1.9 Gti Overfuelling on cylinder four

[205Rallee 59]

Hi Folks, 

 

Ive just had an e mail off an old friend with a 1.9 Gti and his problem is as follows

 

is overfuelling on number four cylinder, I’ve checked all the obvious things and also replaced the plugs, leads, replaced the fuel pump and tachymetric relay, I’ve also checked compressions and spark to the offending cylinder all to no avail, I would be really greatful if you have any ideas where else I could look without having to resort to using diagnostic equipment which I don’t have.

 

Any suggestions would be great fully received as google hasn't thrown up an answer. I'm guessing a stuck injector or dodgy temperature sensor telling the ecu the engine is always cold?

 

Thanks

 

David

[Telf 224 2 Cars]

My first thought as I read the top few lines was stuck injector. It's a common rail so it's to my mind got to be the injector. If the ECU was cold fuelling all the injectors would be recieving the same level of fuel.( That's my logic any way!)

[wicked 103 3 Cars]

The injectors are fired in batch, meaning they all get the same signal at the same time. This rules out temperature sensors etc or other shared component.  

It can only be the wiring or the injector it self (or unlikely; output driver of the ECU). My first bet would be just a clogged up injector; replace or clean (all 4). 

Edited November 26, 2018 by wicked

[jackherer 543]

2 hours ago, wicked said:

(or unlikely; output driver of the ECU)

There is literally one wire that splits four ways so I don't think that is unlikely, it is impossible surely?

 

It can only be an injector problem if over-fuelling affects only one cylinder.

 

How is your friend determining that it is over-fuelling on one cylinder only?

 

If he is inferring it based on one sooty spark plug or similar it could be something else like an ignition problem on that cylinder or even low/no compression.

[205Rallee 59]

Cheers folks, he's checked the compressions and they are all good. Sounds like the injector is the problem, he's going to change it or maybe get it ultrasonically cleaned. Will let you know how he gets on. Many thanks. Wiggy