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fuel pressure in 2.8 by pgold
Started on: 02-15-2014 05:53 PM
Replies: 5 (1116 views)
Last post by: pgold on 02-17-2014 06:37 PM
pgold
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Report this Post02-15-2014 05:53 PM Click Here to See the Profile for pgoldClick Here to Email pgoldSend a Private Message to pgoldEdit/Delete MessageReply w/QuoteDirect Link to This Post
What is the correct standing fuel pressure for the 2.8 when the engine is running and also when its turned off ?
can the pressure regulator be damaged if the fuel pump is left on? I am bench testing my fuel rail for leaks and proper pressure. I have the fuel pump directly connected to the rule rail with no control from the ECM.
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Report this Post02-15-2014 06:20 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
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Report this Post02-16-2014 10:05 AM Click Here to See the Profile for armosSend a Private Message to armosEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just to elaborate a bit on what's mentioned in that thread, the pressure regulator is referenced against manifold vacuum. It maintains a constant pressure differential between the fuel rail and the manifold. So under conditions where there's less manifold pressure (more vacuum), the fuel pressure will drop in proportion, and vice versa.
As measured with a gauge against atmospheric pressure, engine off it's about 42psi, and with engine idling, high 30s is normal.

In the complete installation, the rail shouldn't lose more than just a few psi of pressure in 15-20 minutes with the key off. Much more than that is not normal and indicates a problem. In a perfect Fiero, I don't know whether the theoretical ideal could be zero.
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Report this Post02-16-2014 07:39 PM Click Here to See the Profile for pgoldClick Here to Email pgoldSend a Private Message to pgoldEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the input. So on my fuel rail when i turn the engine off i have 30 lbs of pressure . can the drop in pressure be due to air leaking into the fuel rail? I don't see any fuel leaking anywhere since I'm doing a bench test out of the car. Or can it be a faulty pressure regulator? Do you recommend a adjustable regulator like the ones the fiero store have?
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Report this Post02-17-2014 03:17 AM Click Here to See the Profile for armosSend a Private Message to armosEdit/Delete MessageReply w/QuoteDirect Link to This Post
When you turn off the pump, it's dropping quickly to 30psi, and then staying there?
I'm not sure what any particular likely cause would be. Often it's an injector but you would be seeing that if it's out of the car.
If you can't find any leaks, then perhaps it could be leaking back to the tank (or whatever source you have it hooked up to).

I don't know if this would be the regulator, but if you end up needing one, I wouldn't use an adjustable. That just confuses the ECM, which expects the flow rate of the injectors to be consistent. If for example you increase the pressure, you'd get more fuel at first but then the ECM would see a rich condition and it shortens the injector pulses. It would be fighting you. Unless there's an unusual setup involved that requires non-standard fuel pressure, then I'd just use a standard regulator.
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Report this Post02-17-2014 06:37 PM Click Here to See the Profile for pgoldClick Here to Email pgoldSend a Private Message to pgoldEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks again the pressure regulator seems to be fine. It is discharging excess fuel when fuel pump is on and stops when the pressure drops to 35 psi. There are no apparent leeks so I'm gonna install in this weekend and see how it runs. This is a fuel rail that came out of another car i had. Im gonna trade out the one that is in my car now because it is bleeding off all the fuel pressure after i shut off the motor. Thanks for your help.
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