SDI dont wanna start

jameson

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Hi Ive been having issues with my Caddy SDI not starting (again) of late. Some time ago I had this issue and was told not to park the van facing uphill and that the fuel pump probably need replacing. Since then I've had the fuel pump (in the tank) replaced, and still had issues with it not wanting to start on the odd occasion. Ive lived with this for the last 6 months; when it don't want to start I just crank it for about 30-40 seconds and it starts eventually. Once its started started and warm it runs fine all day long; even if I leave it for a few hours and return. Its when its left overnight I have problems, usually in the morning.

Last year when I had the fuel pump replaced (at a VAGS Specialist) I got it scanned with VAGCOM and was told nothing was amiss. More recently I took it to another garage for a scan, and again its showing as nothing amiss.

So in a nutshell I've been keeping the van almost full of diesel, parking it downhill, had the fuel pump changed, and had it scanned on two separate occasions, at two different garages, but the mechanics can find nothing wrong. Does anyone know what's causing this ??? Please help its driving me mad. I'm thinking maybe the injector seals are leaking but I don't want to spend money on that if it don't fix it. Also I've read online that fitting a non-return valve to one of the fuel lines will help ??? Is that correct ??. The fuel filter is clean, was changed 6 months ago.

It does strike me as odd that two garages (one a VAGS specialist) cannot seem to find the issue and fix it, it seems to have got worse of late. Every morning now I switch ignition 5 times, to get the plugs properly warmed up, and to prime the engine with fuel and I'm lucky if it starts, I need to give it a small amount of gas at just the right time and it fires up. If not it sort of farts, and then wont start unless i crank it for ages. Please help.
 

Crasher

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A problem with the glow plugs should show up as a fault code and bring on the engine warning light. The first thing I would check is the "Torsion Value" as it is known, using a diagnostic system. This reports back the accuracy of the cam timing and anything exceeding+/-3 degrees can cause problems; I don't like a value exceeding +/-1. After a cambelt change we push to get it as close to 0 as possible.
 

jameson

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A problem with the glow plugs should show up as a fault code and bring on the engine warning light. The first thing I would check is the "Torsion Value" as it is known, using a diagnostic system. This reports back the accuracy of the cam timing and anything exceeding+/-3 degrees can cause problems; I don't like a value exceeding +/-1. After a cambelt change we push to get it as close to 0 as possible.
Thanks for reply. I'm fairly sure the glowplugs are okay tbh; I only warm them up 5 times just to be sure. Regarding the torsion values; surely the people who done the diagnostics would have picked up on that. I was under the illusion that it was a fuel problem rather than timing so thanks for mentioning that. Another possible cause that's been mentioned to me regards a cable loom thing, dont know what its called, that runs beneath the rocker cover and attaches to the injectors; is it worth replacing that do you think ?
 

Crasher

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Thanks for reply. I'm fairly sure the glowplugs are okay tbh; I only warm them up 5 times just to be sure. Regarding the torsion values; surely the people who done the diagnostics would have picked up on that
The glow plug controller does all that for you, what you see the glow plug light indicate is not representative of what is actually happening. A lot of mechanics, even highly VAG experienced, have know idea what the torsion value indicates and don't know it is there or to check it. Since I started to mention this value in my agony aunt column in The Golf+ magazine (sadly defunct) in the early noughties, it has become more wide known to enthusiasts but I still get so called Master Techs look at me as if I just dropped out of the sky when I mention it, they go all glazed and confused... The problem is, few people study the measuring blocks and just depend on fault code which is not enough. The injector harness would give fault codes if it was faulty.
 

jameson

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The glow plug controller does all that for you, what you see the glow plug light indicate is not representative of what is actually happened. A lot of mechanics, even highly VAG experienced, have know idea what the torsion value indicates and don't know it is there or to check it. Since I started to mention this value in my agony aunt column in The Golf+ magazine (sadly defunct) in the early noughties, it has become more wide known to enthusiasts but I still get so called Master Techs look at me as if I just dropped out of the sky when I mention it, they go all glazed and confused... The problem is, few people study the measuring blocks and just depend on fault code which is not enough. The injector harness would give fault codes if it was faulty.
Thanks for this info. I will have to get these torsion values checked out then; as ive tried most things regarding fuel supply ect ect, is there anything else could be causing this I wonder. Can anyone recommend a mechanic to check and the torsion values, and readjust if needed ??? Im based in SE London/Kent
 

Crasher

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Value, singular... 😉 With no codes/smoke/bad running I would be checking the fuel filter for engine oil contamination, pop the glow plugs out for a compression test and fit new glow plugs anyway as it is extremely unadvisable to reuse them and after that looking to replace all four injectors. One test I would like you to do is replace one part of the fuel return line (the one with the temperature sender in it) to the filter with clear and see if there are any air bubbles, I think it is 7mm ID. Also another check for whoever plugs in next, check the reading when stone cold from both the engine and aforementioned fuel temp sensors to make sure the reading makes sense.
 

jameson

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Value, singular... 😉 With no codes/smoke/bad running I would be checking the fuel filter for engine oil contamination, pop the glow plugs out for a compression test and fit new glow plugs anyway as it is extremely unadvisable to reuse them and after that looking to replace all four injectors. One test I would like you to do is replace one part of the fuel return line (the one with the temperature sender in it) to the filter with clear and see if there are any air bubbles, I think it is 7mm ID. Also another check for whoever plugs in next, check the reading when stone cold from both the engine and aforementioned fuel temp sensors to make sure the reading makes sense.
OKay thats alot to do and alot of £££ for a set of injectors, the diag showed 3 injectors were fine, one has an intermittent misfire but is otherwise okay. As I say there is no smoke atall, the oil does not smell of fuel, and it runs fine when it starts; it misfires ever so slightly on occasion but i can live with that. Im annoyed that no mechanics can tell me whats wrong with it, its a bit much really in the great scheme of things.
 

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Don't be disappointed in the mechanics, these modern cars can be very stressful and I can assure you they aren't doing it on purpose. At the end of last year I had a T5 that was driving me potty, it happens to all of us.
 

jameson

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Don't be disappointed in the mechanics, these modern cars can be very stressful and I can assure you they aren't doing it on purpose. At the end of last year I had a T5 that was driving me potty, it happens to all of us.
Well if a mechanic cant find out whats wrong with it, I might as well chuck the thing in a skip; ridiculous set up tbh.
 

Crasher

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You should see the nightmares I have to deal with and it is getting worse, by comparison your engine is basic. Whatever you replace it with will be worse.
 

jameson

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So, the issue I have is I need the van fixed, taken it to two garages and they cannot fix it ! Diag is showing nothing wrong. Im at a loose end now with this; is there any good indy VW garages based around London or Kent that can solve it ??? I really dont want to take it to another garage, they plug it in to a computer and tell me theres nothing wrong with it.
 

jameson

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Maybe I should add again, that once the van starts its fine all day long; but sometimes, and it is just sometimes, it wont fire up on ignition, and if that happens I have the crank the ting for about 40 seconds and then it will start, its like theres a fuel issue but i might be wrong. Its got a full tank of fuel, and the fuel pump in the tank was replaced a few months ago.
 

Crasher

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There are VAG indies all over the UK and a lot in London but I don't know who is good but I will ask on a trade forum I go on, so the KENT area?
 

jameson

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Just to update, I took my van back to the VAGS garage. The van was plugged into the diag machine once again and the mechanic says that no faults showing (as expected). He says the ECU in these vans is quite robust, so doubts the problem with not starting is related to that. One thing he did mention thou which I had not thought of: Apparently there is a fuel rail that runs through the cylinder head to the injectors, this fuel rail is encased in a plastic (like a plastic straw if you like); he says if the plastic deteriorates the fuel pressure can fall and cause starting issues, once started the fuel pressure builds up again. He says to change the "plastic straw" is tricky, and says better to replace the cylinder head; the issue with this thou is that a second hand replacement might have the same issue, and a new cylinder head costs £££££

Anyone have any info on this particular problem. Ive found since my last post that if I switch on/off the ignition 5-6 times before starting then it does manage to start up if I give it a bit of throttle just as its starting, if I dont switch the ignition 5-6 times then it just splutters and dies.

Anyhow is this fuel rail through the cylinder head a known problem with the Caddy SDI ??

Thanks
 

Crasher

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Now your chap is worrying me! The fuel rail in a BDJ or BST head is a drilling in the casting pressurised by the tandem pump on the end of the head. The plastic rail within the head is the wiring harness for the injectors, it takes about an hour to chnage and cost £94.32 , I think you need to get it to someone who knows what they are talking about...
 
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jameson

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Now your chap is worrying me! The fuel rail in a BDJ or BST head is a drilling in the casting pressurised by the tandem pump on the end of the head. The plastic rail within the head is the wiring harness for the injectors, it takes about an hour to chnage and cost £94.32 , I think you need to get it to someone who knows what they are talking about...
Yes he said the fuel rail is within the casting after the tandem pump, although he said this casting has a plastic sleeve insert which may be breaking down and causing the low pressure; is this not the case then ? Is there no plastic sleeve ??

Could a breakdown in the wiring harness cause starting issues like Im experiencing ?
 

Crasher

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That is called an "emulsion tube", I have never seen one disintegrate but at £7.60 for a new one... 038 130 085. If there was a problem with the head harness, in my experience this triggers an ECU fault code for the relevant injector or even causes a misfire.
 
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