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Fuel pressure regulator or fuel pump?

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Old 09-12-2009, 09:48 PM
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Default Fuel pressure regulator or fuel pump?

1997 Disco I, 145K.
What is the range for the fuel pressure?
I posted another thread few days ago about my car having problems to start. It eventually starts and stays at very low RPM for a few seconds and then it gets up to 900 RPM and drives normal.
I just noticed that I don't hear the fuel pump when I turn the key like I used to. It used to make a whirling sound, not too loud but easily heard, not anymore. I measured fuel pressure and it is 18 psi with the key turn to ignition and the goes up to 24 psi with the engine running. Is that too low? Second, if it is too low, how do you know if it is the regulator or the fuel pump?
Thanks guys
 
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Old 09-13-2009, 08:07 AM
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Have you replaced your fuel filter?
Yes that is to low, you need to be in the mid 30's when the engine is running.
 
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Old 09-13-2009, 09:28 AM
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Thanks Spike. The gasoline filter has about 15K miles on it, about one year, I don't think it is filter problem, but that is easy and cheap to replace. I will do that. My question now is: Is the pressure low because the regulator is opening too soon, or is it because the pump cannot rise the pressure? Did the sound of the pump go down because the pump is going bad or because the regulator is letting it run easier? How do I find out other than replacing both. Which one to replace first on trial and error testing?
 
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Old 09-13-2009, 09:43 AM
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That is a tough question, I would replace the fuel filter.
I replace mine once a year just so it does not rust into place.
I do not know if it would the the fuel PSI regulator or the pump, I would lean towards the pump.
 
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Old 09-13-2009, 09:51 AM
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I agree, I will replace the filter. However the filter will have very little to do with the low pressure while the engine is not running, since a restricted filter will lower the amount of flow but not the pressure, even after the filter. Since the engine is not running, there is no place for the gasoline to go other than fill up the system and eventually reach the pressure that the pump and regulator are setting.
I think I will replace the pump more because of statistics, it seems to fail a lot more often than the regulator.
I will let you know how it goes, thanks again.
 

Last edited by leadfoot; 09-13-2009 at 09:52 AM. Reason: spelling
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