Reddy

93 FD. Car will not start. After taking apart the ignition cylinder and confirming everything is ok, as well as bypassing clutch switch, was able to determine that the accessory CPU is actively opening start cut relay. Bypassing the relay will allow the engine to turn over. I am getting no codes showing that the ECU has problems, so what could the accessory computer see that makes it want to shut off? Can anyone provide any details about this CPU (listed as CPU in manual whereas the Engine Management is listed as ECU).

The complete story:
Car died while running at 65 mph. Gaughes lit up and I lost all power. Immediately afterward, I would try to start the car, it would turn , but not seem to fire. For 4 days of trying every now and then it would continue to turn. Waited a week to fix, and at that point, the car would not even turn. Batt is ok. 8.4 volts to the starter ONLY if I bypass the start cut relay. Pulled plug to see if it is sparking when relay is bypassed and it is (although I am not sure if the spark is weak).
Could this be a weak spark and therefore indicate a dying ignition?

Thanks
C

J.S.J

Maybe it was just a slip of the keyboard but 8.4 volts wont get it done. Even with the starter cranking there should be at least 9.6 volts there. The universal old style battery load test is at least 9.6 volts at the battery terminals when testing a battery. Thats after cranking the engine for 15 seconds and taking the reading in-between the 14th and 15th second. Even a non obd system must have a default low voltage threshold. I would make sure system voltage is up at least 12.6 volts. Charge the battery first.

Kento

Agreed. There's a lot of engine accessories that take quite a bit of power, and just because the dash lights up and the engine turns over doesn't mean it's going to fire.

Reddy

No, I am not talking about the voltage from the battery. That is fine, over 12.
The starter requires a current with 8.4 volts in order to turn. That is, if you meter the line to the starter in a properly operating vehicle, you should see 8.4 v. That is straight out of the shop manual.

Thanks for your suggestions anyway.

Kento

Check all your fuses carefully.

Reddy

Thanks to everyone for your comments. But the problem which kept turning on the start cut relay was actually coming from inside the door handle on the driver's side door. It thought the alarm had been turned on, and was keeping the starter from turning.

Now off to find out why the car will not start.....
C

lopedl

iTrader: (1)

If it's a 93 and you haven't messed with the wiring. More than likely it's a short. I was having problems with my rear coil pack not firing off. I thought it was because some water got in the system. Well to make a long story short the water had got on some of the wiring which I hadn't seen because the wiring is in there purty good. And the wires shorted each other out because parts of them had gotten cracks and were like an open wound. I took the entire drivers side wiring harness in the engine bay and rewired practically everything. You'd be suprised how many wires in there are completely toasted. It know starts and runs better than ever.