Occasional hot start problem

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littlepolo
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Occasional hot start problem

Post by littlepolo »

My 2002 1.4 BBY auto usually catches first time from cold and then hot starts the same.

Recently, there have been a few (irregular) occasions where it would not start first time from cold. This is no more than one in ten and possibly on damp cold or mornings so I thought nothing of it.

However, there has also been an occasional hot start problem where it would not start on the second crank requiring a third. This happened yesterday (a very mild day) after a first time cold start.When this happens it does not fire/catch at all until the second or third crank. Once running it seems fine.

Generally I'm using Tesco Momentum. On the occasions I use regular supermarket fuel it sometimes goes into it's old pinking habit on a slowdown after a high speed run, or in stop start traffic on short runs around town. It does this on Momentum occasionally, but infrequently as opposed to frequently when on regular fuel.

Any thoughts?
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alexperkins
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Re: Occasional hot start problem

Post by alexperkins »

Change the coolant temp sensor and see if the problem goes away :)
littlepolo
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Re: Occasional hot start problem

Post by littlepolo »

It was changed in January 2018 for a Hella part. Do you think it could be defective?
bvs
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Re: Occasional hot start problem

Post by bvs »

Hot starts on a hot day in Africa were a bit problematic - solution was to chuck some water over the carb(s)/fuel lines to cut down on fuel vapour lock :mrgreen:
Hopefully your Polo is not suffering from vapour lock - not usually a problem with fuel injection unless a fuel pump is not working very well/down on pressure.
As Alex posted - could be cts related - also there is a school of thought that says a hot engine is harder to turn over and might point to weak battery/charge state or starter motor .

Funnily enough warm starts on the Scottish Aviation Bulldog trainer were also tricky - the usual solution was to turn the fuel selector off - crank engine and then quickly turn on the fuel as the engine 'caught'.
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Re: Occasional hot start problem

Post by RUM4MO »

littlepolo, going back to your pinking when using normal UL, I thought that you had done something about this, like I did, which was to replace the oil separator as what is probably happening is that too much engine oil is being drawn into the engine along with fresh air, this forces the regulating Lambda probe to reduce the petrol quantity being delivered and that leads to the pinking, it also leads to heavy coking inside the engine, inlet valve area and spark plugs, and maybe it is that on your spark plugs that is causing the starting issues. So, try checking the condition of your plugs before doing anything else, this extra oil mist being drawn into the engine will continue to cause issues other than pinking, which like me you initially overcame by using UL+ fuel to raise the overall octane rating of what is getting fed into the engine due to dilution/partial replacement of the fuel with oil mist.
littlepolo
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Re: Occasional hot start problem

Post by littlepolo »

Thanks for the suggestions. It has not been using much oil (well within spec) but I did notice a slight uptick in consumption recently (within spec) so it could be related (the oil consumption uptick sort of coincides with more pinking). I'll have a look at the plugs later today while I'm doing another job (caliper piston seals). Can you recall from where you sourced your replacement oil separator?
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Re: Occasional hot start problem

Post by RUM4MO »

I just got my local VW dealer's parts department to order one in for me, they come with new O-ring seals.

Now, some people think that there is nothing much in these separators but I'm sure that there is an air flow control flap motor in them - some else claimed that there was only a small heating element to stop them freezing up in winter time!

So, if there is nothing like a flap motor in there to control the air flow under high vac conditions, I wonder how they reduce the air flow under certain conditions? Also if there really is nothing else in them, then removing it and washing the labyrinth through with petrol should sort it for a while, maybe using something stronger that would break down the carbon curd would help as its successful operation relies on the oil mist clinging to the sides of the labyrinth and flowing back down into the sump while the air with most of the oil mist removed gets drawn into the inlet manifold - which also gets gummed up with that "carbonised grease"!
bvs
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Re: Occasional hot start problem

Post by bvs »

littlepolo wrote: Thu Oct 25, 2018 9:29 am Can you recall from where you sourced your replacement oil separator?
I think I got my oil separator from Autodoc - I will try to check/confirm later,I changed it ok from the top - working over the engine and with aid of a good torch and some inspection mirrors :)
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Re: Occasional hot start problem

Post by bvs »

Hi LP - yes I did get the parts from Autodoc,a little slow delivery because they originate from Germany (but not too bad delay),obviously you would need to cross check/confirm part number for your car.My breather Hose was also kernackered so got one at the same time.Definitely cut down our oil consumption.

FEBI BILSTEIN Oil Trap, crankcase breather
Autodoc PN = 38773
OEN 036 103 464 G

VAICO Hose, crankcase breather
Autodoc PN = V10-2937
OE number: 036 103 493 EB
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Re: Occasional hot start problem

Post by RUM4MO »

bvs wrote: Thu Oct 25, 2018 12:59 pm I think I got my oil separator from Autodoc - I will try to check/confirm later,I changed it ok from the top - working over the engine and with aid of a good torch and some inspection mirrors :)
Yes I remember that leaning very far over the engine, maybe looking at things, then working by touch!

Maybe that is the reason why my daughter's late 2009 Ibiza, which has been getting oil onto the underside of the inlet manifold, which I'm guessing is an oil seperator gasket/O-ring seal issue, has had the new O-rings in the glove box for maybe 18 months!! I did clean off the oil before MOT time as things are tightening up on oils escaping and ending up on the ground/road etc! It has been a reported issue for Fabia/Polo/Ibiza of a certain production period to have oil leaks from one or the other oil seperator O-ring seals, probably a supplier/batch issue.

Edit:- maybe interesting or not, but one of these suppliers listed for this part give it a suggested normal in service life of 3 years or 60,000kms - maybe that is a realistic service life for fault free or efficient operation? Certainly that would tie in with what I found on my wife's old Polo.
bvs
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Re: Occasional hot start problem

Post by bvs »

RUM4MO wrote: Thu Oct 25, 2018 2:00 pm Yes I remember that leaning very far over the engine, maybe looking at things, then working by touch!

Edit:- maybe interesting or not, but one of these suppliers listed for this part give it a suggested normal in service life of 3 years or 60,000kms - maybe that is a realistic service life for fault free or efficient operation? Certainly that would tie in with what I found on my wife's old Polo.
Yes it was a case of look - align - recheck twice at least before being sure that everything was lining up before committing to fully wind in a bolt LOL.

Our engine had done circa 80,000 when I replaced the oil separator - of course it was also 16 years old :)
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