How about some diesel advice from the experts?

[RAD]

On my way to the beach for the weekend I noticed the tach going nuts but no change in engine rpm so I throttle back and all is happy and made a note to look into this, then when I was under way back from the beach today when I hit a small wake the engine rpms raced up for a second then went back to the 2k I had it set for this continued every once in a while I encountered a small wake, I tried lowering the rpm's to see if there was a difference but it did the same
Over the summer I refitted the engine (1978 Westerbeke W30) fuel filter with a spin on type and this same problem showed up after a 12 hour run so I removed it and put the old system back on and all was good until now.
I'm confused to why the tach was going nuts yesterday and whats causing the engine to act up
My thoughts are something with one of the 4 ejectors or the pump and that it had nothing to do with the filter change out or I was letting air get into the system and it came back. The off the wall thought is maybe the alternator is acting up and causing the engine to work harder....again thats an off the wall thought but I had to throw it out there
Any one ever have the same or similar experience?

 

[patrickfarley]

Re: diesel advice from the experts

Sounds like the beginnings of the metering valve in your IP. I only have experience with land based diesels. My experience is based on working on my own and friends diesels.
I had a similar problem with my suburban. The engine would race up under different loads and almost out of control under no load. It happened slowly over time. At first I thought I had forgotten to replace the fuel filter during the last maintenance. Then I checked the electric fuel feed pump. Then I replaced the filter again and made sure there was no air in the line. It would work fine for a time and then start again. Near the end it was just bad. It got really bad when it was cold outside. I replaced the IP and it ran better than new.

 

[Tom J]

Re: diesel advice from the experts

Initially, you said the tach increased with no change in engine rpm's. If this is the case, I've had a similar problem with my Catalina 310. I was able to cure this issue by removing the tach and carefully turning the calibration screw one way and then the other, and returning it to its original position. Apparently the potentiometer builds up oxidation on its contacts, and swiping the contacts helps clean them.

 

[weinie]

Re: diesel advice from the experts

My tach was doing the same thing. Replaced it and updated the rest of the gauges to match. Now it looks pretty and problem solved.

 

[Ralph Johnstone]

On my way to the beach for the weekend I noticed the tach going nuts but no change in engine rpm so I throttle back and all is happy

If this is the case, your tach is probably the cause of the wild fluctuations (barring any corroded contacts). If so, it needs replacing. Might just be able to do it for under $100.00 if you shop around.

http://forums.sbo.sailboatowners.com/showthread.php?p=896626&highlight=tach

 

[AXEL]

My tach acts up once in a while, the needle jumping around all over, then it settles down. It was doing it more the past several seasons then this year. It has no effect on the way the engine was running. I did have the alternator rebuilt last year after a lightening hit. If your engine rpms go up and down it could be a fuel filter. You'll see it more at higher cruising speeds where there is more demand for fuel. If the tach fluctuates without effecting the actual engine rpms it’s probably the tach or a connection to the tach. Sorry I missed you guys at the beach this weekend. LaurieJean.

 

[RAD]

But what is strange is the fact that the tach went psycho on me without any engine rpm change but maybe I didn't hear it....and the fuel filters are new with the primary having a vacuum gauge on it and its at 1 or 2 but close enough to 0 to being clogged so I'm thinking what Patrick posted about the injector pump

 

[AXEL]

If the tach goes psycho and the engine rpms are not changing it's not the engine or fuel componets, I'd say it's the tach and related path. You have to determine if the engine's rpms are changing with the tach. Like I said I had the same problem, tach goes wild, all over the place, engine remains steady as a rock at 2800 rpms. Tach settles down after a while. Problem eventually goes away on it's own. That's my experience.

 

[FastOlson]

Many (most?) of these sailboat diesels have a factory wiring harness with a multi-pin plug located towards one end. This makes the original install go a lot faster.
However, after time and exposure to sea air, it is common to find some corrosion inside that plug. That connection is likely well-taped, and it often lasts for decades without problems...
Sometimes less!

So, DO confirm every wire connection from panel to engine component. Remove each end, one by one, clean up and re-tighten.
If possible (and safe) , have someone move/jiggle that connector while engine is running and you watch that tach.

While instruments can fail, more often it's the simpler matter of voltage drops or temporary open circuits.

 

[anchorclanker]

But what is strange is the fact that the tach went psycho on me without any engine rpm change but maybe I didn't hear it

You should not only hear it, you should feel it. Even a 50 rpm change in engine speed should be quite noticeable to both sound and touch. If your seeing a bounce at the tach and the engine is remaining steady and smooth, you can quit looking at the engine. Its either a failing tach, a failing sender (alternator?), or an intermittent wiring problem. Worse yet, though quite rare, would be intermittent failures of two or all three components you could pull your hair out trying to solve. Nothing worse than an intermittent tach wire connection to a wonky tach. You did say you had a lightning strike, it could have done damage you havnt yet found.

 

[Joe2954]

My tach (VDO) has a couple times gone nuts - maxing out or bouncing up and down. On those occasions, after I kill the engine and start up again it seems to cure itself.
Last winter the engine hour readout went away. i installed a separate hourmeter. Then when it dried out in the spring the tach hourmeter came back. Moisture, contacts, loose connection on the alternator or sender.

 

[patrickfarley]

Is it just the tach that is moving or is the engine racing unexpectedly?
If it is just the tach disregard what I said before.
My diesel has a rotation sensor on the crank, wires, connections and the tach itself. If it is just the tach you can check those.

 

[Stu Jackson]

Listen to anchorclanker and Fast Olsen. It's the tach and/or the wiring harness. Maine Sail and I and Fast Olsen and many others have been warning about the fire hazard of the old harness connections for many, many years. Our C34 website is down for maintenance, so do a search here for "wiring harness" by "Maine Sail" and check what you have one your boat. Check the connections at the back of the alternator, too.

Good luck.

 

[RAD]

Is it just the tach that is moving or is the engine racing unexpectedly?
If it is just the tach disregard what I said before.
My diesel has a rotation sensor on the crank, wires, connections and the tach itself. If it is just the tach you can check those.

Engine racing for a few seconds then getting back to normal rpms and it seems to do this when a load is applied like turning the wheel or hitting a wake......when I first saw the tach going nuts for the first time I was paying attention to the engine to see if the rpms were racing and it wasn't but later it was thats why I'm confused cause having a fuel and a tach issue at the same time seems a little too weird, my tach comes from the alternator via the AC terminals......I have to pull the cover off the engine from under a galley sink to access the front of the engine so its not such an easy task but on my to do list within the next few weeks and I'll check all connections and the alternator,belt....etc

 

[anchorclanker]

If the engine momentarily races, the prop could be sucking air (ventilating) when you hit a wake etc. The governor can allow the engine to loft momentarily before it catches it, its not necessarily abnormal.

Odd that it would do it turning the rudder but it could. Perhaps you have a funky or damaged prop, or something disturbing water flow ahead of the prop, etc..

Another possibility is a slipping shaft connection such as a bad key, keyway, loose prop etc., that lets go momentarily under heavy loads.

 

[RAD]

OK here's a stupid question......wait there's no such thing as a stupid question....any way here goes
if the tach wires going to the alternator become loose for a second would the alternator work harder thus putting a load on the engine and then it would race or the alternator works less for second and the engine race's

 

[Bill Roosa]

Hey Rad
The tack wires have nothing to do with alternator output. It is the regulator that controls output of the alternator. Assuming an external regulator, the tack and rotor field wires are commonly right next to each other as they go into the alternator. if the rotor field wire (other end goes to the regulator) comes loose the alternator will not produce squat as the rotor field is what makes the magnetic field that causes the alternator to produce power
The loss of rotor field current would cause the alternator to stop producing and unload the engine causing a RPM increase on the order of 1-2 HP. I'd not call that a "race" but if the engine is only 10 HP that could be possible.

 

[Stu Jackson]

Rad, I agree with Bill. I turned our alternator's regulator off while we were motoring today. The A was outputting 25-30A at the time, 100A alternator, external regulator on our M25 21 hp. No difference in engine performance. None. NOT "no appreciable" --- NO difference.

The tach is an OUTPUT not an input. It could come off the alternator and all you'd see is nothing on your tach. That's all.

 

[Stu Jackson]

Here's the wiring harness connector stuff, perhaps you know about it already.

http://c34.org/bbs/index.php/topic,5078.msg35943.html#msg35943

Maine Sail also did one in his Musings.

 

[Chris Patterson]

While I haven't had any problems with this plug yet, I decided to investigate it after reading Maine Sail's article about it.

This was a while back, but I did now WANT any problems either.

And while this is not the "correct" marine crimp for this, it's better than what was there, and I intend to do something else later..