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Registered
Join Date: Apr 2006
Location: new jersey
Posts: 56
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fuel pump issue
hi everyone,
on my 80 targa, I noticed that the fuel pump does not turn on when I turn the key, I always assumed that the fuel pump always cycle and then shuts off to build pressure in the system. My other car a 70 mercedes 250 ce (with EFI) does, maybe the CIS in the porsche does not have to? The car runs OK, with some hot start problems, but that is another issue..... Thank-you so much! |
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08-09-2006, 02:49 PM
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sudo apt-get purge 930
Join Date: Jul 2006
Location: Brandon, FL
Posts: 4,838
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The fuel pump doesn't run until you start cranking. There is a contact on the fuel distributer that controls the circuit to the fuel pump. It doesn't allow the pump to run unless there is air flow past the plate.
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Mark 1979 930 Euro ***GONE AND DON'T MISS IT AT ALL*** "Worrying about depreciation on your car and keeping mileage down is like not ****ing your girlfriend so her next boyfriend finds her more appealing" --clutch-monkey |
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08-09-2006, 04:38 PM
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It depends on the car. On my the fuel pump does come on when I turn the key to run before start. I been told that this is incorrect, but since owning this Porsche for the past 6 years I have never had a hot start or cold start problem,
Last edited by ruf-porsche; 08-09-2006 at 06:19 PM.. |
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08-09-2006, 06:06 PM
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Join Date: Apr 2006
Location: new jersey
Posts: 56
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thank-you
it seems to me kind of odd that the fuel pump does not run when turning the key, I would think that having fuel circulating would improve starting the engine...uhmmmm |
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08-09-2006, 07:59 PM
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Join Date: Feb 2001
Location: Ottawa
Posts: 786
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EFI pressurizes the fuel rails and then turns the pump off if the engine has not started.
In CIS the fuel pump should only come on when the engine is drawing air (cranking or running). This is a safety feature, in the event you roll the car and a fuel line breaks the pump isn't spraying fuel everywhere. In CIS the accumulator is used to hold pressure from the last time the engine ran to aid in the next start.
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Tony '78 911SC with BITZRACING EFI conversion kit |
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08-09-2006, 08:32 PM
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Registered
Join Date: Apr 2006
Location: new jersey
Posts: 56
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Thank-you tbitz!!!
your site is VERY interesting.....!
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80 SC targa Teal 78 Lancia montecarlo Teal (in Italy) 70 euro Mercedes 250 CE Blue met. 05 Lexus 470 GX White |
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08-09-2006, 08:35 PM
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Join Date: May 2000
Location: Los Alamos, NM, USA
Posts: 6,044
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It's a safety feature to avoid flowing gas when the engine is not running. For various reasons, too many of the early CIS system cars had non-running engines filled with the gasoline to the point it was running out the tail pipe. Hot start problems can sometimes be traced to a leaking pump check valve or a bad accumulator. Instead of fixing the actual problem, the air flow switch connector was pulled allowing the fuel pump to prerun and repressurize a leaky system.
Last edited by Jim Sims; 08-09-2006 at 08:43 PM.. |
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08-09-2006, 08:38 PM
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Registered
Join Date: Apr 2006
Location: new jersey
Posts: 56
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Thank-you jim,
if by check valve you mean the one way valve connected to the output of the pump, I had to remove it because after replacing 2 pumps, I realized that that little insignificant item (to me) was bad and had caused the pump failures. The Pierburg pump that I purchased has a "free flow valve", so I installed it without it. I do not know if the car had the troubles starting hot before as I purchased the car not running at a very low price.......
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80 SC targa Teal 78 Lancia montecarlo Teal (in Italy) 70 euro Mercedes 250 CE Blue met. 05 Lexus 470 GX White |
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08-09-2006, 09:12 PM
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