94 Civic DX 5 speed stock motor. Lately my fuel pump has been slow to prime. Sometimes I would have to wait 5-30 seconds before I heard it hum then I would be able to start the car. The other night when it was cold (high 20s, low 30s), the battery decided to go out. Jumping the car did not work. So I bought a brand new battery but the car still wouldn't start since the fuel pump wasn't priming. I bought a replacement Main Relay and plugged it in but it still wouldn't start. I let it sit overnight and tried to start it up the next day and then all of a sudden the fuel pump primed right away and I was able to start the car and drive it around the block a couple of times. Now I hear a clicking noise every 5 seconds from the Main Relay / fuse box area. Any idea what's wrong with my car?

 

Try cleaning the G101 thermostat ground.

 

Hey RonJ,

(Thanks for the response. I saw several of your answers to other people's similar problems on older threads)

I cleaned out the thermostat, sanded down the contact area and I am still getting the every-5-seconds-clicking sound from around the fuse box. I swapped back the stock main relay and the clicking sound still exists. Ever since I last drove the car about a week ago, I tried starting it today again and the fuel pump doesn't prime anymore again.

I turned the key all the way and I got down underneath where the fuse box is and the clicking sound every 5 seconds sounds like it's coming from on top of the fuse box somewhere. Any idea what the heck this clicking sound is? (I had the Main Relay hanging low already and it's not the Main Relay clicking)

I also tested the voltage on the yellow/green wire from the fuel pump and I'm only getting 2.5 mV when the key is turned.

A quick google search resulted in an forum post with a guy having a similar problem like me and they concluded that my ECM is going out. Could this be my issue? https://www.askmehelpdesk.com/advice/t-476102.html

 

Update: I purchased a used ECU, plugged it in and it started right up. I plugged back in the old ECU and the fuel pump didn't prime at all. I plugged back in the new ECU and the fuel pump primed instantly and started up no problem. Looks like the ECU was on its way out and finally gave up.