Maybe there is something I'm missing. Same issue as many have had before. Key on, solid CEL, no fuel pump prime, no start.Very itermittent though. Works fine one day, doesn't work the next. Sometimes when you turn the key on, nothing happens for about 5 seconds, then the pump primes and the car fires right up.

Little info on the car. 1994 Civic all stock.

Things that we have alrady done.

-Checked the ground wire at the thermostat housing, going as far as removing the connection, cleaning both surfaces with emory cloth and reinstalling and tightening the dogs*#t out of the bolt.
-Replaced the main relay. Worked just like the old one. I took the new one apart and tried to manually activate the pump. The pump would run, but the car wouldn't start. As soon as the ECU clicked and the relay activated on i's own, the CEL went out, the pump primed and the car started right up.
-Checked all the fuses with a meter, all good.
-Checked all ground connections
-Charged the battery
-Beat head against the wall when the car would suddenly work like it should.

So, before we drop the cash for another ECU, any suggestions?

 

Do you also lack spark when the problem occurs? What codes do you pull when you jump the service connector? Or do you get code 0 (=CEL stays ON without blinking). If the latter is true, this is usually a bad ECU, specifically a problem with the ECU not supplying the proper reference 5V to the MAP sensor.

 

Sorry, forgot to add the code 0 when we jumper the connector.

I would assume the lack of spark when the problem occurs, but I've not checked it. I do know that even with the fuel pump running manually(operated manually through the relay) that it won't start.

I'll check voltage at the MAP sensor tomorrow to confirm this.

Any possible chance a bad MAP sensor could cause this? Or would this throw a code?

 

Just an update, turned out to be a bad ECU.

Replaced it with a junkyard ECU and it works great now. $60 fix.

Thanks for the help.