Fuel Pump Ground Issue

trwebb26 · Post by **trwebb26** » Wed May 24, 2006 8:36 pm

I just got my 78' 280z running with a v3.0 board and MS&SE v29j. When you turn on the ignition - the fuel pump primes for 2 seconds just like it is supposed to, but pin 37 doesn't ground out during cranking. The only way I could start the engine was to manually ground the fuel pump relay ground to the chasis. Megatune reads the RPM fine - so I know that it is sensing cranking. What could be wrong? I would like to retain the added safety the megasquirt provides by controlling the switched ground. Thanks in advance for the help.

boost junkie · Post by **boost junkie** » Thu May 25, 2006 5:55 am

Does it work on the stim? Could it be a hardware problem with the fuel pump circuit?

trwebb26 · Post by **trwebb26** » Sat May 27, 2006 7:55 am

I don't own a stim... but the fact that the pump primes just fine leads me to believe that something is wrong. Anybody?

MegaScott · Post by **MegaScott** » Sat May 27, 2006 1:17 pm

Is your fuel pump relay powered off a source that has power all the time, even when cranking, it sounds like your fuel pump power is going away when you crank, if the Megasquirt is seeing RPM when you crank, even 1 rpm, it will turn on the fuel pump. do you see RPM in Megatune when you crank? You could have an ignition power problem as well.

trwebb26 · Post by **trwebb26** » Sun May 28, 2006 11:07 am

The same switched +12V that powers the megasquirt also powers the fuel pump realy. I do show RPM when cranking in Megasquirt.

MegaScott · Post by **MegaScott** » Sun May 28, 2006 12:15 pm

The best advice I can give when you have a problem like this is to clean the board, check for solder bridges and cold solder joints, check the cables for bad connections.

Oh, you can try reflashing your firmware and see if that make a difference. save your .msq and VE files first then reflash the firmware.