run postion, purple wire shows .6 volts at the back. I followed that wire harness and it runs to the fuse box on the driver's side, under the hood.

The wiring harness says 3620. I assume that's the correct group of wires?

Any particular fuses I should be checking?

thanks : - )

Will

 

As mentioned in post #40 "[the purple wire] goes from the fuel level sending unit directly to the PCM, with no connections in between." The 5 VDC reference voltage is generated in the PCM. If there were a blown fuse for the PCM, or other engine management system, there would be other problems showing up such as DTC's in memory, engine no-start, etc.

There are four connectors at the PCM. Red, blue, black, & clear. Connector C3 at the PCM is listed as "clear". To me, it looks like white In connector C3, terminal #13 is the purple wire. It goes directly to the fuel level sending unit. Disconnect the fuel level sending unit connector from the sending unit. Set your DVOM to the DC volts scale. Connect the black DVOM probe to battery negative. Turn the ignition to the RUN position. Very carefully, back probe the purple wire with the red DVOM probe, as close as possible, to the PCM connector. Do not disconnect the C3 connector from the PCM. Post your results.

 

5.29 volts

 

The PCM is supplying reference voltage to the purple wire. Next step, find out if the voltage is able to make it to the fuel level sender harness connector. Disconnect the fuel level sending unit connector from the sending unit. Set your DVOM to the DC 20 volt scale, just like in the image you posted earlier. Connect the black DVOM probe to a good clean ground. Turn the ignition to the RUN position. Touch the red DVOM probe to the purple wire terminal in the fuel level sending unit harness connector. Post your results. Should be the same 5.29 volts.

Next step: Set your DVOM to the 200 ohm scale. Connect the black DVOM probe to a good clean ground. With the level sending unit disconnected, touch the red DVOM probe to each of the black wires, (2 of them) in the level sending unit harness connector. Post your results.

With the fuel level sending unit disconnected, the fuel gauge on the dash should indicate above the "Full" mark. If you ground the purple wire, the gauge should indicate below "empty". Post your results

 

I can't get out at the moment but I'll check those 2 black wires on Thursday when I'm home next.

Over the weekend I ran a jumper wire from the purple lead at the computer to the purple wire at the harness connector on top of the tank.

I now have a fuel gauge again : - )
I topped the tank off while I was emptying gas cans in the garage so it shows REALLY full.
I need to drive 100 miles or so and make sure it moves or else all I've succeeded in doing is going from always empty to always full.

I still have a SES light and after clearing it, it comes back on with evap problem still. I'll get you your info in a few days Chuck and go from there.

Thanks for sticking with me on this!

Will

 

Good news

 

So I went under the truck yet again and THIS time I found the real problem. Something, maybe snow or ice, crushed the wiring harness that goes to the fuel pump and such. It was crushed against the trans cross member and had split 2 of the wires, one of them being the purple wire.

I spliced and fixed those and now everything is back to normal : - )

She is a happy truck again.

Of course, she doesn't know that I'm going to either sell her or trade her in on a new Cherokee Trailhawk most likely....shhhhh...

Thanks everyone for all the help with this : - )

 

Cherokee Trailhawk? I cant even look at you

 

Yeah yeah...I know. It's a tough decision but the blazer is rotting away and the wife doesn't trust it to make it through another winter or two.

I did briefly look at the Subaru XV......briefly...