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Old 05-20-2009, 05:59 AM   #1
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Default Fuel Pressure WAY high and MAP sensor voltage too low.

I'm pretty sure I am having high fuel pressure issues. I read the service manual last night and it says that FP at key on should be 41-47PSI. At idle it should drop to 3-10PSI. My car is getting to about 45PSI at key on but I know it has never dropped after the car starts (or at least for the past 20K miles because I have a gauge hooked up to an electronic fuel pressure sending unit off of the rail). For the past 1000 miles or so, the FP goes WAY high (>100PSI) when under throttle. I'm thinking I may have a fuel return blockage or something and I probably won't have time to investigate for another couple weeks. Another issue, that I think may be related is, I'm getting an intermittent MAP Sensor signal voltage too low (pressure too high). My vacuum seems to be pretty steady when running and drops when the throttle is goosed. It appears that the FP is regulated by vacuum which is why I'm thinking maybe the two are related. I'm not sure how Manifold absolute pressure and vacuum play together.

The funny thing is, the car seems to run OK even with high FP. I'm looking for comments/suggestions. THANKS!!
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Last edited by jkichline; 05-20-2009 at 06:04 AM.. Reason: Can't spell... :)
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Old 05-27-2009, 05:48 AM   #2
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So I found some information here.
http://shbox.com/1/4th_gen_tech2.htm...essure_testing

It says FP should be 3-10psi less at idle (compared to KOEO). That makes a lot more sense than 3-10psi at idle.

I'm going to check it out this weekend. Still looking for comments/suggestions.
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Old 05-27-2009, 10:40 AM   #3
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You pressure should be 43psi +- 3 psi anytime. 100psi spike I would look at the reg.

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Old 05-31-2009, 09:09 PM   #4
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Well it turns out my FP is totally normal. I have a bad fuel pressure sending unit for my pillar gauge. Stupid crap parts!

Also I replaced the MAP sensor and haven't had a check engine light since...
<fingers crossed>
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Old 05-31-2009, 09:09 PM
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