i have a 91 civic hatch with a d16a6. I've replaced the main relay and also the fuel pump twice the second time with a 255lph wallbro. it won't prime and im out of ideas.

 

Thermostat ground clean and tight?

Main relay fuses good?

If those are fine, try swapping in a known good ECU.

 

i was gonna say the same thing!

 

thermostat ground was clean and tight having ecu rebuilt will post if/when it works

 

got ecu back its known good main relay known good ground is clean and tight but its still not priming. any ideas?

 

Do you have a multimeter?

 

^^^ +1, and have you checked the fuse?

 

multi switch behind the keey tumbler might be bad does it show signs of live when you turn the key to acc?

 

Do you have a 5pin connector to your fuel pump? have a yellow/black wire? If so, use a solid chassis GROUND and probe yellow/black wire for voltage while someone turns the key ON to prime the pump.

If no voltage, "check the main relay and wire harness."

If (while using a good chassis GROUND) you DO have voltage, then proceed to check yellow/black for voltage again, but this time use the BLACK wire on the 5pin connector as the GROUND. If no voltage this time, then your fuel pump does not have a good ground, and will not work (because VOLTAGE+ is nothing without a GROUND).
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If your year/model does not have a 5pin plug or does not have a yellow/black wire, then proceed at your own risk. But you have got to figure out what your pump is missing: voltage or Ground??

If you follow those steps and find that you are missing voltage+, then:

Test the output of the main relay (even though you just replaced it..check your wiring too).
If the main relay is sending voltage, disconnect the fuel pump wire from the relay, and disconnect the harness plug from the pump. While both disconnected, measure CONTINUITY between both ends of the wire. If no continuity, check for a broken/loose/corroded wire/etc. because the voltage has no continuous path to the pump.