I have a 2001 Skoda Octavia from new with 44k on clock regular maintained, it as developed a starting

problem when the engine is hot or just even warm. From cold it starts instantly every time. One garage tells me the the glow plugs need replacing another says it can't be the glow plugs as it would effect cold starts. Any ideas.

JOHN

Shouldn't this be in the Octavia I section?

Sorry i can't help with the query though....

Should be in mark 1 section.... but can offer something... my own mk1 did this at similar age, quite soon after problem became apparent gave me an engine management light and it was air mass/flow sensor, dealer replaced it and started like a dream again everytime. Can't promise it is the same thing of course but I happen to remember warm/hot start problem and its cure on my car.

Edited 11 May, 201115 yr by hugothebear

I did read somewhere on this forum that a bad battery can cause this problem. No problem starting from cold but it can't spin a hot engine fast enough to reach the speed that the management system requires before injecting fuel.

Check the battery first as it might be the cheapest solution?

Moved to Octy1 forum.

I'm not usre how a battery can cause bad hot starting. If anything, it's the other way round as the oil is thicker whn it's cold, glow plugs are on longer etc etc. It's definately worth checking though. As Friendlyfire said, it would be the cheapest solution.

Failing that, it could be a dodgy coolant temp sensor. My seat had this, and it wouldn't start properly when hot, as the ecu thought the engine was at negative temperatures. Might be a MAF too. Best way is get it hooked up to vag-com, or dealer diagnostics and see if any faults have flagge dup. The coolant temp sensor should put a fault up.

Is the engine management light on?

...I'm not usre how a battery can cause bad hot starting...

When the engine is cold, the ECU immediately signals the pump to inject.

When the engine is hot, the ECU only signals the pump to inject immediately when the engine RPM is more than 260RPM. If the engine slower to turnover the ECU delays the signal. The slower the engine, the longer the delay before the ECU signals the pump to inject.

Try jump starting the car when it is warm. You will probably find it starts immediately.

When the engine is cold, the ECU immediately signals the pump to inject.

When the engine is hot, the ECU only signals the pump to inject immediately when the engine RPM is more than 260RPM. If the engine slower to turnover the ECU delays the signal. The slower the engine, the longer the delay before the ECU signals the pump to inject.

Try jump starting the car when it is warm. You will probably find it starts immediately.

Could also be the starter motor not turning fast enough if it's on it's way out.

Likely suspects for poor hot starting:-

1) Duff battery - reasoning already explained

2) Duff starter motor - When the engine is hot, so is the starter, so the resistance of the armature rises, so it spins slower, so it doesn't get the negine over 260rpm...

3) Bad connection from battery to starter and/or bad engine earth. - Again high resistance when engine hot so the starter spins slower...

The connections are the easiest and cheapest to check.

coolant temp sensor its cheap and can give problems when hot starting

quite common accorss the vag range

stevo

Ahh..

Didn't realise that it needed to spin faster when it was hot.

Might be that then..

Should be in mark 1 section.... but can offer something... my own mk1 did this at similar age, quite soon after problem became apparent gave me an engine management light and it was air mass/flow sensor, dealer replaced it and started like a dream again everytime. Can't promise it is the same thing of course but I happen to remember warm/hot start problem and its cure on my car.

Air Mass Sensor already replaced, no effect to starting, but improved acceleration dramatically.

I did read somewhere on this forum that a bad battery can cause this problem. No problem starting from cold but it can't spin a hot engine fast enough to reach the speed that the management system requires before injecting fuel.

Check the battery first as it might be the cheapest solution?

Battery and conections have been checked.

I'm not usre how a battery can cause bad hot starting. If anything, it's the other way round as the oil is thicker whn it's cold, glow plugs are on longer etc etc. It's definately worth checking though. As Friendlyfire said, it would be the cheapest solution.

Failing that, it could be a dodgy coolant temp sensor. My seat had this, and it wouldn't start properly when hot, as the ecu thought the engine was at negative temperatures. Might be a MAF too. Best way is get it hooked up to vag-com, or dealer diagnostics and see if any faults have flagge dup. The coolant temp sensor should put a fault up.

Is the engine management light on?

No warning lights have ever showed, booked in for dealer diagnostics to see if any faults have flag up.

Jump starting the car when warm will allow you to exclude the battery. The owners manual states that 'Batteries, which are more than 5 years old, must be replaced', so if you have the original battery it is very likely to be the cause.

Assuming the car is fine when running, I would rank the possible causes as follows

Battery 50%

Starter Motor 30%

Loose Coonections/Earth Strap 10%

Other 10%

I've excluded general starting problem such as fuel draining back to the tank because the they would apply equally to or be worse on cold starts.