Diesel generator - Pcomp high

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SanMarino
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Diesel generator - Pcomp high

Postby SanMarino » Mon Aug 19, 2019 11:49 am

Good day to all!

I have been lurking around here for a some time and learned so much from you guys. Just wanna hear some thoughts about my problem recently about our aux diesel engine (Hyundai Himsen 7H25/33).

I replaced fuel injectors(new atomizers, adjusted opening pressure according manual) and adjusted valve clearance. After a week I took performance tests and found out that pcomp is almost the same as pmax for all units. Pcomp were high reaching almost the same as pmax. After this, i tried to adjust again valve clearances and made sure it was correct also recalibrated the opening pressure of fuel injectors. Took again performance test after that and i had normal result for some units and the other were still with high PComp. After a week i took again performance test and all of them were back again to high pcomp. And also smoke from the funnel was fine at first but after a few days it produced darker smoke.

It could be the valve clearance because i made it when the engine was not in cold condition and messed up the timing of the valves causing to have high comp pressure? but i have done this with other engines and everything was fine. Im thinking also about the fuel injectors opening pressure dropped again causing to have ignition during compression(Atomizers were were not original from maker). Or it could be the device i used to take the performance test , but it seems good cause i get normal results for other engines.

Will appreciate all your response.

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Big Pete
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Re: Diesel generator - Pcomp high

Postby Big Pete » Mon Aug 19, 2019 3:05 pm

I don't think the tappet clearances would have much effect. I have sailed with engines where the maker sent out a service bulletin to increase the valve clearances by 50 % because it made the engine run quieter. If you had too little valve clearance the valves wdould not close and you would have low pressure. The fuel pressure before the pump rises so quickly that wrong pressure settings on the injectors will not effect the timing.
Is the engine developing full power and does it stop normally or does it tend to keep running?
Possible fuel timing issue, oil leaking from the injector cooling or elsewhere and burning in the cylinder?
Are the fuel rack and governor output readings the same on all the engines for the same power output? How about the exhaust temps?

Good luck and keep us informed.
BP
It is always better to ask a stupid question than to do a stupid thing.

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JK
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Re: Diesel generator - Pcomp high

Postby JK » Tue Aug 20, 2019 9:31 am

We have found with fuel valves to go with the manufacturer and not knock offs. This may be your problem. What you think may be the same, may not be.

SanMarino
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Re: Diesel generator - Pcomp high

Postby SanMarino » Fri Aug 23, 2019 10:34 am

Hello, thank you for the inputs!

Based on BP's suggestions, the fuel racks have diferences +-3 to 5 mm from average, we adjusted it based from the exhaust gases and keep little deviation from each other. I tried to increased the opening pressure from 400 bars(which was from the recent service letter sent by maker) to 450bars( which was the original setting before they sent the recent service letter). But i think the thing that solved my problem was I tried to reset the racks all to zero by setting the governor load limit to zero then adjusted the linkages to let them have the same readings of racks.after starting, we got big deviations from exhaust gases ( -+30 to 50deg) then I took a performance test, the result was successful. We got normal pcomp now. And then i adjusted the racks based on the performance test i got.

Seems we got this problem from adjusting the fuel racks just to get good exhaust gas temperature without making sure if our sensors give the real readings and thus causing unbalanced distribution of load on each cylinder.

Thank you guys for the help!

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Big Pete
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Re: Diesel generator - Pcomp high

Postby Big Pete » Tue Aug 27, 2019 11:18 am

Good News,

Most engine makers nowadays don't care what the individual exhaust temps are, the individual fuel rack settings and timings should be exactly as per makers manual and never changed, on a turbocharged engine small variations in exhaust temperatures, say 50 degrees between cylinders, have no importance unless the maximum permitted exhaust temperature is exceeded, in which case the injector probably needs changing or an exhaust valve is leaking.

BP
It is always better to ask a stupid question than to do a stupid thing.


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