Dead Generator

[Full Moon]

I came to the boat to check it and run the engines and found oil all over the engine room floor. I tracked to the generator which sits sideways between the main engines at the aft bulkhead. I thought it was the oil change fitting that had broken or come loose. My mechanic and friend checked that and found it was the rear main seal leaking. We pulled the gen and split it and found all kinds of corrosion and rust in the generator area. Had that cleaned up and reconditioned. After three months of being told it will be back in by Friday I finally told the mechanic to get his stuff off my boat and he was done working on my boat. I started checking things out and found the clamps for the exhaust hose were never re-installed. Could be, the first time I started it up it would blow off and start sinking the boat. I had an electrician check everything and make sure it was hooked up right. When I tried to start it.....nothing! Not a click, whirr or anything. My right main would try to turn over but never started. The gen and right main uses the same 8D battery and it was bad due to a charger boiling it dry,(another subject). Changed the battery and the main fired right up. After bypassing a switch the mechanic had broken getting the gen out the gen cranked normally too, but never fired.

We spent all day Saturday checking fuel flow all the way to the injectors and ensuring the glow plugs were juice, they are. We tried a shot of WD-40 in the intake, that didn't work. We got desparate and got some starting fluid and still nothing. The mechanic my wife's dad used for years ran out of ideas but he thought the "plungers" (?) may be stuck. My next plan is to take the injectors and plungers out to check them. Before I do that am I going to be surprised by springs and flying parts?

Back to basics, we have fuel and as far as we can tell, fuel flow. We have power to the glow plugs. We tried starting fluid which you ought to be able to start a stump with that stuff and nothing works.

Any ideas?

 

[TedZ]

You don't say what make the genny is.

If it is an Onan they are very hard to start after the fuel system is drained completely as it doesn't prime or pressurize easily. The injectors don't fly apart when removed. If it has compression, really open up the fuel lines to the injectors at the injectors and crank it a lot until clear shots of fuel are coming out every compression stroke. Tighten them and it will start.

Ted

 

[Full Moon]

Thanks Ted, yeah it is an Onan 8 Kw, I think it is model number MKDK or something similar. We did that to the injectors and everything seemed to be pressurized. When we cranked it there would eventually be something like a diesel mist come out of the vent on top of the valve cover.

 

[REBrueckner]

I don't have a single brilliant idea, but here are some suggestions/clues...I assume the genny engine ran before you discovered all this??!!

Diesel gennys need just a few things to start (a starter that turns over via a decent battery), and run: fuel, air, compression, and shut down saftey devices showing "normal".
Sounds like you bled the fuel system ok. And even if you didn't, the starter fluid should have caused some firing...that may be a key indicator. If there was NO firing, then there there would be no compression...why? Open valves? Does that model have a decompression solenoid??... Did the mechanic stuff a rag in the air intake to keep out crud? Maybe you can light a match and extinguish it, and see if the smoke is drawn into the air intake during cranking. Did the mechanic have the injectors off??

I've never tried to start an Onan via starter fluid but maybe someone will post that it's easy...it sure worked on my prior Detroits. Be careful of pre heat coils igniting the ether...and go EASY on the spray....

Think carefully about what the mechanic "worked" on...and check each item...for example, if just one shut down sensor wire was left off or broken, the genny might not start. Did he adjust the valves?

The good news is that likely it's something simple; the bad news is that the one item is too often not so easy to find. (see my recent post on my Onan.)My bet is that something the mechanic did needs to be changed/corrected.

 

[Full Moon]

Rob, I think you are right. While cranking, if you put your hand over the intake the suction is strong, which would indicate the compression is good.(?) They didn't do anything to the engine other than replace the rear oil seal, but when they went to rewire it they didn't remember what went where. They got a wiring diagram from Onan, but I see a couple of unattached wires. But, I've got fuel and when I hold a test light on the glow plug and hit the starter it lights up, so I'm getting electricity to them. Fuel + Fire = Run, but it won't. It's got to be some kind of sensor that is not letting it run.

 

[Trojan]

Full Moon, I think you answered your own question. The guys are right. Sounds like your missing a safety switch. Onan's are hard starting when cold make sure your glow plugs are lit 30 seconds before you crank. You can flood the glow plugs to a point they will do nothing.

BILL

 

[Avenger]

Have somebody look while you are cranking the engine and see if there is any smoke coming from the exhaust. It may take quite a bit of cranking for the smoke to get all the way through the system. If there is smoke, then the fuel system is putting fuel in and the engine is not burning it. If that's the case look at glowplugs, slow cranking or poor compression. Bad injectors are a remote possibility as well. Safety systems will interrupt fuel delivery so if you're getting delivery you can rule those out. Also, if you're gettting fuel when you crack the injector lines and crank the engine, the injection pump it's probably fine. Most of the injection pump failures we see on generators are a result of owners "fixing" them, so be careful what you take apart.

 

[REBrueckner]

As I have posted, I found at least one sensor on my 12KW ONAN is normally open, another normally closed. They must use different mechanisms to shut the engine down. My fuel solenoid engages only when the centrifugal switch closes points at 900 RPM cranking. This circuit is in turn activated via a control box relay which could conceivably be the mechanism for shutting down. I do know there were no safety sensors between the relay and the fuel solenoid so mine was not wired via a NC sensor which would open to alarm. I put a NC sensor in the circuit which had previously been wired to nowhere.
SCROD makes a good point: If you are pumping fuel during cranking, the start and safety mechanisms would seem to be working...which would be puzzling....I tend to agree that suction would indicate compression but am not positive...Anyone know for sure???

 

[yachtsmanbill]

I would look at the exhaust valve setting. If they are too tight, you can still have good intake suction, but they will open too early loosing compression.
Is the unit cranking fast enough? That is critical as well. ETHER should have made it pop or at least buck the starter, no?
The other curious point is the fuel mist out of the valve cover. Something is rotten in Denmark! ws

 

[Bob Bradley]

On my MDJE ('79 7.5 Kw), I seem to recall a similar problem which was corrected by pressing a red "reset" button on the control panel of the unit. Perhaps you have a similar setup?

 

[Salty Dame]

Remember, as you are cranking you are pumping water into your waterlift exhaust. Check your installation manual.

 

[Full Moon]

OK, the bad news continues. I had a mechanic check the engine and he ran a compression test. 85, 110, and 35 psi. Time for at least rings. We are getting better at taking this thing out of the boat than I want to be. At least this time it will be a real-life generator mechanic and not a friend that talks a good story.

 

[yachtsmanbill]

More than likely valves before rings IMHO. Did your mechanic check the valve lash? ws

 

[REBrueckner]

The diagnosis does not match the problem description...

 

[NAN-PO 41]

I agree with both Bill and Rob. Usually a valve problem not rings and the diagnosis doesn't match the problem. It sounds like it is time to start the diagnosis process over again. You are not sure what the first guy did so I would start from square 1 and recheck all of the basics over again. I know that seems like a lot of needless work but you will really kick yourself if later on you find a really simple thing that was overlooked at the beginning caused the problem.
PS Don't forget about the waterlift muffler possibly putting water into the cyls due to excessive cranking.
Good Luck, Fred

 

[yachtsmanbill]

Even tho its a hassle, pull the injectors and put a spoonful of oil in each cylinder and do a compression test again. If the rings are worn this will bump it right back to normal for the test. If that checks out, youll need to do a cylinder leak down test with air. A bad valve will hiss at the intake or exhaust. Shit dont just wear out. You have a valve problem. ws

 

[Avenger]

If the compression is really as bad as stated it probably will not matter, but putting oil into the cylinders of a diesel for a compression test isn't usually recommended. If it has compresssion the engine will see the oil as fuel and your compression gauge could go bang. I would play it safe and skip right to the leakdown test.

 

[yachtsmanbill]

Yer right Scrod. I was just figuring a spin or two on the starter to see if there was a dramatic increase in compression which I doubt anyway. A leakdown test with rings that bad should give you an indication at the oil filler plug or crankase vent line... but 35lbs ??
The way the numbers add up, it seems like the gen ran 10,000 hours without a shutdown. Now its all wore out and wont start. I still say valvitis.
I think after the gear goes back together, Im gonna lift the WB up on deck to go over it. I may need some fatherly advice. If its ok at least I'll be able to clean and paint it and the pad! ws

 

[Avenger]

35 lbs sounds like one of the slugs has gone missing. There's definitely something in the whole equation that doesn't add up. As stated earlier, if it was running before how did it suddenly get that bad? This is always the problem with "remote diagnosis" Unless you're actually there it's very hard to put all the details together.

Speaking of remote diagnosis, give a shout if you want to discuss the Westerbeast.

 

[Trojan]

Page one? A diesel mist coming out the valve cover vent? What was that all about? Bad rings or broken rings. Come on. Blow by at cranking speeds should not be. Won't fire on starting fluid. Come on! Sounds like a major repair. If you can't get it to pop on starting fluid and you have visual blow by at cranking speed. You have a major repair. The crank seal may have blown out from the excessive crank case pressure when the gen was running before shutdown. At running rpms it will probably run, but with a lot of blow by. At starting crank speeds it does not have enough compression to fire. Sounds kaput. Get out the wrenches and your wallet.


BILL