College Times

Under The Hood: Know the difference between starting, cranking

By Brad Bergholdt, McClatchy-Tribune News Service

Published: Friday, July 27, 2012

Updated: Friday, July 27, 2012

 

QUESTION: Lately, every two to four days, I have had problems starting my car. It sometimes happens with a cold start, i.e. after leaving it overnight. At other times, I've driven it a few miles _say to the supermarket or library _ and then the car wouldn't start when it was time to leave.

On four occasions, I waited five minutes, and it started as if nothing had happened. On other occasions, it didn't start after the five-minute wait, but it started the next morning.

I had the battery checked, and it showed no problems. It is not the starter because as mentioned above, it has started normally without a glitch after the event. I thought it was the gas because it the problem began after using a no-name brand so I finished the tank, added a bottle of Techron, and used Shell or Chevron. I had no problems for a few days, but then the problem came back.

_Fabrizio Settepani

ANSWER: In order to help with this, I need to have a better understanding of the offending symptom. Does the engine fail to crank, or fail to start? This is a huge distinction, and a really common communication hurdle to work around. Please don't feel bad; I ask this every time, just to be clear.

If your car intermittently fails to crank, but does so later, we can rule out the battery, a battery drain problem and the charging system. The most likely faults could be the starter, a starter input signal fault, or in some cases an immobilizer, or anti-theft, system intervention. I'd suggest wiggling the key as it's held to the crank position, as well as the shifter or clutch pedal _ this may awake an offending switch. If a repeatable change in symptoms occurs, you've found the problem.

Also, try giving the battery terminals a twist. If they appear corroded, they should be cleaned. If none of these help, a simple check for an appropriate electrical signal at the starter's "S" terminal during a cranking attempt will prove-out or condemn the input circuit, leaving the starter and its cable connections as the only remaining suspects.

If the starter cranks the engine adequately but the engine fails to run, this is an entirely different situation. In a nutshell, there's either no ignition spark, no fuel pressure or no fuel delivery, or possibly a combination. All of these functions originate from the engine control module or powertrain control module.

It's possible there may be a diagnostic trouble code stored that could be a big help in diagnosis. In the event of a no-start/run condition, the check engine light would remain illuminated during cranking for the bulb-check function _ as opposed to the light turning on while driving _ so you wouldn't know there was a detected problem. If the light turns on after the 5-6 second bulb check, there will always be a trouble code stored.

Diagnosing a no-start/run situation will require the services of a pro, and he or she will need to see the vehicle act-up in order to be certain of the cause. You did a great job explaining the "when," but unfortunately, the fault seems absolutely random in nature. The most likely cause of a random no-start/run condition is a loose or corroded electrical connection. A tired fuel pump may also be a suspect; that's easily verified by performing a fuel-pressure check at the time of symptoms. If you're up for it, checking for spark, clicking fuel injectors and a humming fuel pump during an unsuccessful starting attempt would provide helpful information for your technician.

___

ABOUT THE WRITER
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net; he cannot make personal replies.

Comments

Be the first to comment on this article!

Click here to leave a comment
View full site