Well obviously the open wire could be anywhere between the gauge and the senders ground. Or of course you could have a bad gauge or sender but from your description of your problem more than likely that the open is in the contacts of the valve operated by a motor.

This may be because the motor stopped before is shifted all the way from one tank to the other. This could be because of bad electrical wiring or the dash switch along with the power supply to the switch.

You need to take a test light check out where you lose the power going to the valve or its ground.

Yes the valves should be the same for both diesel trucks.

 

The gauge should be OK but who knows.

 

I got out the meter and did some checking, the switch is working fine. I had to pull the plastic cover off the instrument cluster to clean out a couple cigarette butts that were between the cover and the gauges themselves. Don't know how or why they would have been there!!!! While out, I moved the needle for the fuel gauge with the ignition off. I had already unhooked the connector at the fuel selector valve on the frame. Just for grins and giggles, I turned on the key and the gauge went back to the full right side again... I figured it would read empty with no wiring hooked to the fuel selector valve...Apparently someone else has been trying to diagnose this problem, when I pulled the connector off the fuel selector valve, I noticed where someone had slightly skinned the solid black and the yellow with blue stripe wire, along with the other yellow wire, but they were not shorting with the ground wire ..I'm thinking to check the ohms for the sending unit?? I put my ohmmeter on there to check each tank, but got nothing on either tank..
I checked for power to each terminal of the fuel selector valve connector and it was good....
I do not have a digital ohmmeter, could that be why I got no resistance on either tank???
I'm more stumped now than I was...Any suggestions???

 

As I said above if the wire (Yellow with a white stripe) from the gauge is open the gauge will peg. If you ground this wire with the key on it will drop below "E", this is how you test it.

By the way meters are not much good when testing these circuits as they do not load the circuit and give you a false reading. You need to use a test light unless you are checking the resistance of the sender.

I think you need more light at the connector for the fuel valve as there are no solid black wires, the yellow with blue stripe wire goes to the rear sender and the other yellow with a white stripe goes back to the gauge.

You should have zero ohms between the two yellows if the valve has the rear tank selected.

C177 connector has all of the wire plus the ground wire in it, this 12 pin gray connector is on the Left-Hand (driver's) side of the engine compartment.

Can you get the motor to run in the selector valve?

 

Can you physically feel the motor running?? Or does it make enough noise to hear??? If it ain't halfway loud, I may not have heard it this afternoon, as my neighbor was moving right next to where i was working....

 

Verified this, it does drop below "E" when grounding....

 

Then the gauge is good.

 

Yep, that's what I gathered too....Is this a common problem for these trucks with dual tanks??? Any chance you also have a wiring diagram for the alternator, etc. I just posted about the weird charging rig the PO put on this truck due to the alternator/ voltage regulator overcharging...PO put a switch to cut off the output from alternator when voltmeter gets up high....I'm not sure what output alternator he put on, I can't read the sticker...

 

Funny thing just happened, I was out there checking with my test light, and with the test light on the yellow with white striped wire at the c177 connector, the guge reads. I think both tanks are about empty, but gauge reads just above the red, moves slightly when I flip the switch from front to rear. Take the test light off and it goes back to full right side....?????

 

The test lights bulb will have resistance valve and the yellow with white striped wire at the c177 connector is ahead of both senders. So the gauge will react to the resistance of the bulb just like it would the resistance of the sender.

 

Deleted, all gone

 

I have one of these valves MARKED E3TB-9F271-AA and "GASOLINE"

I need one for DIESEL!

What gives with the Gasoline marking as I thought the part number E3TZ-9189-C was for diesel (or both)??

Thanks in advance.

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