Petrol ibiza 1.2 not-starting fault

[seat0040]

Hi, I'm a new arrival on this forum & live near Southampton.

I have a 2003 1.2 3cylinder 12v petrol ibiza (AZQ engine). 50k miles

It failed to start one morning.

It has a fully charged battery and does not show an engine fault (or EPC) warning light. Correct key is used, immobiliser light goes out after a couple of seconds as usual. No previous problems or symptoms. However now no sign of firing when cranked for starting.

No sign of weak battery – very willing cranking, bright headlights etc.
All 3 plugs spark on cranking when outside engine, although are well carboned. NGK Plug gaps are OK(0.8mm)..
Air cleaner is recent and still 'yellow', ie not clogged.
Throttle flap moves with pedal position when engine not running.
Inspection through the cam sensor opening shows the rear camshaft does rotate with the crankshaft.
There is pressurised fuel in the injector feed pipe & fuel can be smelt when venting compression tester – so injectors seem to be working.
Compression test shows No1 cyl 11.2 bar, no 2 cyl 12.0 bar dry. (I ran out of time to do the third.)
Oil & coolant look fine.

I have not had it vag.commed yet. However I assume obvious sensor faults ( crank, cam, MAF, knock) would either suppress sparking or just give rough running post start.

Local dealer suggests timing chain jumping a couple of cogs which he claims would not show a fault code but would prevent starting. However the compression figures seem to counter that since the Haynes manual (Polo) shows 11 bar min for AZQ engine. I assume if valve timing was out it would prevent starting by preventing full compression.

Does anyone have the knowledge or experience to suggest what fault would give these symptoms?

I am also planning to try changing the main engine supply relay ( I understand a high resistance contact can occur and the resultant voltage dips can cause odd behaviour with no fault codes) but I haven't figured out which of the 4 visible relays it is yet (can anyone guide me)?

Thanks for your help!

 

[Nath.]

where abouts near So't'on are you, you're probably near me



My first guess would be a timing chain fault, if you do a search you will find loads to read up on

BTW 50k miles is almost exactly when they seem to go

the chain only needs to jump 1 0r 2 teeth on the sprockets to stop it starting a tow start may get it going if this is the case

 

[seat0040]

nathwarr - thanks for the quick reply.
I'm near Chandlers Ford...

You've set me thinking. From the Haynes manual the upper sprockets look as though they have about 48 teeth so if they slip two teeth, and the spark is timed from the inlet side cam sensor (and the computer isn't bright enough to adjust for the slippage ) then the spark could be 15 degrees late. I can see that would cause problems even if the valves are still all shut at peak compression. So my argument about the compression readings may not stand up.

 

[Nath.]

I think this is the case, one or two teeth jumped still gives full compression but out of time with the fuel and spark

I think that if you can get enough cranking speed or a tow start to second gear sort of speeds, it may catch and start but run a bit lumpy

I think VAG-COM is your friend here and get looking for crank sensor faults

Personally I would avoid Kings seat even though they are the most local to you, they don't seem to know one end of a spanner to the other (10 days to retrofit cruise control after they told me it would be a while you wait thing) but that's another story and why I always go to Meadens in Sway even though I live in Netley

Meadens rule other dealers just drool IMO

 

[bertrum]

The timing chain slipped on my old 1.2, wouldn't start either. Was advised not to even try and start the car, let alone tow start + drive it!!!
I think SEAT UK know it's a common fault and paid half of the repair (if not all of it) when mine broke!

 

[BeEzA]

mine did the exact same thing last week, drove home fine, got in the car the next morning and it wouldnt start. changed map and crank sensor (ran vag com and got these errors) then ran compression tests and found my compression to be ok. getting spark and fuel but no "bang". eventually decided to get the timing cover off and have a look. found that the tensioner was all the way out and the chain was slack so then checked the timing marks on the end of the cams and found out that id jumped 2 teeth. ive bought the timing chain kit (£92 from bickets). all im waiting on now is the TDC tools (£49 + postage from The Motorists Warehouse). If you want to check yourself, take the two caps off the end of the cam cover on the passenger side of the engine, youll be able to see a groove in the end of the cam and if they arent both in the same position then your timing is out.
Let me know how you get on

Beeza

 

[BeEzA]

I am also planning to try changing the main engine supply relay ( I understand a high resistance contact can occur and the resultant voltage dips can cause odd behaviour with no fault codes) but I haven't figured out which of the 4 visible relays it is yet (can anyone guide me)?

Thanks for your help!

i meant to say as well, i get an error in vag com for that relay too but ive changed it and still get the same error :S im assuming i have changed the right relay (429 iirc).
i should have the TDC tools on friday and should have the car running again (i hope) by saturday night, if you can hold off till then i can let you know how it went because it sounds like your problems are virtually identical to mine hehe


Beeza

 

[Ammo84]

My 1.2 is currently in the process of having a head and valves checked. After a all so common timing chain jump my mechanic has timed the engine and the car does start but cuts off straight away. Eventually after holding the accelerator constantly and the car warming it does hold idle but it is very rough. Anything over 2000rpm and loud banging noises and crackling comes from the engine. Been told it was backfiring?

The car has been checked for errors it was diagnosed then that when the car timing jumped it may have bent a valve or two and hence the head off scenario. I'm still not sure if the head/valve work will solve the problem. Could the very rough running be due to a faulty sensor etc?

Any help/direction would be greatly appreciated.
Cheers

 

[bertrum]

Rough running could also be down to another common problem..... Coil Packs?!

 

[BeEzA]

could be coilpacks, did your mechanic do a compression test on it? that should give you a rough idea of whats wrong.

 

[Ammo84]

Compression test was right for all 3. Tested coilpacks and found no issues. Baffled by what it could be! So next route is to take the head off and check for bent valves. Not sure if sensors etc might need changing after timing jump?

 

[BeEzA]

has vagcom been run on it? if not then i wouild strongly suggest running that before stripping the head, it takes 5 minutes and will probably point you in the right direction its saved me a lot of work quite a few times

btw your getting compression on all three cylinders so does that not mean the valves are ok?

 

[Ammo84]

Vagcom test was done after it was re-timed. But nothing unusual came from the test. Just errors from timing jump etc. Yeh compression test seemed ok but mechanic found no other route to check as all have been checked hence head off.

When he checked valves yesterday and tested them, there was very slight valve damage. Could there be another reason for the rough idle and backfiring etc?

 

[BeEzA]

well if theres slight damage to the valves then that could cause the backfiring and rough idle. im hoping i dont have damaged valves should have my car running tomoro night so wont find out till then

 

[seat0040]

Thanks for the suggestions Beeza & nathwarr. I have now checked via the cam inspection cover: with Cylinder no 1 (crankshaft pulley end) at Top Dead Centre - amazingly the exhaust camshaft seems to be 3/4 of a crank revolution behind where it should be so it has jumped a lot of teeth. According to Haynes manual the camshaft slots should be horizontal with No1 at TDC. So it will be interesting to see if there is valve damage - hopefully not given OK compression readings but from Ammo84's experience I'm not sure.
I haven't time to strip so will have to tow into nearby dealer tomorrow.

 

[BeEzA]

well its been a success for me , did the timing and put it all back together last night and the car is running better than it ever was mine had jumped about 4 teeth. ill tell you right now, that was a pain in the backside of a job haha hope i wont be doing that again.

keep me posted on how you get on guys

 

[seat0040]

Congratulations BeEza, The steps I had wondered about when considering whether to do it myself were:
1 would the timing tools be strong enough to hold camshafts & crankshaft when undoing the bolts?
2 how awkward is the access to the crankshaft position sensor hole?
3 do you really need to support the engine from above or will it be supported ok anyway without the mounting at the timing cover end?
What did you find?

 

[BeEzA]

1. Not on their own, had to make up a "Y" shaped tool out of flat bar and 8mm bolts to hold against the cam sprockets incase you sheer the cam holding tool. The TDC tool that holds the crank goes into the crank position sensor hole to hold the flywheel and is strong enough to hold the crank.
2. one you get the sump off, getting to the sensor is a doddle, its in line with where the drive shaft comes out the gearbox (drivers side), you can also follow the wires to it.
3. jack up the engine from the bottom to take the weight but only after youve removed the sump as you may cover the sump bolts with the jack .

its a time consuming job overall but wasnt a "hard" job when you have the right tools. the haynes manual for the polo was quite helpful as we looked over that before we started the job so it gave us a rough idea of what was needed etc.

 

[seat0040]

Thanks for the hints BeEza - very helpful....

 

[bertrum]

Sorry, but just going a little off topic... Haynes Manual... As they haven't made one for the Mk4 Ibiza, which is the best one to go for for reference - Polo, Fabia etc?