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SC fuel pump delivery question
I am having an issue with my fuel pressure. I replaced the pump after the old one died last summer, and troubleshooting the fuel pressure I replaced the fuel pressure regulator (EFI conversion engine). As it is, on my 3rd fp regulator I get 39 psi, other days 34 psi. Needless to say this upsets my fuelling
Did I get the wrong pump for the car ? It is an 1980SC and the pump I got the Bosch 0 580 254 984. The pump was slightly noisy out of the box but as I haven't really tried other 911s until a few days ago I didn't really reflect on the noise level until now. * 165LPH @ 5 Bar (12V), * 12mm (3/8") barb inlet, * M12 x 1.5 female thread outlet, * 180mm long, * 60mm OD, * 10A max draw
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80SC (ex California) Last edited by trond; 06-10-2011 at 03:03 AM.. |
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06-10-2011, 02:59 AM
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This is one (front) of the two 930 pumps. It's for pre-delivery the second pump, which is for pressure. So your pump is probably not the right one for your application.
On my EFI conversion, I stayed with both stock pumps. I suggest you add the second pump too or mount another one instead of the present. There are several threads about fuel delivery for EFI. Turbokraft and others have some pumps for your application...
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Roland 930 Turbo '81 Too many modifications to list |
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06-10-2011, 03:56 AM
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There is no "right" pump for an EFI conversion on a N/A 911SC engine. The pump you have has more than enough flow and pressure for your application. The problem is probably in your regulator or plumbing. Are you using a vacuum referenced regulator made for an EFI system ?
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Paul |
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06-10-2011, 06:50 AM
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yes, the pump should be more than sufficient at 5 bar=72 psi/165 liter pr hr. I am using a new 2.5 bar Bosch vacuum referenced regulator from a Saab Turbo and whats more I am on my third regulator so I really haven't been too clever at my troubleshooting at all.
What could cause a fuel pump to deliver insufficient pressure ? It's puzzling that the fuel pressure changes from day to day. I measure the pressure by running the pump and the engine static. Even on the same day I get 34 psi, then 39 psi and looking at the AFR gauge fuelling is different so it's not just the pressure gauge. I ordered a new fuel pump today, the same fairly expensive one from Bosch. When I install it I will simultanously pull cables to be able to measure for voltage fluctuations at the pump terminals
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80SC (ex California) Last edited by trond; 06-10-2011 at 08:28 AM.. |
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06-10-2011, 08:24 AM
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Why would you chose to use a boost referenced regulator on a N/A engine ? The usual vacuum referenced Bosch regulator for EFI uses manifold vacuum to lower pressure at idle for better pulsewidth control and noise. It is normal to have lower fuel pressure at idle with full vacuum, then higher pressure at WOT when vacuum drops. A Bosch boost referenced regulator increases pressure with boost to maintain the same pressure differential at the injector nozzle. It is not needed on a N/A car. If you are saying the fuel pressure fluctuates at the same vacuum, I would be looking at the vacuum source, hoses and connections and for restrictions in the return plumbing. Are your rails plumbed in a loop and where did you locate the regulator ?
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Paul Last edited by psalt; 06-10-2011 at 11:04 AM.. |
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06-10-2011, 10:19 AM
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911SC
