Mk4 Tdi cut out on motorway and now won't start.

[coolspot007007]

I'm at a bit of a loss for a solution on this one. I went on a 200 mile round trip only for the car to cut out 2 miles from home at 70 on the motorway. No drama, smoke, lost fluids, snapped belts or a rod through the block or anything, just cut out. I tried starting it but it just wouldn't fire into life but turned over fine. I got a mate to come down with jumper cables as the voltage was heading towards 8v quite rapidly when turning over. Even jumpered it was having none of it. I got the AA to take me home and he ran a diagnostic on it - no faults. The lift pump is getting voltage and working, there's fuel to the rail. No fuses blown and I've swapped relay 109 as this seemed to cure a lot of similar problems for ohters but the car was always showing the glow plug light for around 5 seconds so I didn't think this would fix it anyway. I've hooked up Vagcom but I'm not getting any faults. So at this point I'm thinking, crank sensor, temp sensor, ECU (or ecu earth) or a dodgy earth somewhere,immobiliser or tandem pump but I'd of thought it would throw a code in vagcom for any of those. Has anyone got any ideas?

 

[DEAN0]

I'm at a bit of a loss for a solution on this one. I went on a 200 mile round trip only for the car to cut out 2 miles from home at 70 on the motorway. No drama, smoke, lost fluids, snapped belts or a rod through the block or anything, just cut out. I tried starting it but it just wouldn't fire into life but turned over fine. I got a mate to come down with jumper cables as the voltage was heading towards 8v quite rapidly when turning over. Even jumpered it was having none of it. I got the AA to take me home and he ran a diagnostic on it - no faults. The lift pump is getting voltage and working, there's fuel to the rail. No fuses blown and I've swapped relay 109 as this seemed to cure a lot of similar problems for ohters but the car was always showing the glow plug light for around 5 seconds so I didn't think this would fix it anyway. I've hooked up Vagcom but I'm not getting any faults. So at this point I'm thinking, crank sensor, temp sensor, ECU (or ecu earth) or a dodgy earth somewhere,immobiliser or tandem pump but I'd of thought it would throw a code in vagcom for any of those. Has anyone got any ideas?

Is 8v enough for the diagnostics to work ?

If the battery has got that low it would not have enough voltage to run the engine.

I would start with a fresh charged battery and see how it goes.

 

[Leonidas]

Water in the diesel??

 

[pjdj]

Can you read if your crank sensor is working through vag-com?

 

[coolspot007007]

Is 8v enough for the diagnostics to work ?

If the battery has got that low it would not have enough voltage to run the engine.

I would start with a fresh charged battery and see how it goes.

Only drops that low when I keep cranking it, is showing 12v+ normally (have recharged the battery too)

 

[coolspot007007]

Can you read if your crank sensor is working through vag-com?

It wasn't throwing any faults up but will check it in the morning.

 

[coolspot007007]

Water in the diesel??

Would this not present earlier in the journey? It was over 90 miles after I filled up, averaging 60mph.

 

[Leonidas]

In my experiance water stays at the top of diesel so no. Also if theres water in the diesel it'll freeze in this weather.
Iv seen our machines cutting out and been very hard too start again and I know its water in the diesel because we have our own tank at work and water did get into it. But I would imagine it would only happen when the tank is gettin low!!

 

[coolspot007007]

In my experiance water stays at the top of diesel so no. Also if theres water in the diesel it'll freeze in this weather.
Iv seen our machines cutting out and been very hard too start again and I know its water in the diesel because we have our own tank at work and water did get into it. But I would imagine it would only happen when the tank is gettin low!!

Still 3/4 of a tank in it

 

[pjdj]

It wasn't throwing any faults up but will check it in the morning.

Can you check if it is picking up engine speed though?

 

[coolspot007007]

Can you check if it is picking up engine speed though?

God knows, I'll have to check the vagcom site. When others have had a fault vagcom seems to know about it though and shows a code. I think I'll open the tap on the bottom of the fuel filter too, see if i can spot any water contamination.

 

[coolspot007007]

I've emptied the fuel filter, and all seems fine, no water or other contamination. I have however found a leak in a vacuum hose leading from the vacuum reservoir to the 'valve block' as Haynes put it (the box with all the vacuum lines going into it). My understanding is this reservoir is used to open and shut the EGR but I plugged the vaccum line going to the EGR (leaving it redundant, I think well it made a difference in a good way) when I first bought the car. Therefore should the vacuum leak make any difference or is the vacuum reservoir used for anything else important that would stop the engine starting?

 

[coolspot007007]

Have now changed; the fuel filter, all the fuel hoses in the engine bay and the tandem pump. Has anyone got any other ideas?

 

[rf860]

Sounds very like the problem i had in my old astra 1.7 cdti, would cut out only at motorway speed (very scary as it made the whole car 'jolt' violently), no assissted brakes or p/s. When you got to the hard shoulder, the engine would take for ages to start. When left to cool down it would be fine. I called the AA out on one occassion, and his fault reader showed up nothing. Eventually after being in a local indie 5 days of fault finding, i had to take it to the dealer Turns out the ECU was blocked for Vauxhall fault readers only and it was a faulty crankshaft sensor. Hope this helps

 

[darkhorse]

I've emptied the fuel filter, and all seems fine, no water or other contamination. I have however found a leak in a vacuum hose leading from the vacuum reservoir to the 'valve block' as Haynes put it (the box with all the vacuum lines going into it). My understanding is this reservoir is used to open and shut the EGR but I plugged the vaccum line going to the EGR (leaving it redundant, I think well it made a difference in a good way) when I first bought the car. Therefore should the vacuum leak make any difference or is the vacuum reservoir used for anything else important that would stop the engine starting?

A vacuum line goes to the anti shudder valve (part of egr assembly, next to the flying saucer) which operates when the engine is turned off. I can't remember whether it is normally open or normally closed if there is a no vacuum so it's worth a look. Easiest way to check if its opening is to take the intercooler pipe off and have a look to see if the butterfly valve moves when turning the ignition on and off

 

[coolspot007007]

A vacuum line goes to the anti shudder valve (part of egr assembly, next to the flying saucer) which operates when the engine is turned off. I can't remember whether it is normally open or normally closed if there is a no vacuum so it's worth a look. Easiest way to check if its opening is to take the intercooler pipe off and have a look to see if the butterfly valve moves when turning the ignition on and off

Have checked this, butterfly is open and moving fine, so it should be ok Have checked all the vacuum lines for leaks too.

 

[darkhorse]

The things I would check next are temp sensor, fuel pressure sensor, cam sensor and injection quantities. All can be checked through vagcom (don't ask me how though)
Another thing to check is the immobiliser

 

[Leonidas]

The things I would check next are temp sensor, fuel pressure sensor, cam sensor and injection quantities. All can be checked through vagcom (don't ask me how though)
Another thing to check is the immobiliser

Good thinking, could be the key fob!

 

[Viking]

Immobiliser fault would throw an immobiliser light on the dash. The engine would also start and cut out straight away.

Vacuum leak wouldn't (shouldn't) cause a failure such as this. It would cause running issues etc. but should still start.

Wild stab in the dark, have you checked the cambelt hasn't snapped or jumped a tooth or two?

 

[coolspot007007]

Cambelt hasn't snapped, but I was worried it may have jumped a tooth as I was changing gear at 70 at the time it cut out. How can I check it as I've never done anything cam related. I take it there's markings on the belt that should line up with markings on the cam sprocket, or can you use Vagcom to check it?