I have a 93 GS that runs great but recently started overheating. i replaced the heater core and accidentally swapped the send/return lines at the firewall. Now it doesn't crank, dummy light come on and dim but theres no sound at all, replaced main relay and still nothing.

 

is it getting spark? if it is check your timing

 

yes it gets spark and the timing is set correctly, i think when i swapped the heater core hoses i may have exposed the ecu to some water. There is literally no response when key is turned, no click, nothing

 

check your igition switch if that helps

 

yes i replaced the ignition switch as well. I am pretty sure its the ECU. when i swapped the hoses back some water came out from under the glove box. this is so irritating

 

Well you can check your battery if it is working good then you have to check the conections to the battery and starter to see if there is some loose wire, also check your starter or any burn fuse, if everything works good then in my opinion you have to remove your spark plugs and try to turn your engine manually and with a long scrub driver check if your pistons moved up and down, remember the 2 piston on the center goes at the same time up and down, whe the 2 piston at the side are up the 2 on the center has to be down. if one of your piston get stock that means you run your car with low oil and you have to replace your engine. Well I hope this can help you and your problem get resolved soon with any complication, have a great day.

 

Check the starter ground and power wire, sometimes the power wire/plug can come out loose.

 

Like the other guy said, check basic stuff first, battery and grounds, especially the one on the thermostat.

 

Ditto on the grounds. I had that problem too. Check ground at the thermostat Mayb loose or bad connection that's where my problem was. Also as stated check ur starter too.