Polo Starting Issue

Seth Brundle

I received this from someone earlier who wants to remain anonymous. Maybe someone can help?
I had thought that it would be either a fuelling or ignition issue but I guess it could be something else.

My '98 Polo which never starts.

Every SINGLE time, without fail, it conks on the first attempt, so then you have to turn the key for a second time, leave it chug away, then press the accelerator and rev it a bit. Sometimes there's a cloud of smoke from the exhaust after this procedure is followed. Then, it drives all right but you have to give it a LOT of acceleration the whole time. I've had it checked so many times, and my mechanic (who's excellent) cannot find the cause. I put in a new battery which didn't make a difference.

Halfrauds

airfilter or a split hose?? but if the mechanic is good i doubt its them:D

Darragh29

Has it been hooked up to check for fault codes???

Seth Brundle

I don't believe that it has been electoronically interrogated. From what the sender has told me (the only additional technical info to whats above) is that it has been to a local mechanic but not a VW dealer or specialist.

Darragh29

kbannon wrote: »

I don't believe that it has been electoronically interrogated. From what the sender has told me (the only additional technical info to whats above) is that it has been to a local mechanic but not a VW dealer or specialist.

Well that's the starting point. I know loads of excellent mechanics that don't have the hardware for computer diagnostics. Don't want to start a row on the thread but regardless of whether they are indy, specialist, or main dealer, they need some diagnostic equipment to be able to approach diagnostics without having to cross your fingers when identifying a part for replacement.

Owen

If he's around Cork, I have a diagnostic reader I'm happy to use on his car for him. It worked brilliantly in diagnosing a few faults on my Mother's Polo.

crosstownk

I've seen this type of fault plenty of times in Polos. Quite often it is the temperature sender that is at fault. If the fault memory is interrogated, no fault will show. This because the engine temperature sender is returning the wrong value e.g it may be returning 60 degrees when the actual temp is 8. This doesn't show a fault because 60 is an acceptable temperature value. The car won't start because the fuel quantity (and other values) are being mapped based on 60 degress - but the fault memory doesn't recognise this.

The only way to determine if the sender is at fault is to read the temperature value being returned by the sender rather than the fault memory. This is a simple task using VW diagnostic equipment (08 Read Measured Value). I'm sure it's equally as simple on non VW test equipment but I only have experience with the VW equipment.

stek

Could it be the Ignition key barrel? It happened to me twice on different polos.

Darragh29

crosstownk wrote: »

I've seen this type of fault plenty of times in Polos. Quite often it is the temperature sender that is at fault. If the fault memory is interrogated, no fault will show. This because the engine temperature sender is returning the wrong value e.g it may be returning 60 degrees when the actual temp is 8. This doesn't show a fault because 60 is an acceptable temperature value. The car won't start because the fuel quantity (and other values) are being mapped based on 60 degress - but the fault memory doesn't recognise this.

The only way to determine if the sender is at fault is to read the temperature value being returned by the sender rather than the fault memory. This is a simple task using VW diagnostic equipment (08 Read Measured Value). I'm sure it's equally as simple on non VW test equipment but I only have experience with the VW equipment.

I agree you won't get a fault code but in the above problem, but you'd cop it easily enough by looking at real time data from all sensors, if the problem is with this sensor, you'd see a dodgy temperaure like +80 or -12 degrees or something like, same logic applies to air flow & MAP sensor data.

But I think before anything else, you have to be able to eliminate the usual suspects/ECU input sensors, etc...

crosstownk

Yep - the realtime data is the only way to identify some problems. The important thing is to find a mechanic/technician who can do this. Too many mechanics just read the fault memory and when they see no faults recorded it's a case of "computer says no" and they tell the customer that there is no fault despite the fact that the customer has experienced symptoms. These are the people that waste customers time and money and get the motor trade a bad name.

/Sorry if that sounds like a rant:)

Darragh29

crosstownk wrote: »

Yep - the realtime data is the only way to identify some problems. The important thing is to find a mechanic/technician who can do this. Too many mechanics just read the fault memory and when they see no faults recorded it's a case of "computer says no" and they tell the customer that there is no fault despite the fact that the customer has experienced symptoms. These are the people that waste customers time and money and get the motor trade a bad name.

/Sorry if that sounds like a rant:)

I always take "hooking up to a diagnostics system", to mean checking for fault codes, looking at sensor singals and manually cycling components like injectors, fuel pump, etc if necessary. I have an oscilloscope for looking at small signal waveforms if I need to zoom in on a particular component signal, but I don't know many mechanics who get into this particular task, but I'd expect any mechanic to be able to view real time data and see a problem in the data if there is one...

crosstownk

Darragh29 wrote: »

I have an oscilloscope for looking at small signal waveforms if I need to zoom in on a particular component signal, but I don't know many mechanics who get into this particular task, but I'd expect any mechanic to be able to view real time data and see a problem in the data if there is one...

That's the correct approach if nothing obvious is apparent. But quite a few garages out there just read the fault memory. They may be good mechanics, but in some instances they are not familiar enough with the diagnostic equipment to perform a concise diagnosis. Lack of training with diagnostic equipment seems to be the problem, imo.

Seth Brundle

Cheers folks - I'll let them know.