air in fuel line

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Lio
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air in fuel line

Post by Lio »

Hello everybody
I am still struggling with air in fuel line on my turbo diesel from 87. After I have vacuumed the line to remove air and sipped a bit of diesel, it works fine for a few km and then some bubbles appears until it becomes mostly air and it stalls.... Before I go to more dramatic steps ( I was thinking changing fuel line, and dropping the tank to check the different breathing valve etc ...) but any advice are welcome ;-), I was thinking : could this come from the injection pump ? it seems to me that the air is coming from the fuel filter or tank but I am not 100% sure, so has anybody been through this due to a problem on the injection pump ?
Thanks for sharing,
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Middle29
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Re: air in fuel line

Post by Middle29 »

I had recurrent problems starting with air that would always settle between filter and pump. I just changed all the fuel lines and it was fixed. I think the old lines were brittle and let air in. I should have done it sooner as was an easy fix. Added a manual primer too that I never needed after.


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weimarbus
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Re: air in fuel line

Post by weimarbus »

Have had this years ago , ours was a bad fuel filter, worth checking the fuel line to unions, the fuel line can get brittle and not seal to the union well enough to stop air being drawn in. I would think it unlikely to be the tank as the outlet is below the fuel level
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Lio
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Re: air in fuel line

Post by Lio »

Thanks,
Then, i go for the fuel line replacement.
Lionel
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Lio
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Re: air in fuel line

Post by Lio »

Hello
So, now the fuel line has been changed and the issue is still there.
We mounted an extra tank and since this fixed the issue, so the conclusion is that the problem is coming from the fuel tank.
Knowing that the tank is brand new, as it was changed by the previous owner, has anybody any good idea what to look first ? Could it be issues with some breather ? 
One additional info : Whe removing the output pipe from the tank, the fuel is dripping very very slowly....is it normal ?
Thanks
Lionel
 
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davidoft1
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Re: air in fuel line

Post by davidoft1 »

How much fuel is in the tank ?

Lio
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Re: air in fuel line

Post by Lio »

More than half, and it was the same when full...
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davidoft1
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Re: air in fuel line

Post by davidoft1 »

Lio wrote: 01 Apr 2021, 18:08 More than half, and it was the same when full...

Stick something in the outlet to make sure it’s not particularly blocked, fuel should flow out pretty quickly
Last edited by davidoft1 on 01 Apr 2021, 20:27, edited 1 time in total.

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muttleypup
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Re: air in fuel line

Post by muttleypup »

at what point in the fuel line did you put the temporary tank? before or after the filter?
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Oldiebut goodie
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Re: air in fuel line

Post by Oldiebut goodie »

The fuel will only come out of the tank slowly - I can fit a Webasto tee with barely any fuel loss. People always seem to think that it flows quickly on its own whereas the reverse is true.
It is common for the fuel filter assembly to allow air in, I would concentrate on that area. Do a search and there should be several posts about it especially if you have a return to the filter, for some reason these cause problems.
I can feel the pain - I spent a couple of years trying to trace the same on my boat engine, luckily had a fuel primer built in to the fuel filter which made it easier until I sorted it.
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Lio
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Re: air in fuel line

Post by Lio »

The extra tank was put after the fuel filter,  between the fuel filter and the regular tank, so that's why the fuel filter is not the root cause for this problem.
We tried as well to disconnect the Eberspraecher (sorry not sure about the spelling... I mean the aux heater), and it was also rules out...
No, it really seems it comes from the tank.

 
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muttleypup
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Re: air in fuel line

Post by muttleypup »

have you tried running it with the fuel cap off to maybe rule out a vacuum lock, unlikely but worth a try
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Lio
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Re: air in fuel line

Post by Lio »

yes, I did try this as well, removing the fuel cap. No improvement. I bow air as well from the outlet in case something was blocking, put it did not hep.

Well, let's get the tank removed and check it. Whatever I found, I will post it. It got on my nerves ;-)
 
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davidoft1
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Re: air in fuel line

Post by davidoft1 »

Lio wrote: 02 Apr 2021, 05:30 The extra tank was put after the fuel filter,  between the fuel filter and the regular tank, so that's why the fuel filter is not the root cause for this problem.
We tried as well to disconnect the Eberspraecher (sorry not sure about the spelling... I mean the aux heater), and it was also rules out...
No, it really seems it comes from the tank.
 

Sounds like you put the tank before the filter not after, feed the fuel pump in the engine bay straight from your temporary tank , run the return back into the tank too

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Oldiebut goodie
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Re: air in fuel line

Post by Oldiebut goodie »

Pressurize the fuel line with fuel from the pump end and look for diesel leaks - they are easier to spot than air entering. A bicycle pump filled with diesel can be used in lieu of any other equipment.
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