Topic: Diesel Engine trouble-shooting

Hi guys,
I'm looking for some generic diesel engine trouble shooting.  If you have experience with the Farymann K34, then all the better.

The back story is that my trusty engine stalled on my while exiting Port Dalhousie last weekend.  I haven't had a chance to look at anything (almost anything) yet and want to use my time wisely trouble shooting.

- Leaving port, the engine struggled for a second or two, I looked down as the oil pressure suddenly dropped from its cold 60psi to 0psi.  Both warning lights came on.
- Later, i started the engine and ran it for 30 minutes.  It sounded like it was labouring slightly.  Only I might notice it was not quite as free as it normally is.
- Upon arriving in Etobicoke, the I started the engine for less than 5 minutes to get me into the slip.  Our green warning light came on and flickered... this is new, never seen it on before.
- My temperature gauge has not moved... either broken or the engine is not warm yet; Both are quite possible.

Trouble shooting steps
- Pull the fuel filter and check for grunge.  Check the fuel for bacteria growth.  (I have not done this yet)
- Look for water coming out of the exhaust.
- Check the cooling impeller to make sure it is free, clear and all fins are intact.  (I did this yesterday.  All looks well.)
- Check oil level.  (I did this yesterday and it is at the full line with no outward signs of leaks on the engine.)

I'm not sure what the green warning light is.  It's either charging light or temperature.  Anyone know to what it could be connected?

What other steps should I take before I seek the advice from a professional?


2 (edited by Ian Malcolm 2012-08-12 12:17:06)

Re: Diesel Engine trouble-shooting

Is the oil pressure gauge electric or mechanical?  A sudden brief drop of pressure on a mechanical gauge is extremely serious and may indicate a blocked oil-way or oil pickup.  OTOH on the far more common electrical gauges, it is far more likely to be due to a loose connection somewhere or other electrical supply problem.

I suspect you may be having alternator issues - e.g. a diode in its rectifier shorted and it briefly presented a very high load to the engine until the regulator cut back the field.

Remove the belt, check the alternator turns freely by hand,  identify the charge indicator light on the panel and turn on the engine 'ignition' keyswitch but don't start the engine. 

Connect a digital voltmeter to the battery terminals.  It should read around 12 to 13V depending on the state of charge.  The charge indicator light should be on steady.

Spin the alternator at around 2400 RPM with a socket and an adaptor chucked in a drill.  You need a high power drill and it will tend to bog down so don't run it for long or you will burn the drill out and DON'T let the socket slip on the nut.   The charge indicator light should go out and stay out as long as the alternator is spinning fast enough. If it flickers rhyhmically, you have a failed diode or burnt up stator coil.  If it stays on, its probably bad brushes or a failed regulator and if it flickers erratically its bad brushes or a burnt up slip ring. 

If its good you should see the battery terminal voltage rise at least half a volt, and if it is well charged it should settle around 14V.   If you have a suitable ammeter you can also check the charging current. (i.e. with a DC clamp on one round the alternator output lead - usually a thick lead on a stud terminal, or round one of the battery leads.  Most cheap clamp on meters don't have DC current ranges)

You can follow similar procedures to check the alternator with the belt in place using the engine itself to spin it, but if I were you, I'd want to know if I had an engine problem or an alternator problem before running the engine again.

In all cases, if the alternator appears to be faulty, unless you are an electrical geek, isolate the battery, remove the alternator and take it to a specialist automotive alternator shop.   If you need to reconnect the battery while the alternator is off, you MUST securely insulate the bare end of the output lead.

If you are a real geek, brush and regulator replacement is fairly simple, or even fitting a replacement diode plate.   I'd leave slip-rings or bearings to the shop . . .

Re: Diesel Engine trouble-shooting

Thank you Ian.  I'm hoping it's not electrical, but you have provided some much needed suggestions in that area.

FWIW, the "sudden drop" in oil pressure appears to have been due to the engine stalling.  Obviously without the engine turning, the oil pressure pump wasn't turning and did not create pressure.  The mechanical oil pressure gauge, I believe, is functioning and accurate.

The green warning light is the one that concerns me.  If I read your post correctly, you believe this is the "charge indicator light" (and not related to temperature).  I am going to go to the boat and see where this is connected;  Would the charge indicator light be connected to the regulator or the engine itself?

Re: Diesel Engine trouble-shooting

The charge indicator warning light connects between the main switched positive in the engine control panel and the junction of the auxiliary diodes in the alternator that provides the field supply to the internal (or external) regulator.  It usually provides the initial excitation current for the field.

In simple terms, if you trace it down the loom it should go to the alternator or just possibly to an external regulator if you have one.

If it goes to a sensor anywhere on the engine block its either oil pressure, temperature or water temperature, but those are not very likely to fail in a way that makes it flicker and even less likely to have coincidentally failed immediately after the engine has unexpectedly stalled.

Simplest test is pull the multiplug at the back of the alternator (if your alternator has one, if its wires on individual terminals you will have to trace it the hard way) and turn the switch on.  The light should then be out and stay out even if you start the engine.  Don't forget the battery wont be charging . . .

If I were you, I'd hope it *IS* an electrical fault as that is a cheap and easy DIY fix compared to the mechanical possibilities.

If it *IS* a failed alternator, check for loose connections and broken wires that are just hanging in place (tug each one) on the high current cabling between both battery terminals and the engine and also on the alternator output cable and inspect the battery switch carefully, testing its contacts for continuity while thumping the bulkhead next to it to simulate engine vibration as by FAR the commonest cause of alternator diode failure is the output circuit going open circuit, even momentarily under load while the engine is running.  IF there is a wiring problem you need to fix it before installing the repaired alternator.

One more possibility is that the alternator belt is badly worn or the belt tension adjustment has slipped, or some debris dropped into the belt as if the belt rode up onto the pulley edge it could have enough leverage to stall a slow running or idling engine, then drop  back into the pulley groove as the engine stopped. This can leave the belt loose enough for it to slip and cause the warning light to flicker.  However you would normally hear something, probably a thud as the belt tried to jump the groove and a lot of rattling (belt slap) or squealing when you ran the engine again.  It *might* be fairly quiet at low revs. BTDTGTTS

Re: Diesel Engine trouble-shooting

I'm on the boat as I type this.
After sitting for a week, after having the battery used for radio and wind instruments on our last trip with no recharge, the battery sits idle at around 12.15V.

I started the engine and ran it at idle and the battery reads 12.4V
Under load (tied to dock and in forward gear) at about half-revs (no tach), the battery continues to read 12.4V
Under full load (tied to dock, in gear) at full throttle, the battery reads 13.9V
In all cases, the green light is flickering.

On the cooling side of things, I have checked the impeller and it is still looking brand new (only has about 6 hours on it).  There is water being evacuated through the exhaust as per normal.

I like your theory that it is a high-load on the engine; Like I said, it sounds like the diesel is labouring.  I think I will check the fuel filter first though.

Re: Diesel Engine trouble-shooting

Well... the fuel in the filter cup seemed clear with the exception of half a teaspoon of water.  Which I emptied and replaced the filter.  I was having a hard time bleeding the fuel line though so I took off the fuel filter intake hose.

This is the part I hate...  I tried to syphon fuel from the tank and it turned out to be really difficult to pull the fuel and wouldn't continue the syphon once started.  Hmph.  I then blew as hard as I could and blew some bubbles in the fuel tank.  After that, no problem with the syphon.

I would say that implies the problem was a clogged fuel intake and further makes me think this problem will happen again.  *sigh*

Is there an easy way to clean a fuel tank??  The closest thing I have to an inspection hatch is the fuel filler hole and I can't see much in there, and it is impossible to reach in to clean.  Ideas?

7 (edited by Ian Malcolm 2012-08-13 12:23:03)

Re: Diesel Engine trouble-shooting

I am suspicious of apparently unrelated faults.  Was the water much rougher than usual coming out of the marina that day?

To get my tank clean inside, I had to remove it, drain it, fill it with boiling water, detergent and a carefully counted handful of gravel (so I could be certain I had got it all out afterwards)  and agitate vigorously.   Anything less is a sub-standard job.

If you are lucky you may have a gauze screen on the end of the fuel pick-up tube that is blocking up.  If  so and it can be removed, a fuel polishing company *MAY* be able to do a good  enough job of cleaning the tank itself in situ.

Before suspecting a blocked pickup however, DO check for a blocked vent.  The symptoms are somewhat similar but the fuel starvation is slower to occur and can persist for quite some time after shutdown but still fix itself if left for long enough. loosening the filler cap provides an instant improvement.   A blocked pickup either clears itself when the engine shuts down if due to floating debris or remains blocked and is NOT improved by loosening the filler.  I  believe some parts of N. America have populations of 'mud dauber' wasps that build individual nests in holes in broken off hollow twigs and stems or any other similar tubes they can find - i.e. your vent pipe.

Re: Diesel Engine trouble-shooting

We've been through some rough weather this spring;  In June, we pummelled through 8' waves to get out of Toronto harbour, but the remainder of the summer has been reasonably calm.  Exiting Port Dalhousie, when the problem occurred was very rough - 24 hours of north wind had caused a large swell that was working against the 2-4knot current leaving Port Dalhousie.  It was both choppy and reflecting off the breakwalls of the channel.  I can see how that would have stirred up any yuck in the tank and clocked the intake screen.

It was very evident that something was blocking the fuel intake / tank outlet as I was sucking on the hose quite hard to get any sort of flow.

As for the vent, yes, the thought crossed my mind, but while I was testing the syphon, I had the fuel filler hose removed from the tank as I had tried to peer inside.  That, alone, vented the tank with a 1.5"-ish (maybe 2"?) hole.

I have run the engine now for an hour.  The engine plugged away with no signs of problem.  However, the green charging light is still coming on at lower RPM.  I think I will have to trouble shoot that as a second issue.

Re: Diesel Engine trouble-shooting

Well, really rough conditions could cause a plugged pickup and, if there was a loose connection somewhere, also cause alternator problems. 

You certainly have debris in the tank that needs dealing with. How mucky was the filter?  If its not full of gunk, it may just be a case of getting the tank as empty as possible using an oil removal pump to get the last of it, and running all the fuel from the tank through a filter funnel before returning it to the tank.  I would also add a shock dose of biocide and keep a good supply of spare filters aboard.   If it was really nasty, either you need to remove the tank for cleaning or get a specialist in to do it in-situ.     

Assuming your belt is not slipping, it looks like you also have an alternator problem.

Re: Diesel Engine trouble-shooting

We were discussing ways to clean out the tank.  I think it goes beyond just cleaning as I suspect that it may be a little rust in the tank... 35 year old steel tank + marine environment = likely rust, yes?  A friend suggested I swish a magnet to gather up any metallic junk as well. Instead of messing with that, I'm thinking of getting a magnet to put on the outside of the tank after I drain it.  I hope this will capture any loose metal particles that may be slopping around in there in the future.

I like your idea of using the oil sucker to empty the tank.  I'll have to see if I can pick one of those up.

Re: Diesel Engine trouble-shooting

Only worry is that the magnet might have an impact in the compass?

Re: Diesel Engine trouble-shooting

I think it's sufficiently far away from the compass, and we're not talking a giant magnet here.  Just something to keep the metal flakes from floating around.

Speaking of which... I installed my new instruments the other day.  *sigh* The wind sense packs interfere with VHF operation.  The field is so strong that even at the very stern of the boat, my handheld radio is inoperable while the wind instrument is on.  I'll post that in another thread...

Re: Diesel Engine trouble-shooting