Mechanics

JEEP YJ SENSOR PROBLEM

1993 Jeep YJ • 4 cylinder 4WD Manual •

I have a 93 yj 4cyl
the fuel pump won't kick in.I took it out and tested it, it works? The check engine an up shift light stay on with the key out? I just rebuit the engine and trans
everything is pluged in
. I tested the relay for the fuel pump it works as well as the shut down relay. Any help would be great
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Smotpoker
July 28, 2011.



The ASD relay and fuel pump should only run for one second after turning on the ignition switch. They turn on again during engine rotation, (cranking or running). The Engine Computer knows to turn them on by the pulses it gets from the crankshaft position sensor and camshaft position sensor.

Caradiodoc
Jul 28, 2011.
Thank you. So if the pump is out of the tank should it still turn on when the key is turned to on?

Tiny
Smotpoker
Jul 28, 2011.
If it's connected and has a ground, just for that first one second, then again during cranking. If it doesn't run for that one second, check the fuel pump relay, ASD relay, and pump's ground wire. If it DOES run for one second but not during cranking, you won't have spark either. Have you checked for spark? If it's missing, check the cam and crank sensors.

Caradiodoc
Jul 28, 2011.
It's doesn't run I took out the relays and checked them they work. Im wondering if I hooked something up wrong and fried the ecu I had to disconect the battery a few times as well? Im going to check for spark tommorow, not sure how to check the sensors though
thank you for your time

Tiny
Smotpoker
Jul 28, 2011.
Holler back when you know if there's spark or not.

Caradiodoc
Jul 28, 2011.
Hey bro. I have no spark !

Tiny
Smotpoker
Jul 29, 2011.
The fuel gauge is pegged on full? And the batt gauge is reading a little low?

Tiny
Smotpoker
Jul 29, 2011.
Find the feed wire to the ignition coil, any injector, or either small wire on the back of the alternator and measure the voltage on it. You should see 0 volts at first, 12 volts for one second when the ignition switch is turned on, it'll go back to 0 volts, then the 12 volts must come back during cranking. If it doesn't come back during cranking, suspect the crankshaft position sensor or the camshaft position sensor.

Caradiodoc
Jul 29, 2011.
This is weird but I have 12volts at the injectors and coil with the key on or off? Could I have something grounded that should not be?

Tiny
Smotpoker
Aug 2, 2011.
Sorry it took so long to get back to you. Internet provider was down again yesterday for the entire day.

Sounds like you have your voltmeter grounded to the battery positive post. It should be on the negative post.

Caradiodoc
Aug 3, 2011.
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