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Wider is Better
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Fuel pump runs all the time?
I just want to verify something. I have an 87 Carrera, and when I turn my ignition to the first position, my fuel pump begins to run. I read on another thread that this is not supposed to happen, but when I pull the fuel pump fuse the noise stops (and the car won't start). It has done this for the year I have owned the car with no apparent problems.
Is it normal for the pump to run or do I need to look into it? Thanks in advance. Walt
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02-13-2006, 09:46 AM
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Location: Indianapolis, IN
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If I am not mistaken the fuel pump comes on for a few seconds to pressurize the system. That is how you know the fuel pump is working. It should quit buzzing after a few seconds.
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02-13-2006, 09:52 AM
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In my 70 911t the pump comes on when the key is turned to the first stage, its suppose to do this, i would assume that it would also do it in later models as it is necessary to pressurize the system.
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02-13-2006, 10:20 AM
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Wider is Better
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Quote:
The longest I have let it run is about 5 minutes, and it did not stop.
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02-13-2006, 10:45 AM
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Have you tried a new fuel pump relay? Maybe it is stuck open. I have never heard of this problem.
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'94 VW Jetta '85 VW Scirocco '81 911 SC coupe Euro '67 VW Bug |
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02-13-2006, 02:30 PM
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i think it's only a problem if you turn the key and the pump doesn't turn on. most aren't going to just let it run on and on..the idea is to turn it on, some let it run a few seconds to build pressure, then crank..
ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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02-13-2006, 02:35 PM
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Wider is Better
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Anyone with an 84-89 Carrera want to chime in? What does your car do?
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02-13-2006, 04:06 PM
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I had an '86 3.2 engine in my early car.
The pump should shut off and is controlled by the DME relay, which is actually two relays in one. The pump should only run when the engine is running or cranking. This is a safety feature. If the car is crashed and the engine dies, fuel doesn't keep pumping (you get the drift). There is a fuel pump fuse and it would be entirely possible that someone hard wired the fuel pump directly to one of the sources at the fuse box which turn on with the ignition. Not sure why, but you never know what "problem solvers" come up with. Safety issue aside, I'm not sure it is so bad?? The fuel pressure is regulated via an engine mounted regulator and you have a return line, so you are not jambing up the pump with massive amounts of pressure. I'd wire it stock. Doug
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02-13-2006, 04:39 PM
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Wider is Better
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Quote:
Thanks again.
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02-13-2006, 05:08 PM
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What?!?!
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My 72 with an 88 3.2 does the same thing. As soon as I turn the key on, it runs constantly. The other hitch is it still won't start.
Is there anything that senses a pressure increase then shuts off the pump?
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03-14-2006, 08:30 PM
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What?!?!
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Early a.m. bump.
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running shoes, couple tools, fishing pole 1996 Subaru Legacy Outback AWD, 5speed 2002 Subaru Impreza WRX, 5speed 2014 Tundra SR5, 4x4 1964 Land Rover SII A 109 - sold this albatross |
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03-15-2006, 06:15 AM
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heiliges blechle!
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I can't hear mine at all. I know it is working - I just replaced it two days ago because the old one was leaking gas through the crimped area by the electrical connectors. I couldn't hear that one either but the car still ran.
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03-15-2006, 06:39 AM
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I doubt it Don, the pump runs at a set rate.
I mean the pump doesn't cut back or turn off because you let off the pedal and the injectors go half time. The pump should only run when the car is cranking. At least that's what the bosch book says |
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03-15-2006, 06:45 AM
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What?!?!
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I was speaking strickly from a pre-start condition. My DME is wired correctly yet I am not getting spark. The pump running constantly has me bum-fuzzled. There are some conditions that need to be met prior to ignition (pump running, refence sensor, etc.) and I thought maybe there was a method of detection for the pressure.
For instance, if the pressure is never met, the pump keeps running and there is no spark because the pressure is never met......  ???
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running shoes, couple tools, fishing pole 1996 Subaru Legacy Outback AWD, 5speed 2002 Subaru Impreza WRX, 5speed 2014 Tundra SR5, 4x4 1964 Land Rover SII A 109 - sold this albatross |
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03-15-2006, 07:29 AM
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don,
i don't have cis pressure gauges, but i'm sure someone can chime in on their use. i'm pretty sure they could be used on your carrera to check pressure prior to cranking..sounds like you're asking if there's a 'minimum' fuel pressure needed for start? i know in my car that the fuel pump runs to prime the system before you ever start cranking..it's designed to run all of the time, but of course that's why it's called a 'continuous injection system'. but, i have to admit i've never worked on a later engine, nor probably have much business troubleshooting one. ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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03-15-2006, 08:01 AM
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On my 89, pump starts when I turn the key to 'on' and then runs for at least 30 seconds. (I got tired of sitting in my cold garage listening at that point.)
RA
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03-15-2006, 09:19 AM
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spark will happen even if there is no fuel pressure at the rail.
fuel but no spark? I would look at swapping ECM brains, and checking coil and power |
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03-15-2006, 09:33 AM
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Pump should *not* run with the key simply turned to the first indent...
DW SD has it right..... its a safety feature, there is a "permissive" in the circuit that makes the pump run only after speed sensors "sense" that the engine is turning over...like when the key is "far" over on the momentary-contact-to start part of the key "twist"..... - Wil ( stock 85 Carrera)
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03-15-2006, 10:08 AM
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Quote:
 ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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03-15-2006, 10:16 AM
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What?!?!
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Quote:
I have 2 DME relays. I have 2 coils and there is 12V at coil "on and cranking". I'm looking at the 14 pin harness and think I don't have battery voltage there.
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running shoes, couple tools, fishing pole 1996 Subaru Legacy Outback AWD, 5speed 2002 Subaru Impreza WRX, 5speed 2014 Tundra SR5, 4x4 1964 Land Rover SII A 109 - sold this albatross |
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03-15-2006, 11:02 AM
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Porsche 911
FatBoy
Old Blue
1974 Porsche 911 2.7
