Thread: How to install a Fuel sending unit?????????

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I am ready to install the gas tank sending unit. It is a Classic Gauges product and after reading the directions I am confused. It tells me to cut a 1 5/8 Hole in the tank and then insert the unit into the tank and then attach it using the 5 screws provided into the "pre-drilled holes". What pre-drilled holes? The directions to this point does not mention drilling holes. Besides it looks like the screws need a threaded hole. Anyone know how this all works?

http://good-times.webshots.com/photo...99708909ITmsUH

As you can see the tank came with two outlets, one inlet, and a vent.

I believe it's probably refering to "pre-drilled" hole that you make when trial fitting the sender. After the big hole is drilled set the sender in and use it as a template for drilling the screw holes.

On the tank I used on one of my projects it used the screws with drill points that self tapped into the tank top.

Just a tip when you get all the holes drilled before you you install the sender for the final time. Wrap the end of a piece of wire/coat hanger with some masking tape after a few wraps twist the tape and give it a few more wraps sticky side out and use it to fish out the shavings that have ended up in the bottom of the tank.

Thanks Mike.
I still don't know what they expected me to do with these screws if they need threaded holes. Will screws with "drill points" work and not back out? Where can I get these screws?

I've never had a problem with them coming out. Should be able to find them at any hardware store.

STEP 9: Use ONLY the five mounting screws furnished by Classic Instruments (they are
self-sealing) to install the mounting flange onto the tank. DO NOT tighten the screws yet.
First connect the ground wire with a ring (“eyelet”) terminal around on one of the five
mounting screws. NOTICE! Mount eyelet terminal BETWEEN the metal mounting
flange and the topside of the cork gasket.

They assume you already have a predrilled tank. Do not use anything but screws in kit. If your tank doesn't have a predrilled hole for the sender its up to you to get it done. If the tank is aluminum fab the ring from thicker aluminum to prevent corrosion.

If you're worried about using self tappers, you could install nut-serts and use threaded screws....

My experience has been that self drillers work just fine. Make sure you use the cork gasket and do not overtighten. IMO...you will be just fine.

To help with shavings, feed your shop vac hose in the filler hole while installing.....

Watch out where you install that sender. Look in the filler hole and use a mirror to look inside. There should be baffles in the tank that could mess you up.

Not to hijack, but what is best way to ground tank. I think my stock tank needs better ground?
Sorry for the hijack.
Jack

Bad grounds are the number one cause of electrical problems - especially in after market applications. Dirty or loose grounds induce a high impedance (or worse, open) condition that does not allow the circuit to be completed.

I am assuming that we're dealing with a contemporary 12 volt negative ground system. Most fuel senders have a lug that's electrothermically welded to the frame of the sender. Sometimes there's a wire attached from the supplier but in any case, the frame of the sender must be bonded to the frame of your car. Make sure that the connection is clean to bare metal and nice and tight. The sender acts as a variable resistor as the fuel level changes, the resistance changes and the gauge reports the level based on the reading through the sender to ground (the frame of the car)

The ground needs to be at the sender as the gasket between the sender and the tank may prevent the sender from coming into good tight (electronically equal potential) contact with the tank.

Thanks Glenn. That's good info that I believe may solve my problem. My gauge always reads 1/2 full.
Jack

Originally Posted by to-qwk

My experience has been that self drillers work just fine. Make sure you use the cork gasket and do not overtighten. IMO...you will be just fine.

To help with shavings, feed your shop vac hose in the filler hole while installing.....

I am working the Archives and found this article. My problem is I developed a leak after filling the tank completely and sitting on my driveway which is inclined. I removed the tank, sending unit and fuel line cap I am in the process of installing them back to the tank. When I removed the fuel line cap the gasket that came with the fuel tank when it was purchased was deteoriated ; thus causing the leak. I remember using some sort of gasket sealer with the caps when I was building the coupe. The gaskets were rubber. My question is cork vs rubber and sealant to guarantee no more leaks? One thread mentioned Rector Seal (no joke) purchased at Home Depot. Advice appreciated . Also do the mounting screws need a gasket?

Originally Posted by to-qwk

My experience has been that self drillers work just fine. Make sure you use the cork gasket and do not overtighten. IMO...you will be just fine.

To help with shavings, feed your shop vac hose in the filler hole while installing.....

if you tape some garden hose to the end of your vacuum you will be able to get everything out also vacuum the shavings as you drill

Go with rubber and snug real tight.

As to Rector Seal - it's great thread sealant. Several types for everything from compressed air to high pressure liquids of all types..

nunnatax the tank is in use,I am just changing out the gaskets due to a leak. Thanks

Thanks Glenn, I noticed you were on the original thread. At 72 my logic has drifted a bit since my first rod build (32 5/w) in 1959.

I searched the web last night and could only find the sender gasket. The other plate (fuel line, vent and return) is sae 6 screws and larger than the sender hole. I have a 3/16 silicon sheet I might have to make the larger one or is silicon a no,no???