VW T4 Forum - VW T5 Forum banner
1 - 19 of 19 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter · #1 ·
I just finished replacing the tandem pump, starter motor and thermostat and tried to start the van but it won't start. The engine turns over better than ever before with the new starter motor but it doesn't catch. It's not even close... The last thing I did was priming the fuel line by removing the return connection and turn the ignition until fuel arrived. While working on the van I disconnected the injector loom and the connector close to it, on the front side of the engine. I'm a little worried I pulled too hard on the cables when I pulled it off its steel mount. Does anyone know what that connector is for? How do I troubleshoot this? I'm not sure where to start..
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #2 ·
There is lots of air bubbles coming from the return line on the fuel filter, and every time I turn on/off the ignition to run the fuel supply pump I hear a brief vacuum noise. It's very hard to locate the source though.. I think it's from one of the connections on the fuel filter but I'm not sure. I also removed the pressure test bolt from the new tandem pump. Expected fuel to pour out of that hole but it didn't.. The top of the bolt is wet and I can see that diesel squirts out of it when I crank the engine, but shouldn't there be pressurised fuel there even after I turn the ignition off? I can also hear intermittent bubbling noises from that hole and it seems to produce a vacuum if I hold my thumb over it for a moment. I suspect there's a leak along the high pressure fuel line between the tandem pump and the engine, which I also replaced, but I can't see any signs of leakage. Could a broken injector seal give symptoms like these?
 

·
Registered
Joined
·
1,576 Posts
Why did you replace the tandem pump, ie what was the situation before changing it? Bad starting, no starting, misfiring, diesel in the oil?
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #4 ·
It's been hard to start for a while, both hot and cold, and the back and bottom of the pump was wet with what looked like diesel or a mix of diesel and oil. It's also running quite loud and has problems keeping temperature. The thermostat looked ok, but replaced it anyway.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #5 ·
If I remove both fuel pump and return hoses from the filter, fuel flows out from both connections when I turn the key. Is this normal behavior? I thought the fuel has to pass around the engine before it comes out from the return..
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
It does. Maybe the fuel supply is a red herring and the real reason for the non-start now is that injector connection. I haven't had to undo one but it is common to cause non-starting after removal if it not replaced correctly. It is quite easy to get wrong apparently..
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #7 ·
I removed the injectors last spring when I replaced the cam but I haven't touched them since. Although it struggled a bit to start before I replaced the pump it's odd that it's completely dead now. Should the tank pump push fuel all the way around the engine and back again or does it only prime the fuel filter? Do I need to bleed the tandem pump somehow? Haven't read anything about that in the Haynes manual.
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
I disconnected the injector loom and the connector close to it, on the front side of the engine. I'm a little worried I pulled too hard on the cables when I pulled it off its steel mount.
Was it the round connector at the end of this loom? It has some marks that must line up. It should turn and locate with a positive click and when fitted correctly it should be firm and not wobble about.

As far as I know there is no requirement to bleed the section of pipe from the tandem pump to the injectors. On a PD and especially a common rail (2.0 engines) I wouldn't crank the engine with any part of the system undone after the tandem pump because of the vast pressures involved. I think the low pressure tank pump primes the filter and then is free (for the time it runs) to push the fuel back via the return. I am not absolutely certain about this though.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #9 ·
Was it the round connector at the end of this loom? It has some marks that must line up. It should turn and locate with a positive click and when fitted correctly it should be firm and not wobble about.
Yes, the 90 deg male connector that connects to it. I've double and triple checked it and it seems to be fitted correctly.

Is there a relay or fuse for the injectors that I should check?
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
Is there a relay or fuse for the injectors that I should check?
Not a direct injector fuse or relay as far as I know but it's always worth checking all fuses and the relays in the engine compartment Just to eliminate them.

You could do with getting a full diagnostic check of all the controllers on the van (not just the engine).
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #11 ·
Bad news.. There is a leak on the fuel line in the cylinder head 😥. I put some pressure on it today and could clearly hear air leaking when I listened though the oil filler cap. Fingers crossed it's a blown seal.
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
Does the oil smell of fuel? Or does the oil level creep up? We have had a few reports of cracked fuel galleries within the head here. Fuel goes into the engine and the fault is usually accompanied by poor starting. :(
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #13 · (Edited)
I'm quite certain the oil level increased so there is probably fuel in the oil. I changed it a few days ago though so now it's fresh. What are the implications of running with fuel in the oil? Should I expect lifters etc to be worn down again (replaced them last spring) if I'm lucky and the cylinder head is ok?
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
Unfortunately if the head is cracked it scrap. If the oil runs with fuel added it can damage anything it is supposed to be lubricating. Because the heads are so expensive and any possible engine wear is hard to assess without total stripdown, most people look for a second hand engine. But it is important to get one with a known good history so you don't end back where you started. There are firms offering new heads but some won't accept a cracked one back as exchange and will add a steep surcharge. A new head from VW is several thousand pounds.

Watch the oil level carefully because if it gets high it can cause the engine to runaway uncontrolled. All good news tonight eh? 😢
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #15 · (Edited)
This is what the injector bores on cylinder 2 and 5 looks like. Haven't looked at the other ones yet as I couldn't hear any air seeping out from them.
Automotive tire Rim Household hardware Bumper Gas

Don't know how they got worn like that.. Maybe it happened when I removed the injectors last spring.

Cam and rocker is also a bit worn with scratches on the lobes :(

Do you think it's possible to fix?

Edit:
Did a search on the forum and apparently that type of wear on the injector bores is a common issue.
 

·
Registered
Joined
·
1,576 Posts
Normally it's a new head when the bores are worn. I have heard they can be machined out and sleeved, but no idea on cost or success?
Another repair is actually a bodge, which is to fit oversize O rings, which will give the engine a bit more life before the O rings wear out again.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #17 ·
Is there anything specific on the engine, beside the cylinders, that I should check to determine if it's worth a new head? It's done almost 350 000 km.
 

·
Registered
2004 T5 2.5 174
Joined
·
2,583 Posts
Crank and cam plus bearings. You would need an engineering shop to measure if the wear isn't obvious. Running on contaminated/thinned oil isn't good but it depends on for how long it ran with it.

I have read about rebushing the injector bores and also a heavy bracket/clamp thing that fits across all of the injectors like a line of 'C' letters to stabilize them but I no idea if either thing works as a permanent cure. The clamp was made by a German firm if I remember. I think they had a video of a bloke fitting one. It was about 3 years ago I saw it and it was fairly expensive, about £395 I think.
 
1 - 19 of 19 Posts
Top