when relay boards go bad.... Options

[type47]

got a chance to do some work on the teener today. plans were to weld (IMG:style_emoticons/default/welder.gif) in a bung for an O2 sensor for LM-1. rod (root) was going to do some tig work on the bung. problems with car on the way to his shop. car quit twice. i carry a pressure gauge so i connected it on the cold start valve port and got zero pressure. simple i thought, bad fuel pump. even connected a voltmeter to the fuel pump power plug to verify voltage to the pump. however, didn't see that voltage was 12 mV not 12 V (where are my glasses...). long story short, i was able to get to rods shop and, third times a charm, bung got welded in (by the way, this may be a "DUH" to many but don't try to weld in the bung with the plug screwed into the bung, it'll just seize the plug. i/we didn't know any better). attempt to start the car to go home, no start. no pressure then we observe 12milliVolts at the pump connector. rod says all signs are pointing to a bad relay board and graciously lends me his relay board to get me home (IMG:style_emoticons/default/smilie_pokal.gif) so now my question is: how often/frequent do these fail and would like to hear some experiences about how the faulty board was discovered. it's hard for me to believe the board failed and i'm going to do some continuity tests on it. to me, all signs led to a bad fuel pump.

[Tom]

An ohmmeter is a good troubleshooting tool, but it has it's limitations. A circuit that reads good with the ohmmeter may in fact break down when asked to carry current. A better way is to put the load on the connection and then read voltage at the load. If your voltage is low, the the circiut is breaking down some where. Clean all of the connections and where possible solder the rivets on the relay board. Some time back , when I had the engine out , I pulled the relay board and checked it with an ohmmeter and while the meter was hooked up , wiggled and pushed on fuse clips and connectors. Found several suspect one and cleaned and soldered them. Since then "0" problems with the relay board.
Tom