Fuel pressure probs
Thread Starter
Instructor
Joined: Oct 2003
Posts: 198
Likes: 0
From: Dallas tx
Fuel pressure probs
I just installed my new injectors, I'm priming the system looking for leaks. Well, the first time i turned the ignition on, it ran up to about 28psi and held for about ten min. Then i purged my pressure guage, turned on the ignition, and it ran up to about 26psi and wouldnt hold. Third tan only got to 10psi and wouldnt hold. I tried two more times and I'm not getting any pressure at all. :confused: Does this sound like anything to anyone? I was just about to do the pressure test with the fuel pump when all this started. Oh, and my pressure regulator isnt hooked up to anything right now, could that be the cause?
Melting Slicks
Joined: Jul 2003
Posts: 3,493
Likes: 876
From: Saratoga Springs NY
2024 C4 of the Year Finalist - Modified
2022 C4 of the Year Finalist - Modified
Re: Fuel pressure probs (Ras119)
Yeah your fuel preesure regulator does just that and holds pressure...Does the engine run??? I would hook it all up, start the engine with the gauge installed, and see where your at...Running the engine as opposed to turned the key on will be different..The key on pump only gives the fuel rails enough pressure to start the engine.It typically wont tell you crap with the engine not started..Once its running ,you should be at least 38 psi ( AT THE LEAST)..
Then you can fine tune your pressure...
Then you can fine tune your pressure...
Thread Starter
Instructor
Joined: Oct 2003
Posts: 198
Likes: 0
From: Dallas tx
Re: Fuel pressure probs (FostersPerformance)
Thats the thing i was worried about. HOoking everything up then finding a problem. I don't notice any gross leaks from the injectors so I guess I am going to assume they are okay?? I just wanted to pressurize it before i put the plenum back on.
Melting Slicks
Joined: Jul 2003
Posts: 3,493
Likes: 876
From: Saratoga Springs NY
2024 C4 of the Year Finalist - Modified
2022 C4 of the Year Finalist - Modified
Re: Fuel pressure probs (Ras119)
Yeah, if you had a leak you see it right away...Either purge the air with your gauge if u can, or just open the schrader valve a little bit untill gas tries to blind you.But it really is almost impossible to get a leak at the injector assuming you installed them correctly..The biggest thing is not putting oil on the o rings before installation...If you did that and made sure they were all snug in their bores, you will be fine.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Fuel pressure probs (Ras119)
Oh, and my pressure regulator isnt hooked up to anything right now, could that be the cause?
RACE ON!!!
Thread Starter
Instructor
Joined: Oct 2003
Posts: 198
Likes: 0
From: Dallas tx
Re: Fuel pressure probs (CFI-EFI)
Okay, sorry about that. The fuel pressure regulator is inline, where it is supposed to be. The vacuum line to it isnt attached to anything just yet, as there isnt any plenum on it right now.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Fuel pressure probs (Ras119)
Key on pressure should be 38 to 42 and holding. It doesn't matter if the vacuum line is hooked up and you may have to cycle the ignition a couple of times to fill up the rail. If you don't have this pressure, something is holding back flow or if you get some pressure, but it bleeds off, an injector is stuck open or it's leaking somewhere - check closely at the rail and the manifold - it doesn't take much and you may need to cycle the ignition on and off 4 or 5 times before it becomes obvious. Otherwise, remove the rail with the injectors - any with fuel dripping is the problem and whatever cylinder it's located on, remove the plug and turn it over by hand until it's at TDC to force the excess fuel out of it.
For steady but low pressure, flush the inlet by clamping a hose to it and placing it in a coffee can. Then crank the engine until it spits out a quart (if flow is ok you should see a pint after 15 seconds). If flow is marginal, replace the filter. If you still can't get adequate pressure, clamp the return line while applying 12 volts to the fuel pump tester. If it rises above 47, the regulator is shot. If it's still low, it the fuel pump.
For steady but low pressure, flush the inlet by clamping a hose to it and placing it in a coffee can. Then crank the engine until it spits out a quart (if flow is ok you should see a pint after 15 seconds). If flow is marginal, replace the filter. If you still can't get adequate pressure, clamp the return line while applying 12 volts to the fuel pump tester. If it rises above 47, the regulator is shot. If it's still low, it the fuel pump.
Thread Starter
Instructor
Joined: Oct 2003
Posts: 198
Likes: 0
From: Dallas tx
Re: Fuel pressure probs (SunCr)
Looks like the issue was with my fuel pressure gauge. When i pulled it off and cycled the starter a few times to fill it up with fuel, then cycled once more I'm at 40psi and holding. :party: thanks for the help :thumbs:
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