I drive a 2008 Volkswagen Polo 1,9 TDI. The car has treated me very well and I have done 276 000 km with only a few minor niggles. However, a starting problem cropped up about six months ago.
When I start the car from cold, I turn on the ignition, wait for the glow-plug light to extinguish and then proceed to start the engine. It then dies almost instantly. When I turn the key to start it again, the engine just cranks without immediate ignition. When the engine does eventually start, I have to press the accelerator to keep it going. Then all is fine and I can drive away normally. The problem is worse in cold temperatures. To add to the confusion, the problem occurs less often if the car is filled with more than half a tank of fuel.
Initially, I thought it could be a battery problem and so replaced the unit, but the problem persisted. I then took the car to my local Volkswagen dealership. After investigation, the technician said it could be the injectors, but that he wasn’t sure. Asking how much new injectors would cost, I was told R14 000 each. Multiply that by four and the fix will cost more than the value of the vehicle.
I did some research online and found that the cause of the problem could be a cam sensor, but it’s unclear because this also seems to affect a car in a “hot” start as well (which is not the issue in my case). I also noticed I could get the injectors cheaper if I shop around, but I don’t want to spend more money on parts that people are “not sure” will solve the problem.
I would like to know if there are other avenues I could explore.
DYLAN MEEK
Johannesburg
Answer: To start a diesel engine, you need good compression and the correct amount of well-atomised fuel to be injected. We assume your TDI engine runs fine after the start, so we doubt any sensors are faulty (but you should have a diagnostic check done). The glow plugs become active only when the ambient temperature drops below about 10 degrees Celsius – again, we doubt they are to blame, but there is a small chance.
Because of the mileage of the vehicle, we would propose a compression check. Following that, investigate the fuelling system to make sure the fuel pressure is correct and then look at the injectors.
There are specialists that flow-test the injectors on a bench. It might be that the injectors are dirty and only need to be cleaned to be able to supply the correct amount of fuel in the correct spray pattern during start.
Worst-case scenario: worn injectors. But we wouldn’t jump to this conclusion before a thorough investigation/test.
