Hi,

I have replaced Petrol Sending Unit today. After doing that I went to a petrol station and noticed pretty bad petrol leak under my car.
I left the car sitting for some time and about 1/4 of a tank has leaked out.
I removed the back seat and I've opened the cover and appears that the leak is coming from the top of the petrol tank between retaining ring and sealing washer.
When I replaced the Sending unit I didn't replace the sealing washer but I used the old one. I actually had to shorten it a bit because it was too big and didn't fit properly.

Could yo guys please tell me how important is to replace the rubber sealing washer when replacing the sending unit?

Will buying a new sealing washer and replacing the old one resolve the issue?
How tight does the retainig ring need to be?

Thanks, Alem