Engine turns over but doesn’t start on a Yaris VVTi

[YarisVVTi2002]

Hi everybody, new member and major Toyota owner / enthusiast here with 5 different Toyota models in the immediate family.

I got a Toyota Yaris 1.3 Auto 2002 VVTi as a run around and for the school run over a year ago, except for one problem it has been good runner until now.

I’ve been working on cars for years and normally solve most problems on my own but this one has me stumped. I have done lots of checks on this problem, listed below.

Car has been running rough for weeks – very sluggish / loss of power, engine vibration etc

Car started one morning and cut out after a few minutes after engaging drive and trying to pull away. It would not restart again despite cranking over normally. Since the break down I’ve tried many ideas and I got the car started once for about 30 seconds before it conked out- it had been left for a few days and the battery had been taken out to charge it. Sometimes when the engine is turned over, the turn over speed may increase after 10-20 seconds and it feels like it’s close to starting, but this fades away.

History and things done so far:

1. The fuel tank is nearly full, it was filled up with unleaded a few days before.
2. I tried starting it with the other key, in case of an immobiliser fault- No difference
3. Charged car battery and tried jump starting the car off a different car- No difference
4. Used Cold Start spray both in the air inlet and directly into cylinders- No effect
5. Replaced all 4 pencil coil packs with a working set with the same model number- No difference. The voltage on the 4 pins of the coil leads are 0 & 12v on the 2 outer pins and about 7v on the 2 inner pins. The resistance across all 4 pins of the coils are the same on all coils. A break down technician had checked the car, plugged in an OBD scanner and said the error codes indicated a problem with the coils or the coil driver circuit on the ECU but I can’t find any faults here.
6. I took out each spark plug, left them connected and cranked the engine – there was a good spark on all 4 plugs. On removal each plug was slightly wet, indicating fuel was getting through.
7. The fuel line was disconnected and the engine turned over, about 100ml of fuel was pumped out in one crank. Indicating the fuel pump is ok and the fuel line & filter are not blocked.
8. The pistons could be seen moving up and down as the engine was cranked. Both the tops of the pistons and the plugs were quite carbonised. The car has done about 58,000 miles and has been serviced regularly. I can’t see how there can be a problem with the starter motor if the pistons are moving. I think this model has a timing chain rather than a rubber timing belt.
9. Compression was tested by taking out the spark plug and putting a rubber valve grinder suction cup over the hole and cranking the engine, a loud popping occurred indicating pressure in all cylinders.
10. The crankshaft sensor failed about 6 months ago and was replaced. The last OBD check didn’t show any crankshaft sensor error code – which it did before.
11. The petrol had a small amount of diesel contamination about 3 months ago. Since then the car has been filled up over 4 times.
12. The yellow engine warning light has been on continuously since I got the car over a year ago. The Yaris has been to the garage many times about this issue and I was told it was related to the Catalytic converter. The error can be cleared but comes back again after some time driving; it never seemed to effect starting or performance.

If anyone has any ideas or advice on this problem I would be very glad to hear them.