Engine misfiring, likely suspects list

Tim O

Tim O

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Following on from my previous threads....

Engineer came to check out my engine last night.....On the positive side, we sorted, at least for now, the leaking stern gland.

On the negative, we discovered the following:

Engine not firing on one cylinder
Excesve vibration, with engine mounts probably needing replacement
Morse gear cables incorrectly set up.

So, first priority is to sort out the misfire as unless the engine is running smoothly, we can't really set up new mountings properly, and the gear cabling is just a tweaking job hopefully.

You may recall history is boat been out of water 10 months, back in, engine running beautifully out of gear, smoothly and purrng like a kitten.....Took her out for half an hour and returned with these issues!

Have changed fuel filter.....Engineer examined the fuel in the old one and said it was pretty clean looking, certainly no sign of diesel bug.

He is going to try compression test on misfiring cylinder, then look at injector, then fuel pump to try and narrow down the problem

What are people's thoughts on most likely scenario here? Engine is Beta v1505 38 HP.
 
Don't worry about most likely. Just eliminate possible causes.
Injector
Pump
Compression
Valve clearances?
Air in system?
Any micro filters either side of HP pump?
 
He could have simply cracked the injectors one at a time to see if fuel was being injected or if it was a fuel fault But then that would cut the cost down
I'd think you have a damaged valve or head gasket problem the compression check will show if it's piston related or valve.
With the injectors out he could test each injector by using a jam jar for saftey to see if there's good spray pattern also correct end of injection and no nozzle leak
 
Tim O said:
Following on from my previous threads....

Engineer came to check out my engine last night.....On the positive side, we sorted, at least for now, the leaking stern gland.

On the negative, we discovered the following:

Engine not firing on one cylinder
Excesve vibration, with engine mounts probably needing replacement
Morse gear cables incorrectly set up.

So, first priority is to sort out the misfire as unless the engine is running smoothly, we can't really set up new mountings properly, and the gear cabling is just a tweaking job hopefully.

You may recall history is boat been out of water 10 months, back in, engine running beautifully out of gear, smoothly and purrng like a kitten.....Took her out for half an hour and returned with these issues!

Have changed fuel filter.....Engineer examined the fuel in the old one and said it was pretty clean looking, certainly no sign of diesel bug.

He is going to try compression test on misfiring cylinder, then look at injector, then fuel pump to try and narrow down the problem

What are people's thoughts on most likely scenario here? Engine is Beta v1505 38 HP.
Click to expand...
I have the Nanni version
how long did it run after the filter change, could well be an air lock. I wouldnt remove injectors until the system has been bled out
i changed my mounts @ about 12 yrs / 1200 hrs
 
mtb said:
He could have simply cracked the injectors one at a time to see if fuel was being injected or if it was a fuel fault But then that would cut the cost down
I'd think you have a damaged valve or head gasket problem the compression check will show if it's piston related or valve.
With the injectors out he could test each injector by using a jam jar for saftey to see if there's good spray pattern also correct end of injection and no nozzle leak
Click to expand...

There was certainly fuel getting to the top end of the injector as we slacked the nut off and could see it.
 
sailorman said:
I have the Nanni version
how long did it run after the filter change, could well be an air lock. I wouldnt remove injectors until the system has been bled out
i changed my mounts @ about 12 yrs / 1200 hrs
Click to expand...

As I say it was running fine under no load, then half an hour under load developed problem. Was still running but noisily and not smooth. I changed filter in case old one was clogged which it wasn't. Pumped fuel through to fill new filter with the lift pump until it came out from the bleed screw.

We started it up and ran maybe 10-15 minutes to listen, see vibration and discover fourth cylinder not firing.
 
sailorman said:
I have the Nanni version
how long did it run after the filter change, could well be an air lock. I wouldnt remove injectors until the system has been bled out
i changed my mounts @ about 12 yrs / 1200 hrs
Click to expand...

I'm relatively new to diesel engines but am interested in your point. I would have assumed that if any engine is running on all cylinders but still misfiring on one, then after running for a while on the good cylinders the fuel supply to the misfiring cylinder would have cleared through any air locks. Is this incorrect?

Richard
 
RichardS said:
I reckon your engineer is following the right course of action. It will be interesting to see what he concludes.

Richard
Click to expand...

I agree with Richard. Nothing about his approach sounds wrong to me. Any further guessing is pointless, other than for the sake of idle gossip on here :)
 
RichardS said:
I'm relatively new to diesel engines but am interested in your point. I would have assumed that if any engine is running on all cylinders but still misfiring on one, then after running for a while on the good cylinders the fuel supply to the misfiring cylinder would have cleared through any air locks. Is this incorrect?

Richard
Click to expand...

My tank is below the engine & after a fuel filter change she does cough n splutter for a few minutes & will actually stop some times, even after 10 mins. once clear never a problem
 
RichardS said:
I'm relatively new to diesel engines
Richard
Click to expand...

pinocchio-paradox.jpg
 
sailorman said:
My tank is below the engine & after a fuel filter change she does cough n splutter for a few minutes & will actually stop some times, even after 10 mins. once clear never a problem
Click to expand...

I can understand that ..... but Tim describes a different situation where the engine is running steadily on 3 cylinders and would presumably carry on like that ad infinitum, so any airlock would have to be after the high pressure pump. Surely this would therefore clear itself?

Richard

I've just seen Paul's jokey cartoon ...... but I'm really not joking. I've never worked on a diesel car 'cos I've never had one and I've only ever had one boat with two engines but they're self-priming so this "bleeding" thing is something I have never ever done.
 
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Tim O said:
As I say it was running fine under no load, then half an hour under load developed problem. Was still running but noisily and not smooth. I changed filter in case old one was clogged which it wasn't. Pumped fuel through to fill new filter with the lift pump until it came out from the bleed screw.

We started it up and ran maybe 10-15 minutes to listen, see vibration and discover fourth cylinder not firing.
Click to expand...

How do you know its the 4th cylinder?
 
RichardS said:
I'm relatively new to diesel engines but am interested in your point. I would have assumed that if any engine is running on all cylinders but still misfiring on one, then after running for a while on the good cylinders the fuel supply to the misfiring cylinder would have cleared through any air locks. Is this incorrect?

Richard
Click to expand...

I believe that its down to injector pump design. When not injecting fuel the pump can be either closed or free back flow. If it prevents back flow then the system will self prime after the pump. If it permits back flow then the air compressed in the injector pipe will just push back all the fuel that was meant to end up in the cylinder. Perhaps a feature of common rail engines?
But thats why it is/has been necessary to bleed all injectors. I must admit that even a 1970's Ford tractor, not renowned for its technical merits, that often needed bleeding, I only did one cylinder an the rest cleared themselves.
 
Dougal Tolan said:
How do you know its the 4th cylinder?
Click to expand...

When I say 4th, it was the last in the line of four, furthest from the pump!!! I'm sure cylinders have a proper number sequence and be just got it wrong yes???

We unscrewed nut at top of each injector and the first three all changed engine tone, the last one didn't, ergo, it was already not firing, while the others clearly were
 
Tim O said:
When I say 4th, it was the last in the line of four, furthest from the pump!!! I'm sure cylinders have a proper number sequence and be just got it wrong yes???

We unscrewed nut at top of each injector and the first three all changed engine tone, the last one didn't, ergo, it was already not firing, while the others clearly were
Click to expand...

Ahh, and the post where you say you had fuel coming out, I guess you meant that one.....
So, its that injector or gasket./valve trouble on that cylinder...

Next up is essexboy's idea, swap injectors.
After that, you can get exhaust fume sniffer kits, check no exhaust in cooling system.
Then its rocker cover off to have a nosey at valve clearances and, turning engine over slowly, look for sticky valves.
 
Tim O said:
When I say 4th, it was the last in the line of four, furthest from the pump!!! I'm sure cylinders have a proper number sequence and be just got it wrong yes???
Click to expand...

Cylinders in an inline engine are numbered from the front, you were correct.

IMO, your mechanic seems to be doing all of the right things, leave him to it.
 
If your machanic is worth his wages then he will be following a line of diagnosis that has been around since engines were first invented and will eventually get to the root of your problem
 
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