i have a 91 civic DX with a completely stock d15b2 TBI.

Car came to me with a crank no start issue. Owner replaced the ignition switch, which did not fix the issue.

I tested the main relay by attaching the + terminal of the batter to the #4 terminal of the relay and the - terminal of the battery to the #8 terminal of the relay and checked for continuity between terminal #5 and #7 on the main relay just as alldata says. There was no continuity, so i replaced the main relay. Car started and ran until i tried to drive it, then it died and will not restart. I tested the new main relay and it is now bad as in no continuity between 5 and 7. Anybody have this issue before?? Any advice on where to look next would be greatly appreciated.

 

What does terminal 5 or 7 supply power to, is it the fuel injector relays output or the fuel pump relays output?

What colors are the wires to the PGM-FI Main Relay, [all of them]?

Are you not blowing any fuses, there will be 3 power leads to the PGM-FI Main Relay, one will be hot at all times, another will be hot when ign. switch is in run or start and the 3rd one is hot only when ign. switch is in start position.

The "hot at all times" lead may be yellow/white.
The "hot in run and start" lead may be black/yellow.
The "hot in start only" lead mat be blue/white.

Unplug relay and test for the above at plug, even if the colors do not match all 3 power leads must be there. 94

 

pin #5 is to the igniton

pin #7 is to the fuel pump

 

What are pins #4 and #8?

Also what colors are the wires?

Sorry, I do not have a wire guide for the 91 Civic, but other them possible wire color diff. and pin outs Honda/Acura PGM-FI Main Relays all work the same way, turning on the ign. switch energizes the fuel injector relay, [turns it on] the ign. input also supplies the high current side of fuel pump relay, [input] the fuel pump relays coil gets it's power from the output of the fuel injector relay, control of the fuel pump relay is a ground from the ECU/ECM to the other side of fuel pump relays coil.

Fot the alldata test to work the batt. pos.(+) would have to be connected to either the fuel injector relays output or the starter lead input to the fuel pump relays coil and the batt. neg.(-) would have to go to the other side of fuel pump relays coil to energize the fuel pump relay, then there should be continuity between ign. lead, [#5] and fuel pump lead, [#7].

When you connect the batt. to pins #4 and #8 can you hear/feel the fuel pump relay "click on"?

Open PHM-FI Main Relay to expose the fuel injector, fuel pump relays and the circuit board they are mounted to and inspect for damage...
http://www.tegger.com/hondafaq/mainrelay.html

I am not sure I understand how the PGM-FI Main Relay is being damaged, a short in either the fuel injector or fuel pump circuit should blow a fuse, [one of 3] not the relay. 94