Diesel engine question

sailaway78 · Feb 24, 2009

Hard to start diesel

Not much that can go wrong with one of these. You said you hand cranked it and have compression. Since you smell fuel, I would look for a fuel leak. May not be enough to be the actual cause of it not starting, but a very small leak, before the lift pump, will allow it to suck a little air into the line, and I can tell you from experience the Yanmars are very intolerant of any air. Have you checked the fuel filters. I would start by checking/replacing the fuel filters, and bleed the system.

MafaldaII · Feb 24, 2009

Please don't use starting fluid....

You can do some damage with starting fluid in these engine.
How are your batteries? Are the starter revs fast enough? If you can smell diesel its not a good sign, check for leaks. Did you check the filters?

Chuckbear · Feb 24, 2009

Actually there are a number of issues that can go wrong and without being on the boat and checking it will be hard to tell. Injectors can go bad and so can injector pumps. You smell fuel, well you really should not. The fuel pump itself could be bad or your fuel filters could be clogged, when were they changed last? You could have bad fuel or you might have a loose connection in the system somewhere that is sucking air. This can easily happen without leaking fuel. NEVER use starting fluid on the engine.

Deadline · Feb 24, 2009

Not clear if it's a starter problem or an engine problem.

If starter, check all leads for corrosion and tight fittings, including the battery and the main line going to the base of the engine. Or it could be a defective button.

If it cranks but doesn't catch, be sure the raw water intake is closed so you don't flood the engine with water. Then check the Archives here for tips.

Hermit Scott · Feb 24, 2009

You can use WD-40 to start diesels but again as others have said never use ether. Gas engine's compression ratio is like 9:1 diesels are like 20:1. That's why diesel will burn in one and not the other. I believe the reason you can't use straating fluid is it gets too hot and will melt rings or likely burn a valve seat .
If you smell fuel, look for a leak on the high pressure line running from the injection pump.
You can spray WD40 in the air intake and it should run while you are spraying it and when you stop it should die, IF fuel is not being pumped through the injector.
Do you have a YSE or YSM?

Stu Jackson · Feb 24, 2009

And the Candidates are...

1. Your ground wiring to the engine and other wiring, primarily CONNECTIONS. When the wires get hot they conduct less.

2. Fuel

3. Air

Those are the ONLY 3 things a diesel engine needs to start. Other comments are very appropriate.

Don't run your engine at the dock for 30 minutes - it usually won't get hot enough to burn out the carbon and moisture. You've probably heard this all before...like on another thread today.

kloudie1 · Feb 24, 2009

Is the "stop" lever down on the engine loose from the pull knob cable and still in the "stop" position from your last shutdown? It would be strange for it to be running fine and then not start when cranking.. It may run roughly, but it should fire.. I dunno??

Don S/V ILLusion · Feb 24, 2009

dbecker68 said:
The Yanmar 12HP diesel in my 1982 H-30 is being difficult. I cranked it two weeks ago, and let it run at the dock for about 30 minutes, just to "exercise" it. When I shut it down, it would not crank again, and still will not crank. I know there is fuel, I can smell it. I have tried diesel starting fluid (ether) in the air intake. I have tried hand-cranking, so I know it is getting compression.
Does anyone have any ideas?
I have had the boat for four years, and it always cranks, but now it won't.
Please help!

Lots of guesses here but it would help to clarify - does the starter motor crank the engine or not? Does it crank slowly or fast? Does it sound like it normally does when you try to start it? Has any work been done since it last worked?

Hermit Scott · Feb 24, 2009

Another easy thing to check is, disconnect the high pressure line to the injector going into the head, put it at full throttle and crank the engine to see if fuel starts squirting out.

Maine Sail · Feb 24, 2009

Is it not

dbecker68 said:
I have tried hand-cranking, so I know it is getting compression.
Does anyone have any ideas?
I have had the boat for four years, and it always cranks, but now it won't.
Please help!

I am going to ask the obvious here. Did you crank the engine with the seacock open? If you did and you hydro-locked it (water in the cylinders) there is nothing any WD-40 or cracking of injectors will do to make the engine compress water..

1- Never crank an engine with the seacock open for more than 20-40 cumulative seconds.

2- NEVER use starting fluid on a diesel!!

It is unclear from your post if it just wont crank over or cranks but won't fire up??

Steve Dion · Feb 24, 2009

Not sure about what it is NOT doing?

Is the starter trying to spin?

Is there any indication that you are getting power to the starter?

Have you tried the starter with the decompression lever open?

Help us so we can help you!

PS: Don't use any starter fluids in a Yanmar. (see Yanmarhelp.com)

RichH · Feb 24, 2009

Typical problem on 1980s Yanmars.
If the starter is not 'cranking' the engine, you may be experiencing a common problem on typical 1980s Yanmars (especially the QM series). There is usually a fuse for the starter solenoid that is mounted on the aft-port side of the engine adjacent to the starter/solenoid. This fuse holder assembly (and all the other components in this circuit) was made with 'automotive grade' non-tinned wire and components, which corrode very badly over time and prevents the starter from energizing due to the high resistance ............ and *especially* when the corroded wiring DRIES OUT after the engine has been running for some time.

Easy to verify .. next time the starter fails to crank apply a 'momentary jumper wire' between the large positive battery feed wire connection on the starter with the small feed terminal on the solenoid. If the engine now 'cranks' (by bypassing the key switch + pushbutton + fuse assembly) without hesitation with such a momentary 'jumper' ... then replace 'all' the above. Dont get yourself or your clothing caught in the alternator belt, etc. when you attempt this 'momentary jumper' .. and the engine 'jumps' as it starts up - be very careful.

The "fix" (for reliability) is to replace the whole 'circuit': Key ---> pushbutton ---> fuse holder and all the wiring in-between. Use only ***tinned*** wire and ***tinned*** contact, etc. components for reliability.

hope this helps.

Benny · Feb 24, 2009

If you hand cranked it and have compression your engine should be fine. If the engine will not cranck or turn you may have an electrical problem with the starter circuit. Does the solenoid click? Check the battery to ground and starter connections . If it does not click check the voltage at the low side terminal. No adequate voltage may mean failed key switch, push button or shorted control wiring harness. Voltage but no click could point to a faulty solenoid.

Stu Jackson · Feb 24, 2009

Huh?

Hermit Scott said:
Another easy thing to check is, disconnect the high pressure line to the injector going into the head, put it at full throttle and crank the engine to see if fuel starts squirting out.

I sure wouldn't do that on my boat.

"Controlled" is the operative word with diesel fuel, and unless there's an identified and specific issue with the injectors, I never touch mine, nor recommend it for others.

Figure out the obvious first. Like my three things and Don's stop lever. Drats, I keep forgetting that one!

Add #5, Rich's fuse and holder. Rare if it's repetitive, but possible.

But wait, guys, he says he tried it, it worked, and when it got warmed up after 30 mins. in the slip. So, NOBODY worked on it in between. Need to narrow down the recommendations for forensics...

jim 5569 · Feb 25, 2009

I vote for an air leak in the fuel system. It probably is upstream of the pump. Do you have a upsteam fuel filter? My 2GM does (Racor) and has stopped running before, when an air leak upstream of the pump caused it to not be able to pump enough fuel to keep the engine running. All of the air must be out of the fuel system before it will operate properly. The Racor filter tends to trap air and must be bled, then you will need to prime the fuel pump to make sure it is not air locked. Good luck on solving the problem, it took me several tries.

Prime Time · Feb 25, 2009

Sounds like and air problem

If its turning over at an appropriate speed, you have good fuel and no ignition, it is likely an air problem, valve problem, or injector problem assuming compression is fine (stop lever in proper position and decompression lever closes). I had a similar problem this season, due to a bad injector on my 1GM. My buddy also had the same problem intermittantly this season and it was due to an air leak from his racor assembly. He would purge the system and it would start up, then lose rpms and die.

I assume you checked your fuel filter and water separator first.Could be bad fuel or water in the fuel. Then, I'd purge the air out as per the manual.If it still did not start, I would check fuel to the injector (Turning the engine over with the water intake shut, and the fuel line to the injector loosened, I'd check that fuel was being delivered). If I still haven't found the problem, at that point I would call a mechanic or I'd pull the injector and send it to be evaluated.

dbecker68 said:
I understand that it's hard to troubleshoot without being there.

To narrow it down somewhat (I hope), the engine turns over, but will not fire. I have had trouble with the batteries and solenoid before, and I know what that is like. This is not the batteries or the solenoid.

I would not have tried the starting fluid on my own, but a neighbor/buddy suggested it. I did not know there was danger of engine damage, and I will not use it agian.

I thought these engines were pretty much bullet-proof, and as I said, it has always cranked in the past. I will check for fuel leak, but I don't think that is the problem either. I guess that I will have to get the mechanic out, but I was trying to save a few bucks. Since I keep the boat at the house, it costs a ton just to get the mechanic there, before he even begins working on the boat.

Thanks again for all your helpful suggestions.

rpwillia · Feb 25, 2009

Chuckbear said:
... NEVER use starting fluid on the engine.

Here is the deal on starting fluid. Ether and other starting fluids have a lower ignition point than diesel. So, if you spray ether in when it ignites in the cylinder, you still have the momentum of the piston coming up to the top of the cylinder while the ether is exploding. This can cause the connecting rod, crank and other components to get damaged. With a diesel you only have two things needed to run the engine air and fuel. Prime time's post (sorry I have not read all of them) gives some good advice to check your fuel flow as if you are smelling fuel you may have a leak or air getting in.

Steve Dion · Feb 25, 2009

I would check the secondary filter (assuming you have a primary) the one on the engine. It is made from pot metal/aluminum. These can often be a problem that causes an air leak.

Now that you have messed with the bleeding points, you also need to get new banjo washers (the copper ones like on top of the Yanmar filter). Basically these are supposed to be replaced once you crush them.

Now that we know the engine is turning over I am also on board with those you believe you have an air leak. Do you know how to bleed the engine? I have use the starter to help bleed the engine but you are supposed to use the thumb pump on your fuel pump.

You should also advance the throttle to about 3/4 postion when starting the engine.

Good luck! We are all waiting your outcome.

Diesel engine question

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