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Old 18-08-2021, 17:22   #1
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Broken delivery valve springs

I have 2 x Yanmar 3YM30's in my fusion40 Sailing cat. stbd engine had a serious issue with fuel starvation which was finally resolved when debris in the tank was discovered. Since then the engine has been harder and harder to start to where now it won't even run or fire.


Without going through my evolutions in fault finding, I have now found the injector pump delivery valve springs are broken. Not just broken but the one I have pulled out is in 4 pieces. I expect the other two will be the same.


Does anyone have any experience of broken springs and offer a reason this may have happened. The injector shop I am going to has never seen a broken spring.
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Old 18-08-2021, 18:12   #2
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Re: Broken delivery valve springs

Sorry cant help your problem but I'm amazed. Our yanmar ysm8 Bosch/zexel injection pump had internal rust it had so much water thru it & still the delivery v/v spring was intact on a 1980 engine.
Only reason I can think of is insufficient lubrication from the diesel due to starvation so the delivery v/v or spring jams. I'm not an injection tech it has to be said so it's just a guess.
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Old 19-08-2021, 22:33   #3
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Re: Broken delivery valve springs

Quote:
Originally Posted by jacktheflyer View Post
I have 2 x Yanmar 3YM30's in my fusion40 Sailing cat. stbd engine had a serious issue with fuel starvation which was finally resolved when debris in the tank was discovered. Since then the engine has been harder and harder to start to where now it won't even run or fire.


Without going through my evolutions in fault finding, I have now found the injector pump delivery valve springs are broken. Not just broken but the one I have pulled out is in 4 pieces. I expect the other two will be the same.


Does anyone have any experience of broken springs and offer a reason this may have happened. The injector shop I am going to has never seen a broken spring.


Itís quite rare to see a broken delivery valve spring, and to me, unheard of to find 3 in the one pump. Iíve seen a fair few plunger springs broken though.
More common however are engine injection problems caused by faulty or stuck delivery valves. Everything from exhaust smoke to rough idling to very hard starting.
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Old 23-08-2021, 07:42   #4
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Re: Broken delivery valve springs

The fuel trash/fuel starvation is a likely enough source, even if the exact means are not obvious. The hard starting is not surprising if you are running on two cylinders.

Given the minor cost of replacing all the springs, and the major headache when another one fails, I'd replace them, test the engine, and not worry too much about just what happened in there.
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Old 23-08-2021, 13:31   #5
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Re: Broken delivery valve springs

Have replaced 3 injectors and the delivery springs and the engine runs like a top. Would like to understand the mechanics of the failure to possibly prevent it happening again and for my own learning.
Must be linked to the fuel starvation and there is evidence by the gum arund the valve that one spring has been broken for some time. So something I've done has caused the other two to fail in short order.
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Old 23-08-2021, 13:41   #6
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Re: Broken delivery valve springs

What sort of trash was in the tank/s?
Is the filter/ water seperator setup good?

I reckon using a fllter funnel when filling tank is good practice as a surprising amount of crap comes with the pump diesel for no extra charge.
Can understand you wanting to know the cause but it's a rarery.
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Old 23-08-2021, 14:24   #7
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Re: Broken delivery valve springs

The blockage was due to some old gasket material/silicon type stuff that would have been there forever. I have a CAV filter before the Yanmar filter and have never seen free water go through the system.


I have seen in other situations where springs break when release from load without damping. eg a car spring on a corrugated road will break if the shock absorbers are weak. So I'm thinking it may have been that dry while trying to start the springs had no fluid damping and subsequently shattered. One of the last things I did was mist some diesel down the intake which enabled the engine to run at a reasonable rev but still wouldn't sustain.


This may have been the coup de grace for the springs but there was plenty of fluid to the pump at this stage.
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Old 23-08-2021, 14:33   #8
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Re: Broken delivery valve springs

Ok, guess you'd know if it was water as pump & injector internals get rusty.
Your scenario is possible but I guess you'll never know for sure as post #4 alluded to.
Probly never happen again.
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Old 23-08-2021, 17:29   #9
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Re: Broken delivery valve springs

Has the boat ever been in Asian waters? maybe your injector pump got a rebuild overseas in the past and the delivery valve kits were the wrong ones.
Or maybe the engine got an EBay injector pump out of China in its past
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