Fuel system woes and ECU issue

As posted here in this thread, I have fuel issues right now.
http://www.naxja.org/forum/showthread.php?t=58451

Now that I have my tools from work, I am diggin in with some electric work. I have the FSM and going over the schematics for the electrical system.

I found that the fuel system get power through the ballast resistor (obviously) But mine did not have any power. So i traced in the schematic to the EGR solenoid. It routes power to the fuel ballast resistor.

well, the EGR solenoid had no power as well. So i traced it to the connector on the right fender. Its the 4 wire connector. No power there as well. That connector goes to the ECU (or i cant find another connector between the two) and at the ECU I have no power comming OUT of it. The connector niber is A10. Its the green with white tracer on it.

I am not sure what to think as of now. But could someone check on there ECU to see if with the key in run position, if that wire has power?? I know it SHOULD.. but maybe there is a timer or something I took out when I did my dash.




Any help?

Anyone? I am going to check EVERY power, ground, input and output this weekend on the ECU to check the ECU, cuz I dont have a good one to swap.

dammit..

Scrappy, it's easy to mis-diagnose a fuel system issue, because after 2 seconds power is killed to the pump by the ECU. The FP relay is energized when the key is turned on, stays energized for 2 seconds, and then turns off. The ECU re-energizes the fuel pump after the engine starts.

The only way to test the FP circuits is to have a helper turn the switch on, after you have the voltmeter probes already in place. You have a 2 second window to take readings. Or else take the readings with the engine idleing.

If you turn the key on yourself, and then go around to the engine compartment, you'll get zero voltage readings every time, and assume the problem is in the fuel circuits, when in fact they're operating correctly.

Have you changed out the ICM? Those symptoms are classic for a faulty one.... or maybe the coil?

I have a help to turn key on and off while running tests. I am aware of the shutoff time. But I ONLY have power to the system when I jump a lead from the +battery to the ballast resistor.

Still no power at the pump itself. So something internally in the pump may be wrong as well. No way to tell on that until I change the pump.

With the ICM, it checks ok. But it is making an abnormal sound after cranking. But never really have paid attention to it before, so it could be nothing.

Tomorrow I am replacing the fuel pump (mainly because it sat so long and I like reliabilty) I also am going to try to hunt down a ICM, TPS, and ECM. For spares and maybe a replacement.

I hate being a parts changer, but I am really getting my ass handed to me on this.

The green wire to the EGR solenoid is the ground circuit, through the ECU, the ECU grounds the EGR solenoid (it is activated by the ECU supplying a ground). The power to the EGR solenoid is supplied when the fuel pump relay is activated.
Fuel pump relay, 30 pin is always hot, gets it´s power from the battery through a fusible link at the starter solenoid. The 86 pin at the fule pump relay should have power with the ignition on, it grounds through the ECU from the 85 pin (is activated by the ECU spplying a ground). The 87 pin is the activated side of the 30 pin and supplies voltage to the fuel circuit. The 30 and 87 (87a) and the 86/85 pins are pairs and operate together.
The relay the 30 pin and the 87 pin are the power pins, the 86 and the 85 pins are the activator (the magnetic coil that switches the contacts). The relays sometimes have a 87a pin that supplies power with the relay at rest, or unactivated.
When I have trouble, sorting a circuit out, I print a copy of the wiring diagram and color the wiring loops with a highlighter, which really helps sort things out. When you break it down into bite sized pieces (loops) things get a lot simpler (many wiring diagrams look like sphagetti). Activation circuits/controllers , power circuits and ground circuits. A little trick that helps save time, is many of the really necessary circuits for the XJ are yellow wires and have power with the key in the run position. Many (but not all) of the red wires are constant power and come from a fusilble link.