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MOTRONIC: Fuel Pressure Regulator/Damper?
Guys,
Is this a fuel pressure regulator of some sort?  Trying to diagnose my engine flooding problems, I accidentally (call it devine intervention perhaps?) bumped the vacuum line off of the top of this device and when I tried to test start the car, a whole lot of fuel came pissing out of this vacuum port  This is the port that has a vacuum line that runs to the back of the throttle body and T's off to the fuel pressure regulator on the left side of the engine bay. Fuel shouldn't be coming out of the vacuum port, right? The diaphram inside this thing must have torn and as a result, is pumping fuel back into my intake and flooding my engine 
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition 
Last edited by WydRyd; 03-25-2006 at 10:28 PM.. |
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03-24-2006, 11:08 PM
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Is this the same part # from our host?
Pressure Regulator, 911 Carrera (1984-89) Brand: Bosch 928-110-198-01-M14 $83.00 This is the left side regulator. What's the part # for the right side then?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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03-24-2006, 11:27 PM
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Irrationally exuberant
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The red one (on the left) is the fuel pressure regulator. Notice that it has a 3rd fuel line connection. That 3rd line bleeds excess pressure off and back to the tank.
The one that your arrow points to is the fuel pressure damper. I'm no expert on this but I bet you're onto something Merv. Sucking gas into the throttle body like that certainly would make things run richer. On the up side, I bet your intake runners are really clean now.  -Chris
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'80 911 Nogaro blue Phoenix! '07 BMW 328i 245K miles! http://members.rennlist.org/messinwith911s/ |
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03-25-2006, 01:03 AM
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Cant answer your question...but I can say this:
I found that vacuum line disconnected on my car also and had no flooding problems or any other ill effects.
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KC 88 Guards Red Targa (sadly sold  )2005 Boxster S 1st Porsche 73 914 (long gone) |
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03-25-2006, 03:04 AM
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Merv-I suspect that is the culprit. I have to wonder if those things are designed to see boost for any length of time.
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Greg Lepore 85 Targa 05 Ducati 749s (wrecked, stupidly) 2000 K1200rs (gone, due to above) 05 ST3s (unfinished business) |
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03-25-2006, 03:49 AM
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Merv, here's the part number for the fuel pressure diaphragm: 93011060200
Hope this helps.
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Josh '87 911 Carrera 3.2 Coupe |
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03-25-2006, 03:51 AM
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Somewhere in the Midwest
Join Date: Oct 2001
Location: In the barn!
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The FPR creates such a high fuel pressure...that any weak or worn component will fail. The diaphragm in the damper could have been bad to begin with and the higher fuel pressure was the last straw. The damper should not leak...yep..you got lucky finding that sucker on accident after all the earlier hassles.
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03-25-2006, 04:03 AM
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Location: Richmond, VA USA
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That vacuum line is important to the ECU and fuel delivery. The varying intake manifold pressure acts thru the fuel pressure regulator to maintain a constant differential between the manifold pressure and the fuel pressure, so that the fuel delivery with each cycle is predictable.
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03-25-2006, 07:18 AM
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Thanks guys. That's what it's called, a Fuel Pressure Damper!!!
KC, that port on the damper is for vacuum only, not fuel. Mine must have a tear in the diaphram, which is bleeding fuel into the vacuum line to the throttle body and flooding the motor. Oh well, at least when it's replaced with a new one, it shouldn't be a problem for many years  I bet it was the original one anyway.P.S: I didn't know what this damper actually does, so I did a search and came across this post by IanC. "The one on the passenger's side (pictured) is actually a pressure damper. It reduces fuel pressure fluctuations in the system. The hose you ask about does not have a vacuum function, it is there in case the diaphragm inside ruptures, so that fuel will be squirted into the manifold rather than on to the engine. Damper is always on the low pressure side, regulator on the high pressure side. The vacuum line on the regulator is to make sure fuel pressure from the injector stays consistent. Fuel pressure would be constant without the line, but the pressure in the manifold can change, so the vacuum line pulls back on the internal diaphragm to allow less pressure when intake vacuum is high. ianc" 
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
Last edited by WydRyd; 03-25-2006 at 10:23 PM.. |
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03-25-2006, 10:01 PM
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Here's more tech info on the function of a fuel damper:
"Whenever multiple high-flow injectors are installed on a fuel rail, hydraulic pulsations from the injectors opening and closing cause the fuel to “hammer” back and forth. This creates pressure and flow variations within the rail and can lead to large inconsistencies in fuel delivery from cylinder to cylinder. A damper is used to absorb these pressure fluctuations and allow each injector to receive the proper amount of fuel pressure and flow, eliminating rich or lean cylinders, etc. "
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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03-25-2006, 10:31 PM
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Found a new replacement part locally!
Question: How much fuel can I expect to p!ss out when I remove the faulty unit?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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03-26-2006, 02:31 PM
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The Blue Pheonix
1988 Porsche Carerra Targa 3.2
Boxster S
