Return Fuel Line flowing

[mj81]

Hi, I did my first service on the Volvo Penta D1-30 in my boat. Engine is 4 years old but new to me. When I removed the fuel filter diesel continued to flow. After a bit of troubleshooting I discovered this was coming from the return fuel line to the tank i.e. fuel was fowing the wrong way from the tank to the engine. This seems unusual to be and not something i've seen before. I am planning to install a valve on the return fuel line as a temporary fix as difficult to access the fuel tank and i'm going crusing next weekend.
Anybody seen this before have any idea whats happening?

 

[PaulRainbow]

Sounds like the return pipe is below the level of fuel in the tank and it's siphoning back, it would not be able to do this in normal operation, so i wouldn't worry about it. Fitting a 1/4 turn tap would make filter changes easier, but take care that you remember to open it before running the engine.

 

[NormanS]

My boat has port and starboard tanks. The excess fuel can be returned to either, this is determined by which cock I open. However, the returns enter the tanks near the top, and would only give a return flow if the tanks were pressed full. Maybe your return is further down the tank? Anyway, it's nothing to worry about.

 

[prv]

My fuel tank has two identical dip tubes running to near the bottom, one is used for supply and the other return. I have the same engine as you. However, my tank is below the filters, so I've never had any problem with fuel flowing back up the return line.

Pete

 

[mj81]

Thanks folks, sounds like nothing to worry about, I will install a manual valve at the weekend, I don't like relying on the seals/connections on the engine in case of a small leak when i was away from the boat, to come back to 150L of diesel in the bilge would not be a nice surprise

 

[NormanS]

Thanks folks, sounds like nothing to worry about, I will install a manual valve at the weekend, I don't like relying on the seals/connections on the engine in case of a small leak when i was away from the boat, to come back to 150L of diesel in the bilge would not be a nice surprise

I would think it's very unusual to shut off diesel fuel to the engine. But if you can guarantee that you will remember to open any valves fitted, I suppose it's alright. I wouldn't do it.

 

[prv]

I would think it's very unusual to shut off diesel fuel to the engine.

I believe it's standard on charter boats as a fire precaution. A pair of shut-off valves in the flow and return hoses had been obviously retro-fitted on our ex-charter boat when we bought her.

In this case they wouldn't have achieved much since the flexible fuel hose had to run through the engine space anyway to get to where the valves were, but presumably it satisfied the rule...

I replaced them with a couple of valves directly on the top of the tank for maintenance purposes. I don't close those routinely.

Pete

 

[NormanS]

I believe it's standard on charter boats as a fire precaution. A pair of shut-off valves in the flow and return hoses had been obviously retro-fitted on our ex-charter boat when we bought her.

In this case they wouldn't have achieved much since the flexible fuel hose had to run through the engine space anyway to get to where the valves were, but presumably it satisfied the rule...

I replaced them with a couple of valves directly on the top of the tank for maintenance purposes. I don't close those routinely.

Pete

I wasn't suggesting that shut-off valves aren't fitted. Of course they are, but generally they are only used when required, and not routinely.

 

[mj81]

I am going to add a non return valve into the return fuel line, this will allow me complete maintenance without spraying fuel everywhere but not have to remember to open a valve. It also gives piece of mind that should there be a fuel leak on the engine when I was not on the boat that the entire contents of the fuel tank would not leak into the bilges. A friend had a fuel leak at the top of one of his injectors where the return line connects and several liters of fuel made their way to the bilge before it was found. Had he not visited the boat more would have continued to flow. For that reason i always shut off the fuel when i'm leaving the boat for more than a day or so.