Cough, splutter when cold
I HAVE been experiencing starting problems on my one-year-old Proton Waja 1.6. The engine cranks over, but as soon as it starts to fire, it coughs and splutters for about half a minute as if it was starved of fuel.
Since the vehicle is still under warranty, I contacted Proton Edar. However, the vehicle started immediately, and the electronic diagnostics showed up no faults.
I have noticed since that the symptoms are only present after the vehicle has been at rest overnight. I am in a dilemma as the vehicle is under warranty and I can only have it repaired at an authorised EON service centre that have found nothing wrong.
S. T.
The Waja 1.6 has an electronically controlled fuel injected engine in order to meet current exhaust emission standards. Since the Waja uses one of the most modern fuel injection systems, it does not have a separate cold running circuit, but rather, it has a cold-start injector that injects extra fuel during the first few cranks. Cold-start fuel injection stops after a pre-metered amount of fuel has entered the engine. If the engine continues to cough and splutter for about 30 seconds upon firing as you have described, it is a fuel starvation problem, and the possibility of an electrical problem can be at once eliminated.
There are two probable causes to a problem of this type and both are related to low fuel pressure in the fuel system.
The first is a faulty fuel pump as you have described. If the fuel pump jams and refuses to pump when cold, the engine will obviously suffer fuel starvation. The fuel pump is not on the list of diagnostic faults of the Engine Control Unit, and a faulty fuel pump cannot be diagnosed using this method. A sluggish pump or one in the initial stages of failure would result in the symptoms that you have described.
The other possible cause is a faulty or leaking fuel pressure regulator, and this would result in a drop in fuel pressure each time the engine has been switched off.
Unfortunately, the two above faults would result in similar symptoms; hence it would be impossible to pinpoint the problem based on guesswork alone.
Diagnosing fuel system faults is a job best left to a fuel injection specialist.
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