95 Honda Civic Main Relay/ECU Fuel Pump issue
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95 Honda Civic Main Relay/ECU Fuel Pump issue
Hi all, noob here.
Long story short, my buddy gave me a 1995 Honda Civic EX manual transmission because his mechanic could not figure out his no start issue. Cranks but does not fire. Upon looking at it the first time, wouldn't even crank. Checked the starter, banged on it and it turned very slowly. My guess is they ruined the starter by cranking so much, probably continuously too. Anyhow, get a rebuilt starter, put it in and makes a horrible grinding noise. Find out the set screw from the distributor rotor came loose and screw was bouncing around hitting the contact points on the cap. Put a new cap and rotor, check spark, good to go.
Also, the PGM FI main relay is hanging on the drivers side and ECU is on the floor of the passenger floor. CEL stays on in the ignition on position.
I notice the fuel pump is not priming when turning the key on. I run power directly to the fuel pump, car finally fires after multiple cranks, take it for a spin, runs great and no CEL.
I check the main relay by the instructions in the manual by bench testing the relay with 12v and ground. Relay doesnt click, no continuity, etc etc. Get a new relay and bench test it the same way and everything works as it is suppose to. Relay clicks and continuity between the prongs that are suppose to have continuity. I install the relay and have good power (Yel/WHT) and ground (BLK and BLK/YEL) going into the relay. I turn the key on and have power (BLU/WHT)as well. I measure about 12.2 volts.
Here is the weird thing. I first probed the green/yellow wire with a test light that goes to the ECU and the fuel pump turns on with my probe light very dim. I measure voltage on the GRN/YEL wire and I only get 11.3 volts. I have continuity from that wire to the ECU at 0.2 ohms.
I ground the GRN/YEL wire and the fuel pump turns on. My understanding is that the ECU supplies ground to main relay to provide power to the fuel pump. I checked the grounds at the thermostat and they all test good. I ended up cleaning them anyways.
My guess is that the ECU is bad, however I don't have a test one.
So I think to myself, I'll just keep the 12v wire to the fuel pump and drive the car around when I need to. Car doesn't start after multiple cranks. Leave it for an hour, come back and try to start it and finally starts. Drive it around some more, stop and start it a few times and seems fine. Come back this morning to try and start with the 12v direct to the fuel pump and now it won't start after sitting overnight. It's like the fuel system is losing pressure, but I still cant get the car to start now after multiple cranks. I have yet to check the fuel pressure, but it ran a few days ago by this method.
I also read that the ecu ground is dependent on a crank position signal or rpm signal. In the event of a crash, the fuel pump will not continue to run. Also the ground will be supplied 2-3 seconds when first turning to on position to prime fuel system.
Anybody have any tips or clues?
Thanks in advance.
Long story short, my buddy gave me a 1995 Honda Civic EX manual transmission because his mechanic could not figure out his no start issue. Cranks but does not fire. Upon looking at it the first time, wouldn't even crank. Checked the starter, banged on it and it turned very slowly. My guess is they ruined the starter by cranking so much, probably continuously too. Anyhow, get a rebuilt starter, put it in and makes a horrible grinding noise. Find out the set screw from the distributor rotor came loose and screw was bouncing around hitting the contact points on the cap. Put a new cap and rotor, check spark, good to go.
Also, the PGM FI main relay is hanging on the drivers side and ECU is on the floor of the passenger floor. CEL stays on in the ignition on position.
I notice the fuel pump is not priming when turning the key on. I run power directly to the fuel pump, car finally fires after multiple cranks, take it for a spin, runs great and no CEL.
I check the main relay by the instructions in the manual by bench testing the relay with 12v and ground. Relay doesnt click, no continuity, etc etc. Get a new relay and bench test it the same way and everything works as it is suppose to. Relay clicks and continuity between the prongs that are suppose to have continuity. I install the relay and have good power (Yel/WHT) and ground (BLK and BLK/YEL) going into the relay. I turn the key on and have power (BLU/WHT)as well. I measure about 12.2 volts.
Here is the weird thing. I first probed the green/yellow wire with a test light that goes to the ECU and the fuel pump turns on with my probe light very dim. I measure voltage on the GRN/YEL wire and I only get 11.3 volts. I have continuity from that wire to the ECU at 0.2 ohms.
I ground the GRN/YEL wire and the fuel pump turns on. My understanding is that the ECU supplies ground to main relay to provide power to the fuel pump. I checked the grounds at the thermostat and they all test good. I ended up cleaning them anyways.
My guess is that the ECU is bad, however I don't have a test one.
So I think to myself, I'll just keep the 12v wire to the fuel pump and drive the car around when I need to. Car doesn't start after multiple cranks. Leave it for an hour, come back and try to start it and finally starts. Drive it around some more, stop and start it a few times and seems fine. Come back this morning to try and start with the 12v direct to the fuel pump and now it won't start after sitting overnight. It's like the fuel system is losing pressure, but I still cant get the car to start now after multiple cranks. I have yet to check the fuel pressure, but it ran a few days ago by this method.
I also read that the ecu ground is dependent on a crank position signal or rpm signal. In the event of a crash, the fuel pump will not continue to run. Also the ground will be supplied 2-3 seconds when first turning to on position to prime fuel system.
Anybody have any tips or clues?
Thanks in advance.
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