Fuel gauge question

[TexCaliBII]

All,
I have now put 2 different Explorer dashes in my 88 BII and on neither does the fuel gauge read. The fuel gauge was working before I started modding this truck. The first one I spliced into my existing harness for the fuel gauge and it did not work. Okay so I thought I had goofed. I bought a 93 Explorer with all the options and decided I would swap everything into my BII so this time it is the Explorer harness all the way front to back, inside and out. I did have to splice the Explorer harness to my BII tank pump but I double checked by the EVTMs and visually that I was putting the correct wires together but this gauge does not work either. Anyone had an issue with the Explorer gauge not working with the BII sender?

 

[unoleisu]

On my 87 BII the fuel gage has to have the Instrument Voltage Regulator to work. IDK about the EXP dashes, but this would be a place to start. The IVR also controls the coolant temp gage, and oil pressure gage, for this BII dash. It looks like a small (1"x2") sardine can, with 9V battery connectors on it, and mounted on the back side of the instrument cluster.... I imagine, if you are running the stock sending unit, that it may require the IVR to work forthe gage.
This is a big grey area to me, when we start doing swaps.

 

[adsm08]

The two FLI gauges run on very different ohm ranges. A full signal coming from a gen 1 2.9's stock sender will appear to be an empty signal to the Explorer's gauge.

 

[unoleisu]

Curiouse because I plan to do a 4.0 swap later, what is the fix for this, adsm08?

 

[adsm08]

The fix if you use the 1st gen dash is to put a 4.0 pump on a 2.9 sender manifold.

Not sure about going the other way. Haven't looked into it.

I'd have to look up the specs, but if it moves the right way a simple in-line resistor of the proper value would do it.

 

[TexCaliBII]

Okay,
I'll have to dig into this after the weekend. I'm off to a get a way with my church group. Thanks for the info and when I solve this I'll post up the data.

 

[TexCaliBII]

More/clearer info

Guys,
I have yet to look into this more but just to clarify. I put a complete dash from a 93 Explorer into my 88 BII and grafted the Explorer harness to my sending unit harness, matching the wiring per the EVTM and visually comparing the sending unit connector and an Explorer and BII sending unit/ pump on units I had extra. The fuel gauge reads dead empty with power on but after I shut off the ignition, the gauge comes up????? I've already rechecked the wiring and all is correct. The only thing I can think to try now is putting a 4.0 unit into the 2.9 tank. I did not do resistant checks on them when I did this, guess I should have.

EDIT: Okay, checked ohms resiatance from tank, reads 33 ohms with approximately 1/4 tank. Swapped anti-slosh module, same thing, swapped gauge out with a spare, same thing. Pulled the slosh mod and gauge runs to beyond the full side, just like if you ground out the signal. Do that means everyhting is "working" but there seems to be a disparency in what the BII sinder is puttin gouty and what the Exp gauge is reading. Did resitance checks on a 92 model sender and brand new 88 sender, they are only about 2 ohms off from each other. Did the resistances change in the 93 model year?

 

[TexCaliBII]

Allright,
I think I have it figured out now. Even though the restistance checks the same on the old 92 Explorer and the new 88 BII sending units the BII one will not driv ethe gauge but the Explorer one will Oh well, I ordered a new sending unit to match the 93 engine/dash/wire harness I have in the truck