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Old 05-27-2012, 08:53 PM   #1
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Diagnosis Game

Ok, just for fun, let's see how quick you guys can be to solve a problem that stumped me for a while (most of them do), though I finally figured it out and the engine is running great now.

My port engine would not come up to full power, it was stopping at about 1650 rpm, WOT is normally about 2350 rpm.

Here is the background. I want to give you all I know, because some of it led me down the wrong track for a while.

Perkins 4-236. Velvet Drive Transmission.

A few months back my son accidentally put water in the fuel tank on that side when he was supposed to be filling the water tanks. I pumped down until I got clean fuel, then ran a portable polishing system on it for 18 hours. It picked up maybe 1 oz of water.

After hurricane Dennis in 2005 I had that strut, shaft and prop replaced. It has always been a little tougher to turn, I've had both the engine and the strut aligned twice, but I'm still not wild about the alignment, that stuffing box needs attention a lot more than the STB one does.

No black smoke. The engine is not overheating.

Prop is clean.

The STB throttle has always not quite aligned with the port when both engines are running at the same speed.

Rather than telling you up front all the trouble shooting stuff, which would give it away, ask me questions and I will tell you if I did it, and the results.

Doug
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Old 05-27-2012, 09:55 PM   #2
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did you get injectors cleaned or replaced after the water?
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Old 05-27-2012, 10:05 PM   #3
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First thought is that when you re-propped there was too much pitch, but that would presumably have produced black smoke. Plus, you didn't say when the RPM limitation started but the implication was that everything was fine until you waterwashed your port fuel system.
I'm inclined to think it has something to do with your tank vent.
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Old 05-27-2012, 11:19 PM   #4
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Did you change the fuel filters? Did you check the fuel pick up tube?
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Old 05-28-2012, 12:51 AM   #5
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If you disconnected the portside Morse cable at the injector pump and ran the pump from the engine room would it go to full throttle?
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Old 05-28-2012, 07:44 AM   #6
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I did not clean or replace the injectors, but I can tell you that is not what it was. Good guess though.
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Old 05-28-2012, 07:49 AM   #7
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Conrad, I re-propped in 2005, the problem just started. Along those lines though, I wondered about a bearing freezing up, maybe from some sort of alignment issue. I think that shaft is still too tight at the strut, even though my mechanic says it is not. I dove under the boat and while standing on the bottom (in 4.5 feet of water) flexed the shaft as hard as I could to check the cutlass bearing. No movement.

I didn't check the tank vent, but that is a good thought, I've had that issue happen with OB's.
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Old 05-28-2012, 07:59 AM   #8
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Hop,

This was my one of my first thoughts as well. The on engine filters on my boat are hard to change and expensive, so my primaries are Racor 900's and I run 3 micron elements. Since the tank watering I have been paying very close attention to the racor. I changed the element on that side even though very little water made it through to the filter. I checked it and it was squeaky clean.

Next, I checked the on engine filter. It was perfectly clean as well. I also pulled the lift pump apart and checked the screen, also clean.
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Old 05-28-2012, 08:07 AM   #9
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Bob,

Over the years, I've had a few cable issues, namely they tend to pop loose from the retainer. So the first thing I did was inspect the cables, and confirmed that they were moving through the full range. They were.

After all the other things, I went back to the cables and disconnected them. Then I revved up the engine from the engine room.

The nut on the throttle lever on the injector pump had somehow worked itself very loose so the throttle was not engaging completely. I tightened it up, and BINGO! the engine ran great.

Nice guess, you got it way before me.

Doug
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Old 05-28-2012, 08:12 AM   #10
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Game over, bob wins....
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Old 05-28-2012, 08:59 AM   #11
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Quote:
Game over, bob wins....
There should be a prize.
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Old 05-28-2012, 09:29 AM   #12
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Quote:
Originally Posted by Dougcole View Post
Bob,
Nice guess, you got it way before me.

Doug
This is precisely the problem that I see over and over again on a variety of internet forums. It had nothing to do with a guess. You can flail about wildly dreaming up possible solutions to problems and apparently that is how a lot of the world does "troubleshooting". That's like you going to your doctor and saying "I don't feel too good" and he immediately lays you out on the floor, cuts your chest open and checks to see if your heart is OK.

You need to learn how to break problems down and rule out possiblities. You don't start into a problem with a theory that immediately requires massive disassembly or intervention. The point of my question was not to suggest there was something wrong with the linkage or the injector pump - rather it was to isolate the problem to either the control linkage or the engine itself. I'm glad you found your problem but I think you need to work on your process.
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Old 05-28-2012, 10:52 AM   #13
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So true, Bob, and I would not disagree with you about my sometimes random troubleshooting techniques. But in this case it is precisely the backgound info that made it difficult, and also why sometimes it is easier for others to work on our boats. They are not encumbered by all that they know, they can zero in on one single thing.

I knew about the water in the tank on that side, I, just like Hopkins carter, was highly suspicious of water in the fuel system somewhere.

I knew that that shaft turns siffley and the alignment on that motor may be less than perfect. Lending suspicion on the running gear that you may not have had.

I also, more than once, have had a specific cable issue on that side, which can be fixed without removing the cables, that was the first thing that I checked, when it wasn't that, I stopped looking at the cables but came back to them eventually.

You are being a little harsh with the heart analogy. I read through the Nigel Calder troubleshooting guide and it could be read to suggest that the engine was starting to bind. I didn't tear it open, I knew that was likely not the case because it was not overheating or smoking.

Anyway, my point is that tons of info can sometimes make troubleshooting harder, not easier, and that is what was interesting about this case.

Bob, shoot me a PM and I will give you a code for a free pair of Keen shoes as a prize.

Doug
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Old 05-28-2012, 10:54 AM   #14
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Greetings,
Yup, couldn't agree more about troubleshooting. Start with the easiest and cheapest checks first. Once you've eliminated all the "possibles" the "impossibles" become more obvious.
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Old 05-28-2012, 11:04 AM   #15
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Doug,
Good game! I enjoyed that. I went to the fuel system first because in my past experience, with a slow running diesel, it has always been a fuel problem.
Nice job Bob, I think we all learned something.
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Old 05-28-2012, 11:32 AM   #16
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I agree, Bob hit it really well.

To further my point on trouble shooting, in a way we are all victims of our own knowledge base.

Bob even did it a little in this thread. I think that he assumed that checking the prop and the cutlass bearing were a lot harder than they were. He lives in an area where most boaters seldom ever A. anchor in 4 1/2 feet of water or B. go into the water without some serious gear.

I was anchored for the night behind Tilloo Cay in the Bahamas sitting on the swim platform in my board shorts watching the kids swim. I slipped on a mask, dove over the side, looked at the prop and flexed the shaft. It was more pleasant and easier than opening up the hot engine room and looking at the cables.

And yeah, like Robert Earl Keen says, "it's the little things...the itty bitty things that P--- me off."
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Old 05-28-2012, 12:01 PM   #17
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Great exercise, and I'm sure we all learned from it!

Next scenario?
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Old 05-28-2012, 12:31 PM   #18
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Ok, here is another one, that happened a year or so ago.

I had my boat delivered from our marina up here is N. Florida to my brother's dock in Fort Myers by a delivery skipper (he was awful, but that is another story). It's about a 40 hour trip. The boat ran fine all the way (he never shut it off) but when he pulled into the dock the port engine stalled and would not restart.

As it so happened my brother's mechanic (Bill has a 40' Ocean with twin Volvos) was at the dock just finishing up Bill's boat.

He took a look at it and found a loose bleed screw on the on engine FF. He tightened it and bled it but the engine would not restart.

He called and told me that I had a bad injector or a failed injector pump. He was wrong. What was it?

Fire away with questions.
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Old 05-28-2012, 02:42 PM   #19
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I ass/u/me that model of Perkins is a mechanical diesel. If so it is fundamentally the simplest machine known - if it has fuel and turns over it has to run, barring some catastrophic internal failure.

So you start at the fuel tanks and work your way toward the injectors:
- is there fuel in the tanks?
- is there fuel at the lift pump? If not then you suspect filters, hoses, valves
- is there fuel delivered under pressure from the lift pump to the injector pump? If not you suspect the lift pump or any intervening filters
- have you properly bled the injector pump? On my Lehmans it doesn't matter what you do, if you miss the precise two bleed screws on the pump then no joy
- I've seen engines where you had to bleed the actual injectors to get it going but if you have fuel delivered under pressure to the injectors and it still isn't running then you have big problems.
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Old 05-28-2012, 03:52 PM   #20
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He got on the phone and asked me how to bleed the system, I walked him through it step by step. Engine would turn over but not start. At that point he told me it was an injector or the pump.

Yes, they are mechanical, and naturally aspirated, so simple even I can work on them.

A hint: This mechanic is used to working on much more complex engines, he has a bit of an ego about that.
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