If there's no click from the starter relay and no clunk from the starter solenoid, try bypassing the starter relay. Remove the relay cover, then re-install it and squeeze the contacts. If it cranks, suspect a cracked cam on the end of the lock cylinder. A repair kit is available for this common problem.
Another way to bypass the relay is to remove it and jump between the two terminals. Disregard the two parallel terminals on each side. Of the three in the center, the middle one is not used. Use a piece of wire or a paper clip to jump between the two terminals that form the letter "T".
If there is a single loud clunk, suspect worn solenoid contacts.
Friday, April 10th, 2009 AT 6:54 AM