Spark goes out when engine fires up!!!

[Banana Man 0]

I have a strange porblem I ve never come across before and thought I'd put it out on here to see if anyone knows a solution. Right here it goes my car runs on 3 cyls at the moment and it's been buggin me for ages today I have found that cylinder 1 sparks when the engine is crancking over but as soon as it fires up the spark goes out. I have changed all the obvious stuff like rotor, cap, plugs, leads and so forth anyone know what might cause this?The back of my mind says it could possibly be ecu related but wont know for sure till I try another one out on it.

 

ANYONE??? it's driving me mad now as this is pretty much the only thing that is stopping me from getting the car back on the road now so want it sorted asap!!!

[kongo127 0]

What? :shocked!:

Let me see if i understood.

When the ignition is on and the motor is not running there is a cycle spark on cilinder 1?

And it is only at cilinder 1 all the times?

There is no explanation for that...

The rotor does not stop in the same place everytime you turn off the engine.

How can it always be only in cilinder 1? :shock:

 

Is your dizzy well fitted?

What about timing?

You might have a deffo ECU then...

[Banana Man 0]

No kongo it's only when your cranking the engine over it sparks not when the engine is off LOL I didn't explain that very well but have changed my first popst accordingly :) it's when the car actually fires up and is running when the spark goes out it's most perculiar :?

[Banana Man 0]

Come on guys help me out it's not often I put a question out on this forum any ideas would be helpful??? :?

[Henny 0]

You've got me stumped anyway 'nanaman... :|

 

The only points that I can think of are the ECU, dizzy cap, rotor arm, leads or hall sender, but as you've already tried all but the ECU, that's the only point left I can think of... :| It's fecking odd anyway, hope you get it sorted soon... :)

[Banana Man 0]

I cant see how the ecu could be the cause as the hall sender, dizzy, rotor, leads, plugs and coil are the only things that control the spark aren't they?? how could the ecu possibly cause 1 plug not to spark? most odd!!

[Henny 0]

the ECU adjusts the timing signal slightly to give the advance and retardation needed for the engine to run properly. It gets this signal from the halll effect sender in the dizzy so that it knows: A) RPM and B) position of the dizzy (and therefore where to spark)

 

I have no idea past that point if the ECU can vary the timing of each individual spark or not, but it's sounding like it may be able to... :S One thing that may be worth trying is to rotate the dizzy 90 degrees and put the leads on correctly for that position... if the fault doesn't move then it's a lead, rotorarm, or cap... 8)

[Banana Man 0]

tried that one already henny didn't work :( plus I ve tried a new cap, rotor and 2 sets of high performance ht leads so they're not at faul either! I will try another ecu see if that is the cause if not I know a good auto electrician who will help me :D

[Reggit 0]

When you say that the plug sparks when engine is cranking I assume you meen the plug is out of the engine and connected to its HT lead.

 

Possibilities,

plug failing under compression - try and switch plug with one from working cylinder and see if problem moves.

 

Have you checked compression of all 4 cylinders? May have no or little compression.

 

Is the cylinder getting fuel?

 

I'll probably think of another couple of things in a bit.

[Banana Man 0]

checked compression on all four cyls all ok there tried testing a working plug out of the car as soon as the engine fire it stop sparking. There is nothing wrong with fuel or anythhing like that as it is actually the spark that goes out even when it's out of the head. I have also now tried another ecu on it but that has made no difference either bty lost now as it had a new dizzy on it 10 mnths before it came off the road for the x flow conv so that should still be ok! the only thing I can think of is the hall sender in the ecu but cant see how it would only effect 1 cylinder it is very bizzare just put it to my mate who is a VAG mechanic and he is also stumped as he says it would do all four cyls if it was a dodgy hall sender! AAAAAAAAAAAAAARRRRRRRRRRRRRRRGGGGGGGGGGGGGGHHHHHHHHHHHHHHHH :D

[kongo127 0]

What the fu** is going on then? :nuts: :scratch: :silly: :shocked!: :shock: :confused4: :cry: :twisted:

 

It can only be related with the coil power suppy control (on/off) then!

 

Get a scope meter and watch the wavefrom in the coil feed. :idea:

 

It will give you a clue where is the problem coming from (before the coil circuit , or after the coil circuit.

[kongo127 0]

I hope you understand what i mean... :oops:

[Banana Man 0]

Yeah I know what you mean I haven't got a scope so will have to rob one from a mate :D cant think of anything else can only be the dizzy now I think but who nows got it running a bit better now so could at least drive it

[Banana Man 0]

Yay mystery problem solved it was the distributor in the end I bit the bullet and paid £78+ vat slapped it in and bobs your uncle it fired up first time set the strobe on it and got it timed up and she runs like a dream now!! All I ve got to do is slap the rest of the bits on and get it mot'd :D :D Happy man today!!!

[dr_mat 0]

Send the old one back to VW - get them to test it for "weirdest failure mode ever"...

[Supercharged 2]

Nice one dude! - good to have the Banana back on the road 8)

[Henny 0]

Nice one Ant, it'll be good to see the 'nana back on the road again... 8)

[Jim 1]

Think the last time I saw the Banana was at the CCGB National Day last year!!

 

Great news tho Ant :D

[Banana Man 0]

Send the old one back to VW - get them to test it for "weirdest failure mode ever"...

 

I'll go sh&t on they're headquarters doorstep for all the aggro that bl&&dy thing caused me!

 

Thanks for the support guys it'll be good to actually drive it again once its all back together and after the insurance company and road tax has crippled my wallet once again :D :D :D :D :D :D