HELLO, I HAVE A HYUNDAI EXCEL 1991 AND ITS NOT COMING POWER TO THE INJECTORS,HOW I FIX MY ECU,DO YOU HAVE DIAGRAM?

It is usually in the fuse panel under the hood. It's easier to disconnect both battery cables and hold them together for a few seconds. Reconnect the battery cables and the ecu will be cleared

Lacking fuel pressure.Change fuel pump to the 1994 model type.Squeezing the fuel ret line causes pressure to build up in the line and fuel to pass through injecters more efficiently.

what you have to do is connect a noid light on the #3 injector and see if it is wirking, if not there is a broken wire or the drive for that injector in the ecu is bad, which means you need to replace the ecu

MAY HAVE FAULT IN ECU//CHECK FUSES/WIRES AT ECU

Did the 'Check Engine' Light come ON? Whenever the 'CHECK ENGINE' light comes on, the ECU (Engine Control Unit) sets a Diagnostic Trouble Code (DTC). These codes identify the particular engine management system which caused the light to come on.
You'll need to use/find an OBDII (On-Board Diagnostic) Scanner to retrieve any code which have been stored in the ECU computer. Afterward, we might be able to help you DIAGNOSE and perhaps eventually fix the problem.

Whenever the 'CHECK ENGINE' (Service Engine Soon) light comes on, the ECU (Engine Control Unit) sets a Diagnostic Trouble Code (DTC). These codes identify the particular engine management system which caused the light to come on.
You'll need to use/find an OBDII (On-Board Diagnostic) Scanner to retrieve any code which have been stored in the ECU computer. Afterward, we might be able to help you DIAGNOSE the problem and perhaps eventually fix the problem.
Go to www.hmaservice.com and register( Vehicle by VIN). Afterward, you have access to shop manuals, service bulletins, wiring diagrams, etc. about your vehicle.Take/Tow your vehicle to an authorized Hyundai dealership and pay the diagnostic fee... they will tell you exactly what the problem is and the cost of parts/labor to fix it... at least this way you'll know what the problem is and what's required to fix it.

Possible CAUSES for this drivability issue are MANY!... Without looking at it myself, we could be playing musical chairs forever. Does the Check Engine light come ON when this happens? Whenever the "Check Engine" light comes on, there is always a DTC (Diagnostic Trouble Code) stored in the ECM (Engine Control Module). You'll need an OBDII (On-Board-Diagnostics) scanner to retrieve any codes recorded/set in ECM. Once you do this and let us know what, if any codes are set, then we can go from there. Otherwise, Take the vehicle into a Hyundai Service Center (dealership), pay the diagnostic fee. They will tell you EXACTLY what the problem is and what's needed to fix it (parts, labor, tax, time-frame, etc.). This way you will find out which parts, if any, you need to fix it - perhaps fix it yourself. Go to http://www.hmaservice.com/ and register (vehicle by VIN). Afterward, you'll have access to technical information (manuals, wiring diagrams, service bulletins, etc) about your vehicle.

If it has a dizzy then you need to check the ignition module, these are normally mounted inside the distributor. 

it's an ecu related problem .. a component in the ecu is overheating and has to be replaced .. possibly a transistor in the power input area

drian the gas and let it sit for a couple of hours. make sure ALL liquid is out of the tank. do that because there might be some water in the gas.