743 starting problems

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Nomechanic

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Apr 2, 2007
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My first post to this website -- thanks in advance for your help! Recently while trouble shooting a fuel line clog on my older 743 I removed the little round pump on the side of motor and reinstalled it the same as it came off. The problem was at the filter... Now, the motor will only start if I prime it with starter fluid (which I know is bad for it). Once it's running all seems fine, but as soon as the motor cools off it won't start again -- even if I hit the glowplugs for 90 sec. Is it possible that little pump is bad, or could I have installed it incorrectly? p.s. when I crank it over very little smoke comes out the exhaust...so I don't think it's getting fuel. Any thoughts? Nomechanic
 

Fishfiles

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I almost think you have another problem , but first there is a check ball in the hand primer bulb that sometimes gets clogged up with trash , and if you still have the old style fuel tank pick up tube there was a screen on the bottom of the tube that had a check ball in it , 90 seconds for the glow plugs I think is extreme and they are probally burned out by now , I am thinking you have bad compression as if it don't hit on starting fluid you have real problems , from what you have said I would do a compression test thru the glow plug holes and check the glo plugs at the same time
 

Tazza

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I almost think you have another problem , but first there is a check ball in the hand primer bulb that sometimes gets clogged up with trash , and if you still have the old style fuel tank pick up tube there was a screen on the bottom of the tube that had a check ball in it , 90 seconds for the glow plugs I think is extreme and they are probally burned out by now , I am thinking you have bad compression as if it don't hit on starting fluid you have real problems , from what you have said I would do a compression test thru the glow plug holes and check the glo plugs at the same time
I'd also check your glow plugs.
Test the plug by attaching it to your battery, it should start glowing from the tip back to the body. It should only take a few seconds to get bright red. If the tip doesn't glow red the plug is bad.
A compression check wouldn't hurt either.
You did prime the system up after replacing the fuel filter?
 

Nomechanic

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I'd also check your glow plugs.
Test the plug by attaching it to your battery, it should start glowing from the tip back to the body. It should only take a few seconds to get bright red. If the tip doesn't glow red the plug is bad.
A compression check wouldn't hurt either.
You did prime the system up after replacing the fuel filter?
Thanks for your help. Compression could be a problem since my 743 is >5000 hrs, but when I started it with the help of a short blast of ether it runs great with no smoke and I was able to load leveral round bales of hay with no problem. It just doesn't seem to be getting fuel at the start...and the immediate response to ether suggest the glow plus might be ok too, but I will test them. Another possibility -- one of my injector lines has a small leak. Could this be causing an air leak?
 

Tazza

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Thanks for your help. Compression could be a problem since my 743 is >5000 hrs, but when I started it with the help of a short blast of ether it runs great with no smoke and I was able to load leveral round bales of hay with no problem. It just doesn't seem to be getting fuel at the start...and the immediate response to ether suggest the glow plus might be ok too, but I will test them. Another possibility -- one of my injector lines has a small leak. Could this be causing an air leak?
Ether has nothing to do with glow plugs for starting.
The ether can says DO NOT use glow when you give the engine a snort, it can cause pre-detonation.
I would seriously look at the plugs before you do anything else. I had a machine with 5-6K hours on the clock, it was a pig to start, glowing for 60-120 seconds still wouldn't start rite. It would fire then shake and stop. The ends of the plugs tapered to a point. The tip didn't glow at all, just a small red patch at the end of the thread. New plugs made it start with 30 or so second glows.
 

Tazza

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Ether has nothing to do with glow plugs for starting.
The ether can says DO NOT use glow when you give the engine a snort, it can cause pre-detonation.
I would seriously look at the plugs before you do anything else. I had a machine with 5-6K hours on the clock, it was a pig to start, glowing for 60-120 seconds still wouldn't start rite. It would fire then shake and stop. The ends of the plugs tapered to a point. The tip didn't glow at all, just a small red patch at the end of the thread. New plugs made it start with 30 or so second glows.
I forgot to mention, on that machine when starting it didn't puff much white smoke at startup either. It seems the compression was low enough to not smoke a lot. With the glow plugs working it started really well with no smoke either.
With the ether, does it start smooth? or does it still run rough then catch and run smooth? if its pretty good straight up it sounds like its compression and plug problem and not a fuel delivery problem. If the fuel wasn't getting there it would shudder and run really rough.
The leak you have, i doubt that would cause these problems.
 
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