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naturbar · Oct 2, 2004, 03:15 PM

My son's 94 civic has an ongoing problem with starting(fuel pump won't run). I have read several of the posts concerning this problem. The main relay is not energizing when the key is turned on. The only wire in the harness that is getting voltage is pin 1 when the key is on. I took the relay out and put it on the bench and powered it up with a power supply.by placing 12v. On pin5 and grd. On pin to the relay switches and makes pin 5 & 7 closed... also by placing 12v. On pin 3 and grd. On pin 8 , you here the relay switch but not connections are opened or closed. With the relay out , I placed a jumper (in main harness connector) from pin 1 (constant b+) to pin 7 and the fuel pump runs (disconnected fuel line and it squirted out gas) but the car will not start. I read in one of your post about an igniton relay. Does this relay power the "main" relay. I cannot track down where the power is coming "from" that powers the main relay harness. Sorry for the lenghty question, but wanted you to know what I have already done.

guy75 · Oct 10, 2004, 12:39 AM

Hi
I have a honda civic dx 94 which is giving me this problem. The fuel pump does not pump fuel when I try to start the car. The car did not give any problems when it was running. Also, I was able to start the car a couple of times with a jumpstart (though that does not work anymore). I took it to the mechanic and he replaced both the main relay and the fuel pump but it still gives me the same problem. I would appreciate it if you would keep me (us) updated on your progress in diagnosing the problem.

Thanks, mash

charles · Dec 9, 2004, 10:08 AM

I have a 93 civic dx, upon turning the key to the second ignition position the fuel pump doesn't turn on like it should. Seeing that the main relay is often the culprit I changed it, but the fuel pump still doesn't run. Thinking maybe the fuel pump was bad I hooked up 12 volt directly to it and it worked fine. What else could be wrong?

labman · Dec 9, 2004, 10:45 AM

It sounds like Honda has stacked relays on top of relays. The solution to all the problems is checking for fuel and spark, and following the circuit back to where ever the problem is. A wiring diagram will be a big help.

J-WOOD76 · Oct 23, 2007, 09:26 AM

The Main Relay Is Bad.call Any Honda Dealership & Buy The Relay,about 60.00 Bucks.they Should Tell You Where It Is Located As Well,under Drivers Side Lower Panel,behind Hood Latch.

Duane in Japan · Oct 24, 2007, 07:16 AM

The main relay powers up the fuel pump with nothing in between the two except the wire going from the relay to the pump, there is a fuse before the relay for the fuel pump but that is it, it could be a bad ground on the pump, that is also common.

The relay does not control spark, it also powers part of the ECU and the fuel injectors, there are actually two relays in the main relay, the fuel pump portion goes bad quite often, sometimes you can smack the relay with the handle of a screwdriver while cranking the car and the relay will work, then change it for sure. It takes more amperage to close the relay than it does to hold it closed so the smack helps a little.

There may be an FAQ at the top of this forum for testing the main relay. Kicking the fuel tank, smacking it with a hammer, hitting the fuel pump mount under the back seat or in the trunk while cranking the engine, if the jolt gets the pump running, then just change it and clean the ground point too.