Fuel Distributer 911 CIS 1974, 2.7 L
11-25-2001, 03:35 PM
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Fuel Distributer 911 CIS 1974, 2.7 L
My 1974 CIS fuel injection is giving me a
problem. Runs good in high gear,poor acceleration though the gears. Pressure test
was only 50 p.s.i.system pressure, and 16psi
control pressure. Is there a way to increase
pressure? I have replaced fuel pump. Does this low pressure confirm a faulty fuel dist.
Help needed to get my toy well again.
problem. Runs good in high gear,poor acceleration though the gears. Pressure test
was only 50 p.s.i.system pressure, and 16psi
control pressure. Is there a way to increase
pressure? I have replaced fuel pump. Does this low pressure confirm a faulty fuel dist.
Help needed to get my toy well again.
11-25-2001, 10:23 PM
#2
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If your cold control pressure test was done at roughly 50 degrees, 16 psi isn't off by much. If the air temps were towards the 70's, then yes it's low. If the control pressure was done on a warmed up engine, then it's low. If you can find the return line to the gas tank, you want to run the fuel pump for 30 seconds, routing the gas into a container where you can measure the volume output. Should be around 850cc. If less, and you've already changed the fuel pump, change the fuel filter, check the fuel lines to see if there is a crimp anywhere, and replace the in-tank filter. If that doesn't fix it, you can try cleaning the regulator components in the system pressure regulator on the side of the fuel distributor. If that doesn't get the system pressure back up, then it's a new fuel distributor. If that doesn't in turn fix the control pressure, replace the warm-up regulator. This advice courtesy of "How to Tune and Modify Bosch Fuel Injection" by Ben Watson.
11-26-2001, 05:45 PM
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NOT to doubt MR. Gregory's response,BUT
I too fought the same problem with my 74 911.
Mine has a 77 2.7 system on it. As far as the manuals I've read the system pressure needs to be 64-75 lbs. 4.8-5.2 bar. The opening pressure of the injectors is about 49lbs or so. What I found was that when I pushed up on the flow meter arm inside air-box with the fuel pump running.(to simulate full trottle)The system pressure would drop to about 40 lbs. The injector flow would stop.(below opening pressure)
To solve this I shimmed the spring in the fuel pressure regulator in the back of the fuel distributor until my system pressure was more than 60 lbs.(Haynes manual/later model section.(towards rear of book)
I too fought the same problem with my 74 911.
Mine has a 77 2.7 system on it. As far as the manuals I've read the system pressure needs to be 64-75 lbs. 4.8-5.2 bar. The opening pressure of the injectors is about 49lbs or so. What I found was that when I pushed up on the flow meter arm inside air-box with the fuel pump running.(to simulate full trottle)The system pressure would drop to about 40 lbs. The injector flow would stop.(below opening pressure)
To solve this I shimmed the spring in the fuel pressure regulator in the back of the fuel distributor until my system pressure was more than 60 lbs.(Haynes manual/later model section.(towards rear of book)
11-26-2001, 08:13 PM
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Thanks for your help Bill & hdoody.Bill, you
make referance to an article "How to tune and modify F. I." by Ben Watson. Can you give
me any infomation on how I can obtain a copy?
make referance to an article "How to tune and modify F. I." by Ben Watson. Can you give
me any infomation on how I can obtain a copy?
