My 2006 Fabia 1.2 Ambiente has decided to start cutting out for no apparent reason. The car can run fine for a while then just dies completely without warning. I ran a diagnostic and found a fault.

"17769 Cylinder 3 ignition circuit; open circuit. Intermittent."

I've changed the coil packs and plugs, checked as much wiring and connections as I can see. I cleared the fault and the car started fine but the problem has reappeared. When the car stops it is immediate, no hesitation, misfiring or spluttering. Battery power is good and the engine turns but will not fire. It can be left for a while then starts again, there seems to be no particular circumstance that affects it, it appears totally random.

Any insight, advice or ideas would be gratefully received. 

It's a wiring fault, there will be a fractured conductor between the coil pack and the ECU.

Done a continuity test on all the wiring to the ECU and they are all ok.

I'm beginning to think it's not electrical. Would a failed CPS cause it to stop dead, I read a post on a Seat Ibiza that suggest this would happen.

8 minutes ago, GaryI said:

Done a continuity test on all the wiring to the ECU and they are all ok.

I'm beginning to think it's not electrical. Would a failed CPS cause it to stop dead, I read a post on a Seat Ibiza that suggest this would happen.

 

Can check for you shortly if my laptop ever finishes updating...

While I've been busy I noticed the wiring to the Camshaft sensor have been interfered with by a previous owner, they were wrapped with black electrical tape that didn't look original. I had a look and they have been spliced, the connections appear good though. Think I'll do a voltage check tomorrow when I put the battery back on.

Actually I should point out, on the Seat post I mentioned the fault was stated as the crankshaft sensor and not the camshaft sensor. 

From the self study program about the 1.2 htp engines:

 

Substitute functions

Engine speed sender G28, camshaft position

sender G163

If the engine speed sender G28 fails when the

engine is running, the engine stops. It can,

however, be started again.

If the camshaft position sender G163 fails

when the engine is running, the engine

continues running and can also be re-started.

If both senders fail, the engine cuts out and

can no longer be started.

 

Unless they happen to share a fuse, it seems unlikely both have failed so this may not be what's going on.  Can you divulge the engine code of your car so I can check the relevant wiring diagram? BMD or BME I think, shoudl be on the data sticker on the boot floor, possibly on a sticker near the timing chain cover too.

By the way, black insulation tape can be factory fit. As can inline splices in the wires, especially if they look like they've been done by a powerful tool.

2 minutes ago, Wino said:

From the self study program about the 1.2 htp engines:

 

Substitute functions

Engine speed sender G28, camshaft position

sender G163

If the engine speed sender G28 fails when the

engine is running, the engine stops. It can,

however, be started again.

If the camshaft position sender G163 fails

when the engine is running, the engine

continues running and can also be re-started.

If both senders fail, the engine cuts out and

can no longer be started.

 

Unless they happen to share a fuse, it seems unlikely both have failed so this may not be what's going on.  Can you divulge the engine code of your car so I can check the relevant wiring diagram? BMD or BME I think, shoudl be on the data sticker on the boot floor, possibly on a sticker near the timing chain cover too.

It's a BME

The tape was a lot more recent and not to the same standard as factory fit. The engine is a BME.

Cool, will check power source of cam/crank sensors shortly, but I think the fact that it does restart ever suggests it can't be just a blown fuse.

It was restarting after it first happened, it would run fine for a while then die again. Now it doesn't appear to want to start again, I haven't tried for a few days as I've been busy with other things. I'll put it back together tomorrow and see if it fires.

Both are 5V powered via engine ECU I think, so no fuse could explain them both not working. Temporary shutdown of that 5V rail by the ECU could potentially explain it, but it supplies other sensors like MAP, so I'd imagine you'd have other fault codes if it were that.  The one code you have is odd, in that I wouldn't expect that alone to shut the engine down.

 

Have you checked battery terminals for tightness, earth connections to chassis for cleanliness/lack of corrosion?

Does the car sit out in the weather or under cover?

I thought that myself, I'd have expected it to run rough with a fault on only one cylinder not stop altogether. I've checked all the connections as best I can and the battery terminals also checked fuses.

I'm remembering a thread from a while back where the main permanent 12V feed into the cabin had been water corroded at the firewall connector due to blocked scuttle drains; that might worth looking up to see how that exhibited itself. I'll try to find it after eating.

Thanks I'll check that out. All my electrics seem fine. The car was off the road in the summer for a failed OS window mechanism, finally got round to fixing it in November. This problem started a couple of weeks after that. The car was garaged while it was laid up and is in the garage now. It's shares the garage with my other car depending on which one I'm using. It's very good condition with only 47k.

I can't see that water flooding/12V cabin feed issue being relevant in that case.

And besides, if the power to the whole cabin was flaky you'd have noticed far more symptoms than just the engine cutting out.

 

 

 

Perhaps worth checking the fuel pump relay, a failure would produce the symptoms you describe.

Good shout, also the ECU relay.

Fuel pump relay in position 4 (top row far right)

ECU one in pos 12. bottom row third position from left.

 

Look for corroded terminals on the relays at least, I suppose. Not sure what else you can check given that it's intermittent.

Unfortunately this will require lower dash trim removal on that side, see Fabia Guides section and guide for brake light switch replacement for a walk through with good pics, IIRC.

 

35 minutes ago, sepulchrave said:

Perhaps worth checking the fuel pump relay, a failure would produce the symptoms you describe.

Thanks Guys I'll check all those, probably going to be over the weekend now. I'll let you know how I get on.

Well, after pulling the fuel pump relay and testing it with my meter I found it was failing intermittently, replaced it with a new one and the car started first turn of the key.

I won't be holding my breath but I will be keeping my fingers crossed. It doesn't explain the fault codes I've been getting but I suppose there could have been more than one fault, or the codes were due to low voltage as the battery died so many times.

Thanks to Wino and sepulchrave for the insights, if you're ever in Newcastle there's a drink at my bar for you.

Cheers.