1970 GTO Version 2.0

[andrewb70]

I spent all day in the garage today, but I am afraid that there wasn't really anything new to show you guys. I did a lot more of "connecting the dots." I found the wire under the dash that went back to the relay for my fuel pump. This was used by the Commander 950 to turn on the pump. The GMPP harness already had a relay for the fuel pump, but I really like taking power directly from the battery to run the fuel pump. So after consulting with a couple of folks I decided to just run two relays. The relay in the harness activates the relay in the back of the car. After hooking everything up it worked perfectly. When the ignition key is in the "Run" position the pump primes for about 5 seconds and then shuts off.

Since I got all of the coolant hoses hooked up, I went ahead and filled the system. I filled the radiator. Then I filled the block through the upper radiator hose. I fired it up and ran the engine for a while. The O2 sensors are not hooked up and as it warmed up, and went into closed loop, it started idling a little rough, but it did not die. So I let it idle and warm up a bit. The stock thermostat is probably around 205 and the ECU turns on the fans at 212. The lower radiator hose stayed relatively cool until the thermostat opened. Once that happened, I just topped off the radiator and hopefully that will do it. The fans kicked on at around 212 as they were supposed to. Nice thing about the GTO is that I already had a giant Be Cool radiator. I never had any issues with the 502 and I am sure it will cool this engine just fine. The RX7 had half the radiator, and almost no grill, and I didn't have any issues.

Now I need a little help from everyone. The GMPP harness instruction say that the tach signal is a low voltage 2 pulse square wave. It also said that some older tachs may require a pull up resistor in order to function properly. I hooked up the wire from the tack and sure enough it did not work. So, what the heck is a pull up resistor and how do I hook it up?



I am trying really hard to resist project "scope creep." So with some luck this thing will move under its own power next weekend. LS swap in less than 2 months, not bad, if I do say so myself.

Andrew

[wiedemab]

I'm not an Electrical engineer, but I did some Googling and found these links. The first one makes it seem pretty easy in theory.

http://www.seattlerobotics.org/encod...97/basics.html

http://en.wikipedia.org/wiki/Pull-up_resistor

I guess the purpose is to limit the current through the circuit. One site says that the most common sizes for logic circuits are 10K ohm or 47K ohm.

It looks like the resistor just goes in the tach signal line??????????

Good Luck - I'm looking forward to learning something here. If you don't figure anything by the first of the week - I'll be seeing a buddy of mine who is an EE on Monday, so I can ask him.

Keep up the good work!