Low fuel pressure
Low fuel pressure
I have been having to crank my car over 3 or 4 times to get it to start for the last week or so.If I just shut it off for a few minutes it fires right back up.I checked my fuel pressure today and here are the results.
Key on, engine not running: 15 psi for a couple of seconds and then drops to 10 psi.
Engine running at idle: 30 psi. When I rev the engine it raises to 31 or 32 psi.
When I shut it off it slowly drops to 0 psi within a couple of minutes.
I do not hear the pump priming when I turn the key.I was thinking that my fuel pump is getting ready to fail,but now I'm not so sure.Are these the symptoms of a leaking injector or a fuel pump? If so ,how do I test for a leaking injector?
The car runs fine once it starts and I have replaced the fuel filter in the past week.
Key on, engine not running: 15 psi for a couple of seconds and then drops to 10 psi.
Engine running at idle: 30 psi. When I rev the engine it raises to 31 or 32 psi.
When I shut it off it slowly drops to 0 psi within a couple of minutes.
I do not hear the pump priming when I turn the key.I was thinking that my fuel pump is getting ready to fail,but now I'm not so sure.Are these the symptoms of a leaking injector or a fuel pump? If so ,how do I test for a leaking injector?
The car runs fine once it starts and I have replaced the fuel filter in the past week.
Pressures sound way too low. To check it correctly, at idle you need 41-47psi with the vacuum compensation line off the fuel pressure regulator. When you reconnect the vacuum line, it will drop about 6 - 8psi. At WOT/max RPM/max load, you want at least 40psi.
If the system can't hold those pressures, it could be a weak fuel pump, plugged fuel filter, faulty fuel pressure regulator, or unusually large leaks in the lines or injectors. When you pull the vacuum line off the regulator, look for wet fuel or excessive fuel odor in the line. To check for leaking injectors, pull the rails up with the injectors intact and pressure the fuel system (do not turn the key to "start"). Large leaks will be evident from dripping injectors.
If the system can't hold those pressures, it could be a weak fuel pump, plugged fuel filter, faulty fuel pressure regulator, or unusually large leaks in the lines or injectors. When you pull the vacuum line off the regulator, look for wet fuel or excessive fuel odor in the line. To check for leaking injectors, pull the rails up with the injectors intact and pressure the fuel system (do not turn the key to "start"). Large leaks will be evident from dripping injectors.
Today I pulled off the vacuum line off of the fpr and there was no fuel coming out and no strong odor.I pulled the fuel rails up and the injectors were not leaking.There are no external leaks and I just changed the filter.It looks like I get to tackle the fuel pump next weekend.Injuneer, thank you for your input.
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Alex Barnes
LT1 Based Engine Tech
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Jan 24, 2015 10:21 PM



