Deisel Engine poor running question

[MarkW]

Anyone want to take a shot at this before I call in the pro's at close to $100 an hour for what is probably a very simple problem.

Heres the problem with history.

Boat : Elite 32 sloop, with sing cyl Volvo MD5, raw water cooled. Purchased in fall 2002, not used tat year. Winterized as normal etc, engine fine all 2003 until ...

Last October, engine just died as we exitied marina channel, it was mid week so we just droped the hook and the boat yeard called us back in. I suspected filters, so chnaged both and reprimed system - engine seemed to run OK, did a couple of 15-20 runs with engine (out to poop dock etc) and also ran at varying engine speeds at dock for an hour - seemed OK.

May 2004 - running engine at dock, fast idle, running 20 minutes and it died. Pulled filters again seemed really clean, also drained fuel tank, scriubbed all growth from tank interior, filtered fuel going back in with the new WM filter funnel that practical sailor raves about, re-prinmed engine, ran hour plus at dock, seemed OK.

Mid May 2004- Day sailing around the bay, like to pop the motor on going under Mt Hope Brideg because the wind gets very fluky and the current can push you up againt the pier very easily, engine started to flutter, then with full throttle it would barely idle and then died, we sialed through the bridge without issue, went below, reprimed engine noticed that bleed screw was not holding vacuum, restarted engine ran it 30 minutes all way back to marina

Late May - tinkered at the dock, realized wasnt getting a good seal on the bleed screw, couldn't get new one but guy at de paul deisel (Portsmouth RI) recommended new gasket (washer) : 51c. Applied, still seem to have issue with getting this ti seal, but eventually got seal, ran engine 1 hour at dock again, no problems.

Yesterday (Sat 12 June), Grandma and 2 yr old daugher on board, engine died again when I was only 3/4 way out of marina channell, whipped out 100% of the 130 genoa and got out, reprimed again and it ran, then it died in under 10 minutes, couldnt get the engine to run reliably and would lose power. Ended up calling Sea Tow who had to come 30 minutes each direction to tow us the 1/2 mile back to the marina, yeah dont even ask ...

Guy who has a powerboat 2 slips down and is a mechanic (no deisel experience ) suggested air starvation and that I check the filter, I popped that off but it seems to pass air OK, I am going to clean it in some form of cleaner but beyond that I am at a loss,

as you can see from our marina layout I gotta have the motor running relliably :




especially if wife, nanna and baby ar going to come on board again, otherwise I have a floating summer house as far as they are concerned.


The marina charges an arm and a leg for mechanical work and would just love soemthing like this where they could oooh and aaaah for 4,5,6 hours before announcing I needed a widget or something

Now I feel I culd replace most parts on the engine, or address the issue provided it was short of a top/bottom end rebuild, so what do I do, change the entire filter housing,, suspect the fuel pump, something different to find air in the system ?, is it something with the air intake - or something else ?


and finally, how do I test this ?
Do I put additional lines on the boat at the dock and run it in gear under full power for an hour or so or something ????

Or do I just get my check book out and write a large check to Brewers ?

Mark

[dasein668]

The first thing I would do is check to see if you are leaking air into the fuel system somewhere, since it seems to be ok after you bleed and reprime the system. (Rereading I notice you say that the bleed screw wasnt' holding a vacuum?do you mean you were getting air into the fuel? Did you fix that and still have problems?) You may also have a pinhole or bad hose connection somewhere that is letting in just enough air to cause a problem after running for a while.

[Mark W]

What I was finding was that the engine "was losing its prime" - my words.

So I would reprime with the litle lever, 20-30 pumps, but the little screw wouldn't close down to a seal, if I kept pressuring the system with the little lever it would keep bubbling even when fully tightened. thats when I replaced the 'gasket' (what I call a washer).

My non deisel mechanic / IT brain says that the engine is not getting enough fuel to combust, even at full throttle. An engine needs deisel and air to work, so either no air (air filter blocked or the pipes going to the negine bay squashed by things in the lazarette )

or the air cant get out (blocked exhaust ?)

or not getting deisel (bad pump, air in the system...)



when you say hoses - you mean the copper pipes ? I havent seen any tru 'hoses', although I'll take another look next weekend. Million $ question is how would I find them ?

[bcooke]

Don't you just love engines?...

I don't know much about diesels but here goes. Are the engine failures truly random or is there a pattern? It sounds like you consistently get 20 minutes or so of good running before you have problems.

Fuel: If you had a fuel starvation problem I would expect to bleed some air directly from the injectors immediately after the engine quits running. I am not sure if you have checked for this first or if you went straight into troubleshooting the other parts of the fuel system first. I am assuming you have checked the fuel tank vent because from the symptoms you described it sounds like a classic case (in the gas engine world, not sure about diesels and their herculean fuel pumps). The fact that you get so much run time before failure makes me doubt that there could be other faults with the fuel system (low pressure, poor injector timing, failing fuel control...)

Air: As long as the intake hoses are clear, the inlet isn't blocked and the filter is realtively clean you should be okay.

Compression: Again, poor compression should rear its head immediately, not after 20-30 minutes. It is possible a valve could be sticking but that should produce a rough running engine and not an immediate stoppage I would think. Then again with a single cylinder engine it wouldn't have to stick long to cause a problem. I would expect it to start up again though. Sticking valves can be intermittent and frustrating to identify.

What sort of exhaust do you have? Any chance of water slowly building up in the exhaust causing the engine to "choke"? If the exhaust becomes excessively restricted it would reduce the air flow through the cylinders, leaving exhaust gasses and oxygen-depleted air in the combustion chambers.

You wouldn't have a low oil/high temp automatic cutoff switch would you? Silly question I know but that got me once before.

Before you write that big check to the marina you might check around for a good freelancing mechanic. The problem probably doesn't require the high overhead of a full maintenance shop.

It is true that maintenance facilities charge what seems to be outrageous amounts of money but in their defence I need to add that maintenance is an expensive buisiness to be in. The overhead expenses such as facilities, tools, publications, inventory, permanent staff and staff training/re-training have to be paid for regardless of the amount of work in the shop. Machines are only convenient, cheap and easy until they start to wear out. All machines wear out.

I don't think I helped much. Are there any real mechanics out there?

-Britton

[Mark W]

Fuel tank vent ???
Hm, thinking about it (I know I have half tank of fule or half tank of air) so could it be sucking that air till it cant expand it any more but thn between when I restart its re-compressed or whatever), Hmmmmm

and no - feel dumb-a** now coz I didnt check that (not sure I even know where the vent goes !

Thanks

start creating a list for next weekend

and ideas on testing ? boat under load at the dock ?

[Tim]

Before calling in the big dogs, check the following "simple" things:

1. Ensure (ensure!! ) that all aspects of your fuel supply are sound, and that there is no possibility (NO possibility) of air entering the system anywhere. Your problematic bleed screw or pump lever with the gasket sounds like the first thing to check--and deal with, it sounds like--but check all connections.

It takes very little for an older diesel, in particular, to become airbound--though sometimes under varying circumstances. It sounds like you have annealed copper fuel lines, which are less likely to have failures than hose, but you need to check them carefully, and check all of the flare nut or compression connection fittings. You may have short lengths of hose somewhere in the system also: all you can do is trace the whole thing out. Better you than some monkey at $100/hour! Hoses, if you have them, can leak at the clamps, or may even become semi-permeable with age. If it's in question, whatever it is, replace it, and thereby eliminate it from the "possible" list.

Air is the first killer of a diesel engine fuel system. You must ensure that no air is getting in. This is always the first thing to check, followed closely by fuel filters for debris or water.

2. Yes--do check out your fuel tank vent system as well. It is possible that some weirdness here could create the sort of fuel starvation/air invasion symptoms you seem to be describing. Be sure to check the hull fitting for clogging corrosion in the screens, too.

3. If you find no signs of air entering the fuel supply, check out your exhaust elbow. These tend to carbon up over time, and the back pressure can cause problems or inconsistent running. Check out the whole exhaust system whie you're at it, just to ensure you have no kinks or obvious issues.

These first three issues are simple to check, and should be eliminated first. (OK, checking the elbow can be a little challenging...and probably isn't the problem in this instance. Still...) Now, we move on to more complicated issues.

4. You describe manually priming the fuel pump continually when you experience this problem. It's very possible that your pump is not operating correctly, and therefore your engine runs only on the small amount of fuel in the lines and filters and then dies once that supply is exhausted. If you eliminate issues #1-3 above, then checking out the pump more thoroughly might be in order. Replacement pumps shouldn't be too bad, cost-wise, and their installation should not be difficult. If you have inclinations to do this sort of thing yourself, now and going forward, then consider getting the service manual for your engine model. And a parts listing, too. The pump is mechanical and pretty rudimentary, but they do fail.

5. Another possibility is your high-pressure fuel pump. This is the precisely-metered pump that delivers fuel to your injectors in the correct quantity and at the correct time. They do fail, though not frequently. I had this problem with that POS Yanmar SB12 that I had. It took forever to troubleshoot. This is time to call in the experts, if you think this might be the problem.

The overhead expenses such as facilities, tools, publications, inventory, permanent staff and staff training/re-training have to be paid for regardless of the amount of work in the shop.

And don't forget one of the highest costs of being in business today: insurance! Both for the facility, the worker's health, and, of course, liability in today's lovely litigeous society.

All the more reason to take matters into your own hands, roll up your sleeves, and get to know your diesel inside and out. They are pretty simple machines, but are still daunting to the unitiated. But there is no better way to learn than to simply do.

The above are simple possibilities and ideas, and I have surely left some things out. I hope the ideas get you started in at least something of the right direction!

Good luck!

[bcooke]

there is no better way to learn than to simply do

A true life lesson here. Reading the maintenance manual like the bible helps. I have a copy of Nigel Calder's diesel engine book but I really can't recomend it because I never got around to reading it. It is still on my to-do list as it was recomended to me.

Better you than some monkey at $100/hour!

Who are you calling a monkey!

-Britton

[MarkW]

STUPID !

Sorry, no other word for it - however I do condition that with a big "MAY" versus "HAVE"

I still suspected that bleed screw, but when I got to the boat today I began checking all the connections, one was a tiny bit loose up between the coarse filter and the pump but only a 1/4 turn or so.

I removed the 'fine' filter (the one on the block) and it was almost empty, maybe 1/4" or so of deisel in the bottom. Now I think that the pump is downstream of this, right ? Keeping this under so much pressure that it feeds the injectors ???

So has the pump been pushing air into this filter or (as I suspect) did dumbkoff boat owner (me) forget to fill the filter with deisel when he changed it and the boat has been running on fumes and whats manually primed into that filter.

Does this cause explain my symptoms ?

Anyway, I filled (to the brim) the filter with deisel, filed down the mating surface for the washer on the bleed screw (it was pitted and thus not sealing weel), reconnected it all, primed it until I had pure desiel shooting up from the bleed screw hole, reinsserted the screw and primed again and then ran the engine for 2 hrs 15 minutes at the dock, half of that being with the transmission engaed at varying throttle settings, straining the dock lines - she didnt miss a beat.

So is this just luck ??? have I overlooked something, is there anything else that would cause that filter to empty like that other than being left empty to start with ?

Tell me I'm a fool if u like

either way, I have secured the services of a marine mechanic who armed with my complete tale as told to you and access to the boat should be able to tell me whether this is the cause or if there is more, all for 2 hours of his time (hopefully no more)

Mark

[Tim]

I don't know for sure whether you've licked the problem or not--I guess only time will truly tell, but I can say that it takes only the smallest air leak in diesel engines (and some are more picky than others) to screw up the whole fuel system. The system really does need to be absolutely air-tight.

With a properly-operating fuel system, the secondary filter should fill itself as you prime the system. You can certainly reduce the amount of priming needed at any given time by filling the filter with fuel first, which you just did. But the priming lever on the pump would fill it also--it would just take more pumping.

If you had a bad seal on the bleed screw, that could certainly account for the fact that no amount of pumping or priming would fill the filter bowl the whole way with fuel. This filter bowl, under normal conditions, should always be full when you open it.

I think what might have been happening, as you suspect, was that the filter could not seal properly at the bleed screw, thereby allowing air into the system. When you manually primed the lever, you added fuel to the filter, which then allowed the fuel system downstream of that to operate temporarily. When that small fuel supply was exhausted, the engine would become airbound and stop. Repriming and bleeding would restore operation temporarily.

Keep your eye on that screw. I stripped out the bleed screw in my new Yanmar the second season I had it (from overzealous tightening), and no amount of hoping or coaxing would get the engine to run; I had to replace the whole filter housing, since the female threads were trashed; new bleed screws would not work. If you keep having these problems, I would replace that screw and washer before doing anything else. I keep a few in stock for my engine.

I hope you've got it! Good luck. Thanks for the update.