4x4_Welder Posted November 8, 2006 Share Posted November 8, 2006 Getting ready to strip and rebuild the Hatch, put a fresh battery in it, and fired it up. All the warning lights are on, the voltmeter is going nuts but staying below about 10v, and it won't run over an idle for more than about 10seconds at a time, even though it starts back up fairly quick. I'm thinking that either mice got into the harness again, or the voltage regulator is dying, unless this is another one of those known issues these cars can have. My options right now are to either track out this problem, maybe pull the main harness out, inspect, and re-wrap, or strip it all and run bare essentials with my own harness (I have made harnesses before, and don't have any issues with that). At least this time around the car is actually down, and I can afford the time to screw with it- Link to comment Share on other sites More sharing options...
idosubaru Posted November 8, 2006 Share Posted November 8, 2006 i'd' certainly look into the alt/voltage regulator right away. as well as battery and cables. swap alt and regulator with new or have them tested. all the stores now are doing free electrical system testing if you can get it there. Link to comment Share on other sites More sharing options...
4x4_Welder Posted November 10, 2006 Author Share Posted November 10, 2006 Ok, I know that this thing isn't electronically controlled, but it still has that goofy PCM under the dash. When the car is running, the little led is on, but once it starts to die out, the light goes out (somewhere around 800rpm) and stays out. Once I turn the key off and back on, the light comes on and stays on. The fuel pump has power intermittently, maybe for about ten seconds after the engine first fires up, then shuts off. None of the connectors look bad, all the fuses are good. I'm starting to lean heavily towards ripping the harness out and doing my own when I swap the engine and throw EFI on it, but I would like the car to move under it's own power for more than 10seconds at a time right now. Link to comment Share on other sites More sharing options...
4x4_Welder Posted November 12, 2006 Author Share Posted November 12, 2006 Ok, I'm getting lost on this car and it's startingto agravate me- What exactly does this little psuedo-computer control? What parameters need to be met for the fuel pump to come on and stay on, like oil pressure, rpms, etc? Link to comment Share on other sites More sharing options...
GeneralDisorder Posted November 12, 2006 Share Posted November 12, 2006 The ECU does not control the fuel pump. The pump is controlled by a Fuel Pump Control Unit (FPCU) located right above the hood release cable mount under the drivers kick panel. It's got a 6 pin connector on it (only 5 are used on feedback vehicles). It gets ignition power from the accesory circuit to run the pump for like 2 seconds (it's got a timer in it). Then it gets power from the ignition coil positive, and the tach pulse signal from the negative side. If the engine shuts down it cuts power to the pump to prevent fires in case of an accident. The other two pins are fuel pump power, and ground. GD Link to comment Share on other sites More sharing options...
4x4_Welder Posted November 13, 2006 Author Share Posted November 13, 2006 So, without an O2s, TPS, etc for input, what does this computer actually control? Link to comment Share on other sites More sharing options...
GeneralDisorder Posted November 13, 2006 Share Posted November 13, 2006 It does have a narrow band 02 sensor, a coolant temp sensor, and it uses the tach signal to determine engine RPM. With a carb that's really all it needs (TPS wouldn't be useful because in a carb fuel flow is accomplished with engine vacuum, not an injector). It uses two "duty solenoids", a main, and a slow speed solenoid. These are switched on and off rapidly (as in many times per second) by the ECU. The frequency (or duty cycle) of the solenoids determines the amount of engine vacuum that is allowed to act on the fuel flow. If the 02 goes lean from stoichiometric, the duty cycle increases and allows more fuel in, and if it goes rich it works the other way. Despite all the vacuum lines, the system is extremely simple in design - the duty solenoids rarely fail, and most problems are related to bad vacuum lines, bad 02 sensor or CTS. GD Link to comment Share on other sites More sharing options...
4x4_Welder Posted November 13, 2006 Author Share Posted November 13, 2006 Are you sure about that? I dropped the exhaust out of it a few months back to put on new flanges and front pipes, and there was no O2s in the exhaust anywhere. My 82 had one in the center of the Y at the front of the cat, but none for this one, as near as I can tell. Although, if it's supposed to have one, that could explain why it gets 25-27mpg. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted November 13, 2006 Share Posted November 13, 2006 Are you sure about that? I dropped the exhaust out of it a few months back to put on new flanges and front pipes, and there was no O2s in the exhaust anywhere. My 82 had one in the center of the Y at the front of the cat, but none for this one, as near as I can tell. Although, if it's supposed to have one, that could explain why it gets 25-27mpg. 100% positive. The 02 is the only real sensor it's got. Besides having owned two of them, I have the FSM open on my desk.... Y-pipe could have been replaced before you got it. Look for the 02 connector in the harness right above the tranny. GD Link to comment Share on other sites More sharing options...
GeneralDisorder Posted November 13, 2006 Share Posted November 13, 2006 And yes - it would get typically bad mileage as the ECU goes rich when it can't find a sensor. If you rip off the solenoids entirely they get about 18 - 20 MPG because the carbs are jetted very rich and then the solenoids are used to restrict the flow as needed. GD Link to comment Share on other sites More sharing options...
4x4_Welder Posted November 13, 2006 Author Share Posted November 13, 2006 Ok, I was just under the impression they didn't have an O2s until late 81-early 82. Link to comment Share on other sites More sharing options...
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