Engine stalling after one hour

[GDJones]

Hi, my engine runs for approximately 1 hour then stalls. After checking both my filters, my secondary one (nearest to the engine) is low on fuel. After priming the fue and clearing the air lock, the engine runs again for about an hour then the same thing happens again. I have checked all pipes for leaks, I have replaced the fuel filters, I have checked the breathing tank for any vacuum and I can't find any air leaks. 

[GDJones]

I forgot to mention, it's a beta marine 35 engine. 

[Tracy D'arth]

Lift pumps on Beta35 are tiny mechanical things and fail fairly often IME. A pin hole in the diaphragm will reduce the pump's performance. Is there any sign  of fuel getting into the engine oil, diesel smell on the dipstick?

Can you rig up a direct feed to the injection pump without the lift pump from a can above the engine as a day tank to prove the point?

[Tony Brooks]

I certainly sound like air build up. Tight unions on the pipes does not mean that the olives have not been crushed and you can suck air in without fuel leaking out.

 

If the other filter is a CAV 296 type, then they are notorious for causing air leaks where the myriad of O rings have not been correctly fitted.

 

It would be worth blowing back into the tank in case a raft of floating muck blocks the pickup pipe.

 

Some Beta priming pump cum filters have been found to be porous so they let air in.

 

 

 

[Tracy D'arth]

13 minutes ago, Tony Brooks said:

I certainly sound like air build up. Tight unions on the pipes does not mean that the olives have not been crushed and you can suck air in without fuel leaking out.

 

If the other filter is a CAV 296 type, then they are notorious for causing air leaks where the myriad of O rings have not been correctly fitted.

 

It would be worth blowing back into the tank in case a raft of floating muck blocks the pickup pipe.

 

Some Beta priming pump cum filters have been found to be porous so they let air in.

 

 

 

If the filter head has a push button priming pump built in as Tony suggests, they are known to occasionally let air in.

[GDJones]

Hi Tracy, thanks for replying. There is no signs of fuel in the oil, however the priming pump does appear to be very flimsy. I didn't consider the primary pump being the cause but food for thought. 

Hi Tony, thank you for replying. The filters both seem fine. As I release the air bleed valve on the first filter, fuel spills out ok. I have removed the fuel link to the second filter in and fuel seems to be flowing through there ok as well. As I mentioned to Tracy, the priming pump does feel very flimsy and doesn't always pump fuel through (and assuming if the priming pump is drawing in air, would make sense) 

The priming pump is lever operated and is below the filter. 

[Tony Brooks]

As Tracy said, try to rig up a direct gravity feed into the filter, with the container sat well above the engine to give it plenty of head. If that solves the issue then you now there is an air leak, but not if it is the primer or the rest of the system.

[Ex Brummie]

Another place to check is the flexible hose to the engine. If they are of a certain age, then the pipe under the ferrule may be split and allowing air to be pulled in. A quick check is to remove the hose and see if the tails can be twisted in the ferrules. If they can, that could be your problem. I have had similar on my Perkins 4108M.

With the inreasing vegetable content of fuel, it is searching out the nitrile content in hoses and filter seals. I used to work with oil boilers and cookers and this became a significant cause of failure in appliances.

[GDJones]

Ex Brummie, the only flexy hose is from the water separator filter to the secondary filter. Have checked this for any air leaks and can't seem to find any issues with it. The issues seems to stem somewhere between the priming pump and the filter as far as I can work out.