VW T4 Forum - VW T5 Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
39 Posts
Discussion Starter #1
I have a problem starting my diesel T5 transporter (2005, 2.5L DIESEL automatic)

The car starts perfectly (within one second of turning the starter) if it has been running in the previous 12 hours or so. If it is longer than this, it fires within one second but then dies, and then can take for 5 seconds or even longer to start. It does this every time it has been sitting longer than a half day or so and has been doing it for the last few months consistently.

There seems to be a slight diesel leak at the top of the tank (near the filler).

However, the Volkswagen dealer suggests this may be something more serious: they say something to do with diesel at the injectors seeping back 'through the block'. They say it has happened on several cars of this model and age. I'm not sure what their fix would be but the word 'block' makes it sound expensive ;-)

Obviously I would prefer it is just related to the diesel leak at the top of the tank…

Anyone with any experience or suggestions?

Thanks in advance...
 

·
Registered
Joined
·
2,129 Posts
From what I've read on this forum there's a few things you could maybe check.
Number one would be the oil level. Check it is not going up, fuel can leak into the engine & mix with the engine oil.
There are things like leaking injector seals, an indication of which can be as described above, i.e. engine oil level increasing.
Another thing is there is a one-way valve in the fuel system, (sorry don't know exactly where it's positioned in the fuel system) which prevents fuel draining back into the fuel tank when the van is not being used. It can leak & allow fuel to drain back into the fuel tank. Then, when you come to start the engine it takes a while to pump/bleed the fuel back to the injectors before the engine will start.
You could try parking the van on a hill. Try parking with the van facing up the hill & see what it's like starting & also try facing it down the hill. Quite often I heard that if you park facing down the hill it can make starting easier.
As to what will eventually be your specific issue is very hard to say, it's going to be a process of elimination I'm afraid. Hopefully though when you get to the parting with money stage you will be reasonably sure you know the exact cause.
 

·
Registered
Joined
·
378 Posts
Like CAT3 says, it's most likely the one-way valve that's leaking. This is somewhere in the line from the fuel pump at the tank to the fuel pump of the injectors, but I don't know which end this is on the T5. A leaky one way valve allows the diesel pressure at the feed end of the injector pump to leak away over time. It shouldn't be an expensive part (says he unknowingly), so it's worth trying it as a fix. Even if it's not the cause, at least you'll have a spare for when it does go.

I had exactly the same problem with a Renault Scenic diesel a few years back. Unfortunately the Renault garagists' complete incompetence ended up costing me dearly, as they tried replacing almost every other component of the diesel system, including the glow plugs and the injectors themselves before some really helpful and insightful amateur diesel mechanic on the Renault Forum helped me out.

Kudos to all those who keep knowledge sharing as the primary purpose of these forums, and keep the politics and snide remarks for the pub. T:
 

·
Registered
Joined
·
39 Posts
Discussion Starter #5
Cheers guys. It'll likely be a few weeks before I get it fixed but I'll report back for info when done.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #6
So, the VW garage tells me there's no one-way valve. They say they can try changing injector seals but they think the only solution is changing the cylinder head...

It seems to be getting slightly worse but not terrible. Engine needs to turn for max 5 secs before firing when cold.

Opinions anyone?
 

·
Registered
Joined
·
7,548 Posts
So, the VW garage tells me there's no one-way valve. They say they can try changing injector seals but they think the only solution is changing the cylinder head...

It seems to be getting slightly worse but not terrible. Engine needs to turn for max 5 secs before firing when cold.

Opinions anyone?
I think the dealers are correct about the valve - AFAIK there is not a one way valve between the tank & the high pressure pump.

However, there is a "lift pump" in the tank - this moves diesel from the tank to the main pump - if this fails the fuel drains back into the tank over a period. When you crank it over the main pump has to suck the fuel up from the tank making starting diffecult.

Leave the van overnight & listen under the van near the tank - get someone to turn the ignition on (don't crank it) & you should hear the pump run for a few seconds. If you can't hear it you have a wiring fault or a faulty pump or get someone who has full diagnostics & they can "force" the pump to run to help find the problem.

Had exactly the same symptoms with mine (also a 2.5, but a manual) - secondhand pump fitted (which subsequently failed) which cured the problem.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #8
Thank you Brian.

When I switch on the ignition it's difficult to tell if the lift pump operates because my car has been adapted with an extra brake servo (I drive from a wheelchair), and the servo pump is quite loud. However, if I switch on and off the ignition several times the brake servo reaches the required pressure and this extra pump no longer comes on. At that point, there is no noise when I switch on the ignition. So no lift pump noise either. The question I have here is, does this mean that the lift pump is not working or does it also only pump the first couple of times until diesel pressure has been reached?

Another thing that I did not say (and should have) is that there is a slight diesel leak (diesel on garage floor under the tank area). It's not massive and seems mainly when tank full.

I've searched quite a bit online and I do see an example where there are a worn injector bores but I still hope it's a cheaper fix …

I'm based in Belgium and looking for specialist garages to get second opinion, but if anyone has more thoughts here that would be great.

Gordon
 

·
Registered
Joined
·
7,548 Posts
The lift pump only runs for a couple of seconds to prime - it then only runs as required after the engine has started so you won't hear it.

What part of Belgium are you in ? I have a friend in Brugges that runs a T4 - he may know of an independent specialist.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #10
Thanks again Brian

I will PM you my contact info in case your friend could help.

Just to clarify, I have not started the engine during those tests. So the question is, should the lift pump prime every time you switch on the ignition or just the first couple of times until it has enough pressure?
 

·
Premium Member
Joined
·
4,075 Posts
The lift pump usually primes and then runs continually when the engine is started.
You can run the lift pump through VCDS for testing.

For reference Chris Munford had a starting issue on his 2.5 after it was left for a day or so, it was the lift pump at fault.
 

·
Registered
Joined
·
2,129 Posts
So, the VW garage tells me there's no one-way valve ...................
I'm just questioning this fact, NOT saying any one person is incorrect, but I have a basic drawing of the fuel supply for these VW engines & it shows a one-way valve in the line between the fuel filter & tandem pump. Can't for the life of me remember where I got the drawing from !

It doesn't specify exactly where it might be fitted, whether it's a stand alone part or an integral part of maybe the fuel filter or tandem pump, so is it possible it's an integral part of the tandem pump or even the fuel filter ?
Next time I change my fuel filter I will cut it open just to have a look.

I'm just curious to find out for definite if there is or isn't a one-way valve somewhere in the fuel line.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #17
Hi all, here with ann update...

So I went to a diesel specialist:

1. They fixed the leak (was in the hose from filler to tank, so cannot be related to starting problem :(
2. They say there's no non-return valve between the tank & the motor, so the issue is either the fuel pump, the injector seals or leaks in the fuel lines in block. They recommend doing nothing since car starts okay (though needs to turn 5-8 secs if has been sitting for a day).

Anyone have thoughts on tis?

I'm still grasping at straw that it may be a simple fix. I find this online that shows a non-return valve on p20... but it's 2004, not 2005... https://vwpress.files.wordpress.com/2012/01/ssp-305-e.pdf
 

·
Registered
Joined
·
39 Posts
Discussion Starter #18
Hi all

A friend suggested using a fuel additive that fixes leaks. Anyone got thoughts on this? A diesel additive that might fix leaks in injector seals and head?

Thanks in advance :)
 

·
Premium Member
Joined
·
4,075 Posts
Hi all

A friend suggested using a fuel additive that fixes leaks. Anyone got thoughts on this? A diesel additive that might fix leaks in injector seals and head?

Thanks in advance :)
If it's going to fix a leak it would probably block the fuel feed holes in the injector bodies, the are so small they are quite hard to see, also fuel pressure when the engine is revved is around 10bar!
 

·
Special Rapporteur
Joined
·
9,761 Posts
I would first check with VW that it's approved by them for use in their fuel injection systems (Hint: it won't be! They won't even approve anything other than the least "bio" of biodiesels).
 
1 - 20 of 23 Posts
Top