rebuilt v1702 engine not starting in 743ds

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brambleberry

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Sep 2, 2020
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I had posted a year ago about my '91 743ds that had engine troubles, compression was too far gone to even start.

In the meantime, I found a 743 in pieces that had a rebuilt engine with it. I bought it for the engine, but it had a full set of brand new bobcat brand hydraulic hoses in boxes, brand new bobcat instrument panel and wiring harnesses, and loads of other new stuff.

I started off by running the engine outside of the machine, to be sure it was indeed in working condition. It has the Engine Rebuilders Inc plate and stamp on it, so I know it was rebuilt. Just not sure when :)

I used a suspended funnel with diesel for fuel feed, and disconnected the belt to water pump and alternator. After sounding awful for about 5 seconds, the engine purred beautifully and I felt great about it (I had to stop it with a thick rubber flap over the air intake because the kill switch was stuck, could this have damaged something?). So removed my old engine and put in the new one.

Unfortunately, I have not been able to get it to start again. The wiring is all correct to my knowledge, the starter cranks it no problem. All that comes out is white smoke. Not even a try at catching on a few compressions.

I assumed there was something wrong in the fuel line so I disconnected the hose from the filter and put the funnel back in, and removed the return line, and had it go into a jar. That didn't change anything. I opened up the kill switch to make sure it was moving freely in there and not still stuck, and it was moving fine. I even left it in the open position and didn't touch it after replacing the cover.

I have tried cracking the injector nuts to let air out at each stage, and fuel definitely is seeping out of those. So it seems that the pumps are moving fuel. The only things that are different from when I had it running on the ground are that the coolant system is hooked up (is there a chance that coolant is leaking into the cylinders?), the wiring is hooked up, and it's now connected to the hydraulic pump. To my knowledge, there's no electronic valves or anything in this engine that would be preventing fuel from getting to the cylinders. There is a second solenoid in back of the starter solenoid, that is labelled as a "fuel shutoff solenoid (optional)" in my parts manual. I can't imagine what this would do to shut off fuel but maybe that's what's keeping it from happening?

The only other things I can think of are that somehow the injectors all got clogged at once, but that seems so unlikely since it was just running great. The next steps I would go to are pulling an injector, and putting an endoscope down into the cylinders, see if maybe coolant is leaking in there? Maybe send the injectors off to get checked for spray pattern?

I also don't know for sure that the glow plugs are working, the relay clicks when I engage them, and I checked for power going to them which it is, but I haven't checked the plugs for resistance yet. Seems though that with all the times I've tried cranking it for 15 sec, it would have at least tried to catch on a few of the compressions.

Anyways, thought you all with more experience than I have would have some good thoughts or ideas about this. I still feel like there's something incredibly obvious that I'm missing, but can't figure out what it could be.

TIA
 

foton

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Mar 1, 2018
Messages
1,255
you will need to verify that the glow plugs are working, the 1702 does not like to start without them when cold. Pull the strap off the glow plugs using a VOM set to ohms you should read less than 5 ohms on each one. if they read more than that replace, and if I was gonna do one I would do them all and save the good ones as spares. If they all read good ,you are not getting 12 volts to them from the dash.
 

foton

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Mar 1, 2018
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oh by the way it might be a good idea to carefully see if the glow plugs unthread if they are good ,if they do without much effort take them out and add neversieze to the threads.
 

Tazza

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Dec 7, 2004
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Give it a snort of ether, see if it fires up.

As you said you needed to shut the engine down by stopping the air, i believe you have a sticky injector pump rack.
 
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brambleberry

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Sep 2, 2020
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so just a snort of ether one time won't hurt the kubota engine? I'm a little oversensitive to ether now that my ex-mechanic ruined whatever little compression was left in the old engine with 2 cans of ether :)
 

haymaker

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Mar 14, 2023
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so just a snort of ether one time won't hurt the kubota engine? I'm a little oversensitive to ether now that my ex-mechanic ruined whatever little compression was left in the old engine with 2 cans of ether :)
There is some debate about that but most agree a short shot of ether once in a while will not damage the engine.
I occasionally had to do it on the old tired 743B I had years ago.
 

laurencen

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Oct 3, 2016
Messages
189
from the 3 machines one 843 and 2 743 all were purchased as fixer up machines, what I will say all 3 machines were started on either, lots of it and all needed motor rebuild, I would never use it on my machines.
 

Tazza

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I work for a diesel engine rebuilding company and asked the boss about ether causing damage, he said it doesn't..

It is a diagnostic tool really, it is not something you should use every day to start an engine, if it needs ether to start, you have other issues, a lot of the time it is cylinder wear causing low compression, ether just gets you over that bump to get things moving. It is a stop gap.
 

haymaker

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Mar 14, 2023
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Agreed, Not for daily use. If you need it all the time you have other problems that need to be addressed to have a reliable machine.
 
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brambleberry

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Sep 2, 2020
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So just to wrap this up, turns out the glow plugs were all bad, put in new ones and it started right up. Sorry to waste everyone's time!
 

haymaker

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Mar 14, 2023
Messages
130
Conversation about these machines is never a waste of time. Someone probably learns something from each post.
In this case, if a machine starts hard, an easy thing to check that may fix it is checking the glow plugs.
Not everyone that comes here will know that so after reading it they could be started in the right direction.
I am happy yours was a happy ending.
 
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