2.3L ('83-'97) Fuel Pressure Bleeding Down

[ylidk]

Hello all, I'm currently in the middle of a distributed turbo 2.3 conversion from a 1988 Thunderbird Turbocoupe into my 1991 Ranger, which had the EDIS 2.3 stock. I am running into a bizarre issue where the fuel pressure is bleeding down after letting the fuel pump prime the engine. I have done many tests and keep ending up confused as to what is actually causing the issue. I can't get the truck started for more than a second or two, so I can't say what the behavior is while running.

To start: I have tested the turbocoupe fuel rail with the stock turbocoupe fuel pressure regulator, the stock ranger regulator, and a Stinger Performance adjustable fuel pressure regulator, as well as the stock ranger fuel rail with all 3 regulators as well. The fuel pressure bleeds down in all 6 cases, very quickly. I have tested the test kit on my '89 F150 with the 4.9L and the fuel pressure holds strong at 45 PSI, so the test kit gauge is good. I have also disconnected my F150 fuel lines and hooked them up to the ranger and turbocoupe fuel rails, and they bleed down as they did on the ranger's fuel system, with each regulator, so I can safely say the problem is isolated to the fuel rails, injectors or regulators. I have replaced the o-rings on the fuel injectors, and the fuel pressure still bleeds down quickly. I do not see any fuel leaks anywhere, on the rail, at the connections by the fuel filter or along the frame rail toward the tank. I have not dropped the tank and checked the pump, but since the problem transferred to the F150 I feel confident enough in not messing with the pump.

I also disconnected the fuel return line from the rail, and plugged the return port, primed the engine and it pressurized to 55 PSI, and held steady. This makes me believe the drain is coming through the regulator, but since the issue occurred on 3 different regulators on two different fuel rails, I'm not so sure. I don't want to fire the parts cannon and buy another regulator or deal with replacing the performance regulator if it isn't bad. Is this normal behavior for a fuel pressure regulator on the 2.3L engines? I am basing my knowledge on experience with my F150 where it primes and holds steady - I can't imagine the 2.3 behaves differently, but between 2 fuel rails and 3 regulators all having the same behavior I'm starting to wonder.

I also noticed that as the pressure drops, it briefly ticks up in pressure after a certain point, depending on what pressure the regulator is set to. With the adjustable regulator set to 45 PSI, the pressure will tick up at around 35 PSI back to 40 PSI, then continue dropping to ~20-25 PSI, where it slows down a bit, eventually bleeding down to 0 PSI. I have a video of the gauge, but wasn't able to attach it here. Let me know if there are any details or tests I missed. Thanks in advance for any advice you guys might have.

 

[RonD]

If you don't smell gasoline, external leak, then there are only 2 places that can leak out fuel in a pre-1998 fuel system where you won't smell it
If injectors were leaking then you would smell it if you opened throttle plate

Fuel pump has an internal check valve that is pushed open when pump is on and then closes(pushed closed by pressure) when pump is off, its a "backflow" prevent type valve, basically a "flap", lol

Pumps fuel line runs to the fuel filter and from filter to the IN connection on the fuel rail, NOT the FPR(fuel pressure regulator)
Fuel pump--(20-40psi)------filter------(20-40psi)---------------IN on fuel rail

FPR has the Return line attached, it runs to the gas tank, no pressure in the line just flow, it has open end inside gas tank, so can't hold pressure
Fuel rail--FPR----------(0psi)----------------------gas tank



If you squeeze the return line or block it and system holds pressure, then FPR is the issue
But pressure should go up to 70+psi when you do this, because FPR is the only pressure control for the system, fuel pump is capable of over 70psi

So make sure your fuel lines are hooked up correctly, sometimes the IN line gets hooked to FPR and you will get what you describe
FPR is hooked to the OUT line, back to gas tank line

 

[ylidk]

So make sure your fuel lines are hooked up correctly, sometimes the IN line gets hooked to FPR and you will get what you describe
FPR is hooked to the OUT line, back to gas tank line

Double checked to make sure, they are hooked up properly and the supply line goes to the rail and the return line from the FPR. The connections are different sizes so they only go on one way. I do have a set of o-rings coming in today to replace the seals at these connectors, though I don't think that is the issue. Sounds like you are confident it is the FPR based on the behavior when plugging the return line, I can pick up a 4th regulator from a parts store today to test a new standard replacement regulator and see. I'm just very surprised at the fact that 3 regulators, including the Stinger performance regulator, are all having this problem on two different fuel rails. I would've thought that would rule out a bad FPR and a bad fuel rail. I'll replace the regulator with another new one and report back I guess. As for fuel pressure, I only primed the pump one time, and all the gas leaked from the fuel rail after I disconnected the return line, so I think if I blocked the return line and primed it again it would reach a higher pressure, I can test that as well. I've also been tempted to add in extra check valves in the fuel lines to make sure that isn't the problem, but I'll try to rule out FPR first. Thanks for the quick response!

 

[RonD]

You can pull off Return line from FPR, put a towel down under its port
Cycle key on and off
NO fuel should come out of FPR until fuel pressure gets above 40psi
Each key on and off is about a 10psi increase

If fuel comes out FPR is bad/leaking

FPR is a valve held close by a spring, spring is set to hold pressure, hold valve closed, up to about 40psi, then the pressure will push open the valve a bit and release pressure until its below 40psi and spring can push it closed again

Much like radiator cap valve and spring setup, but its set for 18psi, pushed open at 19psi and closes under 18psi

These are very simple setups and have been used for at least 75 years because they are simple, and reliable

 

[ylidk]

Turns out yes, it was in fact the fuel pressure regulator! Thanks for the help, I guess I just had bad luck with all three FPR's happening to be faulty. Performed that check and it was bleeding out. Replaced the part with a cheap parts store regulator yesterday and it is now pressurizes to 40 PSI and then holds at 35 PSI.

 

[RonD]

Good work