I encounter the same. If you can figure out how to upload them, we always like pictures!
 

dalmatiangirl61

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Last Subscription Date
07/10/2019
Hmm. Let's hope the original owner didn't have good reason not to pay the "rebuilder's" bill.
I kinda got the impression that these were never really meant to be worked on, at all. Mine came in a Generac unit too, control board for gen was smashed, I just wanted the engine, took at least an hour to get the sheetmetal off to even have minimal access to the motor. Installed in an RV (pretty sure where mine came from), to bleed injectors would require pulling the whole unit, then getting the enclosure off:bonk:
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
Okay I started with the fuel shut off solenoid. I figured out that after if high revved on start up and the fault light lit up it was killing power to the fuel pump and fuel shut off solenoid.

It was siphoning enough fuel from the tank to keep running. I pulled the solenoid and tested it, works fine. I used a small screwdriver and discovered the rack does not move. It might go in about 1/16th of an inch.
 

Birken Vogt

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Pull the nuts that hold it on and lift it up a half an inch and you should be able to see how the linkage works and maybe figure out why it is stuck.

There is also an external shutdown lever in front of the pump on the side of the governor area that should be able to push the rack down, maybe it is stuck too.
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
I removed the injector pump. The lever moves freely, the rack moves freely. When I connect the lever and reinstall the pump the rack does not move freely.

---------- Post added at 08:29:52 PM ---------- Previous post was at 07:35:06 PM ----------

It appears the spring that should be pushing the lever for the rack is very weak. It moves freely but just doesn't have enough oomph to move the rack.
 

Birken Vogt

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I don't really understand what you are saying. But I have not been inside one of these for a long time either. So I may not be remembering what is in there. But this system is about as simple as it gets so find what is hanging and fix it and then it should be better is all I can say.
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
The rack is attached to a lever/linkage that goes towards the front of the engine/ timing gear cover. It is attached to the stop lever, because the stop lever moves the rack lever/linkage. My understanding is that the rack is suppose to have spring tension that keeps it pressed towards the fuel shut off solenoid. This spring tension comes from the lever/linkage.

What I'm seeing is that there is barley enough spring tension to move the lever/linkage when it is not attached to the rack. It doesn't appear to have enough strength to move the rack.

The rack will move back and forth via gravity when the injector pump is out of the engine.

---------- Post added at 11:29:20 PM ---------- Previous post was at 11:10:24 PM ----------



The rack moves good.
 

Birken Vogt

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What is confusing is that the spring pressure is supposed to move the rack to the full on position and your problems seem contradictory.

Pushing the rack forward shuts it down and the spring returning it rearward makes it send more fuel.

But in any case the pump seems OK for now. The governor is in front of the pump there and consists of a spring and some flyweights. See if you can figure out what is wrong with it. It should be free moving and spring loaded and it sounds like it is not.
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
Im pulling the timing gear cover tomorrow. Do I just remove the bolts and pull the cover off or is their more to it than that? Looks like I will need to remove the radiator.

---------- Post added at 06:50:40 PM ---------- Previous post was at 06:26:44 PM ----------

What is confusing is that the spring pressure is supposed to move the rack to the full on position and your problems seem contradictory.
I agree! What else could be causing this? Something wrong with the injector pump or governor?
 

Birken Vogt

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There could be something wrong with the pump but seems unlikely. You could manually control the rack somehow but the easiest way would be to get the governor working correctly and then manually control the rack with the shutdown lever. I don't know specifically what is under the covers there.
 

The Grand Pooh-Bah

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Last Subscription Date
07/03/2019
After pulling the timing gear cover off and not finding any broken parts I put my attention back to the injection pump. After close examination I found that one of the three pins that slide back and forth when you slide the rack, was not engaged with the rack. I removed the two screws and retaining bracket that holds the rack. I rotated the one pin so that it would engage in the slot on the rack like the other two. I put it back together and reinstalled.

It is running much smoother but still over revving. On the plus side, it now shuts off when the fault light goes on. It will not shut down with the stop lever. The stop lever linkage is moving the rack with full motion. This points back to something not right with the injector pump.

I have talked with the mechanic that worked on it 10+ years ago and he revealed his son put the pump back in and may have partially disassembled the pump after it came back from the injection pump rebuilder. :bonk:

What now?
 

Birken Vogt

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I guess it needs to go back to the rebuilder to check it out at least.

Injection pumps are not to be opened outside of a pump shop.
 

dalmatiangirl61

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Last Subscription Date
07/10/2019
When you say over-revving, what speed is it running at? If its a fixed rpm engine, you get full speed and off, no idle, no choosing the speed you want.
 
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