Daihatsu diesel generator troubleshooting

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rohanmariner1987
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Daihatsu diesel generator troubleshooting

Postby rohanmariner1987 » Tue Jul 30, 2019 6:21 pm

Hello everyone, this is my first post in this forum. I am presently sailing as a 3rd engineer in a Belgian LPG vessel. I am unable to troubleshoot my aux engine.,
While taking performance I find unit no 1 is showing a very low maximum combustion pressure (pmax) of value 70. Where as the rear of the seven units have a normal pmax ranging from 101-103 bar.
It would be of great help if you engineers can throw some light into this matter out fof your profound expertise.
Looking forward,much appreciate.
Model : daihatsu 8k20.
Actions taken : I have checked the indicator cock valve, they are fine.. I have changed the fuel Injector as well !
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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Wed Jul 31, 2019 6:18 am

We talking compressions readings here in psi?
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rohanmariner1987
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Re: Daihatsu diesel generator troubleshooting

Postby rohanmariner1987 » Wed Jul 31, 2019 9:15 am

Yes sir,.. compression pressure of unit 1 is 70 bar. Where as the other seven units are normal within a range of 101-103 bar.
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Re: Daihatsu diesel generator troubleshooting

Postby rohanmariner1987 » Wed Jul 31, 2019 4:50 pm

Both pmax and pcomp is low dor unit number 1. Do you think I need to change the fuel.pump timing ?? Or it has something to do with the suction and exhaust valve timing ?? Please revert.!!
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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Thu Aug 01, 2019 12:41 am

Is it an 8 dk20 or 8k20 model?
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rohanmariner1987
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Re: Daihatsu diesel generator troubleshooting

Postby rohanmariner1987 » Thu Aug 01, 2019 1:54 am

My bad.. it's a 8dk20 model. Daihatsu.!!
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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Thu Aug 01, 2019 3:23 am

I understand this to be a dead engine compression test has been conducted here and that no. one cyl. Is lower than the rest and you want to determine why?
My take would be the first check here is to check the tappet clearances on no. one cyl.
A tappet with no clearance or too tight a clearance would obviously produce a low bar/psi readings as it's not airtight.

To determine where the leakage is exactly?
Many, many years ago I made up a tool to locate where any bar/psi leakage might be.
Tapping off a airline via a pressure regulator and into a spare injector body with the pintle needle removed to allow an unrestricted airflow supply you tap or weld/braze a PCL fitting into the injector body this being for the purpose of instant easy access.
Attaching an airline hose ( good for 200 psi at least ) you bolt your modified injector back into the head and start off with 50 psi winding it up to over 150 psi with all tappets rocking on TDC.
Watch the gauge, any drop off in psi is going somewhere.
If the needle does not remain constant off with the air induction system from the manifold and listen closely to see if any compressed air is being passed.
If it is then suspect inlet valve not seating properly.
Ditto the exhaust manifold system, coolant system ( for cracked head ) although a cracked head into the waterway would pump up the coolant system resulting in an obvious overheat system normally.
But the crack a lot of times cannot be seen until all valves are out and is not always into the water jacket.
The only other way for your leakage test psi to go is down past the rings into the lower half of the engine, in a lot of cases into the sump.
Again access required here via any openings i.e. breathers, pipes or dipsticks present and listen for any compressed air being passed.
Your problem here might be the surcharge on the old injector ( which sometimes is very heavy on exchange units ) and/or workshop facilities available to you at this time.
If you are unsure about any readings whip another cyl. injector out and compare readings taken.
That's how I would tackle it anyway, best of luck and do let us know the outcome as it all furthers our interest/ education in to the subject of diagnostics.
I would hate to be in a position whereby owing to lack of made up test equipment you had to sub the job out as to me that removes a lot of challenge/ interest in it all.
Don't sail off over the horizon without letting us all know what you find mind.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Re: Daihatsu diesel generator troubleshooting

Postby Revolver » Thu Aug 01, 2019 8:47 pm

Exh temps?
Knocking or detonation?
Take off the valve cover and make sure everything's rocking like it should.


Keep the feedback coming. We're just narrowing down some things. There's an easy answer, just narrowing down some things.
You keep thinking about it too.

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Re: Daihatsu diesel generator troubleshooting

Postby rohanmariner1987 » Fri Aug 02, 2019 2:35 am

@merlyn : I really appreciate your reply and expertise. I will surely do accordingly and make the tool, letting you know about the findings. Your acute troubleshooting explaination gave me a new window to further inference. I will do so.
@revolver (chief engineer) : the exhaust temp of unit one is 380 degrees almost same as the rest (range of 380-400 degrees @600 KW) .. I can't hear any knocking from unit 1. Yesterday I checked the valve clearances( tappet clearance ) i had to re adjust a little and the clearance of both inlet and exhaust are same now acc. To manual or. 0.3 mm for both. I have also checked the fuel pump timings ..they are fine as well. My inference is that may be suction or exhaust valves are leaking or something is wrong with the piston rings. I will attach the performance file of this auxiliary engine in few hours time ..to have a better understanding. Thanx a lot for all the efforts from your side.. !!
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Big Pete
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Re: Daihatsu diesel generator troubleshooting

Postby Big Pete » Sat Aug 03, 2019 11:42 pm

Rather than modifying an injector to put air pressure into the cylinder, it would be easier and cheaper to make a connection to the Indicator cock, that is what I have done in the past.

BP
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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Sun Aug 04, 2019 4:07 am

Cylinder compressions, are they showing 1000 to 1500 psi?
Seems a tad high?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Tue Aug 06, 2019 12:13 am

On smaller stuff Cats /Perkins Cummings / Volvo etc you can measure each and every cylinder compressions within minutes by not removing anything whatsoever on the engine to be tested.
24v 12v engines.
Introduced to me in approx. 1980 and used it regularly since.
Not cylinder leakage tests but straight each cyl. Compressions.
Anyone?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Big Pete
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Re: Daihatsu diesel generator troubleshooting

Postby Big Pete » Wed Aug 07, 2019 11:39 am

If they have indicator cocks and individual fuel pumps it is easy, just hold the fuel pump up so it doesn't pump.
If they have indicator cocks but not individual fuel pumps, disconnect the fuel pipe from each injector in turn and let it squirt into a plastic hose draining into a bucket while you check the compression.
If you don't have indicator cocks or Glow Plugs or something else that you can unscrew from the head, and replace with a pressure sensor, then you have a problem, not sure what you do then short of fitting strain gauges to the cyl head Bolts or Studs to measure the load on them.

BP
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Merlyn
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Re: Daihatsu diesel generator troubleshooting

Postby Merlyn » Thu Aug 08, 2019 7:26 am

Remember my " What's the difference between a R/H machined liner and a L/H one? "
Nobody got it over several months period.
The answer was staring you in the face every time our read the question?
Things are not always what they appear to be speech again.
The clue is in the question.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

Revolver
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Re: Daihatsu diesel generator troubleshooting

Postby Revolver » Fri Aug 09, 2019 1:30 pm

Very good then, merlyn
Spose we'll have to wait for Arthur to pull the sword from the stone.


But also: "...not removing anything whatsoever ON THE ENGINE..."


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