starting problem when hot

[Joe Wicked]

Blas,
To answer the question, yes the car may still have a bit of charge, but it will have discharged through you to ground. What you really should do is touch the filler with one hand and the pad with the other. This equalized you, the car and pump to the same potential (ground in this case). What a lot of people don't realize is it doesn't actually matter if you have a charge on you as long as the charge is the same, there will be no discharge. When you open the filler you are grounding out any charge to the potential at the gas station parking lot, which the Pump is at the same charge. This is equalizing. Touching the pad only serves as a secondary "check" that you are grounded. I have never felt a discharge by touching the pad. Just an extra safety check.

PS. The stations that you see with signs warning that cell phones can cause a static discharge and explosion are wrong. A phone will have the same static charge as the person holding it, and the RF emitted cannot cause an explosion. That whole thing came from a false email that a few news stations ran with and now it is everywhere.

[Wayne Maybury]

Originally Posted by Blas

Then why are both my Mercedes not grounded at the fuel filler? I'll check the Passat tomorrow and the Porsche over the weekend...

The gas filler caps on these cars are grounded assuming they have metal bodies. The gas inlet/filler is bolted to the body so there is no need for a separate ground wire. My Cobra has a fiber glass body, hence I grounded the filler cap to the metal frame. It may or may not be necessary but I figured, what the heck?

I have worked with flammable chemicals for over 40 years. All tank trucks must absolutely be properly grounded before loading or unloading to avoid the chance of a static spark igniting the product.

Wayne

[Blas]

Wayne,
When I take an ohm meter and connect one end to the car chassis and then touch the other end to the filler pipe there is no conductivity on either of my Mercedes. I then touch something else on the car and there is...No two ways about it? The gas caps are both plastic where you grab them, so you probably don't really connect electrically to the car when you remove it...Surely the TANK is grounded by way of its mounting to the car...

[Blas]

Interesting point: I called Fuelsafe and they did not appear to have a definitive answer either way on the grounding of the filler neck....

[Ron61]

Blas,

On my 1965 Comet I can take the gas cap off, it is a locking one and some kind of metal, then touch my ohmmeter lead to the edge of the filler tube and the other to the chassis and I do get a reading. It could be via the tank straps that hold the tank in but when I looked under it I saw a wire that went off to the side and to a bolt on the frame. Don't know if that was stock or if it was added as I bought the car used. When it warms up enough I will go check on the 69 Cobra and see if is is grounded. As I said in my earlier post, I tend to err on the side of safety. To many grounds won't hurt.One to few could possible hurt.

Ron

[Joe Wicked]

Good to point out Ron, I was talking about the filler tube. The fuel nozzle does not normally touch the cap, so the filler tube is what is important. Plastic does hold a charge if left alone, but if it is making contact to the filler tube, which is then in chain making contact to the car chassis, then it will not be able to build a different charge.

As far as the Mercedes, it may well be an isolated, ESD (ElectroStatic Discharge) coating or isolator that would completely isolate the filler and the rest of the car. It would also prevent a sudden discharge. Standard Plastics and Rubber will not work. It would have to be ESD specific. These have a Very High resistance and many will read this as open, but it is not. These materials are used in Electronics Manufacture and Repair all the time. It will cause a very slow discharge that will not produce an arc. On a higher end luxury automobile, I would not be surprised that they incorporated something like that into the design.

Edit: The purpose of the ESD materials is to protect sensitive electronics, but the same principals apply, so it would be a good application.

[Blas]

Ron,
On the '65 Comet, doesn't it have a one piece filler tube, all metal, and actually part of the fuel tank itself? Or is the tank also connected to a seperate filler tube with a rubber hose...

[strictlypersonl]

I've include a in-harness ground on our filler from the beginning. I figure it's better to be safe than sorry. And growing one's eyebrows back is a slow process.