Vrs choosing when it wants to start

[capoot]

Hi all,

I was wondering if anyone could shed any light on why my 52 VRS is now decided when it wanted to start. Tonight i've driven home from work (5miles) and parked on the drive. Just gone to go to the gym and the car won't start.

It turns over, but won't fire! I've read the codes on my codereader (that I got from eBay) and it's thrown up 11 codes!!

17635

17636

17634

18733

17955

17525

17843

17938

17829

17697

17633

I've checked through them and they mainly seem to be "short to circuit" problems, any one have an idea what could be causing this? Spark Plugs? Coils?

If you have any ideas i'd appreciate them!!

Dan

[capoot]

Could this be relay 409?

Anyone had this before?

Dan

[rk696]

Could be that, or maybe a bad earth on the ecu or battery. Did you try clearing them?

[capoot]

Could be that, or maybe a bad earth on the ecu or battery. Did you try clearing them?

Yes, I've cleared the codes and checked the battery connections. Wouldn't know where to start with the ECU earth?

It's really weird as it started first time this morning!

[Interphase]

There are either two or three earths (can't remember) under the battery carrier - you'll have to take off the cover and fusebox, slide out the cable guide at the back, remove the battery and unbolt the plastic carrier. They tend to get amazingly corroded.

The ECU earths are in the plenum chamber, which will require you to take the wiper arms off (may need a puller), and remove the scuttle panels. Those earths tend to sit under piles of damp leaves and the connections go south very quickly. After cleaning all of mine the difference is noticeable - I used to see the headlights dim slightly under heavy loads, eg ABS activating while the aircon was on.

While you're there, check that the black earth strap that connects to top of the leftmost fuse in the battery fusebox hasn't started to melt the plastic around it! If it has you'll also see that the copper strands inside the crimp will be blackened, as the lead is breaking p and introducing resistance to the circuit. If that's the case, you'll be stumping up nearly £40 for a replacement lead which you'll notice is a lot heavier duty and has better crimps. The alternative is a dead battery, alternator, an engine bay fire or all three No design fault eh?

Edited 30 June, 2011 by Interphase

[capoot]

There are either two or three earths (can't remember) under the battery carrier - you'll have to take off the cover and fusebox, slide out the cable guide at the back, remove the battery and unbolt the plastic carrier. They tend to get amazingly corroded.

The ECU earths are in the plenum chamber, which will require you to take the wiper arms off (may need a puller), and remove the scuttle panels. Those earths tend to sit under piles of damp leaves and the connections go south very quickly. After cleaning all of mine the difference is noticeable - I used to see the headlights dim slightly under heavy loads, eg ABS activating while the aircon was on.

While you're there, check that the black earth strap that connects to top of the leftmost fuse in the battery fusebox hasn't started to melt the plastic around it! If it has you'll also see that the copper strands inside the crimp will be blackened, as the lead is breaking p and introducing resistance to the circuit. If that's the case, you'll be stumping up nearly £40 for a replacement lead which you'll notice is a lot heavier duty and has better crimps. The alternative is a dead battery, alternator, an engine bay fire or all three No design fault eh?

Wow!! That does sound a little like a design fault!! I'll have to give that a try and check out all the earths. Is there any "Logical" reason why it would choose to start then decide not too? Surely if the earths are on the way out it wouldn't start?

[Interphase]

Earths are weird, especially when you combine them with something as finicky as the Motronic ECU. Sometimes you'll find yourself fractionally on the wrong side of a threshold and that'll be enough to stop it working.

The codes in that list I can find are all short to ground though, which makes me wonder if the affected components are on a common +ve rail and that's earthing out somewhere?

[pauldazzle]

Check to see if you have the old type black coolant temp sensor, it's notorious for failing, & can cause a lot of running problems as the ECU gets it's temp information from it. If your car is starting ok when cold, but not when it's hot or vice-versa I'd put my money on it being the CTS failing.

[Matty_turbo]

as for earths if you stick a pair of jump leads from your negative battery cable to a earthing point on the engine that will create a good earth from the engine and it that cures the problem its def a earth strap somewhere hopefully that will save you some time instead of checking for all the earths.

[fordfan]

It could be a power supply relay. I came across similar some years ago on a VRS, non start, lots of codes, I recall that there are two relays in the engine compartment, replacing the grey one (I think, though they both might be grey) cured it.