Fuel pressure regulator test?
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Senior User
Joined: Oct 2008
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From: Denmark,WI
Fuel pressure regulator test?
Is there a way to test the fuel pressure regulator? Im buying a gauge in the morning to test the pressure. When i take the vac line off there is no effect on the idle or when i rev it, even with my finger on the end of the vac line. 
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Here's how it works.
With no engine vacuum applied 'hose off' and engine running, the regulator regulates to it's basic design pressure plus or minus some tolerance.
That pressure should be betwen 35 and 38 psi.
With application of engine vacuum through the vacuum regulator, the fuel rgulator has a diaphram that is pulled on. This will lower the outlet pressure to the fuel rails, about 5 psi +/-.
To test this function you can pull the hose off or use a hand vacuum pump to apply vacuum to the fuel regulator with the motor running.
To test for cold start fuel operation, install gage.
Turn key to run , observe gage reading. If 15 to 20 psi, return ignition to off and do it again several more times. If the gage climbs toward full pressure with several on-off cycles, the pump is picking up the pressure normal
Observe the results on your pressure gage hooked to the fuel rail test port.
To finish off, the pump pressure can be as high as 100 psi that is regulated downward by the regulator.
A hint; if the motor runs out of fuel from an empty tank, after putting fuel in, cycle the key to run 5 or 6 times. This will prime the system back to normal.
Good luck.
With no engine vacuum applied 'hose off' and engine running, the regulator regulates to it's basic design pressure plus or minus some tolerance.
That pressure should be betwen 35 and 38 psi.
With application of engine vacuum through the vacuum regulator, the fuel rgulator has a diaphram that is pulled on. This will lower the outlet pressure to the fuel rails, about 5 psi +/-.
To test this function you can pull the hose off or use a hand vacuum pump to apply vacuum to the fuel regulator with the motor running.
To test for cold start fuel operation, install gage.
Turn key to run , observe gage reading. If 15 to 20 psi, return ignition to off and do it again several more times. If the gage climbs toward full pressure with several on-off cycles, the pump is picking up the pressure normal
Observe the results on your pressure gage hooked to the fuel rail test port.
To finish off, the pump pressure can be as high as 100 psi that is regulated downward by the regulator.
A hint; if the motor runs out of fuel from an empty tank, after putting fuel in, cycle the key to run 5 or 6 times. This will prime the system back to normal.
Good luck.
Senior User
Joined: May 2006
Posts: 147
Likes: 0
Here's how it works.
With no engine vacuum applied 'hose off' and engine running, the regulator regulates to it's basic design pressure plus or minus some tolerance.
That pressure should be betwen 35 and 38 psi.
With application of engine vacuum through the vacuum regulator, the fuel rgulator has a diaphram that is pulled on. This will lower the outlet pressure to the fuel rails, about 5 psi +/-.
To test this function you can pull the hose off or use a hand vacuum pump to apply vacuum to the fuel regulator with the motor running.
To test for cold start fuel operation, install gage.
Turn key to run , observe gage reading. If 15 to 20 psi, return ignition to off and do it again several more times. If the gage climbs toward full pressure with several on-off cycles, the pump is picking up the pressure normal
Observe the results on your pressure gage hooked to the fuel rail test port.
To finish off, the pump pressure can be as high as 100 psi that is regulated downward by the regulator.
A hint; if the motor runs out of fuel from an empty tank, after putting fuel in, cycle the key to run 5 or 6 times. This will prime the system back to normal.
Good luck.
With no engine vacuum applied 'hose off' and engine running, the regulator regulates to it's basic design pressure plus or minus some tolerance.
That pressure should be betwen 35 and 38 psi.
With application of engine vacuum through the vacuum regulator, the fuel rgulator has a diaphram that is pulled on. This will lower the outlet pressure to the fuel rails, about 5 psi +/-.
To test this function you can pull the hose off or use a hand vacuum pump to apply vacuum to the fuel regulator with the motor running.
To test for cold start fuel operation, install gage.
Turn key to run , observe gage reading. If 15 to 20 psi, return ignition to off and do it again several more times. If the gage climbs toward full pressure with several on-off cycles, the pump is picking up the pressure normal
Observe the results on your pressure gage hooked to the fuel rail test port.
To finish off, the pump pressure can be as high as 100 psi that is regulated downward by the regulator.
A hint; if the motor runs out of fuel from an empty tank, after putting fuel in, cycle the key to run 5 or 6 times. This will prime the system back to normal.
Good luck.
Senior User
Joined: Sep 2011
Posts: 448
Likes: 1
Its on the fuel rail between cylinder 3 and 4 ( back two on passenger side) you need a fuel pressure gauge with the fittings to connect, looks like a tire valve ,i always just cover it with a rag and with a tiny scewdriver release the pressure,like letting air out of a tire, as im covering it with a rag to absorb the gas as it relieves then connect the tester, the tester should has a bleed down line on it to relieve the pressure for disconnection
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