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Dr. Hamman
Dr. Hamman, Technician
Category: Classic Car
Satisfied Customers: 6286
Experience:  I have 30 years experience repairing, restoring, and customizing cars, and pickup trucks.
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I have a 1976 911s that sits in storage in the winter. When

Customer Question

I have a 1976 911s that sits in storage in the winter. When I put it away there was have a tank. This spring the tank was empty?? I filled it with fas but it was hard to start. It drove okay. I tried to restart when warm it would not fire. Then fired when cold but rough start. The fuel pump may be a little noisy.
Submitted: 6 months ago.
Category: Classic Car
Customer: replied 6 months ago.
I had a service where the fuel tank was cleaned out and since that time the car has had a rough time starting. Before that not problem.
Customer: replied 6 months ago.
Is Anybody out there?
Customer: replied 6 months ago.
It has been 40 minutes. Goodbye
Expert:  Dr. Hamman replied 6 months ago.
I saw your question. I just logged on for the day, my apologies for no one being available who knows this system any earlier. The Bosch injection system your 911 uses can be pretty sensitive to gas residues when the gas evaporates. You have a device called a CPR(control pressure regulator), it is also called a warm up regulator,or cold start regulator. The CPR acts like a choke on the injection system and allows good cold starting and operating. If it gets stuck in the cold start mode the engine will have trouble starting when the engine is warmed up. Then when it cools down it will start again. If this is the case the engine will run rich, and wont run perfect. I would suggest some fuel system cleaner, and then afterwords change the fuel filter. If this doesn’t clear it up you need to find someone with the special Bosch CIS injection pressure test setup,this will tell you right away if you are running too rich, or lean.One other thing on this setup there is an odd pressure issue. Low pressure creates a rich mixture, and high pressure creates a lean mixture. Always be ready for that if you are dealing with one of these fuel system's. If you have anymore questions feel free to ask.Good luck with it and thanks for using Just Answer.
Customer: replied 6 months ago.
Why does all of the gasoline evaporate?
Expert:  Dr. Hamman replied 6 months ago.
You mentioned the vapor recovery system possibly being disconnected. That could factor in. Gasoline naturally is prone to evaporation unless it is held in an air tight container. There are additives like the product called Sta-Bil, that help prevent evaporation. Using Sta-Bil keeping the tank relatively full, and running the engine a couple of times a month for 30 minutes or so can help a lot. For now try some cleaner, change the fuel filter, and see if that helps. If not then get to someone who can preform the pressure tests that can tell if the CPR is causing problems. If you have anymore questions feel free to ask.Good luck with it and thanks for using Just Answer.

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