cis problem
 

I hope someone can help on this one. I have a huge vacuum on my fuel tank.1983 930 turbo. After driving for a while, my fuel tank collapes and has destroyed my sending unit.The car runs fine, but have noticed a slight hesitation at 5 grand. any Ideas or help is appreciated. Anyone know if the tank is vented.

I would post this question on 911turbo.com or on Rennlist.com.
Or maybe c2turbo.com.

Someone there will surely have an answer.

Brian

Thanks Brian. I'll give that a try..

83930,
First off there should be plenty of room internally between the sender and the bottom of the tank. If there isn't then the problem sounds as if it has been hit, or pushed up. The system is somewhat open through the charcoal canister so it is not sealed per say, rather does vent. Something else is going on for sure. Did someone perhaps try to jack the car up by the tank and the tank is damaged that way?

Hey Stephen - glad you came over for a visit. We could use a seasoned turbo guy.

Neil - this doesn't sound like a typical problem. I'd drop the tank and take a thorough look at the entire system. Does this happen if you drive with the gas cap loose?

I've seen this problem twice, both times it was caused by an obstruction in the very small diameter steel vent line that runs behind the fuse box, through the driver's side inner wheel apron. A hose goes from the steel vent line in the wheel well to the top of the vent tank behind the head light. On one occasion, the obstruction was the result of a body shop getting a little rough when they changed out the front fender. The other occasion, it was caused by a very fine piece of debris, which got trapped at the spot where the factory welded the tube to the inner apron(you will find this weld if you pull the fuse box back from its mount). I think that the factory collapsed the tube slightly by putting a little too much heat on it when they welded it.

The obstructed vent line meant that the fuel pump pulled down a vacuum in the tank by pumping out the fuel.

I don't know if you have the exact same problem, but I am 99% sure that you have a venting problem of some kind there.

Once you trouble shoot the venting problem, you need to puff up the tank. Drain the gas, block all the inlets and outlets, and pump it up with a compressed air hose. The tank should spring right back into shape, and you can then put in a new fuel sender. I like to do this with the tank off the car.

P.S. Check your tank very thoroughly for rust, especially around the vent connection, when you fix this. Also, I see that you have a RoW model. These vented to atmosphere in Europe. Your car has probably had an inferior quality carbon canister, evaporative emission control system fitted in order to get the EPA certification. You might want to investigate your options.

My gas tank has just done the exact same thing.

I am going to look at it tomorrow and try to figure out where the vent problem is.

I will also take a pic of mine. It is unbelievable how the thing is deformed.

Brian