I have been having on going problems with my Octavia mk1 AGR 90BHP engine type year 2000 with 150,000k.

I have done the following:

checked air filter and air box

changed fuel filter

changed MAF

air intake removed and cleaned - done by garage

reseated pressure release valve on injection pump

Checked for fuel restrictions

Replaced a vacuum hose which was leaking (done at garage)

Inspected hoses for any leaks

RAC man removed the plunger and spring from the stop solenoid on the pump

No codes after a scan.(done at garage)

My symptoms are:

long crank time

requires three pumps or so on accelator to aid starting

temperature light comes on occasionally on starting then goes out

black smoke and smell of fuel on starting

slight screech at the end of the crank.

RAC man reckoned the screech was the starter motor on the way out but it shouldn't affect starting.

He believed it was a possible pressure build problem with the injection pump or injectors although he didn't do any diagnosis.

I have had most problems after a long run of about 2 hours. Very difficult/impossible to start.

.

It has been into the garage, a local back street, and he is unable to figure it out.

Once it is running it runs as sweet as a nut. I have loads of power.

I am in the process of getting VCDS lite sorted out. Having communication problems with laptop and VCDS lite freeware version.

Hopefully this will help to look at the CTS sensor and see if the injection of fuel is what is should be.

Also now going to flush injectors with liqui Moly

Anyone got any suggestions

Loosen the union nut on injector 3 and put a rag around it. Do you get fuel on the rag when you crank?

Check that the butterfly valve next to the inlet manifold is in the open position.

temp light = borked CTS?

I'm wondering about the battery or the starter motor, so I'd check the following:-

1. Cranking speed. This should be at least 250rpm, so if it's not continue to
   
2. Battery load test. If it fails this, change the battery.
   
3. If the battery load test passes, change the starter motor, particularly since the problem is worse on a hot engine when the starter woeks least well.
   

CTS failure or as sated above insufficient cranking speed.

I'm wondering about the battery or the starter motor, so I'd check the following:-

1. Cranking speed. This should be at least 250rpm, so if it's not continue to
   
2. Battery load test. If it fails this, change the battery.
   
3. If the battery load test passes, change the starter motor, particularly since the problem is worse on a hot engine when the starter woeks least well.
   

How can I know what the crank speed is. Can I only check this with VCDS?

I have read it is better to purchase new CTS as non OE ones are likely to fail. Can anyone recomend a good place to purchase on the net?

How can I know what the crank speed is. Can I only check this with VCDS?

Once you've heard a known healthy cranking speed, a low one is obvious even to my tin ears. Also garages often have tachos that read this slow.

I have read it is better to purchase new CTS as non OE ones are likely to fail. Can anyone recomend a good place to purchase on the net?

This is a case where you're actually best, and cheapest long-term, going to the dealer.

Another question, how does the CTS impact on the starting of this engine?

I am a novice but learning fast.

Neither a bad CTS nor slow cranking speed will prevent the engine starting (although you may have to crank for longer).

You only need fuel and air for the car to run. First step is to see which one you are missing - see post #2.

Neither a bad CTS nor slow cranking speed will prevent the engine starting (although you may have to crank for longer).

You only need fuel and air for the car to run. First step is to see which one you are missing - see post #2.

Sorry but a low cranking speed will stop the engine firing, because the EMS will detect the low cranking speed and kill the fuelling.

Another question, how does the CTS impact on the starting of this engine?

I am a novice but learning fast.

The ECU relies on the CTS for the engine temp, so if it's not getting an accurate reading from the CTS it won't fuel correctly.

Sorry but a low cranking speed will stop the engine firing, because the EMS will detect the low cranking speed and kill the fuelling.

It doesn't.

There is a formula for warm starting that allows an instant start at 270+rpm and is progressively delayed at lower speeds, but it will always supply fuel after a delay.

On a cold there is no rpm check. That's why people can have a delay on warm start but an instant cold start when the starter begins to fail.

The ECU relies on the CTS for the engine temp, so if it's not getting an accurate reading from the CTS it won't fuel correctly.

The coolant temp does affect the fueling, but within limits and never to the point it won't supply enough fuel to start in warm weather. After initial injection, the ECU changes the position of the fuel quantity adjuster to ensure idle is stabilised at nominal idle speed.

Not sure about the TDI's but certainly from my own experience the petrol VAG 1.8T's can suffer from both hot & cold starting problems when the CTS is goosed.

I think the problem he's having is probably a cranking speed issue though.

Not sure about the TDI's but certainly from my own experience the petrol VAG 1.8T's can suffer from both hot & cold starting problems when the CTS is goosed.

I think the problem he's having is probably a cranking speed issue though.

Diesels are different. The fuel is burnt in an excess or air. There isn't a narrow AFR range like a petrol.

If the CTS reports a temperature lower than reality, then the engine is overfueled. The car will start but you will get unburnt fuel and poor MPG as there is no sensor in the exhaust to detect the unburnt fuel.

If the reverse is true, the start will be rough until the ECU adjusts the fuel quantity, but it will start.

Have been more investigation.

The fuel pump is not drawing diesel.

Not sure where to go with this.

Will try to get VCDS running so i can check the various things you have all mentioned.

Ah, if the fuel pump isn't drawing, forget most of the foregoing.

Start with a new fuel filter, filling it with diesel before fitting, and try to bleed out the supply line. This would be way easier if VAG had supplied a manual primer pump!

Edited 27 June, 201313 yr by KenONeill

Have already replaced fuel filter.

Its a really strange phenomina.

Last night it wouldnt start now this morning it does with a laboured start.

Have ordered CTS. Will see how that goes.

Have you tried jump lead starting?

Here are a few things to check...

Is the fuel filter plumbed in correctly. The feed to the pump connects to metal pipes on the filter. The return goes via the plastic valve. Make sure it is the right way around.

I suspect the fuel may be draining back into the tank. Was the fuel filter OE? The valve o-rings on some of the aftermarket ones do not seal correctly. Use fuel clips for the filter hoses - not worm drive.

If there is is a clear section of fuel pipe, can you see any bubbles?

Crack the union nut on injector 3 and crank the engine. If the fuel has drained back to the tank it will prime so much faster if you do this.

Check the resistance of the needle lift sensor on injector 3. It should be somewhere between 80 and 120. Check the connector is good.

Here are a few things to check...

Is the fuel filter plumbed in correctly. The feed to the pump connects to metal pipes on the filter. The return goes via the plastic valve. Make sure it is the right way around.

I suspect the fuel may be draining back into the tank. Was the fuel filter OE? The valve o-rings on some of the aftermarket ones do not seal correctly. Use fuel clips for the filter hoses - not worm drive.

If there is is a clear section of fuel pipe, can you see any bubbles?

Crack the union nut on injector 3 and crank the engine. If the fuel has drained back to the tank it will prime so much faster if you do this.

Check the resistance of the needle lift sensor on injector 3. It should be somewhere between 80 and 120. Check the connector is good.

Thanks for that. Do you hav a link where I can find how to measure the resistance on injector 3. Have been searching round but cannot find the exact procedure.

Have you tried jump lead starting?

I havent tried jump lead starting. What will this rule out. I guess the battery?

thanks for all the help guys.

I havent tried jump lead starting. What will this rule out. I guess the battery?

Yep.