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Low Fuel Pressure 10PSI

 
Old 02-25-2019, 08:17 PM
  #16  
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Originally Posted by mj951 View Post
Did the new fuel pump come with a new check valve, they're two separate parts and part #'s?
I don't know what's causing fuel to get into your intake manifold but a bad check valve is a common cause for fuel pressure to drop after shutting down the car.
Still not a bad idea to replace the regulator and damper if original.
considering most of the parts on this car are 30 years old I don't mind changing them. New regulator and damper etc. I can do it I just need this thing to be running. It rolled off a flat bed onto my driveway about two months ago and I've been dumping money and time into it ever since.
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Old 03-05-2019, 10:57 PM
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Default Replacing Fuel Pressure regulator next...

Originally Posted by StoogeMoe View Post
There's no way you're losing 30psi through a leaking injector. If it's not your regulator, then you have some kind of obstruction in the fuel lines. Check for kinked or crushed lines. Or something back at the filter area. Maybe even the screen in the tank.
I'm glad you said that. I'm thinking the Fuel Pressure Regulator is punctured. I ordered a new one, should be here tomorrow, so I will put that on and see what happens. I took the throttle body off and found a couple inches of gas in the intake manifold. I drained that with paper towels. I also have one new injector, but I may replace them all before too long if the fuel pressure regulator doesn't help things. Basically I've bought all new everything from the tank to the fuel rail. I put a new in tank filter (I have a plastic tank and it was seized and the aluminum collar spun out so I had to pull it out and put an after market alloy cog inside the tank to seal it ($165.00) Not fun, after that all rear fuel lines are new factory Porsche and a new fuel pump (not bosch) I also put on new ignition wires, new flywheel sensors, new spark plugs, new coil etc. Pretty much everything and now I'm down to FPR and I also ordered a new throttle position sensor. (Did I mention I'm on a first name friendly basis with almost all the major Porsche 944 parts suppliers now???) It's costing a small fortune but I'm hoping this adds the reliability of the car later. Fuel pressure is hitting 35psi but like I say it drops almost instantly when the pump stops, I don't think it's the check valve in fuel pump because it's new, but I guess it's possible it could have been bad. Noid lights show all injector leads are firing too. I put the injectors in bottle and got spray from all, I set the jars on a bench and fuel looked consistent between them. I'm just hoping to move on from this and get the car running as soon as possible. As soon as the parts come on I will put them on and see what happens. I pulled the vacuum lines off the fpr and fuel damper to smell for gas and didn't see or smell any gas so I'm not convinced this will help but I'm going to try everything until this gets going.

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Old 03-05-2019, 11:03 PM
  #18  
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Default low pressure was caused by a kink

Originally Posted by 400hp944 View Post
How about disconnecting the fuel line at the fuel rail and disconnecting the other end at the filter. Using compressed air at the front (fuel rail side) blow out the line to see if you have an obstruction. While you are at it, follow the line all the way back and inspect for kinks or damage. Do the same for the return line as well. If that is clear, put a bucket under the filter and turn on the fuel pump to ensure flow from the filter. You may find your issue in one of these areas.
I found the kink it was because I was working on my fuel pump and left the metal shroud on, but the strap was off and the weight of everything was pulling on the line by the filter and flattened it aka pinch. I fixed that, but now I'm loosing pressure too fast when I shut the pump off so I'm looking to change out the fuel pressure regulator in case there is a puncture in it. I also had fuel in my intake manifold like an inch or two...
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Old 03-05-2019, 11:05 PM
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Default haven't checked the voltage

Originally Posted by StoogeMoe View Post
Here's another thought-

What is the voltage AT the pump when it is RUNNING?
I haven't checked the voltage, but I did put a test light on and it came on bright, I also jumped the DME Relay so the pump comes on when the key is in "ON" position and it's running. The problem was a hose in the back was kinked.

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Old 03-13-2019, 08:58 PM
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Default Fuel pressure regulator and damper bad.

When I started the car and it ran and I shut it off and then I pulled the vacuum lines off of the fuel pressure damper and the fuel pressure regulator and both of the vacuum lines had gasoline dripping out of them . So that was why I was losing my fuel pressure so quickly and also how I was ending up with gasoline in my intake manifold. Both will be replaced and I will go from there.
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