Jeep

Tiny
SMOTPOKER
  • 1993 JEEP YJ
  • 4 CYL
  • 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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Thursday, July 28th, 2011 AT 4:40 PM

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Tiny
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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.

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Thursday, July 28th, 2011 AT 4:53 PM
Tiny
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Thank you. So if the pump is out of the tank should it still turn on when the key is turned to on?

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Thursday, July 28th, 2011 AT 5:41 PM
Tiny
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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.

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Thursday, July 28th, 2011 AT 6:03 PM
Tiny
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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

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Thursday, July 28th, 2011 AT 7:52 PM
Tiny
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Holler back when you know if there's spark or not.

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Thursday, July 28th, 2011 AT 8:17 PM
Tiny
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Hey bro. I have no spark !

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Friday, July 29th, 2011 AT 2:53 PM
Tiny
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The fuel gauge is pegged on full? And the batt gauge is reading a little low?

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Friday, July 29th, 2011 AT 6:40 PM
Tiny
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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.

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Friday, July 29th, 2011 AT 7:20 PM
Tiny
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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?

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Tuesday, August 2nd, 2011 AT 6:57 PM
Tiny
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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.

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Wednesday, August 3rd, 2011 AT 9:22 PM
Tiny
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Remember when we used to talk to people. The good old days
i tried it again and im getting 12.45v on the injectors and the back of the alt! I checked the two grounds off the batt and the one off the alt as well as the one going from the block to the firewall they read good. Comeing off the starter I have the pos to the batt and the two wires coming out of the harness.I can understand a sensor going bad but I think I have something hooked up wrong that's allowing power to stay on when the key is off?

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Thursday, August 4th, 2011 AT 1:11 AM
Tiny
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Pull out the ASD relay. If you still have voltage to the coil and injectors you'll have to follow the wires back to see where it's coming from.

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Thursday, August 4th, 2011 AT 5:36 AM
Tiny
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Wow this is making me feel stupid. So it seems it they go to the pdc or the ecu. And all the fuses and relays seem to work. The ecu works by using the ground right? So is it possible that if it went bad that would be why there's a voltage reading even with the key off? And why the check engine light stays on. This is why I hated electric class.

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Thursday, August 4th, 2011 AT 4:37 PM
Tiny
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Electronics is actually very easy to understand, ... IF you are the type of person who can learn by visualizing things you can't see. Most automotive students don't learn that way. They are the type of people who learn best by touching, taking apart, manipulating, and seeing how parts interact. Can't do that with electricity, but you've played with water and a garden hose. In my Auto Electrical classes I compared everything electrical to water flow in a pipe. My students had real good success and have a dandy reputation in the community. Don't feel stupid. You probably learned electronics from someone good at visualizing and they think everyone learns the same way.

The ASD relay socket should have 12 volts on two terminals all the time. One supplies one side of the coil and one supplies the current that will go through the contacts. The Engine Computer grounds the other coil terminal, then the magnetic field pulls the arm down to connect the contacts. Current flows through the contacts to the ignition coil(s), injectors, alternator field, oxygen sensor heaters, and possibly the fuel pump or pump relay.

With the relay removed, if you have voltage to any of those parts, you have your meter probe grounded to the battery positive post. It must be grounded to the negative post. If you still read voltage there, something is wired wrong and is bypassing the relay.

If you find 0 volts, plug the relay back in. If you feel it click, something is grounding the coil. That could be the computer, although that type of failure is real uncommon. Again, I'd look for something wired wrong. If you unplug the Engine Computer and the relay turns off, the computer would have to be suspect.

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Thursday, August 4th, 2011 AT 7:40 PM

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