Fuel gurgling when cold (1 Viewer)

[Bongani]

Sorry for the poor title. I just don't know how to explain it better. It is getting colder here in ZA now with night temperatures aroudn 10 degrees celcius. Of late I noticed the when starting my vehicle in the morning that the fuel would gurgle all along the pipes from the fuel tank to the front of the vehicle. It sounds like air is trapped in the pipe and then it runs along the length of the pipe. I have two fuel tanks with OE fuel pumps and both fuel lines are doing it (by the sounds of it). One would typically explain this sounds as the same as when air is trapped in the water pipes in the house and the whole house would resonate the sound when the tap gets opened.

My truck is starts on the 4-6th swing and it has not had any starting problems. When the vehicle has driven a distance then it would not do the gurgling again. I have only heard it after it stood for example overnight when it is cold. Whether it is truely related to temperature or standing for a period of time I don't know. I am using the same garage for fuel and the fuel filter is new.

Where do I start?

 

[Rich]

Are you certain you are not hearing air moving through the coolant lines? Is the radiator full? Is the coolant level in the overflow resevoir remaining constant?

 

[Bongani]

Rich

While seated in the drivers position it sound as if the sound is coming from the left back and moving to the left front. The sound is only there once I turn the engine over and the sounds runs for about 3 seconds. Everything else appears to be normal. When I turn the ignition to AC I can hear the fuel pump getting power and the power up sound stops after 60 seconds. This is still normal behaviour. (Q: What is actually happening during thsi 60 seconds? Is the fuel pump building up pressure?) As soon as I actually start the motor the gurgling starts.

What is bothering me is that the gurgling is lasting longer every day. This evening I could hear it for a good 15 seconds or more.

 

[Bryan062087]

i think my 80 does that when its cold too or some similar gurgling

 

[Rich]

With power on the pump will pressurize the fuel system. I have not heard the noises you are hearing.

I asked about the radiator coolant level because air in the cooling system can make audible noise, which I would expect to sound as if coming from behind dash and or about the rear heater. I am not suggesting that this is your problem, only trying to clarify if that is possible. From your description it does not seem likely to be coolant lines.

 

[Bongani]

Rich
Thanks for the advise. I am pretty clueless to what can be causing this or to what actually the problem is and I appreciate all suggestions.

 

[Bongani]

Is there any change that this could be brakefluid eg air in the brake system?

 

[Rich]

You're not hearing gurgling from the brake system. Do check that your radiator is full.

 

[Bongani]

thanks rich

I will check the radiator.

 

[Bongani]

Rich

The Radiator is full and is pushing into the overflow as and when it is required.

 

[RavenTai]

Are you getting sub 0 C temps there right now? Could be ice crystals forming a partial blockage? Or possible rubbing along the line until they get to the filter?

Might be a good idea to run some water remover in the fuel,

Don’t think this is going to be it but maybe will lead you to something else.

I popped the hood once and heard a faint buzzing noise coming from the charcoal canister, pulled the "from tank" hose off and heard a gurgling noise, sounded like fuel vapor pushing past a slug of fuel in a low spot somewhere, IIRC is was a hot day not cold. Neither the buzzing nor gurgling were loud enough to be heard from the drives seat especially with the engine running.

Of the three lines to the tank only the one to the charcoal canister should have any gases (as in air) in it, the other two (pressure and return) should be solid fuel. that may get more complicated with the dual tank system.

Not sure I would give up on the heater lines yet; you could be getting air in somewhere like the PHH wile it sits? Maybe check for bubbles at the over flow as it warms up?

Is the air bleed that connects to the top of the radiator connected properly? Not Kinked or deleted.

 

[Bongani]

Raven

The temperatures are around 10 degrees C at the moment. I will run some cleaner in the fuel tanks and see what it does.

My charcoal canister makes it normal sounds as the gas pass through it. With the engine running it is not audible at all.

While sitting the in the cab the sound comes from the rear and runs to the front. I must still get the misses to start the vehicle while I lie underneath it. (just need to check my policies before the timw )

What is PHH? The Radiator air bleed is fine. I have checked it out.

 

[Bongani]

I just spoke to my mechanic and he also thinks this is some trapped air in the heater hoses. Now lets assuem this is. Is this something to worry about, can it be fixed?

 

[Bongani]

Well, I found it some time ago but stumbled accross this post now. Turned out to be the low pressure fuel return valve that splits the fuel between tank 1 and tank 2. When it is cold the fuel gurgles through the line. It is getting warmer now again and the sounds are now gone.