No Fuel ECU?
 

Hi all, I am new to the forum but been working on various cars for some time now. I recently picked up a 94 civic DX that does not run. There is no fuel getting to the motor. I can get the car to run off starting fluid so I began to run the basic diagnostics for the car. I checked and there is no power getting to the fuel pump. If I jump the main relay the fuel pump will come on. I tested the main relay as outlined on this site and several other sites and it tests OK. After running through the manual the next step in their diagnostic procedure is to try a known good engine module. Unfortunately I don't just have one of these laying around. I went to the local pick and pull to try to pick up a cheap one and none were available. I did grab another Main relay just to be sure and have an extra after I have read so much on this. I popped it in just for good measure and still no start.

OK so here is where the questions come in:

1) did I miss anything that could cause this issue?
2) Has anyone here had the same issue? ECU no turning on the fuel pump?
3) Any idea where I might be able to get this tested before I drop the cash for a new ECU?
4) Where to get a new ECU if that is indeed the issue?

Thanks for any help you can give me.

-Chris

I had a problem of the same sort.

Check all your grounds and clean them. That solved the problem for me.

just to make sure .. check all your fuses under dash and under hood.
check your ground wires... the motor and frame must have a ground each and the wire harness.
your fuel pump turns on from the ignition.. is there any cel.....

Do you also lack spark?

Check whether main relay fuse 31 (hood), 24 (dash), or 18 (dash) is blown.

Is the CEL on? Does the CEL remain on steady both with and without the 2P service connector jumped?

Have you cleaned and tightened the important ground wire located on the thermostat housing?

OK I will check the grounds. I do have spark, the vehicle will start and run off gum cutter. I am not getting any power to the fuel pump at the connector on the pump. I read that it cycles on for 2 seconds when the ignition is first switched to the on position. Nothing at the pump or coming out of the main relay when the key is switched on. I tested all fuses using a test light. I have not traced out to verify which fuse was which but every fuse that had power coming in has power going out both under the hood and under the dash. I also verified I have power coming in to the main relay as outlined in the wiring diagram. Pin 1 has battery voltage and pin 5 has voltage with the ignition on.

There is something I forgot. I need to check for codes by jumping the 2P connector. I did not pay much attention to the CEL. I will do this tomorrow and report back.

Definitely check for CEL codes.

You also should consider installing a new main relay. If it doesn't help, return it.

Remove ECU connector A and turn the key to ON(II). Do you measure battery voltage at terminals A23 and A24 of this connector?

Thanks for the input. I did check the A23 and A24 connectors and have voltage with the ignition on. I had grabbed a main relay from the junkyard for good measure and plugged it in and no luck. A new one is $70 from the local parts store and they will not allow it to be returned as it is an electrical component. I already tried that route and without even asking they made sure to let me know there were no returns on electrical items.

I still need to check for CEL codes

Ground the A23 and A24 wires directly to the important G101 ground on the thermostat housing. Does the fuel pump now prime and engine now start? If so, replace the ECU.

OK sorry for the delay I have been out of town but started working on this a bit yesterday and will do some more today. I took the ECU for an hour drive yesterday and plugged it in a buddys 95 civic and his car ran off it with no issues. I have a P06 ECU and his was a P28 or something to that effect but it ran just fine.

I came home plugged it back in and still nothing. I undid the grounds at the thermostat and cleaned the contacts, nothing. I began to recheck the system and came to the point where the ECU is not providing a ground to the Main relay on pin 8 of the relay ( I checked this at the ECU but do not remember the pin off the top of my head.) The battery is a little weak now but I was getting about 3v on the wire. I saw in the diagram the resistor internal to the relay but if there is no ground it does not matter what the positive voltage is. From my understanding the ECU should provide a ground for a couple seconds when the key is switched to the on position. I am not getting this.

I still have not checked codes as I was running out of time and since I had a running car to test the ECU on I figured I would do that first. The next thing I guess I need to figure out is what the ECU is looking for to activate the fuel pump. Hopefully the codes will help provide this. I also am going to ground the #8 pin and see if the car runs that way as well.