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phoenix_iii's Avatar
 
Join Date: Oct 2007
Location: Philadelphia area and Morristown NJ
Posts: 948
Smile Fuel Pressure Regulator vs. Fuel Pressure Dampener... How do they work together?

N00b question...

Researching some things, I may be replacing the Fuel Pressure Regulator.

How does the Fuel Pressure Dampener come into play?

I have an 85.5 944 NA.


I am looking to replace my fuel lines (Lindsey kit) and vacuum lines (again, kit, etc)



944-110-201-03-M14 --> Fuel Pressure Damper, 924S 1987-88, 944 1983-84, 944 02/85-88, 944 Turbo 1986-89
http://www.pelicanparts.com/cgi-bin/PartsLookup/search.cgi?command=search&part_number=94420106101

944-110-198-03-M14 --> Fuel Pressure Regulator, 924S 1987-88, 944 02/85-88, 944 Turbo 1986-89
http://www.pelicanparts.com/cgi-bin/PartsLookup/search.cgi?command=search&part_number=94411019803
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89 951 Turbo S - Revival in progress...
Old 05-28-2008, 12:52 PM
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the fuel pressure dampener dampens the pulses coming into the fuel rail from the fuel pump so it doesn't surge really bad due to the pump. the fuel pressure regulator is on the outlet side of the rail and it regulates how much pressure is in the fuel rail at all times and lets the rest of the fuel go back to the fuel tank once the pressure is met.
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Brian

'86 944 NA
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Old 05-28-2008, 01:34 PM
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There's also pulses caused by the injectors. Each time an injector opens, there is a slight drop in fuel pressure. The Damper compensates for this temporary drop in pressure. It's basically a spring loaded device that keeps pressure up.

Where as the fuel pressure regulator releases fuel (back to the tank) when pressure is too high. It keeps the pressure down to a prescribed, safe level.

They work together to keep pressure even.
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Vern

'74 911 Coupe - Silber Metalic (963-93), PMO ITB Injection and Electromotive Management
'88 944 Coupe - Nougat Brown Metalic
'74 914 Targa - Light Gray 2.0
Old 05-30-2008, 07:58 PM
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^ You guys really know how this works!

I wouldn't add anything to what was just stated above. Good job on explaining the fuel pressure regulation and dampning.
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Ed Paquette
1983 911SC
1987 944 Manual (Donated to the Nat. Kidney Foundation)
1987 944 Automatic
Old 05-30-2008, 09:57 PM
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Not necessarily a "safe" level, but a consistent level, since the injectors will flow more or less fuel depending on the pressure.
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Old 05-31-2008, 11:25 AM
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There's a third part of the equation and that is the fuel pump check valve. This is a one way valve that prevents fuel pressure from leaking down after the car is shut off.

By keeping the pressure up, even when the car is off, it enables the car to start on the first few cranks - otherwise the system would have to build up pressure before having enough fuel pressure to squeeze fuel thru the injectors - taking 10 or 20 cranks before the engine will start.
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Vern

'74 911 Coupe - Silber Metalic (963-93), PMO ITB Injection and Electromotive Management
'88 944 Coupe - Nougat Brown Metalic
'74 914 Targa - Light Gray 2.0
Old 05-31-2008, 07:55 PM
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