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Software Logic inside the ECU Computer? 200 1987

posted by  someone claiming to be Mr. Tool on  Wed Dec 2 02:00 CST 1998 [RELATED]

Hi all: I have a 1987 245 DL. B230F engine. LH 2.2 Jetronic. I'm try to get a handle on what specific signals (inputs and outputs) are involved in both the Ignition Control Unit and the ECU computer. I'm having intermintant problems with the main fuel pump relay (system relay) being energized to turn on the main fuel pump. Yes, I have check all the basics, such as a new relay, grounds, etc. I have put some of Don Fosters home made test equipment on the car (neon bulbs to monitor spark and a test light at the main fuel pump power connections), and I'm currently monitoring these. Here is what occurs. You will get into the car and it won't start, but it's cranking. During this condition there is no power (12vdc) at the main fuel pump. The system relay is not being pulled in (energized). This relay is activated by an output from the ECU computer. However, other inputs to this ECU computer AND THE LOGIC programmed into it will determine if the computer will provide this signal to the relay. My understanding that there needs to be an "engine running" (cranking) signal as well to this ECU in order for the ECU to activate the relay. This signal I belive comes from Ignition Control Unit, which come from a pick up (Hall Sensor??). I'm trying to monitor the various signals that are all needed to make this relay turn on. If I don't know the internal logic to both units it will be more difficult. I suspect that I have bad wire, connection, or sensor, that causes this. This "not starting" condition happens only once every 1 to 2 weeks. Then the car will start fine after a while. The Air Mass Meter (AMM) is good. That's why I put the monitor lights on the car. That's how I noticed that the main fuel pump wasn't getting power during this condition.....HELP...Thanks for the help in advance.....Mr. Tool.......





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