How do I remove/repair the fuel gauge on my 250 PF Cab?

Greg Brendel · Post by **Greg Brendel** » Thu Nov 16, 2006 10:34 am

Can anybody give me some hints on how to remove the fuel gauge from the dash on my 250 PF Cab? Any suggestions for sending it out for repair? Thanks. Greg

Post by **330GT** » Thu Nov 16, 2006 12:14 pm

1. Are you sure the it's the gauge and not the sender in the tank? The senders suffer from water condensation unless the tank is kept full enough to cover the bottom of the sender.

2. Removal of the gauge will earn you some scraped hands. It is held on by a W shaped piece of metal. The W fits on the back of the gauge with a stud going through the center of the W. There is a knurled nut that screws on the stud. The outside ends of the W turn at 90 degrees and go down along side of the gauge. These ends then press against the back of the dash to pull the gauge tight against the front as you tighten the nut. Assuming the dash in your PF cab is like a coupe, there is little room to reach directly up under the dash from the bottom (the heater is in the way). It might be easier to pull the tach first so you have a big hole to reach in behind the other gauges. Then unscrew the knurled nut, remove the W piece and the gauge can be pulled out of the dash. Be sure and mark the three wires for re-installation.

Tom has D&M Restoration in his suppliers page for an instrument rebuilding place. Another is Palo Alto Speedometer (http://www.paspeedo.com).

PM me with an email and I can take some pictures as the dash and gauges are out of my coupe (along with most everything else except for the running gear).

David Booth · Post by **David Booth** » Thu Nov 16, 2006 12:54 pm

Kerry's right - it's much more likely to be the sending unit - which is even more fun to get out than the gauge; since it involves dropping the fuel tank, which in turn leads to issues with getting the fuel line fittings to seal properly when you put it all back together. I got the fiber washers in an assortment set from Wurth/Winzer, and Ted Rutland probably has them too. John Wolf Company in Willoughby Ohio can rebuild the sender.

Greg Brendel · Post by **Greg Brendel** » Thu Nov 16, 2006 7:36 pm

Thanks guys. Its a minor inconvenience and I have been living with it for while, I just add gass in 10 gallon increments and keep track of miles:). I was hoping it was something as simple as a loose wire as I don't really want to get involved with the sending unit. I thought I would try to pull the gauge and check the connections first.

Post by **330GT** » Thu Nov 16, 2006 9:40 pm

330GT wrote:...The senders suffer from water condensation unless the tank is kept full enough to cover the bottom of the sender.

I just reviewed some pictures for Greg and realized that the part of the sender that has problems is at the top, not the bottom.

It might be possible to use the access hole under the package shelf to open the top of the sender. Then you could clean all of the contacts. However, without taking the sender out of the tank, you can't really test it by swinging the float back and forth.

Sleeper · Post by **Sleeper** » Thu Nov 16, 2006 10:51 pm

This unit can be removed from the top of the tank while in the car. I have done it several times.

Post by **330GT** » Fri Nov 17, 2006 8:28 pm

Sleeper wrote:This unit can be removed from the top of the tank while in the car. I have done it several times.

I was only thinking in terms of a coupe. I don't think that the gauge would come out with the rear window in place. Of course, a cabriolet wouldn't have that issue at all. Given that, I think that it'll be easier to remove the sender than the gauge in the dash.

kare · Post by **kare** » Sat Nov 18, 2006 3:28 pm

Does anyone know how to connect the fuel gauge. There are two wires coming from the tank and one terminal on gauge says "serb" (=serbatoio, =fuel tank) which is really helpful, isnät it...

Post by **tyang** » Sat Nov 18, 2006 3:51 pm

Hi Kare,

The fuel gauge measures the resistance at the sender, so 12 volts goes to the sender, through the windings in the sender, and then out to gauge.

Tom

Post by **330GT** » Sat Nov 18, 2006 8:36 pm

tyang wrote:Hi Kare,

The fuel gauge measures the resistance at the sender, so 12 volts goes to the sender, through the windings in the sender, and then out to gauge.

Tom

Tom, yes it does measure the resistance of the sender, but not the way you describe. Doesn't your America have a low fuel warning light?

The GTE wiring diagram shows the two wires between the gauge and the sender. One is for the low fuel warning light and the other for the fuel level. +12 goes to the gauge and splits to the low fuel warning light and meter part of the gauge. Two wires go from each part respectively to the sender. The low fuel light wire connects to the low fuel switch part and the fuel level goes to the resistance wire. The other side of the low fuel switch is grounded, so the light goes on when the switch is closed. The resistance wire has a wiper which is grounded. As the wiper slides along the resistance wire (based on the float arm), the gauge reflects the position, i.e. differing resistance to ground. Note, the ground for both of these is through the sender body, to the fuel tank and then to the chassis. It's probably a good idea to run a ground wire from one of the screws holding on the sender to a nearby body ground.

Now the GTE wiring diagram (in the owner's manual) isn't correct. It shows one side of the fuel warning light as grounded. It can't work like that, it has to have +12V instead of a ground.

Post by **330GT** » Sat Nov 18, 2006 9:05 pm

kare wrote:Does anyone know how to connect the fuel gauge. There are two wires coming from the tank and one terminal on gauge says "serb" (=serbatoio, =fuel tank) which is really helpful, isnät it...

Hi Kare,

I'm wondering if your gauge has been replaced? Even my PF coupe has a low fuel warning light in it. It's in a special holder as one side isn't grounded as the other lights are, but instead is connected to +12V.

Looking at the back of the PF coupe gauge, you can see the terminal of the left. This is marked SERB (fuel tank). The other is the +12V (marked INTER). The hole in the upper left is for the gauge illumination bulb. The hole in the upper right is for the low fuel bulb. Notice that it is insulated where it attaches to the gauge back because it is connected to the +12V terminal. So the wire from the low fuel warning bulb is the second wire to the tank.

Post by **tyang** » Sat Nov 18, 2006 9:20 pm

Tom, yes it does measure the resistance of the sender, but not the way you describe. Doesn't your America have a low fuel warning light?

Hi Kerry,

You are correct! I am wrong. I'm spending too much time with my Mustang, I'm forgetting how the Ferrari was wired!

Tom

t walgamuth · Post by **t walgamuth** » Mon Nov 20, 2006 4:04 pm

i dont know if yours is like my pf coupe, but in mine the pivot(s) were just rusty. i lubed them and worked it back and forth a few times and it worked fine.
it came out the parcel shelf area.

tom w

kare · Post by **kare** » Tue Nov 21, 2006 6:51 am

330GT wrote:So the wire from the low fuel warning bulb is the second wire to the tank.

I just find it funny that one terminal on gauge is identified as "SERB" (=fuel tank) when there are TWO wires coming from the sender unit. Best wishes, Kare