tinner06

Ok...I have an 88 cherokee laredo that sat for about 5 years before it landed in my yard...GREMLINS...so the fuel tank and all that was inside was crap!
I replaced the whole unit from a donor rig that was running..tank and pump all in one.
after installing and hooking up the electrical and hoses it all worked fine..pump ran fuel..BUT the fuel gauge works backward and it isn't accurate..
is there some ground that i missed (as soon as snow leaves I will be running down ground wires), or does the years have different wiring for sending units?
BTW the gauge worked fine before the swap.

freegdr

What year donor ?

tinner06

Pretty sure it was a 92 or 93

ajpulley

This happens with some aftermarket replacement pumps when new. You'll have to reverse the leads from the float switch. As for the accuracy issue, I was gong to ask if you might have swapped a 13 gallon tank pump/float assembly into a 20 gallon tank. However, I don't think the post-90 assemblies are exactly the same as '87-90 for the 4.0L.

tinner06

Ya I'm thinking that the original might have been a 13 gallon...I do know that the new one is a twenty...so the switch will be on the pump assembly?

djgrayxj

Note from DJ
If my notes are correct the Renix era Sending Unit resistance values should be 1 ohm at empty, 44 ohms 1/2, and 88 ohms full.
And the early 90’s values should be Empty 105 ohms, 1/2 Full 33 ohms, and Full 5 ohms.
The Sending Unit is just a variable resistor and as you can see the half full vales are almost the same between the two unites. I don’t know if you removed the Fuel Pump assembly if you can reverse the leads on just the Gage Sending Unit only or not.

freegdr

Simple fix...