Alright, I'll get right to it. My '90 Si has a mind of it's own in regard to when it decides it doesn't want to start. It cranks up just fine 90% of the time, but the other 10% it will crank beautifully but not start. It does not throw a CEL. But when it won't start, I can leave it alone for 20 minutes and come back and turn the key. Vroom! It starts right up. WTF!?!

This has been going on for over a year, but it's getting worse (more frequent). It does not seem to be weather related whatsoever (does it randomly in cold/warm/hot temperatures). It also doesn't seem to matter if the engine itself is warm. I can turn the key, dash lights up, and the check engine light turns off after about two seconds. It cranks... but no start. Battery is good. Alternator is good. Tried to jump it just out of curiosity - no change.

The only discernible difference I can tell between when it won't start and when it will is that when it does start, I can hear the fuel pump click on and then stop when fuel pressure is built and the CEL clicks of (when I turn the ignition on but don't crank the car over).

Help?

 

main relay?

 

Never thought of that because I've changed it out before when I fried it by hooking up the battery backwards. Possibly needs replacing? Or could it be that it's loose?

 

ive hooked up a battery backward but it never fried the main relay, it just blew a 100amp fuse at thr shock tower fuse box...

 

Main Relay FTW!!! Don't buy one tho just take yours apart and touch a solder gun to each of the points...

 

How to repair Main Relay

http://techauto.awardspace.com/mainrelay.html

 

Second this.