Main Relay Buzz & No Start/No Fuel Pump Power

[cp___32]

Hey everyone...I have a strange situation with my civic and was hoping for some help:

91 Civic HB 5Spd (DX model), 325 000KM.

When the ignition is turned to the ON position, the main relay makes a buzzing noise and the fuel pump does not kick on as normal. I swapped the main relay with a known good one and it did the same thing. I unplugged the fuel pump and turned the ignition to the on position and there was no noise until I plugged in the fuel pump again. I pulled the tank (as it had a leak for some time) and replaced it with one from the salvage yard. Before installing the tank I did the same fuel pump test with the replacement tank and there was no buzz from the main relay, and the fuel pump did click on for a few seconds (as is normal). Once the new tank was installed the buzzing returned and the car will not start.

When the problem started I had just changed the thermostat and was running the car to bring it up to temp to bleed the system. The car stumbled then regained idle, stumbled twice more before stopping entirely.

I did perform the test on both main relays that I have (as per the chilton manual) and both relays when connected to the battery only passed the test. (test involving pins 4 & 8, and continuity between 5 & 7 I believe).

Any help would be great!

[cp___32]

Haha, I figured it out!

The ground wire on the thermostat housing was 1/2 turn from being completely tight. I snugged it up and the car started no problem.

[BullShifter]

Good job
Sounded like a lack of power some how.