bandit67

Hi Guys, acquired a 93 that has not run for a long time. In tracking down no fuel pressure at the fuel filter , I found the fuse had been removed.Installed new fuse, Got voltage down to #5 pin on the fuel relay, and then checked at the fuel pump under back seat . Here is the funny part, when placing a jumper between 5 and seven at the main relay and switching on ignition, have a constant 12 volts at connector at fuel pump. But when I install fuel main relay and switch on ignition I get 12 volts for a second, then relay clicks , and then lose voltage. Tried this with two know to be good relays, and they work the same. Is this correct........seems to me the relay should hold voltage on the fuel pump continuoulys after switching on ignition. Have not put straight 12 volts to fuel pump yet...will do that next.....any opinions.......J

Former User

When the key is turned to ON(II), the main relay supplies power to prime the fuel pump for 2 seconds. This is how the system is designed. Check the fuel pump ground wire if it does not prime. If the ground is fine, then the fuel pump is bad.

bandit67

Thanks RonJ, Not sure what you mean by checking the ground other than does the fuel pump read to chassi ground and yes , it does. Checked the pump also and it does not read open........but since it will not prime, I suspect a bad pump. So, as you said , pump is to prime up for two seconds after switched on, then no voltage to pump. At what point after ignition is voltage sent to the pump again.....and I assume this is by the main relay. btw, the computer was missing from this car and I replaced it with one from a working 95.....any concerns with this......J

Former User

When the key is turned to ON(III) or when the engine is running in ON(II), the fuel pump runs continuously. This is accomplished by the ECU supplying continuous versus 2 second ground to the main relay.

The 95 ECU should be fine if it was taken from a Civic with the same engine and transmission.

bandit67

Thanks, again, RonJ, the 93 and 95 are both Civics with D15 s but 93 is a manual and 95 ECU is from an automatic tranny car.....do I need an ECU from a manual car........

Ty M

I've had relays act up on me if not enough power is getting from the battery to the car. Maybe check and clean the battery terminals?

Zen-civic

I have a 93 civic ex with a d16y8 and I have been having the same sorta prob recently. When I put the ignition on, the check engine light would come on for 2 secs then click off and the car would start, thats perfect operation. NOW, its doing this... I turn the ignition on, and the motor would crank but not start. There is no click from the relay and the check engine light stays on. It goes sometime up to 3 mins before it clicks then the car start. Now in hot weather it starts fine but in chilly weather it goes like 3 mins of delay. Now its having serious misfires when I step on it. Thats what bugs me the most. Could it be a weak failing pump not delivering enough juice?