FI fuel system

[BammBamm]

I bought an aftermarket fuel pump from Amazon for $30 and when I put it on I was showing 40 psi on the fuel rail. The engine and fuel system had been completely taken apart and not it hasn’t run right for at least two years. I then bought a factory fuel pump, installed it and still showed 40 psi at the fuel rail. I then tried all three of my factory pressure regulators and continued to show 40 psi. So I bought an Amazon. so I bought an Amazon adjustable, fuel regulator. It had so much restriction it would only produce 55 pounds in above. I’d rather just install an inexpensive adjustable, fuel regulator, but they all seem to be the same. Any suggestions?

[TX82FIAT]

Your fuel rail is downstream from the fuel pressure regulator. The fuel pressure regulator has a diaphragm in it that gives out after many years of use. The pumps put out 40 to 45 psi and the fuel pressure regulator brings it down to around 36 psi. All the pumps wont fix the fuel pressure if the problem is with the fuel pressure regulator. I replaced my fuel pressure regulator about a year ago as I noticed a higer than normal gas smell and a little fuel collecting on top of the regulator. Thought it was just a leak but car was running rough and haveing a hard time starting as fuel pressure needed to rebuild on start. If that is what you need shop around. You can find the fuel pressure regulator for as little at $79 on sites like parts geek or you could pay $400 is you buy from the first site that pops up.

[18Fiatsandcounting]

Your fuel rail is downstream from the fuel pressure regulator.

Is this correct? I thought the sequence of fuel flow was:
Gas tank > fuel pump > fuel filter > fuel rail (to injectors and cold start valve) > fuel regulator > return to gas tank

I agree about the importance of a working fuel pressure regulator. This FI system was designed to work on 2.5 bar, which is a little over 36 psi.

-Bryan

[TX82FIAT]

Brian, I stated that wrong. The pressure regulator is not downstream in fuel flow but measures the pressure. You are correct in the fuel entering the fuel rail where it has a passage to the pressure regulator so excess pressure can be released through the pressure regulator and routed back to the fuel tank. The other line is from the intake for vacuum pressure to help manage the diaphragm and pressure based on engine. Sorry I was misleading in my response.

[18Fiatsandcounting]

Thanks for the clarification. Being an old-school carb guy, I'm trying to teach myself the basics of the L-Jetronic system and just wanted to make sure I wasn't missing something.

-Bryan

[spider2081]

I don't think 40PSI fuel pressure would greatly effect engine performance. I think I read somewhere that pinching off the fuel return hose would cause the fuel pressure to increase to the pumps max pressure out. That is something over 50 lbs. Maybe there is a restriction in the fuel return line causing the pressure to be a little high. Also there is a 2 way check valve in the canister vent system located above the rear axle. It is common for this valve to clog with junk and not work properly. If clogged maybe it could cause the pressure to increase. If air can't leave the tank maybe it would take more pressure to return gas into the tank.