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Old 22-10-2009, 23:57   #1
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Yanmar 10hp Diesel Runs 'Backwards'

Have a Yanmar 10 HP single cylinder Diesel engine in a Soverel 33. Engine rebuilt last winter. Ran fine added a fuel filter and started the old won't start right away thing and no high rpm thing. Resealed threads on fuel filter causing air leak maybe. Lost water pump. Replaced impeller and noticed after cranking and no start up right away then on the last little bit of a turn of the flywheel the engine started up running backwards pumping exhaust into the cabin from the air intake.

Reblead the fuel system both low and high pressure systems and engine starts right up. Can even hear the injector pop.

Let it sit a while and crank and no start and no pop from the injector. Crank some more and then it does the start backwards thing again. Cut off engine with decom release. Crank and it is off and runnung clockwise.

So we think air is getting in at the High pressure side. Maybe the return line is letting air in? Don't know but she is a odd one.

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Old 23-10-2009, 17:37   #2
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G' day,
many years ago as a young apprentice i was given a job to fix a old lister that had come into the shop with the this problem, if you put throttle on just as the motor kicked back back away it would go in reverse--very entertaining.Went thru fuel & valve timing checked one way pin in grank handle had not been turned around by some jocker,finally after much rousing from the tradies i found the fuel pump delivery valve badly worn replaced problem fixed. suspect fuel timing altered enough to cause problem. 40+ years on still i manage to get the odd similiar brain teaser.

Cheers, Doug.
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Old 23-10-2009, 18:36   #3
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I was told once that the yanmar cant run backwards. That it is most likely a stuck exhaust valve and wont exhaust normally and pushes the exhaust out when the intake valve opens. But I have no personal knowledge about this. Just a thought
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Old 23-10-2009, 19:19   #4
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A lot of diesels can run backwards.....some are designed to.....what is probably happening is that when you get up to cranking speed and then release the switch, as the engine/flywheel slows down it comes up to compression and fires...kicking it into reverse.

I have had this happen on a couple diesels...it is rather "interesting" to say the least.

How much throttle do you have on when you try to start?

This is so cool!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Old 23-10-2009, 21:55   #5
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Neat! What was he doing to start it?
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Old 23-10-2009, 22:13   #6
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Found this link

Yanmar 1GM10
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Old 24-10-2009, 03:38   #7
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G'DAY , Solitude,
When he was barring it over he was setting one dedicated piston to about 10 degs a.t.d.c. so that when air is applied to that cylinder the piston descends, the other cylinder had been decompressed allowing it to fire on one cylinder, as the engine speeds up he brings the the other cylinder into play . On larger multi cylinder engines a cam timed air starting

valve delivers air to each cylinder in turn. Most ship engines are direct reversing the engine is brought to rest then the cam is slid along by air or hydraulics the engine is then restarted in the reverse direction a gearbox therefore not needed,if the direction does not tally with the telegraph a siren is activated.

Doug.
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Old 24-10-2009, 05:41   #8
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!5 yrs back, spent a lot of time with an engineer friend on a 500 ton passeger ferry built in Ireland. Power was 2 straight-8 Crossley diesels without clutches. Engineer stood between engines to operate throttles and air-start and cam-timing wheels.
Throttles were 3ft high cam-and -ratchet type, which stood up out of the floor plates. 24inch brass wheels were parallel to centre-line 0n either side of operator. Rotating wheels clockwise or counter-clockwise set cam timing and opened air-start valves to engine idle speed. Engine RPM was displayed at eye level below telegraphs.
Wheels were very low-ratio gear mechanical connection to engines. Getting alongside a 30,000ton cruise ship swinging at anchor, in a 25kt breeze, was always fun

Chihuahuas, -if you keep feeding that Yanmar, it may grow up to be a Crosley or a Sulzer
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Old 24-10-2009, 09:29   #9
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Just trying to make things clear

Quote:
Originally Posted by chihuahuas View Post
Have a Yanmar 10 HP single cylinder Diesel engine in a Soverel 33. Engine rebuilt last winter. Ran fine added a fuel filter and started the old won't start right away thing and no high rpm thing.
Here you aded a filter? or changed it?


Resealed threads on fuel filter causing air leak maybe.
Resealing causing air leak?

Lost water pump.
Now Im lost where did you loose the waterpump?

Replaced impeller and noticed after cranking and no start up right away then on the last little bit of a turn of the flywheel the engine started up running backwards pumping exhaust into the cabin from the air intake.

Reblead the fuel system both low and high pressure systems and engine starts right up. Can even hear the injector pop.

Let it sit a while and crank and no start and no pop from the injector. Crank some more and then it does the start backwards thing again. Cut off engine with decom release.
In my 1gm10 manual it clearly states do not use decompression lever to stop the motor it will damage the valves.

Crank and it is off and runnung clockwise.
It should run counter clock wise viewed facing the fly wheel.

Not tryig to be a jerk but I could not understand this.
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Old 24-10-2009, 11:37   #10
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Reaasealed threads on fuel filter.....(secondary?) they should have crush washers.
If you have to put sealant on the threads, you need to buy a new secondary filter

If you added a fuel filter like a Racor do you have the in and out in the correct location.

From the front of the engine it will rotate clockwise....from the flywheel end it will rotate counterclockwise
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Old 24-10-2009, 13:15   #11
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Got boat...
Engine Bad...
Rebuilt Engine TAD...
Ran fine...
Added inline filter racor...
Ran bad...
Added threadtape to raycor 1/4 npt fittings...
Added a squeeze pump...
Ran engine no water out...
Ran engine got smoke from cabin...
Ran engine ran normal but no water pump...
Replaced impeller failure was caused from running backwards...
Noticed engine running backwards....
reblead low and high side lines and starts right up...
Let it sit and no start right away. Crank and crank then starts sometimes backwards.
Boat is Blue in color..................
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Old 24-10-2009, 16:25   #12
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Did you hook up the racor with the "IN" from tank and "OUT" to engine?

Fuel Fittings on a Racor do not need Thread tape....some are a different thread
Some NPT, some UNF.

Sometimes a low cranking speed can cause this to occur. The engine comes up to compression, fires and runs backwards....This occurs when start key/button is realeased. This is the way that some old diesel and gas engines were started.
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