Diesel fuel tank pipework

sharkojoints · May 29, 2015

My new Series IIA lwb diesel in disguise has two problems with the fuel tank:

1. It leaks fuel from the top of the tank, which looks like it's an unsealed sender unit, so an easy fix.

2. It only seems to be able to use about 3 gallons of diesel at a time, after which it runs out. It then only takes 3 gallons to fill the tank. Given the tank is 11 gallons (it's a rear fill tank), this seems odd.

I'm wondering if the diesel outlet and return pipes have been mixed up?

I also know that my landy started life as a petrol - is the fuel tank for a IIA petrol different from a diesel?

tottot · May 29, 2015

The 2a petrol did not have a return pipe so yours will be an addition and you may be on the right track about the pipes being mixed up.
A common problem on old vehicles is the pick up pipe developing a hole some way up it giving the symptoms you describe.

sharkojoints · May 29, 2015

tottot said:
The 2a petrol did not have a return pipe so yours will be an addition and you may be on the right track about the pipes being mixed up.
A common problem on old vehicles is the pick up pipe developing a hole some way up it giving the symptoms you describe.

Ah - very interesting, thanks.

I think the tank will be coming out this weekend so we can see what's what...

sharkojoints · May 30, 2015

So, here's the tank:

You can see the knackered and leaking link pipe between the two halves of the tank.

The RH stub was connected to the fuel pipe to the lift pump.

The LH stub was connected to the fuel return pipe from the injector pump.

Is this correct?

tottot · May 30, 2015

The pick up on the right looks like an addition,take fuel sender out and with a torch look inside and see which pipe goes to the bottom of the tank.

sharkojoints · May 30, 2015

tottot said:
The pick up on the right looks like an addition,take fuel sender out and with a torch look inside and see which pipe goes to the bottom of the tank.

I just unscrewed and removed the pick up stub on the right. It goes all the way to the bottom of the tank, and isn't holed or damaged. Hmmm.

I drained about 7 gallons of diesel from the tank before I could remove it.

Any thoughts?

tottot · May 30, 2015

Take it pick up was clear,did it have a mesh on the end ? Can not understand why you had to drain tank to remove it,it's on the top after all?

sharkojoints · May 30, 2015

Yes, the pick up was clear, although there are signs that it previously had mesh on the end.

I wanted to remove the tank so I could do a good job of re-sealing the level sender, as well as investigating the pipework. I have a Pela pump, so draining the fuel is not hard, and makes removal much easier without the weight of several gallons of diesel.

tottot · May 31, 2015

Might be worth checking if your lift pump is working right.

sharkojoints · May 31, 2015

tottot said:
Might be worth checking if your lift pump is working right.

It's a thought, isn't it? I'm not sure how a faulty pump would create the symptoms this has though - it managed 80 miles from Hemel to Bibury before conking out, and ran fine again after 2 gallons of diesel were added. I got another £12 worth in at the next petrol station, half of which leaked out of the sender, I reckon...

The fuel filter looks old as the hills, so might be worth changing as a precaution. The tank to lift pump pipe is one continuous run of clear plastic braided pipe, so shouldn't be letting in air, but I'll check everything, obviously.

Just ordered some 2BA screws for the tank sender unit, since half were missing or the wrong type, so will put everything back together when they arrive.

ivanhoe · May 31, 2015

Aren't those symptoms consistent with a tank that cannot breathe. The pump works fine for a while until a vacuum builds in the tank, until the pump can't overcome the vacuum.

Test with tank on vehicle is to run with the filler cap removed.

Basically, check breather is clear.

Edit.... Looks like your breather is being used as the return.

sharkojoints · May 31, 2015

ivanhoe said:
Aren't those symptoms consistent with a tank that cannot breathe. The pump works fine for a while until a vacuum builds in the tank, until the pump can't overcome the vacuum.

Test with tank on vehicle is to run with the filler cap removed.

Basically, check breather is clear.

Edit.... Looks like your breather is being used as the return.

That was a thought I'd had too. However, the first time it "ran out of fuel" was after only a few minutes running.

In any case, the sender unit was leaking plenty of air into the tank...

ivanhoe · May 31, 2015

Still think it's got a 95% chance of no breather syndrome. Look up at your filler neck, the hose yours is returning to should be connected to the filler. You need a new return connection on the tank.

ivanhoe · May 31, 2015

http://i273.photobucket.com/albums/jj215/andyshirley/Mobile Uploads/DSC_0074_zpsy9usbaso.jpg

sharkojoints · May 31, 2015

ivanhoe said:
Still think it's got a 95% chance of no breather syndrome. Look up at your filler neck, the hose yours is returning to should be connected to the filler. You need a new return connection on the tank.

You're right - there's nothing connected to the breather stub on the filler neck.

I reckon putting a T piece into the balance pipe, and running a pipe off this up to the breather stub would sort it out.

ivanhoe · May 31, 2015

Or for not alot of money get a new sender, with the fuel pick up built into it. Have a Google.

sharkojoints · Jun 23, 2015

So, for completeness here's the solution:

1. There was no breather fitted to the tank, so I tee'd one off the balance pipe with a plastic Y connector from B&Q.

2. There was a non-standard one way valve fitted in the fuel pipe, which seemed to be causing issues and once removed she now purrs like a kitten.

honolulujoe · Jun 24, 2015

just for my own clarity are you saying you removed the valve altogether or did you replace it with a standard one?

sharkojoints · Jun 24, 2015

honolulujoe said:
just for my own clarity are you saying you removed the valve altogether or did you replace it with a standard one?

Removed altogether.

herby1 · Dec 19, 2022

Hi all, fitting a second hand brand new tank on my 79' 109 diesel, tank has the 4 pipes & clip in sender.
This is probably going to sound really, really dense, but don't know which pipes connect to where (original tank wasn't connected)
can someone add a photo with idiot proof labels (for me ) please

Diesel fuel tank pipework

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