Odd engine behaviour - cause?

[Cardo]

Our engine has started playing up a bit when starting it up. It started doing it just before Christmas. I thought it may have been a cold thing, but it still did it yesterday when the boat was plenty toasty.

The engine starts up immediately, as it always has previously, however then splutters and dies after around 5 seconds. The engine then takes around 10 seconds of turning over for it to start again. Once it restarts, it'll splutter a bit for a few seconds before getting back to normal. It then behaves fine once it's up to temperature.

I'm thinking it may be air in the fuel line? Though I don't know how it got in there. The CAV filter looks fine. The engine is a reasonably new Beta 35.

Thoughts?

 

[30boat]

I'd say there's air getting in somewhere.

 

[Cardo]

I'd say there's air getting in somewhere.

But wouldn't that stop the engine from running altogether?

 

[dunmor]

i would agree with 30 boat. air gets sucked in but wont leak diesel. try changing your fuel filter first its the most
likely culprit

 

[pvb]

But wouldn't that stop the engine from running altogether?

No, the air entering the fuel system from a small leak will probably self-purge. A small air leak can allow fuel to drain away, which is why you need to crank it for a while to get it restarted. Air leaks aren't easy to find, some people recommend using talcum powder but that's unlikely to show a leak unless the system is gravity fed (in which case air won't leak in). Have the symptoms coincided with any changes you've made (new filters, etc)?

 

[Cardo]

i would agree with 30 boat. air gets sucked in but wont leak diesel. try changing your fuel filter first its the most
likely culprit

I see. Engine's due a service before we set off in April, so I'll be replacing the fuel filter then (as well as various other bits).

Thanks for the advice.

 

[Cardo]

Have the symptoms coincided with any changes you've made (new filters, etc)?

Nope! No changes whatsoever. I'll see what happens once I've serviced the engine, hopefully it'll solve itself.

 

[vyv_cox]

The amount of fuel passing through the injectors is extremely small. For the engine to die after five seconds suggests the leak is very close to them, certainly not as far as the primary filter or lift pump. Try nipping up the connections to the injectors and the high pressure pump first. If you have a secondary filter on the engine the leak might be there but probably no further back.

 

[Cardo]

The amount of fuel passing through the injectors is extremely small. For the engine to die after five seconds suggests the leak is very close to them, certainly not as far as the primary filter or lift pump. Try nipping up the connections to the injectors and the high pressure pump first. If you have a secondary filter on the engine the leak might be there but probably no further back.

It sounds like it's likely to be the fuel filter on the engine. This is due replacement anyway, so fingers crossed!
At least it seems fairly certain that this is a small air leak in the system not far from the injectors. Shouldn't be _too_ difficult to locate/fix. Hopefully.

 

[Mistroma]

My Yanmar 4JHAE had similar problems and the problem was due to the priming pump on the filter. Quite a few people had this problem. The shaft seals leaked after approx. 12-18 months and air entered when engine wasn't run for several hours. The fuel tank was lower than the filter and so air was sucked in.

I'd say that it could well be a problem around the region of the filter. Our engin became increasingly difficult to start unless a the "throttle" lever was pushed well forward. Even then, it died after a few seconds but would be fine when started again. Sounds familiar, so could be some sort of seal close to the filter (assuming your tank is also lower than the filter).

 

[Momac]

I hope replacing the fuel filters cures the problem.
Don't forget the air filter. Mine was surprisingly grubby when replaced recently, after one year. (not the same engine).

 

[Cardo]

I hope replacing the fuel filters cures the problem.
Don't forget the air filter. Mine was surprisingly grubby when replaced recently, after one year. (not the same engine).

Worry not, this will be a major service. The usual filters and even the heat exchange stack.

Question: If the impeller looks fine, should I still replace it?

 

[Heckler]

Worry not, this will be a major service. The usual filters and even the heat exchange stack.

Question: If the impeller looks fine, should I still replace it?

The heat exchanger stack? why?
Stu

 

[Cardo]

The heat exchanger stack? why?
Stu

Manual says to give it a good clean every so many miles. Should I not bother?

 

[Momac]

If the impeller looks fine, should I still replace it?

I have a new impeller at each annual service.
The impeller that came off this time is okay so it will be kept as a spare in case of emergency.

 

[Heckler]

Manual says to give it a good clean every so many miles. Should I not bother?

Ah! take the end off that the raw water pumps to and have a shufty, see if any bits of impellor are in there. I must say I took the end off my 10 yr old VP MD22 one. and it was the first time it had been off, it was as clean as a whistle.
Stu

 

[jdc]

Don't forget the O ring

... Engine's due a service before we set off in April, so I'll be replacing the fuel filter then (as well as various other bits)...

My Beta 50 had a similar problem, which started off just as you describe but eventually got so bad that after a few days at sea in rough weather the engine would not start until re-primed. It was never possible to trace the fault definitively, but changing the secondary filter didn't entirely cure it. What (touch wood) seems to have done was replacing the tiny O ring in the bleed-crew in the top of the filter. A new O ring is not supplied with a new filter, and it's apparently against the rules of the professional mechanic's guild ever to change them, so it may not have been done for years...

It's item 24 in the attached snippet.

Unhelpfully the parts list describes it only as 'Part of the Filter Assembly', so you have to measure it to select the correct O ring size.

 

[GrahamM376]

Some fuel lift pumps have a non return valve, may be the problem if it's stuck open. Would allow the engine to start with residual fuel in the injector pump and then stop until more pumped through after prolonged cranking.

 

[Cardo]

My Beta 50 had a similar problem, which started off just as you describe but eventually got so bad that after a few days at sea in rough weather the engine would not start until re-primed. It was never possible to trace the fault definitively, but changing the secondary filter didn't entirely cure it. What (touch wood) seems to have done was replacing the tiny O ring in the bleed-crew in the top of the filter. A new O ring is not supplied with a new filter, and it's apparently against the rules of the professional mechanic's guild ever to change them, so it may not have been done for years...

It's item 24 in the attached snippet. View attachment 28530

Unhelpfully the parts list describes it only as 'Part of the Filter Assembly', so you have to measure it to select the correct O ring size.

Why would the mechanics refuse to replace the O ring? Thanks for the suggestion, though. I shall keep it in mind when I poke the engine.

Some fuel lift pumps have a non return valve, may be the problem if it's stuck open. Would allow the engine to start with residual fuel in the injector pump and then stop until more pumped through after prolonged cranking.

Thanks for the suggestion. Another idea to keep in mind!

 

[30boat]

Manual says to give it a good clean every so many miles. Should I not bother?

Definitely.Clean the tube stack every year or so.Mine (Beta 20) is always half clogged with white stuff deposits.