Trouble with 5 KVA Diesel Genset

[carlyai]

After an absence, when I tried to start the genset, it would not start.

 

The engine turned over OK, but wouldn't start.

 

I found that the fuel pump valve wasn't working, and on further inspection, looks like the mice have eaten through 6 wires going from the genset to the front control panel, one of the wires going from the start/stop key to the fuel pump valve.

 

I repaired the wires and bled air out of the pipe from the fuel tank to the fuel pump and the output of the fuel pump.

 

The genset now runs but low revs that finally ( after about 10 mins) increased to where I could read 180 V output, then this slowly increased to 200v output. At about 200V it really started to rev, then closed down.

 

Could this be due to air in the fuel line?

I'm hoping that could be the case as I didn't bleed the injector.

 

 

 

 

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[Artisi]

I would say a good chance of air in the fuel system "somewhere" .

I would recheck the fuel pump delivery outlet for air- as for the injector - can you access the injector input it and check for air . Any signs of water in the fuel filter or blockages? 

[carlyai]

Hi thanks. Hope all is well with you.

I changed the fuel first thing when the engine wouldn't start initially.

Because I have to remove all the top off the genset, I didn't check for air at the other end of the high pressure pipe coming from the fuel pump.

I'll get back in there tomorrow morn and recheck all the fuel line this time.

Hopefully air is what it is and not anything to do with the governor or regulator. Just hope I didn't stuff anything cranking it over before with those wires eaten through.

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[Mattd]

If the engine has ran for a period, then it is doubtful that it is air in the system, as the air should have worked its way out, it is easy enough to check by cracking open the union on the top of the injector for a very short period and then tighten it again.

It may be an issue with the AVR, if one is fitted?

[Crossy]

Run for a bit then stop, check the fuel filter and the crud gauze in the tank (if it has one) if you haven't already, bleed the injector again.

 

Check your connections again, make sure they are good the fuel solenoid can be a bit ampy.

 

[carlyai]

If the engine has ran for a period, then it is doubtful that it is air in the system, as the air should have worked its way out, it is easy enough to check by cracking open the union on the top of the injector for a very short period and then tighten it again.
It may be an issue with the AVR, if one is fitted?

Hi, yes, will check the injector tomorrow. It's a bit of a pain to get too. Hopefully not the AVR.

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[carlyai]

Run for a bit then stop, check the fuel filter and the crud gauze in the tank (if it has one) if you haven't already, bleed the injector again.
 
Check your connections again, make sure they are good the fuel solenoid can be a bit ampy.
 

Hello Crossy, thanks for the reply.
Yes I did have the fuel solenoid out to test the spring operated valve. I'll go thru all the bleeding steps again tomorrow.

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[Crossy]

4 minutes ago, carlyai said:

I'll go thru all the bleeding steps again tomorrow.

Cue major power failure tonight ?

 

[sirmud63]

its not a fuel problem , its electrical problem ,most likley the AVR.

[Crossy]

6 minutes ago, sirmud63 said:

its not a fuel problem , its electrical problem ,most likley the AVR.

How so?

 

This is a simple, mechanically injected diesel, the only electrical control to the engine is the fuel solenoid.

 

Easily checked by monitoring the voltage on the fuel solenoid, if the controller is stopping the engine coz of no output it should be obvious (and it should start on the key until the controller decides to stop the beast again).

 

[carlyai]

its not a fuel problem , its electrical problem ,most likley the AVR.

Oh well if it is it is...I'll do all the bleeding first. Thanks.



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[Mattd]

Just now, Crossy said:

How so?

 

This is a simple, mechanically injected diesel, the only electrical control to the engine is the fuel solenoid.

IF it is fitted with an AVR and I have no idea if it has, then this may well be interfaced to the control of the engine to regulate the voltage.

[sirmud63]

2 minutes ago, Crossy said:

How so?

 

This is a simple, mechanically injected diesel, the only electrical control to the engine is the fuel solenoid.

 

Easily checked by monitoring the voltage on the fuel solenoid, if the controller is stopping the engine coz of no output it should be obvious.

 

he said the engine over reving till it shut its self down .thats not a fuel or air problem on a diesel engine .

[Crossy]

7 minutes ago, Mattd said:

IF it is fitted with an AVR and I have no idea if it has, then this may well be interfaced to the control of the engine to regulate the voltage.

Please explain, this is not an inverter unit. The engine speed (on a mechanical governor) determines the output frequency, the field strength is controlled by the AVR to fix the output voltage.

 

[Crossy]

5 minutes ago, sirmud63 said:

he said the engine over reving till it shut its self down .thats not a fuel or air problem on a diesel engine .

Did he?

 

I see he said it started to rev (this is a 3000 RPM genset) then shut down.

 

On a mechanically governed and injected diesel what else could it be? 

[Mattd]

It is not possible to tell from the photos, there are some systems that use the interface between the AVR and governor to control the frequency and to prevent overspeed.

If it is mechanically governed, then I agree it is not likely to be the AVR, though an erratic voltage to the stop solenoid would more likely cause the engine to hunt as opposed to the symptoms described.

It is also unlikely to be air given the symptoms.

[sirmud63]

3 minutes ago, Mattd said:

It is not possible to tell from the photos, there are some systems that use the interface between the AVR and governor to control the frequency and to prevent overspeed.

If it is mechanically governed, then I agree it is not likely to be the AVR, though an erratic voltage to the stop solenoid would more likely cause the engine to hunt as opposed to the symptoms described.

It is also unlikely to be air given the symptoms.

yep , you know your shit mate . 

some more piks would be good.

[Crossy]

Our genset controller will shutdown on overspeed, by killing the fuel solenoid (ignition in our case as it's a gasoline engine).

 

Of course, it will happily re-start until it happens again.

 

These Chinese units are not at all sophisticated, simple engines, simple AVRs. 

 

@carlyai do you have a fancy auto-start controller or simply turn the key?

 

[bankruatsteve]

I think the problem is rat shit in the doohinky.

[carlyai]

'@carlyai do you have a fancy auto-start controller or simply turn the key?'

Simple turn the key.

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[carlyai]

I think the problem is rat shit in the doohinky.

Could be.....plan B is no more rats.

I like this saying: "While the cat's away, the mice will act like rats."

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[Crossy]

I've been thinking about this. A few thoughts.

• Does the engine behave as described every time you try to start it?
• Is it actually overspeeding, or just running up to its normal operating speed?
• Can you check the fuel solenoid is energised when the engine stops? i.e. is the fuel being "deliberately" cut off?
• Does the engine have a low-oil warning, is the wiring for that OK?

[carlyai]

So far so good. Retraced my footsteps and bled everything, then took the top cover off and bled the injector.

Started engine and it runs under no load at 225 V.

New Question

While I had the top cover off, I noticed that a 30 cm round spot on the underside of the fuel tank had started to rust, so before I start the machine again I was thinking of buying some rust converter and coating the rust spot.
Any problems applying rust converter to a surface rust spot on a diesel fuel tank?
Thanks

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[carlyai]

I've been thinking about this. A few thoughts.

• Does the engine behave as described every time you try to start it?
• Is it actually overspeeding, or just running up to its normal operating speed?
• Can you check the fuel solenoid is energised when the engine stops? i.e. is the fuel being "deliberately" cut off?
• Does the engine have a low-oil warning, is the wiring for that OK?

I didn't get round to all your tests Crossy as bleeding the air from the system seems to have fixed the problem, on no load that is.

The unit does not have a low oil pressure light.

Thanks for your thoughts. Will see what happens on load.

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[Crossy]

11 minutes ago, carlyai said:

I didn't get round to all your tests Crossy as bleeding the air from the system seems to have fixed the problem, on no load that is.

If it's apparently fixed then all is good.

[Crossy]

18 minutes ago, carlyai said:

While I had the top cover off, I noticed that a 30 cm round spot on the underside of the fuel tank had started to rust, so before I start the machine again I was thinking of buying some rust converter and coating the rust spot.
Any problems applying rust converter to a surface rust spot on a diesel fuel tank?
Thanks

Is there any rust inside the tank?

 

If it's just surface rust on the outside and the tank isn't compromised I would use something like Hammerite which will stop the rust getting any worse.

 

[carlyai]

Is there any rust inside the tank?
 
If it's just surface rust on the outside and the tank isn't compromised I would use something like Hammerite which will stop the rust getting any worse.
 

I can't see inside the tank. You've got me worried now as the area where the soundproof material touches the tank was wet. I just thought moisture, but better have a good look.

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[carlyai]

I decided to take the tank out for a closer look. Thanks for keeping me honest.


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[carlyai]

Tank's of and it doesn't look spectacular. The inside of the tank is all covered in gunk, or rusting as well. Will have a closer look inside when it dries out a bit.

My feeling is that I will probably have to take the tank somewhere for major surgery as I probably won't find a replacement out here.

Any ideas?

Thanks to SWMBO who took selfies as I struggled along. No she was a good help.

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[Artisi]

You should be able to source a stand alone tank which you could mount on the wall at some convenient spot and run a fuel line to the pump.