After two months of replacing parts, tracing wires and getting nowhere i sit with a dead 90 yj in the driveway. After reading other forums i have replaced all but the computer. As it sits right now the fuel pump stays running when the key is switched to "run" fuel is making it to the tb. Any thoughts?
I hate to say it, but I'd guess it's time to replace the computer. I had a 94 YJ, 4 cyl, rebuilt and modified, spent over $4000 just in parts...and a week after we got it back from the shop, it did exactly what yours is doing. Dead...turn over all day but nothing. Mechanic said to order a new computer-give them the VIN number or something-they ask for it-and it arrived a couple days later. Plugged it in...and as far as I know it is running still-sold it last year. When we took the old one out, when the case came off-you could see the smoke and charred contacts where it had overheated and committed suicide.
I think the ECM controls the fuel pump in the '87-'90 and if it doesn't see a crank signal (from the CPS) in a couple of seconds it shuts the pump off. Later models have an ASD relay in the PCM. Sounds like you may have an ECM issue.
There's a wide open throttle switch that's supposed to cut off fuel supply when you put the pedal to the floor (when it's flooded). It's a white plastic thingie with a microswitch on the throttle cable bracket at the TB. You can try disconnecting it and see if that's the issue.
Thanks i have. I even replaced it a month ago. With no success i dropped the tank once more and verified the pump once more. After i installed the refurbished computer yesterday its not getting voltage at the pump (checked with s meter).
12V off the relay but nothing at the harness for the pump? Did you use harness ground or good clean metal ground point on the frame?
It would be a real fluke but is it possible the ECM connector isn't quite right...may be worthwhile to unplug the harness at the ECM and reconnect it if that's all you've changed since the pump last ran.