TDi Hot Starting Problem

[Nic H]

Hi All,

Was wondering if anyone else had had this problem and better still the solution!

My 2001 110bhp TDi (120,000miles) has recently started to struggle a bit to restart when warm.

When cold no problems starts first go but when warm and you try and restart after a few mins you have to crank it quite a bit before it fires up.

Any ideas???????????

Thanks in anticipation.

[rwbaldwin]

Take a look at this thread

http://briskoda.net/ask-tech/octavia-1takes-longer-start-when-warm/155131/

[Nic H]

Thanks for that (I did try searching the forum but did not come up with that thread)

Had a new temp sender a few months back so will try the jump lead idea and then a new battery if it works.

Can't complain as it is still the original battery (8 1/2 yrs and 120,000miles)

Cheers

[Railroad]

A faulty battery's much more likely to show up when the engine's cold. Does the engine crank over well when it's warm? If not I'd check the starter motor connections and engine earth. Measure the voltage drop on both sides of the starter motor with a multi-meter, it should not be more than 0.5volts.

If the engine cranks over properly then I'd next look at the crankshaft speed sensor. I think they're the inductive pulse type, and if they are it's resistance may be too low when warm which would mean the ECM doesn't get to know the engine is turning. You can check this with a multi-meter too. Disconnect it and measure it's resistance. I don't know the actual value, but I'd guess it'd be somewhere between 200 & 1,500 ohms. Then switch to AC volts and crank the engine. Your meter should read upwards of 0.5volts AC. If this is not achieved the sensor should be replaced. Having said that this test will prove nothing if it's the Hall Effect type. Often the IP type will have two wires, or possibly three but one will be a screened earth. The HE type will definitely have three wires, labelled +, O -. (positive, zero & negative). In the case check for a live supply at +. Make sure - has a good earth, and then crank the engine with your voltmeter probed between O and earth. You should see a switch on and off. If you do it's working.

From there check to make sure you have a good supply to the fuel stop solenoid, and check to make sure that fuel is not draining back to the tank, but again this will be much more likely when left overnight......

[vicfurpac]

Hi everybody. Have the same problem, engine starts fine when cold, problem is when it's hot, so I first umplugged the heat sensor below vacuum pump, engine starts at first turn of the key either way cold or hot, so changed sensor €44.00 at VW dealer cause skoda didtn't have one, noticed that part # is different but sales man at VW said it has been upgraded. Plugged it in, still not working when hot. Checked all plugs to find out they didn't light up, so replaced them.Still not starting. When´t to get diagnostics check both at engine cold and hot. Mechanic said engine starter was not reaching it's 250 rpm's. So he got it desmantled and lubricated, says diagnostics read no errors and that engine starter was reaching it's rpm's now. But problem is not solved yet engine still doesn't start at first turn of key when hot like it does at cold engine he says it might be a problem with the fuel sensor in the fuel pump cause at diagnostics reading fuel temperature wouldn't go above 34.5Cº. Any ideas what it might be? Read all threads attached will try the batery change tomorow to see if it's from it, doubt it cause the engine starts nice at cold. Any sugestions are welcome.

Thanks in advance.

Edited 13 September, 2009 by vicfurpac
Forgot few things.

[Stormchaser]

Is there a fuel temp sensor on those? Might be worth checking as i think i read somewhere on here long time ago about this.

[rwbaldwin]

It's a well known problem. The solution is to replace the battery. What confuses most owners is that the battery tests 'OK' when you go to get it tested. The is because they don't test the CCA.

In the car manual it states 'Batteries, which are more than 5 years old, must be replaced'. This is for average use. If you do a lot of stop/start jouneys you will need to do it sooner.

Below is my post from a previous thread...

This is a known problem with these cars.

When cold, the ECU instructs the injection pump to supply fuel immediately - regardless of engine rpm.

When warm, the ECU instructs the injection pump to supply fuel immediately only when the engine is cranked at 260rpm (or greater).

As the starter motor loses efficiency and/or the battery starts to degrade, it takes longer to start the car. My understanding is that it takes 1 second longer for every 2 rpm under 260. At 30 seconds the pump always receives the instruction to inject regardless of engine rpm.

A good number of people who have had this problem opt to get a new battery and it usually works. The current battery will test 'good' (Delphi batteries will have still have a green 'eye'). They are just not as good as they used to be. The CCA which is not usually tested, will be way down from when new.

A quick test to see if this is your problem would be to use jumper leads when the car is warm. My guess is that it will start immediately

[Nic H]

Hmmm.

A few things to try.

When it is hot it seems to turn over ok.

It only does it if you have only switched off for just a couple of minutes.

It started doing it a few months back but only very occasionally but now it is doing it more and more.

Silly question but what does CCA stand for?

Thanks for all the suggestions.

[rwbaldwin]

CCA stands for Cold Cranking Amps. It is a measure of the battery's ability to supply energy. Battery's tend to perform less well at lower temperatures and we really want to know the worst case for the conditions we are likely to face - hence the 'Cold'.

[Julian15]

I also have this hot start problem but have found that leaving the ignition switched on for about 5-6 seconds or longer (wait for seat belt light to go out) before attempting to start means it is more likely to start first time.

[octywagon]

new battery fixed mine - rwbaldwin has said it all really.

here is a link to a thread - read the bottom half,

http://briskoda.net/octavia-i/octavi...en-hot/149290/

hope you get it sorted.

[Jamesyboy]

RWBaldwin-had my battery tested at a specialist battery place. Tested the CCA and its good. My mechanic said the starter sounds ok too. Any suggestions?