1985 1.9 Autosleeper Fuel tank

[Jeff J]

Is it possible that petrol can be prevented from passing from the level sensor side of the tank to the flow output/filler side?
Could not get it started the other day, spark OK but no fuel getting to the pump. Gauge says 1/4 full so I suspected flow pipe blockage then noticed filter only half full so thought must be a blockage at tank outlet.
A niggling feeling made me add a gallon from a can & low & behold engine started. Went & got filled to top but only took approx. 28 litres of fuel.
This has made me think petrol is not passing from one side of tank to the other. Another niggling thought was that I had read about this happening years ago in the forum but I cannot find any thread that mentions it, nor in the wiki. Before I start removing the tank to investigate has anyone else had this happen? Thanks

[Da dan]

Sounds more like blocked filter or poo pump. Climb under and take the fuel line off the tank to see if you have flow for peace of mind. Note you will probably have petrol spilling everywhere so be careful. When did you last change fuel lines and filter? Electric pump or original?


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[Jeff J]

Sounds more like blocked filter or poo pump. Climb under and take the fuel line off the tank to see if you have flow for peace of mind. Note you will probably have petrol spilling everywhere so be careful. When did you last change fuel lines and filter? Electric pump or original?


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The nylon/plastic fuel lines to/from the tank have never been changed only the rubber ethanol proof ones for the pump & carb, but the fuel is obviously getting to the mechanical pump ok now that it is filled to the brim as the engine starts & runs fine.The petrol is flowing from the tank as the filter can now be seen to be full. Filter was replaced at last service not that many miles ago. What is a poo pump, do you mean the pump may be faulty? If as I suspect there is a blockage inside the tank then I would get petrol coming from both flow & return outlets if I removed the pipes, so do not think that will prove much. Thanks
 

[Da dan]

If you have flow from the outlet this proves inside the tank is not blocked.
Yes the mechanical pump can start to play up when it gets tired.


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[Jeff J]

If you have flow from the outlet this proves inside the tank is not blocked.
Yes the mechanical pump can start to play up when it gets tired.


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But I did not have flow when the gauge said 1/4 full and it only took about 30 litres to fill to the brim. That is the confusing part & makes me think the fuel is not passing from one side of the tank where the level sensor is to the other where the flow outlet is.

[Da dan]

It’s an open tank on my understanding for the dg. 30l is half a tank. 60l full. I would be looking at fuel pump first. But the wise oracles will I’m sure come to hand too enlighten us all.


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[Jeff J]

It’s an open tank on my understanding for the dg. 30l is half a tank. 60l full. I would be looking at fuel pump first. But the wise oracles will I’m sure come to hand too enlighten us all.


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Yes the info I found said that it was a 60L full, 30L half full which was one of the reasons I thought there might be a blockage inside it. Apparently there is an "old type" & a "new type" according to Brickwerks site. Mine is the old type & I wondered if there was a difference between the way the fuel crosses between the 2 sides. My latest thoughts were to either buy and push an endoscope into the tank, but thought that might be possibly risky as they seem to have a built in light. Or to use an air pump ( not a compressor)  to blow down the return pipe from the carb & listen for bubbling at the filler pipe. Had no problems starting/running recently so I am still doubtful the pump is the problem . Thanks for all your suggestions.
 

[shepster]

What do you mean by 'crossing to each side'?

Isn't the tank just one tank and the pipe running across the top is just for expansion in hotter climates when completely full, I don't think there is a situation where only 'half' the tank is full?

The filter is only ever half full, mine is under the van in a horizontal position so may be different to one that's situated elsewhere.

The old and new reference is the filler tube size if I recall.

 

[Jeff J]

What do you mean by 'crossing to each side'?

Isn't the tank just one tank and the pipe running across the top is just for expansion in hotter climates when completely full, I don't think there is a situation where only 'half' the tank is full?

The filter is only ever half full, mine is under the van in a horizontal position so may be different to one that's situated elsewhere.

The old and new reference is the filler tube size if I recall.

Yes my filter is mounted horizontally too, but when I was not getting petrol to the fuel pump the level in the filter was below the level of the output tube so no fuel was getting into or out of it.
My tank is like this one below so it seems feasible that there could be an obstruction between the sections
 

[ZsZ]

The crud settled on the bottom blocking the pickup screen and was stirred up when you added fresh fuel.

May worth to flush the tank.

As already told: the tank is not separated on the bottom, it has only some baffle plates. The crosspiping is for letting air move between the humps when it is filled above half.


Pics:

https://www.thesamba.com/vw/forum/viewt ... p?t=630469
https://www.thesamba.com/vw/forum/viewt ... p?t=606102

[shepster]

Isn't the fuel filler on the same side as the outlet anyway so surely if somehow the one half was 'blocked' off then fuel wouldn't be able to reach the 'other half '?

Get the tank off and flush it out as suggested, replace all the grommets while you're at it.

I removed the expansion tanks and capped the metal pipes off as well as they're just rust traps, never had any problems.

Obviously if you use your van in hotter countries you may need them but the time it takes to use a gallon of petrol up in these things I doubt you'll have any issues.

[Jilldub]

If there is no fuel coming out of the fuel feed line it could indicate a blockage in the internal pipe.
Have you tried removing the filler cap, placing an air line over the fuel feed pipe and gently blowing air into the tank to clear any potential blockage?
Beware! If it does clear, you could end up with fuel exiting the tank so you’ll need to either stop it’s flow or cap it off quickly.

[Jeff J]

The crud settled on the bottom blocking the pickup screen and was stirred up when you added fresh fuel.

May worth to flush the tank.

As already told: the tank is not separated on the bottom, it has only some baffle plates. The crosspiping is for letting air move between the humps when it is filled above half.


Pics:

https://www.thesamba.com/vw/forum/viewt ... p?t=630469
https://www.thesamba.com/vw/forum/viewt ... p?t=606102

Thanks for those links, it does reinforce my thought that it might be possible, in extreme circumstances to have fuel not flowing from one side to the other. I think I will try blowing down the return tube & see what happens then remove & clean out the tank if necessary. When I have seen waxing in other fuel tanks it looks like thick sugary wall paper paste, so maybe that is a possibility.
 

[Jeff J]

If there is no fuel coming out of the fuel feed line it could indicate a blockage in the internal pipe.
Have you tried removing the filler cap, placing an air line over the fuel feed pipe and gently blowing air into the tank to clear any potential blockage?
Beware! If it does clear, you could end up with fuel exiting the tank so you’ll need to either stop it’s flow or cap it off quickly.

Yes, thanks I am intending to try that but with an air pump rather than a compressor.

[ZsZ]

The crud settled on the bottom blocking the pickup screen and was stirred up when you added fresh fuel.

May worth to flush the tank.

As already told: the tank is not separated on the bottom, it has only some baffle plates. The crosspiping is for letting air move between the humps when it is filled above half.


Pics:

https://www.thesamba.com/vw/forum/viewt ... p?t=630469
https://www.thesamba.com/vw/forum/viewt ... p?t=606102

Thanks for those links, it does reinforce my thought that it might be possible, in extreme circumstances to have fuel not flowing from one side to the other. I think I will try blowing down the return tube & see what happens then remove & clean out the tank if necessary. When I have seen waxing in other fuel tanks it looks like thick sugary wall paper paste, so maybe that is a possibility.
 

I think the holes under the baffles are big enough to let fuel through in any circumstances. You need really big chunks of crud to block those

As I see the lower part of the pickup is clogged, as you added fuel the level got above the screened plastic part and could sip fuel from the top rather than the bottom.

Maybe a boroscope worth to borrow to peek into the tank.