ashemorris

I'm having a problem that I just cant figure out. Been trying for weeks now. I have a 2000 Civic Si and the problem is the fuel pump is not coming on at all times. Some days I will go out to start my car and the fuel pump works fine. Other days like today I go to start the car and the fuel pump does not prime. I have replaced the fuel pump, distributor, and the main relay. I held onto the main relay while turning the car on and can feel and hear it click. Even tested it with a test light and both the power from the ignition and the RPM power to turn on the fuel pump both work so I know the relay is getting power but the fuel pump is still not coming on. I also have a Fuel Pressure gauge and I am not getting any fuel pressure when the pump doest come on but I get pressure when it comes on, just thought I would let you know I have that to be able to see if its working or not. I am running the new Hondata S300 and have a turbo setup on the car. The chip is band new and has been tested on another car to rule out it could be the chip, which of course got ruled out because it worked just fine in the other car. So I am stumped. I know the relay is getting power, but the fuel pump isn't. So what is between the relay and the fuel pump that would keep it from coming on some days but work fine the next. Also I have noticed that I usually get this problem EVERY day it rains or even sprinkles. I thought maybe somehow water was getting into the fuse box under the hood so I went through the hassle of moving the entire fues box from under the hood to where the passenger air bag used to be. So I know its not getting wet now. But if water was getting into it could it have corroded the mother board inside to the point that even the slightest temp change could make it not work? AND also I have noticed that sometimes when the fuel pump doesn't come on if I leave the keys to the ON position and walk away for about 5 minutes that the fuel pump all of a sudden comes on. I know this is a lot of information but I have tried everything I can think of other than taking it to a wiring shop like Tidewater Auto Electric. Please help if you can. Thanks.

sleepypanda23

I feel like there is some sort of short or corrosion that due to the changes in temperature, it causes some loss in power. best bet is go to the actual fuel pump and test to see if there is power.

i would open up the gas tank, remove the fuel pump, attach test leads (i recommend removing the fuel also and letting the fumes air out, safety reasons), attach those leads to a multi-meter and confirm if its getting power. trace the wires from the fuel pump to the relay. it has to be the wires in this case because if you tested everything else, including your ecu on another car.

best of luck

ashemorris

I already used a test light on the positive wire on the fuel pumps power plug and no power comes to it at all. So I'm pretty sure something has happened between the relay and the fuel pump. Do you know what color wire sends the prime signal to the pump? Ive looked on you tube and thus far everyones wire colors are different from mine on the relay side.

sleepypanda23

On the relay (most relays however) there should be numbers; 86, 87, 85, 30

86 goes to a switch (ignition)
30 goes to the battery
85 is ground
87/87a goes to the pump

As you said, youre probably 99% right about it being between the relay and the pump.
-Testing the 86 slot (in the actual fuse box) it should read some voltage (12.4v) when the key is set to on.
-85, you can put the negative wire there and touch the positive with the other. Making sure its actually being grounded.
-30; is positive from the battery. Make sure you have power there.
-87/87a; that is what goes to the fuel pump.

I know you've mentioned that you replaced the relay. But could be that the coil in the relay isnt getting enough volts.
(I dont remember what colour the wires were...)
Hope this helps