1.7D Sucking Air into Fuel Line - Query

Post by **moth** » 18 Mar 2006, 20:08

Hello,

This afternoon my T25 lost all power as though running out of fuel. Checked it out and established that it's sucking air into the fuel supply line - apparent in the clear pipe supplying the pump from the filter and of course in the return line. Renewed the connection where supply pipe fastens to the filter - still loads of air in the supply pipe.

Any common places that these T25's suck air into the diesel fuel line?

What is the funny loking gizmo for in the return line where it runs over the filter top? It's held in place by an R Clip - seems to have some sort of T connection with the filter via an O ring ??

Help / ideas appreciated

Thanks

TM

Post by **angry vanagon** » 18 Mar 2006, 20:36

the white valve on top of the filter is a pre heat valve which at certain temperature's allows returned fuel to leak back in to the filter to heat fuel in the filter. The air bubble's in the line are there on my golf diesel and my t25 diesel and both run ok are you sure the filter and tank pick up are free from blockages when i have had problems i found air leak's = poor cold starting, blockage's = cutting out and looseing power (mainly during a driving will but idle all day ok and will restart again after a couple of minute's

Post by **moth** » 18 Mar 2006, 20:51

Hello,

No I'm not sure whether the pick up or filter are blocked or not - interesting that air in the supply line is evident in your two vehicles - I'd just assumed it shouldn't be there at all and haven't looked further - will check these things out tomorrow. How do I get at the pick up??

You have me thinking now - my T25 has been laid up for the last three months - I took it out for a 40 mile spin today and as I was approaching home it started losing power - have I perhaps disturbed something that has settled in the fuel tank during the lay up and blocked my filter or pick up?? Point to note is that it will tick over continually and will drive on the flat - but show it a hill and it dies - to get up the hill to my house I had to take it a few yards at a time - allowing the T25 to tick over for a while between each attempt!

TM

Post by **HarryMann** » 18 Mar 2006, 20:54

Could water have got into the tank whilst laid up?

Maybe muck has settled a bit.. not sure how to purge, need diesel experts (Simon Baxter), mayb pmail him if can't get to bottom of this (sic!)

Post by **andysimpson** » 18 Mar 2006, 21:35

Its normal to have some air bubbles visible in pipes especially when we have cold weather. When the t piece goes onto recirculation(back into filter) if there is any air it just keeps going round in circles between the filter and pump, when the fuel reaches aprox 25-30 degrees the valve then sends all fuel back to tank and any air that is in the filter. These valves can stick on recirculation so the air never gets released and it keeps building up untill you have running problems, they can be difficult to test as the problam can be intermittant, they are about £8 from euro or gsf, when fitting their is a direction of flow indicated by a small arrow on top, this must be towards tank. They can also draw air bewtween this t piece and filter.

Post by **HarryMann** » 18 Mar 2006, 21:37

Thers you go, the lowdown on T pieces and air holes...

Post by **moth** » 18 Mar 2006, 21:51

Tremendous - reckon I now have a few avenues to explore now - thanks very much to all.

Incidentally I followed the supply pipe back to the tank and found no evidence of leaks so reckon the air that is evident is likely to be recirculating via the T piece - guess this can be bypassed? (Of course would need to block the hole in the filter or fit a simpler in line filter).

How do I get at the fuel pick up to check that it is clear?

Tim M.

Post by **andysimpson** » 19 Mar 2006, 21:33

moth wrote:Tremendous - reckon I now have a few avenues to explore now - thanks very much to all.

Incidentally I followed the supply pipe back to the tank and found no evidence of leaks so reckon the air that is evident is likely to be recirculating via the T piece - guess this can be bypassed? (Of course would need to block the hole in the filter or fit a simpler in line filter).

How do I get at the fuel pick up to check that it is clear?

Tim M.

It can be by passed but it would look messy, for the price of a valve its not worth the hassle.

Post by **moth** » 10 Apr 2006, 21:17

Thanks to all who helped. Fuel filter was completely blocked. Replaced it and the the van now runs and pulls as it should. It's now up for sale, see classifieds. I can only warrant keeping one of my T25's and my 33k miles 2.1 Syncro ambulance wins the day.