Mysterious Problem!

[Guest Patbest]

Howdy People,

I really need your help on this one please!! This is my 4th Pug and I've yet to experience a problem like this, hopefully someone will say "oh that's an easy one"! So a quick rundown on history pre problem..... just finished reconditioning the head on my 1.9 gti, new valves, guides, springs etc, re-shimmed and obviously skimmed, new water-pump and cam belt kit and a few other bits and pieces.... car was running superbly.... until yesterday! My wife was returning home when the car suffered a sudden loss of power she pulls in car is idling fine...... attempts to pull away and the engines dies. I ended up having to tow the car home... straight into the garage to make a few checks... I thought it was the ignition module 'cos I'd had to effect a repair on the wiring into it a couple of weeks earlier.... however it was fine..... here's the problem (finally) I have a spark, I have fuel being delivered, I have compression, the spark appears to be timed right but the engine is dead... not even a fart from it...... my heads melted, anyone got any pointers?

Sorry for the essay,

Thanks,

Pat.

[Tom Fenton 1,542]

Hello Pat, I had a similar problem with my car, it turned out that the air flow meter was at fault in the end.

[Guest Patbest]

Hello Pat, I had a similar problem with my car, it turned out that the air flow meter was at fault in the end.

Howdy Tom, Thanks for the speedy reply! How did you determine it was the afm in the end, and how would it completely kill the engine... as in it doesn't even cough?

Ta Pat.

[Tom Fenton 1,542]

On my car it was a process of elimination- I changed dizzy cap, rotor, tried a different dizzy, tried different ignition modules, different plugs, different leads. In the end about the only thing I hadn't changed was the air flow meter, tried a different one of these and hey presto all was well.

 

The thing from your description that sounds similar is the bit where you say the car would idle, but not rev up, this is what mine was (intermittently) doing.

 

Another one to check is the blue ECU coolant temp sensor, there are resistance values on here somewhere to check it, if it has failed then it can drastically overfuel the engine to the point where it will not start.

[Guest Patbest]

Food for thought, not having a spare afm lying around will make things a bit difficult, I 'spose an easier one to start with will be the temp sensor, but can you explain how this can fail to the extent that it fools the ecu into massive overfuelling?

[hengti 2]

i can't remember exactly how it manifested itself (i think it would just die completely, not return to idle) but i had a similar sounding problem and found that the plastic cap that covers the AFM internals wasn't airtight.

[Guest Patbest]

Yeah, it's all a bit wierd, it went from being a reliable strong runner to completely dead with no warning, now I know this is how these things usually happen but to find no apparent cause is a bit mystifying! Can the butterfly in the afm be wedged open a bit (carefully of course) to give some airflow?

[welshpug 1,657]

my 205 decided to die in this exact manner! the day after I'd driven it the 165 miles home to Cardiff from Newcastle under lyme!

 

at the time I was new to 205's so left it to a local PSA specialist to have a fiddle for me, one new AFM, oil change and a setup from scratch and all was good (oil was full of fuel!)

[hengti 2]

for the sake of 10mins and some silicone sealant, it could be worth resealing the AFM lid to see if that helps at all

 

ed. should say that, if the AFM lid isn't airtight, it'll allow unmetered air in, leaning the mixture instantly - opposite problem to that which Tom describes. iirc, it would just stall completely and not return to idle (suggests that yours does have some sort of running mixture if it still idles) - so perhaps a different problem

Edited December 23, 2008 by hengti

[Guest Patbest]

for the sake of 10mins and some silicone sealant, it could be worth resealing the AFM lid to see if that helps at all

Gonna run down to the garage now and have a look at the afm for any obvious signs that it is the cause of all this!

[Tom Fenton 1,542]

The one that failed for me looked fine visually.

[Guest Patbest]

OK.. afm has obviously been opened at some time but how will the lid not being air tight affect its performance? Tom I was thinking more on the ecu water temp sensor and was wondering if this would affect starting from cold, presumably not isn't that what it's there for. By the way thanks everyone for the replies!

[welshpug 1,657]

yes it can cause similar issues, I recently had a look over a non-starting car that had had a cylinder head replacement.

 

temperature sender wasn't plugged in and was flooding all the time and not catching, once plugged back in it fired first time.

[hengti 2]

depends how bad any leak is but it'll lean the mixture (sorry - i edited my last post to add an explanation after your following post)

 

i've honestly no idea if it can be related to your prob and have only suggested it as it's no real bother to reseal the lid to see if it helps. the lid prises off and has a shoulder around the inside edge - i'd just clean up both mating faces and smear silicone sealant around the shoulders, slap the lid back on and clean up any excess sealant

[Guest Patbest]

Tried bridging the two pin ecu water temp sender block in an attempt to "fool" the ecu into disabling the auto-choke, is that right? Well it made no difference at all, the problem does seem to be mixture, although I'm not gonna swear on it, any other suggestions chaps?

[DamirGTI 342]

If in doubt , bring the multimeter out ! set it to 20K (K ohm) and measure the resistance of the ECU temp 2pin sensor (the blue one) first on stone cold engine and then on hot engine , fully warmed up to the operating temp , if it's fine you'll expect to see results as follows :

 

Engine completely cold (20C) - 2,000 to 3,000 ohms (if the engine coolant is colder than 20C such as near to the 15-10C mark because of the lower ambient temp. the resistance will be higher so around 3,000 to 4,000 ohms will be fine at 10/15C)

 

Engine fully warmed up to the operating temp. (82C) - 200 to 400 ohms

 

As the sensor temp decreases the resistance value will increase , as the sensor temp increases the resistance will decrease .. as these ones are NTC principle sensors (Negative Temperature Coefficient)

 

If you have fuel and spark and engine still refuses to start up then it might be way too rich or way too lean fuel mixture or an weak spark (is it bright blue spark ?)

 

Regarding the AFM , can check it by removing the black plastic cover and looking at the black carbon track inside the AFM - if it's scratched or if you see any white spots/areas on the black carbon track then it's worn out , but this can be fixed (if it's not badly damaged/scratched) by re-tracking the AFM you can read more about how to test the AFM and how to perform AFM re-tracking here :

http://frwilk.com/944dme/afm.htm

 

Apart from all this , did you check the dizzy signal cable ? the black one which goes form the dizzy onto the ignition amp connector ? this one is very important cos it provides main switching pulse/signal from the dizzy pick up coil for triggering the ignition amp/coil ..

 

Damir

 

EDIT : by the way , how does the spark plugs look like ?

Edited December 24, 2008 by DamirGTI

[nick 3]

I had a similar problem on the Mi not long back. It went from a first time starter to a non starter overnight. I had fuel and sparks but it just wouldn't fire, my problem was the earth wire on the ecu temp plug had broken where it joins the other earths on the loom, so it just flooded every time I tried to start it, I reconnected it and it fired first time. Wasted two whole days of my life sorting that one out!!!

 

Nick

[Guest Patbest]

Thanks Damir and Nick, more lines of innvestigation to follow. Deffo seems like it's flooding so the ecu temp plug is the next thing I'm gonna investigate!

Thanks again chaps!

 

Pat.

[mikie 0]

mine did exactly this a week ago and the ecu temp plug had come dislodged. that was all it was. It overfueled massivley.

[philfingers 5]

try this. Comes from the Autodata 2004 CD, which you can download from various sites and is very useful

Bridging out the ECT won't help. If the ECT is bad then it won't start, will smell very rich.

I know it's a pain in the arse to get hold of stuff for 205s in Ireland as there aren't too many about.

ECT.pdf

[Guest Patbest]

try this. Comes from the Autodata 2004 CD, which you can download from various sites and is very useful

Bridging out the ECT won't help. If the ECT is bad then it won't start, will smell very rich.

I know it's a pain in the arse to get hold of stuff for 205s in Ireland as there aren't too many about.

Yep, looks like next course of action. Changed the afm today.... no difference, changed the ecu...... no difference, disconnected the injectors and the car fired and ran briefly!!! Now just to make 100% sure I know where my ect is..... it's the blue 2 pin connector on the alloy water housing..... hopefully!

And yes getting parts over here is a pain in the arse, however my old 205 is available for "borrowing" parts off of!

[CosKev 16]

Now just to make 100% sure I know where my ect is..... it's the blue 2 pin connector on the alloy water housing..... hopefully!

 

Thats the one m8

 

Good luck with it

[Guest Patbest]

Woo Hoo!!! Sorted! 'Twas the ect, well actually the wiring to it, took a bit of searching but found a break in the wire, mended it and the car fired up! Thank you all for your hints and input..............

Happy New Year!!!

 

Pat.

[DamirGTI 342]

Nice one !

 

Damir