Fuel Gauge Drops Off After 3/4 of a Tank

Hey Guys,

Trying to decipher what my issue is with my 89'. The fuel gauge will read accurately just so long as I have a full tank of gas. As soon as the tank hits 3/4 full, the fuel gauge drops down to like 1/4 of a tank and then not move until I hit 'E'. Kind of annoying especially for long hauls and trail riding.

Does this sounds like a sender/pickup issue? I checked all of my grounds (they're fine). I didn't see any damage to any of the connectors or wires. I'm thinking that my pickup/sender may be faulty?

Thanks in advance,
Jim

SeeingSpots said:

Hey Guys,

Trying to decipher what my issue is with my 89'. The fuel gauge will read accurately just so long as I have a full tank of gas. As soon as the tank hits 3/4 full, the fuel gauge drops down to like 1/4 of a tank and then not move until I hit 'E'.
Does this sounds like a sender/pickup issue?

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Yes, it sound like the fuel level sender's rheostat is worn out out, not uncommon in older vehicles.
The sender is part of the fuel pump assembly. I wasn't able to find the sender separately, only with the complete fuel pump assembly.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=NFPP76542M_0383214630
Unless the pump has been replaced in last few years, changing the whole assembly would be the best choice, considering the tank needs to be lowered or removed to install it.
It's not too hard to do especially if the tank is empty or near empty.
Try not to use an Airtex pump.

My YJ did pretty much the same thing, it showed full and then hit around 3/8 tank and stayed there until it was empty.

I haven't had that issue with my Renix. If I did I'd likely try the YJ solution and pull the contact strip out of the back of the instrument cluster, rub it down with a pencil eraser and then wipe it down with a good contact/electrical cleaner. That is what fixed my YJ.

Pulling the instrument cluster, on a hunch, is a pain. Pulling the pump and sending unit on a hunch is a bigger pain.

I hooked up an ohm meter to the sending unit in the tank and had my son jump up and down on the back bumper until he got the fuel sloshing around real good. My ohm meter showed the ohms fluctuating, so I went went after the wiring instead of the sender. In the end I was happy I did.

8Mud said:

I hooked up an ohm meter to the sending unit in the tank and had my son jump up and down on the back bumper until he got the fuel sloshing around real good. My ohm meter showed the ohms fluctuating, so I went went after the wiring instead of the sender. In the end I was happy I did.

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This.

IF the sending unit is bad, you can get a fuel pump MODULE--pump & sending unit combined--from rockauto.com for under $85, but I wouldn't trust the pump, I only like the Bosch units.