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Old 10-18-2001, 08:24 PM   #1
stimpy
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Default Wierd Fuel Delivery

I'm seeing some rather interesting fuel pressures as of late. In the morning, I am seeing fuel pressures of about 37.5psi. That is rather unusual since I have a stock FPR and a 255lph fuel pump. Until recently, my fuel pressure was about 49psi. Before I did the fuel rail mod, I had ~50-51psi though it dropped a couple psi after the mod. Currently, my car will warm up at 38psi and drive around town at that pressure. But, once I jump onto the freeway, the pressure will rise up to 45-47 (lower than it was previously). Any ideas?
The other part of this, though I'm not sure it's related, is my idle is now a hair under 500 rpm (closer to 400) and the car is idling a little rougher. I haven't checked to see if I have a leaky gasket since I removed the intake manifold, but it is something I plan on checking.

-Jon
www.nothingserious.net
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Old 10-18-2001, 11:09 PM   #2
kaos200
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Default Re: Wierd Fuel Delivery

Quote:
Originally posted by stimpy

The other part of this, though I'm not sure it's related, is my idle is now a hair under 500 rpm (closer to 400) and the car is idling a little rougher. I haven't checked to see if I have a leaky gasket since I removed the intake manifold, but it is something I plan on checking.
Jon, you DO realize that the first mark on the Tach is 500RPM right?
It wont idle at anything less than that.
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Old 10-19-2001, 02:40 AM   #3
8Complex

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Maybe the diaphram in the FPR is made of a material that causes lower pressures when it is colder? It has been getting a lot colder lately...
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Old 10-19-2001, 08:51 AM   #4
Scoobyslack1
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Jon does this mean you have your turbo on finally?
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Old 10-19-2001, 09:04 AM   #5
stimpy
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Haha, no turbo yet . I am trying to correct my fuel system first.

It's a definite possibility that my FPR is dead. Guess it's time to see if I can locate the SVX FPR. For some reason, my fuel delivery has never quite been on par with others' with a high flow fuel pump.

After looking at my tach again, I do see what you mean kaos200. I guess the car usually idles at 750 and it is now idling around 650 or so. Either way, its not idling quite as high as it was before.

Thanks for the ideas.

-Jon
www.nothingserious.net

Last edited by stimpy; 10-19-2001 at 10:01 AM.
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Old 10-19-2001, 12:21 PM   #6
skywalker
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When was the last time you reset your ECU. I am not saying to reset it, but I am just curious if your ECU might be learning and dropping the fuel delivery from the Walbro Fuel Pump. Doubt it though.

In any case that is kind of interesting. I wonder if the cold does it affect it that much?

~Bill
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Old 10-19-2001, 12:23 PM   #7
stimpy
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I'll try resetting the ECU but I doubt it will do anything either. I have had the pump in there for over 6 months and it is only now acting up. Only things different are the cold and the parallel fuel rails.

-Jon
www.nothingserious.net
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