Both FD's at my shop have a similar problem. One of them the fuel Gauge goes up to a 1/4 tank when filling, then just stays at 1/4 tank even when full... but it goes down to empty at the right time. and the Low fuel light does work right. Do you guys think its the gauge or the sending unit... anyone have a test i can run.
And these gauges i just bought out of a working car.

The other FD just stays at empty now. just happened all the sudden. any ideas here will help too.

Josh

 

Most likely the sender. I'd check to see how much the sender assembly is new - I know they're not that pricey for an FC.

My wife's old convertible RX-7 had a bad sender for the "low gas" light. There are 2 senders in the tank - the float arm that gives the level, and a sensor that trips the low gas light. I think you get both if you get a new sender - it's like the whole assembly.

The circuit is VERY simple - just a sliding resistance for the level, and a short to ground for the idiot light. I would suspect the sender before the cluster.

Dale

 

FD fuel senders fail one of two ways. I've been lucky enough to experience both, but they're easy to fix

There are some steel baffles inside the tank that are known for having the spot welds break. The baffle then becomes loose and is capable of jamming the float on the sender and not letting it rise to the top of a full tank. Reach inside the tank towards the middle and make sure there is nothing loose.

The second is that the wiper on the rheostat of the sender itself gets very dirty. Pull the sender and thoroughly clean the wiper and the "track" is wipes across. This will remove the carbon and make it work more better again I cleaned mine recently and noticed that when my tank is full the gauge reads slightly higher than it did before. The carbon makes a poor connection and gives faulty readings.

 

Well, one point i forgot to adress is, Is hasn't worked right since i WOTTED it against a guardrail in DEC. took our the whole passenger side. you think the jolt is enough to cause the sending unit to break or mess up. Cause it hasnt worked since.

 

Until you go outside and pull the sender all any of us can do is guess.

 

where exactly is the sender located at? i tried to look it up in the FSM but didnt have any luck finding it.

 

bump

 

It's on the same assembly the fuel pump is mounted. Pull the access cover on top of the fuel tank and remove the oval shaped hatch. The fuel pump and fuel level sender are attached to this.

 

I had this same issue. Fuel gauge was working, and then after a hard-drive, not working.

While the factory RX7 manual has a test for the fuel-gauge not working (section C1-13); I could not find the a section on testing the fuel-sender mechanism (not the gauge).

As DamonB states, it's very simple (see picks). So I removed mine, and measured the resistance (Ohms) at the connector for the float mechanism (see pic), BTW: I could have measured at the connector OUTSIDE of the fuel-sender.

Measured with the float at "empty" position was about 5-ohms, and the roughly the same when the float was at "full" position.

I took some spray electronic cleaner, followed by a gentle wipe of a 3M scotch-brite, then another spray of cleaner, and then DeOxit.

Using a dental pick, I gently lifted the "wiper" sprayed with electronic cleaner, a swipe of the scotch-brite (cut piece on the end of tweezer) another spray of cleaner, and then DeOxit.

New resistance measurement now showed about 23-ohms empty and 50-ohms full.

I also cleaned up the ground, and coated it with DeOxit.

All is good now.

:-) neil