1991 Honda Accord: When trying to start it turns, but doesn't start. Normally only when it is hot and humid (Thank you San Antonio), but when it's a nice cool evening or morning it starts right up. Ran it for four hours in the cool breezy weather, no problems at all. Began checking parts: rotor cap a little burnt (cleaned and brushed silver again), Plugs good, Ignitor passed electrical check, fuel pump turns on no problem, Battery good and strong, everything seems to point to the Main relay COULD THE MAIN RELAY BE AFFECTED BY WEATHER?

Possible causes: The anti-theft lock cylinder isn't recognizing the chip in the key. The key is bad or the anti-theft module is bad. If you have multiple keys then you need to try them. If only one works then the other is bad and you need to get another one.

The other possibility is the lock cylinder is bad and some cars like the 1998 Honda accord had a recall on it. Check into this by calling the dealership.

One other possibility: When you insert the key and turn the ignition, the anti-theft reads the key. Normally, you will see a green key light (depending on the car) blinking and go out shortly after the car starts. This means it is working obviously.

If you see the green key light blink but your not getting any start, it may be that the Main Relay for the car is bad. This happened on my 1998 Honda Accord. It was an $80 relay that is under the steering column. You may have to get a repair manual in order to locate it. You will have to get a replacement from the dealership.

I would try the different keys first, then the relay, these are cheaper to try. The lock cylinder being replaced is the last thing as this is very expensive and the dealership will gladly do it even if its not broken because they often guess and do whatever the customer asks rather than actually do a good job. At least in my experience with San Antonio dealerships. Hope this helps. Cheers.

Hey man if you already changed out the relay i would try changing your fuel pump and sending unit that should stop both of your problems.

car overheated can cause failure at the head gasket.Overheated till the car just stops can cause ring failure thus no compression and worped head.car will not run in some cases.

from experience ive replaced loads of distributor assemblies as the wiring goes bad inside. check for a spark when the vehicle wont start and if theres no spark id change the distributor..
hope this helps

I had that porblem on mine. try replacing the master relay under the dash should fix your porblem it did mine

Some vehicles have sensors that can control the electric fan with the ignition off to keep the heat buildup that naturally occurs right after turning off the engine. This can prevent hard starting that can happen with a hot engine. If it is doing this an abnormal amount, the sensor that is operable with the ignition off may be failing. Before turning off the ignition, check to see if the engine temperature is pushing the 'red zone;' if it is, then the fan operation may be normal but your engine may be running hot.

Replace main relay.

is it turning over normally or slower,have u got a spark,fuel ,if turing slow poss battery/poor connection in the earth,if turning ok check spark if none then check distirbutor,if ok check fuel.

I had a problem with a 1991 Honda Accord and the fix was a weird one. My car would run fine and start fine if it was cold outside. If I left my car in the sun and the interior got hot, my car wouldn't start.

(Since you drove to San Diego this may be the problem)

I found out that if I left my windows open and let the inside of the car cool down, it would start. Strange.....

Apparently, there is a main relay box under the steering wheel that triggers the starter motor and fuel injection. In the Honda's made around 1991, the contacts in that box would expand and would not let the electricity flow.

I guess you can repair the relay box, but replacing it might be a better bet ($50). I took my car to three different mechanics before any of them had heard of this problem.

The fix was simple, but the problem was hard to diagnose.

May be, Your coolant machine is working too hard.. Because when hot/summer day , if my machine in long journey , and you resting your car , the fan sound is still on although you turn off your machine.. It's means, the coolant machine , or your engine component must be changed... I hope so.