Hi, I am trying to find out why my VX V6 sometimes has trouble cranking. Battery has been tested ok using a battery analyser at the local battery shop. Alternator output is around 14.2-14.3 Volts and gives 14.0 Volts at battery terminals. I have driven around with a multimeter across battery terminals and get constant voltage of 14.0 volts. Are these voltages normal? Thanks.
Check the voltage drop on the engine to earth, IE, next time you test, keep the positive on the battery and alternate the negative probe from battery to engine and then to chassis earth connection.
You'd basically want no drop, if it's dropping significantly there's something wrong with your earth connection, wiring or battery terminals. Could be ur starter or positive wire at starter. But what's the actual problem first? Does it crank slowly? Not at all? Or does it crank but just not start running until it's been cranking for a while? If the actualcrank is ok but it takes a bit to actually start then could be leaky injectors or inlet manifold. Any smoke coming out when it starts? What colour?
does the red mode light go off when you have trouble cranking and as asked does it crank slowly, just make a loud click noise or make no noise at all you want to see absolute minimum 9 volts when cranking,
Yeah you want basically zero voltage drop on the short distance between engine and battery, Anything more than 0.01V requires further investigation as to the cleanliness and quality of connections etc.
if this happens or is worse when the engine is hot the it's your starter motor drawing huge amount of current, i recently had the same problem and a new starter fixed this new starters can be bought on ebay for under $80
oska, it does seem to be worse when the engine is hot. No problems for several days now, but every time the car has failed to crank or cranked sluggishly was after driving then stopping for a few minutes and then starting the engine again. Do you know why that would indicate starter motor? Also does anyone know how I can measure starting current? Thanks.
^^^^ what you describe is exactly the problem i had, you'll be amazed at the difference a new starter makes i wouldn't bother trying to measure the current drain as it's probably over 100 Amps
Starter motors can get a bit tight with age, when they get hot expansion can make them tighter and harder to turn. That's my theory anyway. To measure starting current I think you just measure the voltage at the battery while the car is cranking.
when wiring gets hot its resistance increases which creates more heat which creates more resistance etc after time the windings inside the starter motor increase their resistance and require more voltage to operate
Thanks to everyone who posted. I've changed the starter motor and it now cranks effortlessly. It was the simplest of jobs to do with the front of the car on ramps.
