Hi, I have a 1991 Honda civic si which was given to me by my late grandfather. I am having major problems starting the car. I replaced the battery and tried to start it, when it didn't start I looked online for suggestions. I found something that told me to check the ECU and to check it by lifting the carpet and looking for a blinking light, but when I turned the key the light didn't come on so I ordered a new ECU and when I plugged it in the car still did not turn on. Then a friend suggested that I check for an alarm system that might be blocking power to the ECU and preventing it from starting, and remove it. So I did. The car still did not start and the ECU light will still not come on. I checked that all the spark plugs are sparking and that I have good compression in each cylinder. After all of this I decided to just pour gas directly into the cylinders, put the spark plugs back on and start it that way. After doing this, the car started but once all the gas I had put into the cylinders was used up, the car turned off. If anyone has any suggestions or advice it would be greatly appreciated. I also believe that my fuel pump might not be getting power either

Does the Check Engine Light come on and go off after 2 seconds, when the ignition switch is turned to ON (Position II)? If so, then see if this link helps:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1245523

The check engine light comes on and it actually stays on. But. Thank you

The problem is with the ACG (ALT) (S) fuse, in the under dash fuse/relay box; ECM (perform the K-Test); main relay; or the ignition switch. Perform tests in that order.

Many of the ECMs on older Hondas are failing.

OK, thanks. I checked the main relay and it is working fine. I am not sure which fuse is the ACG (ALT) (S) fuse, I checked the fuse box and there isn't one by that name. And I'm also not familiar with ECM's I bought a new ECU if that is the same thing. And the light on the ECU still doesn't turn on

. Test all under dash and under hood fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145

Be very thorough, since it will save a lot of time and money.

. Clean the main ECU ground, located on the thermostat housing.

Thanks, I checked all of the fuses in both fuse boxes, and the only blown fuse was the alternator solenoid valve. I also looked at the housing for just a few moments and it looks like there is something missing. Soon, when I get a chance, I'm going to look up exactly what the thermostat housing should look like, take a closer look and if its needed, take it apart

I finally had another chance to work on the car again. I was running through all of the wires that the alarm system is connected to and I jumped one of the alarm relays and now I have power to the ecu. I tried starting the car again and it turns over but doesn't totally start. I can still hear the fuel pump click, but it doesn't pump for two seconds like it is supposed to. But now the check engine light is turning on for two seconds and going off like you mentioned earlier. I am following the instructions on the other page. Thanks for all your help

Do you know where I can find a fuel pump wiring diagram for a 91 civic si?

Buy a Hayne's Manual and see if they provide a fuel pump wiring diagram. Meanwhile, see if this link helps:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1245523

Ok, so I jumped the relay and checked the power on it, and the relay is good. I then ran power directly to the fuel pump and it made a thunk sound but never fully came on. I then took the fuel lines in the engine and disconnected them, ran power to the pump again and no gas came through. Could it be the actual fuel lines clogged or maybe just a bad fuel pump in general?

If you performed all of the steps in the previous link, and the pump still doesn't run, the fuel pump is likely bad.