mazda b2600 computers

so i got two computers both g188s but on the seriel number one has the letter A at the end othere dont does it matter?my truck is a 91 5 speed fuel injeted and my distibuter has no A on it i know theres two diff ones also.my truck was running fine and just died and cranks.getting spark to plugs.it has new ignition control module new complte distibuter and all new fuel pump and filters oil etc.at the moment it is getting no power to the fuel pump.so is there anything othere then the computer that would stop it from getting juice the relay on driver side floor doesnt have power unless u ground the plug under the hood to test it.if theres a relay under the hood i may be missing?i checked all fusses and relays.all seem to be in order.i did take case off computer and it has a white color or back of board so any help be great.i talked to guys in flordia and he said he wasnt sure if comp was bout just it could be.so if anyone else can help be great.and sorry i know i have ask before just thought a better idea of what happen to it would help.

Sounds like the main relay the plug is round and it has 4 wires. right by the battery on the passenger side.

The computer with the A at the end of the serial # will most likely be from an automatic truck. You most likely have a dead fuel pump relay if you are getting no voltage at the pump. There is a plug under the hood that you can jump with a test lead to bypass the relay for diognostic purposes. The relay is located under the drivers side kick panel , its a little black cube with yellow on the bottom of it. Hope this helps you out some man, good luck!